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Review

Research on the Characteristics of Electrolytes in Integrated Carbon Capture and Utilization Systems: The Key to Promoting the Development of Green and Low-Carbon Technologies

School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
*
Author to whom correspondence should be addressed.
Energies 2025, 18(12), 3039; https://doi.org/10.3390/en18123039 (registering DOI)
Submission received: 13 May 2025 / Revised: 2 June 2025 / Accepted: 6 June 2025 / Published: 8 June 2025

Abstract

:
The core challenge of integrated carbon capture and utilization (ICCU) technology lies in developing electrolytes that combine efficient carbon dioxide (CO2) capture with electrocatalytic conversion capabilities. This review analyzes the structure–performance relationship between electrolyte properties and CO2 electrochemical reduction (eCO2RR), revealing the key regulatory mechanisms. Research shows that the performance of bicarbonate electrolytes heavily depends on the cation type, where Cs+ can achieve over 90% CO selectivity by suppressing the hydrogen evolution reaction (HER) and stabilizing reaction intermediates, though its strong corrosiveness limits practical applications. Although amine absorbents excel in carbon capture (efficiency > 90%), they tend to undergo competitive adsorption during electrocatalysis, making formic acid the primary product (FE = 15%); modifying electrodes with ionomers can enhance their activity by 1.15 times. Ionic liquids (ILs) demonstrate unique advantages due to their tunability: imidazolium-based ILs improve formate selectivity to 85% via carboxylate intermediate formation, while amino-functionalized task-specific ILs (TSILs) achieve a 1:1 stoichiometric CO2 absorption ratio. Recent breakthroughs reveal that ternary IL hybrid electrolytes can achieve nearly 100% CO Faradaic efficiency (FE) through microenvironment modulation, while L-histidine additives boost CH4 selectivity by 23% via interface modification. Notably, constructing a “bulk acidic–interfacial neutral” pH gradient system addresses carbonate deposition issues in traditional alkaline conditions, increasing C2+ product efficiency to 50%. Studies also highlight that cation–anion synergy (e.g., K+/I) significantly enhances C-C coupling through electrostatic interactions, achieving 97% C2+ selectivity on Ag electrodes. These findings provide new insights for ICCU electrolyte design, with future research focusing on machine learning-assisted material optimization and reactor engineering to advance industrial applications.

1. Introduction

Global climate change has emerged as a critical challenge, marked by increasing extreme weather events [1]. Industrial carbon emissions are a primary driver of this crisis [2]. To address this, carbon capture and utilization (CCU) technologies have been developed. Based on process differences, carbon capture methods fall into three categories: pre-combustion, oxy-fuel combustion, and post-combustion [3]. Among these, post-combustion capture holds the greatest practical value due to its direct applicability to existing industrial infrastructure.
Among carbon conversion technologies, carbon dioxide (CO2) electrochemical reduction (eCO2RR) has attracted significant attention due to its mild reaction conditions and controllable product selectivity [4]. To improve the overall energy efficiency, researchers have proposed integrated carbon capture and utilization (ICCU) systems [5]. These systems impose unique requirements on electrolyte materials: they must simultaneously exhibit high CO2 capture capacity and catalytic activity for electrochemical reactions.
The current electrolyte systems face several key challenges: bicarbonate electrolytes exhibit strong corrosivity [6]; amine-based absorbents are prone to side reactions during electrocatalysis [7]; and ionic liquids remain limited by high costs [8]. The fundamental challenge lies in balancing an electrolyte’s capture capacity, catalytic activity, and economic viability. Recent studies suggest that modulating the electrolyte microenvironment (e.g., through pH gradients) can significantly enhance reaction selectivity [9], though the underlying mechanisms require further investigation.
This review systematically examines recent advances in electrolyte development for ICCU systems, with particular focus on material design principles and performance optimization strategies, providing theoretical guidance for developing efficient and cost-effective carbon cycling technologies [10]. By analyzing the current technical challenges and the future research directions, this work aims to accelerate the practical implementation of ICCU systems [11].

2. Electrolyte for Carbon Capture and Electrocatalytic Applications

In contemporary research, the predominant electrolytes for eCO2RR fall into three categories, i.e., (1) bicarbonate-based, (2) amine-based, and (3) ionic liquid electrolytes, along with some hybrid systems. These electrolytes play crucial roles in the following:
  • Enhancing reaction efficiency through improved CO2 adsorption [12,13] and facilitated electron transfer [7,14];
  • Controlling reaction selectivity by suppressing side reactions [8,15,16,17,18] and directing reaction pathways [12,14,19,20];
  • Expanding system compatibility with various electrode materials [7] and operational conditions.
The classification of carbon capture electrolytes and the investigation of their behavior during eCO2RR constitute the fundamental research on electrocatalytic carbon conversion. This review will systematically examine both conventional and emerging carbon capture electrolyte systems.

2.1. Bicarbonate Electrolyte

Sodium hydroxide (NaOH) [21] and potassium hydroxide (KOH) [22] solutions are widely employed as strong alkaline CO2 absorbents in laboratory settings, exhibiting rapid reaction kinetics and high absorption efficiency. The solid bicarbonate products can be thermally regenerated to release CO2 while recovering the absorbent. As Group 1 elements, Na and K demonstrate increasing metallic character and hydroxide alkalinity with higher atomic numbers.
Studies reveal that the dissociation degree of bicarbonate ions (HCO3) in aqueous solutions (20 °C) of alkali metal bicarbonates (Mx(HCO3)y, where M = Li, Na, etc., significantly increases with the group number (Figure 1). Notably, cesium bicarbonate (CsHCO3) shows approximately 60-fold greater solubility than lithium bicarbonate (LiHCO3) [16]. This enhanced dissociation behavior makes higher-atomic-number alkali bicarbonates particularly suitable for eCO2RR due to their superior ionic conductivity.
Endrodi and colleagues [16] developed a periodic Cs+ replenishment strategy (every 12 h) that maintained a CO Faradaic efficiency (FE) of >90% for 200 h at 400 ± 15 mA·cm−2, demonstrating that dynamic cation supplementation effectively prevents cathode salt deposition and ensures eCO2RR stability. The complementary in situ wide-angle X-ray scattering (WAXS) studies by Garg et al. [6] revealed distinct cation-dependent interfacial phenomena: Li+ rapidly forms passivating Li2CO3 layers that deactivate catalysts, while Na+ and K+ exhibit a dynamic deposition–dissolution equilibrium, and Cs+ shows no observable deposition (Figure 2).
Beyond deposition effects, alkali metal cations influence eCO2RR selectivity through three primary mechanisms:
  • Electrostatic stabilization of key reaction intermediates [23];
  • Cation hydrolysis-mediated local pH modulation [24];
  • Induced interfacial electric fields that alter reaction pathways [25].
Endrodi et al. [16] systematically investigated product distributions on Cu gas diffusion electrodes in 1M alkali bicarbonate electrolytes, revealing a clear periodic trend: as the atomic number increases from Li to Cs, the FE of carbonaceous products significantly improves while the competing hydrogen evolution reaction (HER) is progressively suppressed. Multiple research groups have confirmed that CsHCO3 exhibits the optimal HER suppression, demonstrating the highest eCO2RR selectivity among alkali bicarbonate systems (Figure 1). However, the practical application of strong alkaline absorbents (e.g., NaOH/KOH) faces substantial challenges. Their high corrosivity may damage reactor components, and the potential leakage poses serious ecological risks, significantly limiting their viability for industrial-scale implementation.
Ammonia solution, a widely used industrial chemical with mild alkalinity, has demonstrated exceptional potential for CO2 capture due to its high absorption efficiency, strong CO2 capture capacity, excellent oxidation resistance, and low regeneration energy requirements. In ammonia-based CO2 capture systems, the resulting ammonium bicarbonate-rich solution can be regenerated through a combined crystallization–thermal decomposition process. Research has shown that the decomposition kinetics of ammonium bicarbonate crystals are significantly influenced by temperature and heating rate: while slow decomposition begins at room temperature, the rate increases dramatically with rising temperatures and faster heating rates, achieving an activation energy as low as 48.38 kJ/mol. Notably, an optimal regeneration rate is attained at 80 °C [26].
Studies by Li et al. [27,28] and Yu [26] have demonstrated that employing ammonium bicarbonate as an electrolyte in eCO2RR systems can triple the CO2 concentration at the electrode interface (Figure 3), attributable to the rapid equilibrium reactions of HCO3 [29,30]. This innovative strategy of directly utilizing ammonium bicarbonate-rich solutions from ammonia-based CO2 capture for eCO2RR not only reduces the energy consumption for absorbent regeneration but also simultaneously produces valuable carbon-containing energy storage products.
However, ammonia-based CO2 capture technology still faces several challenges. Process simulations conducted by Xiaoxu et al. [31] using ChemDraw Professional (Version: 20.0) for a 350 MW coal-fired flue gas CO2 removal system revealed two critical trade-offs: (1) increasing ammonia concentration under optimal flow conditions exacerbates ammonia slip, and (2) it simultaneously reduces CO2 removal efficiency (Figure 4). To establish an efficient closed-loop technological system, coordinated optimization is required between upstream carbon capture processes (controlling ammonia slip) and downstream electrochemical conversion (regulating electrolyte concentration). This systems-level approach is essential to ensure both the operational safety and economic viability of the integrated process.

2.2. Amine-Based Electrolytes

Amine-based compounds, as the most mature chemical absorbents in post-combustion carbon capture, have attracted extensive attention due to their diverse molecular structures (e.g., primary, secondary, and sterically hindered amines) and high CO2 affinity [32]. Monoethanolamine (MEA), a typical unhindered primary amine, forms stable carbamates with CO2 through its exposed amino group (-NH2), exhibiting strong CO2 binding characteristics. In contrast, 2-amino-2-methyl-1-propanol (AMP), a sterically hindered secondary amine, shows significantly weaker CO2 binding capacity due to the steric hindrance effect of the α-carbon methyl group. These structure–performance differences directly influence their behavior in subsequent electrochemical conversion processes.
The Boundary Dam coal-fired power plant in Saskatchewan, Canada, serves as a representative industrial application [33]. This facility employs MEA as the core absorbent, achieving 90% CO2 capture efficiency in commercial operation and utilizing the captured CO2 for enhanced oil recovery (EOR). However, the high energy consumption during amine regeneration (primarily due to the thermal decomposition energy barrier of carbamates) remains a critical bottleneck for large-scale implementation.
A recent work by Bruggeman et al. [7] using in situ characterization techniques has elucidated the transformation mechanism of amine-CO2 complexes at electrochemical interfaces. Employing copper (Cu) as a model catalyst—whose unique d-electron configuration facilitates inner-sphere electron transfer through surface coordination bonds with reactants—the study combined cyclic voltammetry (CV) and Fourier-transform infrared spectroscopy (FTIR) to sequentially identify key intermediates via their characteristic vibrational signals:
  • 2345 cm−1: gaseous CO2 consumption (O=C=O asymmetric stretching, vas);
  • 1675 cm−1: carboxyl group formation at the electrode interface (C=O stretching, v);
  • 1607 cm−1: carboxylate ion generation (COO asymmetric stretching, vas);
  • 1604 cm−1: free amine regeneration (N-H in-plane bending, δ).
Notably, despite their differing CO2 capture capacities, both AMP and MEA participate in reactions through carbamate intermediates on Cu surfaces (Figure 5). The reaction pathway involves the following: (1) amine-CO2 complexes accepting electrons via Cu 3d orbitals, (2) C-N bond cleavage to form formate, and (3) amine desorption from the electrode surface. These findings provide crucial theoretical foundations for developing integrated “capture–conversion” processes.
The Bruggeman research group [7] further investigated the influence of different electrode materials on the electrochemical reduction behavior of amine-CO2 complexes. When replacing the Cu electrode with lead (Pb), experimental results demonstrated significantly enhanced eCO2RR activity for both MEA-CO2 and AMP-CO2 complexes on Pb surfaces. This phenomenon can be explained by two key mechanisms: (1) on Cu electrodes, the strong interaction between MEA-H+ and Cu preferentially occupies active sites, competing with MEA-CO2 adsorption and consequently inhibiting the eCO2RR process (Figure 6), and (2) the outer-sphere electron transfer characteristics of Pb electrodes result in weaker surface interactions with amine molecules, creating a more flexible reaction interface that facilitates eCO2RR (Figure 6).
To address challenges such as high reaction barriers and low product selectivity in MEA-CO2 systems during eCO2RR, Li [34] developed an innovative electrode material. The study employed Sustainion ionomer as a binder to fabricate hydrophilic nano-silver electrodes, which significantly improved the wettability of MEA-CO2 complexes on the electrode surface and effectively increased the electrochemical active area. Experimental results showed that, at −1.3 V vs. Ag/AgCl, this electrode system achieved an FECO of 15.02%, representing a 1.15-fold improvement compared to conventional electrodes (Figure 7). This enhancement primarily stems from improved charge transfer efficiency and mass transport rates.
These findings collectively demonstrate that organic amines represented by MEA and AMP exhibit remarkable potential as carbon source materials for eCO2RR. To achieve the direct application of these CO2-capturing organic amines as carbon sources in electrolysis processes, it is essential to thoroughly investigate the microscopic interaction mechanisms between electrode catalysts and electrolytes. By systematically studying the structure–activity relationships between organic amine molecular characteristics and eCO2RR performance, and establishing scientifically robust screening criteria, the most promising carbon source materials can be selected from numerous amine candidates. This multi-scale optimization strategy not only enables the synergistic optimization of efficient CO2 capture and directional conversion but also holds promise for constructing a complete closed-loop “capture–conversion–utilization” carbon cycle system. The breakthroughs in this technological approach will provide innovative solutions for advancing carbon neutrality goals while establishing important theoretical foundations for developing next-generation carbon-neutral technologies.

2.3. Ionic Liquid Electrolyte

Ionic liquids (ILs), a class of molten salt systems composed entirely of ions at or near room temperature [35], have emerged as novel CO2 capture materials to replace traditional alkanolamine absorbents [36] due to their unique physicochemical properties. These materials demonstrate remarkable advantages in carbon capture, including negligible volatility, exceptional thermal stability, and high CO2 affinity. Studies show that 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) can achieve a CO2 molar absorption ratio of 1:0.75 under 8.3 MPa high-pressure conditions [37]. Systematic gas solubility comparative studies by Anthony et al. [38] (Figure 8) confirmed that ILs exhibit significantly superior selective absorption capacity for CO2 over other gas components like O2.
Among various ILs, imidazolium-based ionic liquids have attracted particular attention [39,40,41] owing to their low viscosity, rapid mass transfer characteristics, and excellent CO2 solubility. Research reveals that imidazole–carboxylate complexes formed between imidazolium groups and CO2 play a pivotal role in eCO2RR processes (Figure 9). This unique interaction not only reduces the reaction energy threshold but also effectively suppresses CO2 conversion to oxalic acid (C2H2O4), thereby promoting formic acid (HCOOH) production and significantly enhancing product selectivity. These distinctive characteristics endow imidazolium-based ILs with exceptional potential for developing integrated carbon capture and conversion systems.
Numerous studies have demonstrated that ILs as electrolytes exhibit remarkable advantages in eCO2RR systems. Their exceptional CO2 capture capacity provides abundant active sites for reactions, effectively reducing overpotential, suppressing the HER, and enhancing target product selectivity. Under mild conditions, ILs enable simultaneous efficient CO2 capture and directional conversion, making them ideal electrolyte candidates for eCO2RR.
The current research has identified three primary reduction products in IL-based eCO2RR systems: HCOOH, CO, and C2H2O4. While the formation mechanism of HCOOH via imidazolium-based ILs has been previously detailed, the CO generation pathway involves distinct intermediates. Chen et al. [42] revealed that imidazolium ILs can form [CO2-bmim] complexes with CO2 radical anions (CO2), which subsequently react with additional CO2 to yield (CO2)2 adducts before ultimately reducing to CO and carbonate ions (CO32−) at the cathode surface (Figure 10). Through the density functional theory (DFT) calculations, Hu et al. [43] systematically compared the effects of different anions (Cl, [PF6], and [Tf2N]), discovering that Cl significantly alters the linear configuration of CO2, thereby improving reaction efficiency.
In the mechanistic study of C2H2O4 formation, Yang et al. [8] systematically evaluated various ILs using nuclear magnetic resonance (NMR) and identified tetraethylammonium 4-(methoxycarbonyl)phenolate ([TEA][4-MF-PhO]) as the optimal catalyst. The reaction proceeds through the following steps: (1) the reduction of CO2 to CO2*− radicals, (2) protonation to form [4-MF-PhO-COOH] intermediates, and (3) subsequent dimerization to yield C2H2O4 (Figure 11). This system exhibits three distinctive features: (1) the proton-deficient environment effectively suppresses the HER, (2) aromatic ester anions provide dual active sites, and (3) significantly enhanced C2H2O4 selectivity.
These findings provide crucial guidance for designing functionalized ILs. Future research should focus on elucidating how different functional groups influence catalytic performance to achieve precise control over eCO2RR product selectivity. The strategic molecular engineering of ILs will advance integrated carbon capture and conversion technologies.
Inspired by the carbamate formation mechanism between amine solvents (-NH2 groups) and CO2, researchers have developed task-specific ILs (TSILs) to enhance CO2 capture performance. These TSILs feature covalently tethered functional groups (e.g., -NH2) on either cations or anions. Bates et al. [44] synthesized 1-butyl-2-bromopropylamine imidazolium ([NH2p-bim][BF4]), which demonstrated a CO2 absorption ratio of 1:0.5 (mol/mol) with characteristic carbamate peaks confirmed by FT-IR and NMR. Zhang et al. [45] further developed dual-amine functionalized TSILs ([DNH2EMIM]Br) achieving near 1:1 CO2 absorption capacity, significantly outperforming mono-amine systems.
To address the mass transfer limitations caused by the high viscosity of conventional ILs, Wang et al. [46,47] systematically investigated the influence of component ratios in a [bmim][PF6]/H2O/MeCN ternary system on eCO2RR performance. The following is evident from Figure 12: (a) when the mass fraction of [bmim][PF6] increased from 5% to 60%, the Faradaic efficiency and current density exhibited a “volcano-type” trend, peaking at 30% [bmim][PF6] content, and (b) with fixed [bmim][PF6] content, similar behavior was observed as water content increased from 0% to 15%, with optimal performance at 5% water content. These results demonstrate that the appropriate regulation of IL/water ratios can effectively optimize interfacial mass transport. In catalyst modification, Sun et al. [13] achieved 91.9% FECO and 120 mA·cm−2 current density using an IL-modified Ni/Fe dual-atom catalyst, attributed to enhanced CO2 adsorption and reduced onset potential. Vichou et al. [18] found that [Emim][BF4]-modified copper nanoparticles significantly improved C2+ product selectivity under acidic conditions (0.05 and 0.1 M H2SO4, Figure 13), demonstrating the effective HER suppression through IL modification.
These studies provide critical guidance for IL applications in eCO2RR:
  • Functional modification enables the precise control of CO2 capture capacity;
  • Solvent system optimization improves mass transport properties;
  • Interface engineering enhances catalyst selectivity;
The current applications of ILs in CO2 capture and eCO2RR face several technical limitations. First, their high viscosity, particularly in amino-functionalized ILs due to hydrogen bonding networks, reduces mass transfer efficiency and conductivity while requiring energy-intensive agitation to maintain adequate current densities. Second, their relatively high production costs hinder large-scale implementation. Third, conventional ILs exhibit limited CO2 adsorption capacities, often necessitating energy-consuming pressure or temperature swings. Fourth, the complex synthesis and elevated costs of functionalized ILs impede industrial adoption. Finally, most ILs show poor product selectivity in eCO2RR, typically yielding mixed C1, C2, and C2+ products.
Ongoing research aims to address these challenges through strategic improvements in IL design and system optimization. Key priorities include elucidating ILs’ mechanistic roles in modifying reaction pathways and enhancing electrode stability, investigating synergistic effects between ILs and electrode materials, and developing cost-effective synthesis routes. Further advancements require optimized electrode–electrolyte combinations characterized by advanced techniques, along with scalable reactor designs to bridge laboratory and industrial applications. These efforts may enable more efficient CO2 capture and conversion systems based on IL technology.

2.4. Other Electrolytes

Beyond the three mainstream electrolytes for eCO2RR, researchers are exploring alternative carbon sources for capture and conversion, including ternary electrolytes and amino acids. Ternary electrolytes, composed of three organic or inorganic components, represent a promising direction. Yang et al. [48] developed an IL-based ternary system containing 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C12mim][BF4]), and acetonitrile (MeCN). Using small-angle X-ray scattering (SAXS) and molecular dynamics simulations, they investigated the electrolyte’s microstructure and its interfacial interactions with electrodes. This optimized system enhanced current density, improved CO2 adsorption, facilitated proton diffusion, and suppressed HER, achieving nearly 100% FECO within −2.2 to −2.5 V vs. Ag/Ag+ (Table 1).
In biochemical systems, amino acids—organic compounds containing both amino (-NH2) and carboxyl (-COOH) groups—demonstrate remarkable CO2 capture potential in their salt forms. These amino acid salts exhibit four key advantages: (1) negligible volatility, (2) excellent environmental compatibility, (3) strong oxidation resistance, and (4) low dissociation energy barriers, making them particularly suitable for oxygen-rich carbon capture applications while significantly reducing regeneration energy requirements.
Tsuda et al. [49] systematically investigated five amino acids (L-histidine, L-tryptophan, L-citrulline, L-phenylalanine, and L-arginine) as electrolyte additives for Cu-catalyzed eCO2RR using energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and linear sweep voltammetry (LSV). Experiments conducted in CO2-saturated 0.5 M KHCO3 electrolyte at 1.27 V (vs. RHE) and 3 C·cm−2 revealed that amino acids specifically adsorb on electrodeposited Cu surfaces, modifying reaction pathways by altering interfacial potentials and reducing average Cu grain sizes. Significantly, L-histidine containing an imidazole group showed optimal catalytic modification, enhancing FECH4 from 55% to 67.6% (Figure 14), highlighting amino acids’ unique role in tuning eCO2RR selectivity and activity.
This section reviews the key characteristics, mechanisms, and applications of three major electrolyte systems (bicarbonates, amines, and ionic liquids) and emerging alternatives for ICCU (Table 2). Bicarbonate electrolytes (e.g., CsHCO3) demonstrate efficient CO2 conversion but face corrosion issues, while mature amine-based systems (e.g., MEA) require high regeneration energy. Although ionic liquids offer tunable selectivity and stability through functionalization, their high viscosity and cost remain challenges. Promising alternatives like ternary electrolytes and amino acid salts show synergistic potential. Future development should focus on electrolyte–electrode interactions, cost-effective synthesis, and scalable designs to enable closed-loop ICCU technologies.

3. Electrolyte Engineering for Product-Selective eCO2RR

3.1. pH-Mediated Control of Electrolytes in CO2 Electroreduction

Electrolyte pH critically determines eCO2RR selectivity and reaction kinetics through distinct dual mechanisms. Under strongly acidic conditions (pH < 1), carbonate deposition is effectively suppressed, achieving 77% single-pass CO2 conversion, though requiring high K+ concentrations (e.g., 3 M KCl) to maintain interfacial charge balance while enhancing C2+ production to 50% [9]. In 1 M H3PO4 electrolyte, high current density (1 A/cm2) establishes a pH gradient (bulk pH = 1 → local pH = 6.3 at 33 μm from electrode), which critically governs C-C coupling. Moderately acidic conditions (pH 2–4) alter proton donor species (H3O+→H2O), substantially modifying reaction barriers as demonstrated by the increased HER activation energy on Pt(111) from 0.04 to 0.42 eV [50]. While neutral/alkaline conditions (pH 6.8–13) promote C2H4 formation (40% selectivity on Cu(100) at pH 6.8), carbonate precipitation reduces CO2 utilization below 25% [9,51].
A breakthrough strategy involves establishing “acidic bulk–neutral interface” pH gradients. Phosphate buffer systems (1 M H3PO4 + 3 M KCl) maintain a bulk pH of <1 while generating neutral interfacial conditions through OH accumulation at high current densities [9,52]. Microkinetic modeling indicates a mechanistic transition from CPET to SPET when pH exceeds 4.66 (HCOO* pKa), favoring HCOOH production [53], thereby providing quantitative criteria for pH-zone control.

3.2. Concentration Effects of Electrolytes on eCO2RR

Electrolyte concentration profoundly influences eCO2RR performance by modulating the electric double-layer structure and interfacial reaction kinetics [54,55]. The primary mechanism involves local electric field regulation—for instance, 2.5 M KAc enhances C2H4 selectivity to 44.2% on Cu catalysts [55] through cation enrichment (K+/Cs+) that stabilizes OCCO intermediates [54,56] and modifies CO coverage to promote C-C coupling [57].
Mass transport effects are equally significant. While 1.0 M KHCO3 achieves 60% FE for HCOOH [58], 0.1 M CsHCO3 yields a C2H4/CH4 selectivity ratio of 4.8 [57]. However, excessive concentration (e.g., 3 M KHCO3) reduces C2+ FE from 70% to 30% due to HCO3-mediated competing reactions [59,60]. Optimal ranges are 0.1–0.5 M KHCO3 for C2+ products, 1.0 M KHCO3 for HCOOH pathways [58,59], and 0.7–0.9 M for ILs to balance activity and selectivity [56,60].

3.3. Cation–Anion Synergistic Effects in eCO2RR

Cations modulate reaction pathways through three primary mechanisms: (1) interfacial field effects—large-radius cations (Cs+, K+) induce a 3.7 cm−1 redshift in C≡O vibration frequency [19]; (2) proton transfer mediation—acidic cations (Li+) optimize proton-coupled electron transfer, reducing methanol (CH3OH) production Tafel slope to 47 mV/dec [14]; and (3) surface reconstruction—K+ enrichment forms high-activity Cu facets, achieving a C2+ current density of 225 mA/cm2 [20]. Multivalent cations (e.g., Sr2+) further enhance CO2 adsorption via oxygen vacancy generation [12].
Anions primarily modify interfacial microenvironments through specific adsorption: in the competitive sequence I > Br > Cl, chloride electrolytes enable 97% C2+ FE on Ag electrodes [61]. *OH adlayers reduce C-C coupling barriers by 34% via K+ electrostatic attraction [62]. ILs (e.g., [EMIm]+) maintain >100 mA/cm2 steady current by preventing OH interference [63], while organic additives (e.g., T-Pyr) boost C≥2 products to 80% efficiency through local pH regulation [64].
Synergistic cation–anion interactions operate through the following: (1) electrostatic coupling—K+ enrichment and I adsorption jointly enhance C2+ selectivity (97% FE on Ag) [61]; (2) dynamic proton management—multivalent cations (Al3+) provide secondary proton sources at pH = 3, while buffer anions (HCO3) maintain optimal microenvironments [65]; and (3) cooperative surface restructuring—K+-induced facet reconstruction and Br site-selective passivation synergistically optimize Cu active sites, increasing C2H4 FE from 3.1% to 9.3% [9,52].

3.4. Design Strategies for Dopant Engineering

Dopants enable selective control by reconstructing interfacial microenvironments. In aprotic solvents (e.g., acetonitrile), proton concentration management suppresses the HER while achieving near 100% C2+ FE [15,17]. Hydrophobic PVDF–Nafion membranes similarly restrict proton transport [17]. Under alkaline conditions, OH-induced *OH adlayers promote K+ enrichment, reducing C-C coupling barriers from 0.68 to 0.45 eV [62].
Surfactant design demonstrates precise modulation:
  • Cationic CTAB lowers the proton concentration via hydrophobic chains, yielding 50% HCOOH FE [15];
  • Double-charged quaternary ammonium salts tune product selectivity (28% C2H4 with C8 chains vs. 41% CO with C2 chains) [66];
  • Hydrophobic [NTF2] enriches CO2 for 38.7% HCOOH FE [15];
  • Immobilized imidazolium cations achieve 85% HCOOH selectivity in acidic media [67];
  • Lewis acids (e.g., boric acid) form [B(OCH2CH2O)2] chelates for 85% ethylene glycol FE [68].

3.5. Rational Screening Strategies

Three targeted electrolyte systems have been established based on the reaction mechanisms:
(1)
For C1 products (HCOOH/CO), optimal performance requires pH > 4.66 buffered systems [53] with 1.0 M KHCO3 [58], combined with hydrophobic anions ([NTF2]⁻) [15] or immobilized imidazolium cations [67] to promote SPET pathways.
(2)
C2+ production necessitates constructing acidic bulk–neutral interface gradients (1 M H3PO4 + 3 M KCl) [9,52] with Cs+/K+ cations and specifically adsorbed I/Br anions [19,61], supplemented by organic additives like T-Pyr [64].
(3)
Alcohol synthesis (CH3OH/C2H5OH) benefits from Li+-containing electrolytes [14] at concentrations of 0.1–0.5 M paired with Lewis acid additives for directed synthesis [68].
Future advancements should integrate operando characterization with multiphysics modeling to establish comprehensive reaction phase diagrams across pH, ionic composition, and potential parameters, enabling precise electrolyte engineering.

4. Application of ICCU

Electrochemical cells serve as fundamental components in eCO2RR systems, playing a pivotal role in both experimental research and industrial applications. The current eCO2RR studies primarily utilize five cell configurations: H-type cells, flow cells, solid oxide electrolysis cells, membrane electrode assemblies, and microfluidic cells. Among these, liquid-phase flow cells with continuous material renewal demonstrate particular advantages for ICCU systems due to their superior mass transfer capabilities (Figure 15).
The electrolyte functions as a critical CO2 carrier throughout the capture–conversion process, operating dually as follows: (1) an absorption medium in upstream capture towers, and (2) a liquid-phase CO2 transporter to downstream flow cells for eCO2RR. This creates an efficient industrial synergy between liquid electrolytes, absorption towers, and flow electrolyzers.
As illustrated in Figure 15a, conventional CCU systems employing H-cells require complete “capture–regeneration–separation” processes to supply pure CO2 for eCO2RR, resulting in significant energy penalties and operational complexity. To address this, researchers have developed directly coupled ICCU systems (Figure 15b) where CO2 desorption and conversion occur in situ within a single reactor [69,70]. This innovative design eliminates energy-intensive CO2 storage, transportation, and regeneration steps, establishing a streamlined technical pathway for carbon utilization.
The ICCU system faces three primary challenges: (1) flue gas impurity interference, (2) absorber–electrolyzer coordination, and (3) system-wide efficiency optimization. SOx/NOx impurities significantly degrade electrolyte performance: SO2 dissolution (SO2 + H2O→H2SO3) reduces pH and competes for active sites, causing a U-shaped trend in CO2 reduction selectivity (minimum 53.7% at 0.6% SO2) [71,72]. Solutions include Ni single-atom catalysts (Ni-NC), which maintain 92% CO selectivity under 0.3% SO2 [72], and functionalized ILs (e.g., [aP4443][2-Op]) with 1.57 mol CO2/mol IL capacity, though the challenges of viscosity and impurity sensitivity remain [73,74]. Electrochemical desulfurization reduces H2S from 1330 ppm to <0.5 ppm at 29% current efficiency [75].
Absorber–electrolyzer synergy and process optimization: The effective integration of absorbers and electrolyzers requires precise capacity matching. Conventional amine regeneration methods demand significant energy inputs (3.5–4.0 GJ/tCO2 at 120 °C steam) [76]. In contrast, electrochemically mediated amine regeneration (EMAR) in ICCU systems reduces this energy requirement to 40–80 kJ/molCO2 [11]. Advanced EMAR reactors employing multi-electrode configurations with gradient potential (ΔE = −0.04 V) demonstrate 20.05% enhanced desorption rates with only 4.04% additional energy consumption [11]. Flow dynamics optimization reveals that increasing flow velocity from 0.005 to 0.01 m/s improves desorption rates by 2.91‰ [11]. Similarly, in PEM water electrolysis (PEMWE) systems, membrane electrode assemblies (MEAs) show reduced temperature rise rates (from 69.6 to 50.4 °C/min) when flow rates increase from 20 to 100 mL/min [77]. Furthermore, multi-cycle topological optimization through density optimization and k-medoid clustering algorithms significantly improves system performance, increasing waste heat utilization from 8.5% to 51.3% while reducing operational costs by 17.9% [78].
Economic viability and carbon footprint optimization for ICCU systems: Techno-economic analysis (TEA) reveals that HCOOH and CO production achieve competitive levelized costs of USD 0.468/kg and USD 0.449/kg, respectively, while C2 products (e.g., C2H4) require >90% FE at <2 V to become economically viable [79]. Significant energy reductions have been demonstrated through heat pump-assisted pressure-swing distillation (HPA-PSD), lowering HCOOH separation energy from 19.85 to 12.2 kWh/kg [79]. From an emission perspective, concentrated solar power (CSP)-driven ICCU systems achieve negative carbon footprints (GWP = −1.05 kg CO2-eq) [79]. Operational efficiency gains are further achieved through intelligent control systems, with the Autoformer–DQN–Deep Forest model demonstrating 97.83% prediction accuracy for real-time carbon capture optimization using reinforcement learning on the CARMA dataset [80]. These advancements collectively establish a robust foundation for industrial-scale ICCU implementation.

5. Conclusions

While most eCO2RR research focuses on catalyst development, systematic electrolyte studies remain limited. This work comprehensively analyzes three major electrolyte types for ICCU systems, providing critical insights for efficient carbon cycling.
Bicarbonate electrolytes are widely used due to their excellent pH buffering and rapid CO2 equilibrium, with NH4HCO3 showing particular promise owing to its low regeneration energy (48.38 kJ/mol) and dual hydrolysis properties, though ammonia escape remains an engineering challenge. Amine-based electrolytes like MEA demonstrate commercial viability in carbon capture (>90% efficiency), but their eCO2RR reaction mechanisms require further elucidation through advanced characterization techniques. ILs represent highly tunable candidates, with functionalized ILs achieving both efficient CO2 capture and enhanced catalytic selectivity. For instance, imidazolium-based ILs enable 85% HCOOH selectivity, while amino-modified TSILs achieve 1:1 CO2 absorption ratios. Although viscosity and cost limitations persist, strategies like aqueous blending and anion optimization can improve performance. Additionally, emerging amino acid salts show unique potential—additives like L-histidine significantly enhance product selectivity—though their standalone use as electrolytes warrants further investigation.
Recent studies demonstrate the significant potential of machine learning for electrolyte optimization. Salomone et al. [10] developed a two-step approach combining gradient boosting classifiers (GBCs) and regressors (GBRs) to predict CO adsorption energies on Cu-based bimetallic alloys with high accuracy (error < 0.05 eV2). By analyzing 13 chemical and 2 geometric descriptors, the model achieves precise CO adsorption energy predictions (F1-score > 96%), enabling the rapid screening of efficient CO2RR electrocatalysts. This breakthrough highlights machine learning’s capability to accelerate the optimization of electrolyte–catalyst systems.
When applied to process simulation, Aspen Plus demonstrates distinct capability variations across different electrochemical systems. While Aspen Plus is well established for water electrolysis, its application to electrocatalytic CO2 conversion faces limitations. The software performs system-level process simulations but cannot model micro-scale electrochemical processes. Dedicated modules for this application are also lacking. The introduction of AI Model Builder in Aspen Plus V12 addresses these challenges by combining machine learning with process simulation. This integration enables cross-scale optimization from molecular to system levels, offering new possibilities for eCO2RR development.
Effective ICCU systems demand electrolytes that simultaneously satisfy multiple criteria: high CO2 capture capacity, direct participation in electrocatalytic conversion, balanced conductivity and fluidity, suppressed side reactions, and environmental compatibility with recyclability. Emerging machine learning approaches, particularly graph neural networks (GNNs) for predicting functionalized ILs’ performance and reinforcement learning for dynamic reaction condition optimization, offer promising avenues to accelerate electrolyte development.

6. Future Prospects

Future research on electrolytes for ICCU systems will witness a deepening interdisciplinary convergence of electrochemistry, artificial intelligence, and materials engineering. The integration of in situ electrochemical characterization techniques, multi-scale computational modeling, and intelligent optimization algorithms is expected to enable comprehensive innovation spanning from molecular design to industrial-scale implementation.
At the fundamental level, advanced characterization methods such as time-resolved spectroscopy and synchrotron radiation should be prioritized to elucidate the solvation structures of ions and the dynamic evolution of interfacial electric double layers, particularly the competitive adsorption behavior between amine-based electrolytes and electrode surfaces. Concurrent efforts should focus on developing cost-effective synthesis routes for ionic liquids while employing machine learning-assisted high-throughput screening to optimize their viscosity, conductivity, and CO2 affinity.
For practical applications, bridging atomic-scale DFT calculations with system-level Aspen Plus simulations is critical. When complemented by the COMSOL multiphysics coupling analysis, this approach establishes reliable cross-scale correlations from molecular structures to reactor design. With advancements in adaptive control algorithms and modular electrolyzer technologies, ICCU systems are poised to achieve intelligent integration with renewable power generation, ultimately achieving industrial-scale carbon cycling solutions with high selectivity and low energy consumption. This approach will not only reduce the operational energy demands of conventional carbon capture but also facilitate the transition of electrolyte materials from lab-scale gram-level production to industrial manufacturing, providing critical technological support for global carbon neutrality goals.

Author Contributions

G.Y.: Conceptualization, Literature Synthesis, Writing—Original Draft, Visualization; Y.L. (Yunzhi Li): Literature Search, Data Curation; L.D.: Methodology Validation, Writing—Review & Editing; Y.L. (Yichun Li): Resource Collection, Formal Analysis; Y.Z.: Supervision, Project Administration, Funding Acquisition; All authors have read and agreed to the published version of the manuscript.

Funding

This comprehensive review was supported by: National Key R&D Program of China (Grant No. 2022YFE0204100)—Supported the literature analysis and synthesis. National Natural Science Foundation of China (Grant No. 52376102)—Enabled the systematic evaluation of research trends. The Article Processing Charge was covered by institutional funding from Harbin Institute of Technology.

Acknowledgments

We acknowledge Harbin Institute of Technology for providing access to scholarly databases and research infrastructure essential for this literature review.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Davis, S.J.; Caldeira, K.; Matthews, H.D. Future CO2 emissions and climate change from existing energy infrastructure. Science 2010, 329, 1330–1333. [Google Scholar] [CrossRef]
  2. Boubou, H. A Review of Global CO2 Emissions and Total Energy Consumption. SEA—Pract. Appl. Sci. 2021, 9, 135–142. [Google Scholar]
  3. Jiangnan, T.; Yuan, A.; Jing, J.; Yang, L.; Jingkui, T.; Desheng, C. Technical Solution for Decarburization in Context of Carbon Neutrality. Distrib. Energy 2021, 6, 63–69. [Google Scholar] [CrossRef]
  4. Zhenmin, B.; Huihong, L.; Keyu, C.; Zhibin, Z. Recent Progress on Chemical Conversion of Carbon Dioxide. Shandong Chem. Ind. 2018, 47, 70–72+76. [Google Scholar] [CrossRef]
  5. Xiusong, H.; Shujuan, W.; Junjie, X. Review of Integrated CO2 Capture and Electrochemical Reduction Utilization System. J. Combust. Sci. Technol. 2022, 28, 679–686, https://kns.cnki.net/kcms2/article/abstract?v=79O6ZE_Rn2rjpMW-EUVEPf89BAarlDojvBOqQ2WVVO1TLiNwGZjpMO3RaLpDUhUcTDcQRUguToVe8T0-0W68Xp4RV-ygIKCDfsWm1t7gK0fsMlPKrbbdGMNmOngtwuZi2TrJuqTtEZsJHYFk47_suXe87kZYvvFnO9MPItsSE6F_jYKSiC7qdn3fWoXnfFVme2RNH0wfTC4=&uniplatform=NZKPT&language=CHS. [Google Scholar]
  6. Garg, S.; Xu, Q.C.; Moss, A.B.; Mirolo, M.; Deng, W.Y.; Chorkendorff, I.; Drnec, J.; Seger, B. How alkali cations affect salt precipitation and CO2 electrolysis performance in membrane electrode assembly electrolyzers. Energy Environ. Sci. 2023, 16, 1631–1643. [Google Scholar] [CrossRef]
  7. Bruggeman, D.F.; Rothenberg, G.; Garcia, A.C. Investigating proton shuttling and electrochemical mechanisms of amines in integrated CO2 capture and utilization. Nat. Commun. 2024, 15, 9207. [Google Scholar] [CrossRef]
  8. Yang, Y.L.; Gao, H.S.; Feng, J.Q.; Zeng, S.J.; Liu, L.; Liu, L.C.; Ren, B.Z.; Li, T.; Zhang, S.J.; Zhang, X.P. Aromatic Ester-Functionalized Ionic Liquid for Highly Efficient CO2 Electrochemical Reduction to Oxalic Acid. ChemSusChem 2020, 13, 4900–4905. [Google Scholar] [CrossRef]
  9. Huang, J.E.; Li, F.W.; Ozden, A.; Rasouli, A.S.; de Arquer, F.P.G.; Liu, S.J.; Zhang, S.Z.; Luo, M.C.; Wang, X.; Lum, Y.W.; et al. CO2 electrolysis to multicarbon products in strong acid. Science 2021, 372, 1074–1078. [Google Scholar] [CrossRef]
  10. Salomone, M.; Fiorentin, M.R.; Risplendi, F.; Raffone, F.; Sommer, T.; García-Melchor, M.; Cicero, G. Efficient mapping of CO adsorption on Cu1-xMx bimetallic alloys via machine learning. J. Mater. Chem. A 2024, 12, 14148–14158. [Google Scholar] [CrossRef]
  11. Fan, H.; Mao, Y.; Sultan, S.; Yu, Y.; Wu, X.; Zhang, Z. Performance enhancement of desorption reactor in the electrochemically mediated amine regeneration CO2 capture process: Thru modelling, simulation, and optimization. Appl. Energy 2024, 376, 124287. [Google Scholar] [CrossRef]
  12. Hu, S.Q.; Zhang, L.X.; Liu, H.Y.; Cao, Z.W.; Yu, W.G.; Zhu, X.F.; Yang, W.S. Alkaline-earth elements (Ca, Sr and Ba) doped LaFeO3-δ cathodes for CO2 electroreduction. J. Power Sources 2019, 443, 227268. [Google Scholar] [CrossRef]
  13. Sun, J.L.; Liu, Z.; Zhou, H.H.; Cao, M.X.; Cai, W.M.; Xu, C.X.; Xu, J.W.; Huang, Z.Y. Ionic Liquids Modulating Local Microenvironment of Ni-Fe Binary Single Atom Catalyst for Efficient Electrochemical CO2 Reduction. Small 2024, 20, 2308522. [Google Scholar] [CrossRef]
  14. Yu, S.; Yamauchi, H.; Wang, S.; Aggarwal, A.; Kim, J.; Gordiz, K.; Huang, B.T.; Xu, H.B.; Zheng, D.J.; Wang, X.; et al. CO2-to-methanol electroconversion on a molecular cobalt catalyst facilitated by acidic cations. Nat. Catal. 2024, 7, 1000–1009. [Google Scholar] [CrossRef]
  15. Banerjee, S.; Han, X.; Thoi, V.S. Modulating the Electrode-Electrolyte Interface with Cationic Surfactants in Carbon Dioxide Reduction. ACS Catal. 2019, 9, 5631–5637. [Google Scholar] [CrossRef]
  16. Endrodi, B.; Kecsenővity, E.; Samu, A.; Halmágyi, T.; Rojas-Carbonell, S.; Wang, L.; Yan, Y.; Janáky, C. High carbonate ion conductance of a robust PiperION membrane allows industrial current density and conversion in a zero-gap carbon dioxide electrolyzer cell. Energy Environ. Sci. 2020, 13, 4098–4105. [Google Scholar] [CrossRef]
  17. Pan, H.Q.; Barile, C.J. Electrochemical CO2 Reduction on Polycrystalline Copper by Modulating Proton Transfer with Fluoropolymer Composites. ACS Appl. Energ. Mater. 2022, 5, 4712–4721. [Google Scholar] [CrossRef]
  18. Vichou, E.; Perazio, A.; Adjez, Y.; Gomez-Mingot, M.; Schreiber, M.W.; Sánchez-Sánchez, C.M.; Fontecave, M. Tuning Selectivity of Acidic Carbon Dioxide Electrolysis via Surface Modification. Chem. Mater. 2023, 35, 7060–7068. [Google Scholar] [CrossRef]
  19. Gunathunge, C.M.; Ovalle, V.J.; Waegele, M.M. Probing promoting effects of alkali cations on the reduction of CO at the aqueous electrolyte/copper interface. Phys. Chem. Chem. Phys. 2017, 19, 30166–30172. [Google Scholar] [CrossRef]
  20. Heim, G.P.; Bruening, M.A.; Musgrave, C.B.; Goddard, W.A.; Peters, J.C.; Agapie, T. Potassium ion modulation of the Cu electrode-electrolyte interface with ionomers enhances CO2 reduction to C2+ products. Joule 2024, 8, 1312–1321. [Google Scholar] [CrossRef]
  21. Zeman, F.S.; Lackner, K.S. Capturing carbon dioxide directly from the atmosphere. World Resour. Rev. 2004, 16, 157–172. [Google Scholar]
  22. Holmes, G.; Keith, D.W. An air-liquid contactor for large-scale capture of CO2 from air. Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci. 2012, 370, 4380–4403. [Google Scholar] [CrossRef]
  23. Murata, A.; Hori, Y. Product Selectivity Affected by Cationic Species in Electrochemical Reduction of Co2 and Co at a Cu Electrode. Bull. Chem. Soc. Jpn. 1991, 64, 123–127. [Google Scholar] [CrossRef]
  24. Ayemoba, O.; Cuesta, A. Spectroscopic Evidence of Size-Dependent Buffering of Interfacial pH by Cation Hydrolysis during CO2 Electroreduction. ACS Appl. Mater. Interfaces 2017, 9, 27377–27382. [Google Scholar] [CrossRef] [PubMed]
  25. Ringe, S.; Clark, E.L.; Resasco, J.; Walton, A.; Seger, B.; Bell, A.T.; Chan, K. Understanding cation effects in electrochemical CO2 reduction. Energy Environ. Sci. 2019, 12, 3609–3610. [Google Scholar] [CrossRef]
  26. Yu, Z. Research of Carbon Capture Processusing Ammonia as Absorbent Based on antisolvent Crystallization. Harbin Inst. Technol. 2019. [Google Scholar] [CrossRef]
  27. Li, H.; Gao, J.; Du, Q.; Shan, J.; Zhang, Y.; Wu, S.; Wang, Z. Direct CO2 electroreduction from NH4HCO3 electrolyte to syngas on bromine-modified Ag catalyst. Energy 2021, 216, 119250. [Google Scholar] [CrossRef]
  28. Li, H.; Gao, J.; Shan, J.; Du, Q.; Zhang, Y.; Guo, X.; Xie, M.; Wu, S.; Wang, Z. Effect of halogen-modification on Ag catalyst for CO2 electrochemical reduction to syngas from NH4HCO3 electrolyte. J. Environ. Chem. Eng. 2021, 9, 106415. [Google Scholar] [CrossRef]
  29. Ismail, A.M.; Samu, G.F.; Balog, A.; Csapó, E.; Janáky, C. Composition-Dependent Electrocatalytic Behavior of Au-Sn Bimetallic Nanoparticles in Carbon Dioxide Reduction. ACS Energy Lett. 2019, 4, 48–53. [Google Scholar] [CrossRef]
  30. Dunwell, M.; Lu, Q.; Heyes, J.M.; Rosen, J.; Chen, J.G.G.; Yan, Y.S.; Jiao, F.; Xu, B.J. The Central Role of Bicarbonate in the Electrochemical Reduction of Carbon Dioxide on Gold. J. Am. Chem. Soc. 2017, 139, 3774–3783. [Google Scholar] [CrossRef]
  31. Xiaoxu, Z. Study on CO2 Capture from Flue Gas by Chemical Absorption. 2016. Available online: https://kns.cnki.net/kcms2/article/abstract?v=79O6ZE_Rn2qzeHMgbHg9U6nzARWtygqYJWSamoyN1lHOUCXiVWfWS-XBWXwRu2G7MznMssLS64gQdCYgwSAPTcKKW71JER4SCTox8ETt2Dzmc-j0NehD8I-rozjEM7Y7K212aZaVfzwLz2bKN3ckXAcqlfu3h1qOKD-MW9NydZn1dkuzatlDGerHqEV15gP20BqGOSZYGa4=&uniplatform=NZKPT&language=CHS (accessed on 1 January 2025).
  32. Liang, Z.W.; Rongwong, W.; Liu, H.L.; Fu, K.Y.; Gao, H.X.; Cao, F.; Zhang, R.; Sema, T.; Henni, A.; Sumon, K.; et al. Recent progress and new developments in post-combustion carbon-capture technology with amine based solvents. Int. J. Greenh. Gas. Control. 2015, 40, 26–54. [Google Scholar] [CrossRef]
  33. Manuilova, A.; Koiwanit, J.; Piewkhaow, L.; Wilson, M.; Chan, C.W.; Tontiwachwuthikul, P. Life Cycle Assessment of Post-Combustion CO2 Capture and CO2-Enhanced Oil Recovery based on the Boundary Dam Integrated Carbon Capture and Storage Demonstration Project in Saskatchewan. In Proceedings of the 12th International Conference on Greenhouse Gas Control Technologies (GHGT), Austin, TX, USA, 5–9 October 2014; pp. 7398–7407. [Google Scholar]
  34. Li, G. Electrochemical Reduction of Ethanolamine CO2 Capture Solution Energy Transfer Enhancement and Full Life Cycle Assessment. Chongqing Univ. 2023. [Google Scholar] [CrossRef]
  35. Cui, G.K.; Wang, J.J.; Zhang, S.J. Active chemisorption sites in functionalized ionic liquids for carbon capture. Chem. Soc. Rev. 2016, 45, 4307–4339. [Google Scholar] [CrossRef]
  36. Zhou, T.; Gui, C.; Sun, L.; Hu, Y.; Lyu, H.; Wang, Z.; Song, Z.; Yu, G. Energy Applications of Ionic Liquids: Recent Developments and Future Prospects. Chem. Rev. 2023, 123, 12170–12253. [Google Scholar] [CrossRef] [PubMed]
  37. Blanchard, L.A.; Hancu, D.; Beckman, E.J.; Brennecke, J.F. Green processing using ionic liquids and CO2. Nature 1999, 399, 28–29. [Google Scholar] [CrossRef]
  38. Anthony, J.L.; Maginn, E.J.; Brennecke, J.F. Solubilities and thermodynamic properties of gases in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate. J. Phys. Chem. B 2002, 106, 7315–7320. [Google Scholar] [CrossRef]
  39. Feng, J.P.; Zeng, S.J.; Liu, H.Z.; Feng, J.Q.; Gao, H.S.; Bai, L.; Dong, H.F.; Zhang, S.J.; Zhang, X.P. Insights into Carbon Dioxide Electroreduction in Ionic Liquids: Carbon Dioxide Activation and Selectivity Tailored by Ionic Microhabitat. ChemSusChem 2018, 11, 3191–3197. [Google Scholar] [CrossRef]
  40. Rosen, B.A.; Salehi-Khojin, A.; Thorson, M.R.; Zhu, W.; Whipple, D.T.; Kenis, P.J.A.; Masel, R.I. Ionic Liquid-Mediated Selective Conversion of CO2 to CO at Low Overpotentials. Science 2011, 334, 643–644. [Google Scholar] [CrossRef]
  41. Wu, H.R.; Song, J.L.; Xie, C.; Hu, Y.; Han, B.X. Highly efficient electrochemical reduction of CO2 into formic acid over lead dioxide in an ionic liquid-catholyte mixture. Green Chem. 2018, 20, 1765–1769. [Google Scholar] [CrossRef]
  42. Chen, T.Y.; Shi, J.; Shen, F.X.; Zhen, J.Z.; Li, Y.F.; Shi, F.; Yang, B.; Jia, Y.J.; Dai, Y.N.; Hu, Y.Q. Selection of Low-Cost Ionic Liquid Electrocatalyst for CO2 Reduction in Propylene Carbonate/Tetrabutylammonium Perchlorate. ChemElectroChem 2018, 5, 2295–2300. [Google Scholar] [CrossRef]
  43. Hu, Y.; Gan, Z.D.; Xin, S.X.; Fang, W.H.; Li, M.; Wang, Y.L.; Cui, W.; Zhao, H.; Li, Z.X.; Zhang, X.P. High performance carbon dioxide electroreduction in ionic liquids with in situ shell-isolated nanoparticle-enhanced Raman spectroscopy. Chem. Eng. J. 2023, 451, 14. [Google Scholar] [CrossRef]
  44. Bates, E.D.; Mayton, R.D.; Ntai, I.; Davis, J.H. CO2 capture by a task-specific ionic liquid. J. Am. Chem. Soc. 2002, 124, 926–927. [Google Scholar] [CrossRef]
  45. Zhang, J.Z.; Jia, C.; Dong, H.F.; Wang, J.Q.; Zhang, X.P.; Zhang, S.J. A Novel Dual Amino-Functionalized Cation-Tethered Ionic Liquid for CO2 Capture. Ind. Eng. Chem. Res. 2013, 52, 5835–5841. [Google Scholar] [CrossRef]
  46. Hu, Y.J.; Feng, J.Q.; Zhang, X.P.; Gao, H.S.; Jin, S.M.; Liu, L.; Shen, W.F. Efficient Electrochemical Reduction of CO2 to CO in Ionic Liquids. ChemistrySelect 2021, 6, 9873–9879. [Google Scholar] [CrossRef]
  47. Wang, H.; Yang, D.X.; Yang, J.; Ma, X.X.; Li, H.P.; Dong, W.W.; Zhang, R.J.; Feng, C.Y. Efficient Electroreduction of CO2 to CO on Porous ZnO Nanosheets with Hydroxyl Groups in Ionic Liquid-based Electrolytes. ChemCatChem 2021, 13, 2570–2576. [Google Scholar] [CrossRef]
  48. Yang, J.H.; Kang, X.C.; Jiao, J.P.; Xing, X.Q.; Yin, Y.Y.; Jia, S.Q.; Chu, M.E.; Han, S.T.; Xia, W.; Wu, H.H.; et al. Ternary Ionic-Liquid-Based Electrolyte Enables Efficient Electro-reduction of CO2 over Bulk Metal Electrodes. J. Am. Chem. Soc. 2023, 145, 11512–11517. [Google Scholar] [CrossRef]
  49. Tsuda, Y.; Yoshii, K.; Gunji, T.; Takeda, S.; Takeichi, N. Electrodeposition of Cu with Amino Acids toward Electrocatalytic Enhancement of CO2 Reduction Reaction. J. Electrochem. Soc. 2024, 171, 054507. [Google Scholar] [CrossRef]
  50. Lamoureux, P.S.; Singh, A.R.; Chan, K.R. pH Effects on Hydrogen Evolution and Oxidation over Pt(111): Insights from First-Principles. ACS Catal. 2019, 9, 6194–6201. [Google Scholar] [CrossRef]
  51. Nitopi, S.; Bertheussen, E.; Scott, S.B.; Liu, X.Y.; Engstfeld, A.K.; Horch, S.; Seger, B.; Stephens, I.E.L.; Chan, K.; Hahn, C.; et al. Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte. Chem. Rev. 2019, 119, 7610–7672. [Google Scholar] [CrossRef]
  52. Zeng, M.; Fang, W.S.; Cen, Y.R.; Zhang, X.Y.; Hu, Y.M.; Xia, B.Y. Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids. Angew. Chem.-Int. Edit. 2024, 63, 21. [Google Scholar] [CrossRef]
  53. Xiang, S.Q.; Gao, S.T.; Shi, J.L.; Zhang, W.; Zhao, L.B. Developing micro-kinetic model for electrocatalytic reduction of carbon dioxide on copper electrode. J. Catal. 2021, 393, 11–19. [Google Scholar] [CrossRef]
  54. Lu, X.; Zhu, C.; Wu, Z.; Xuan, J.; Wang, H. In-Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO2 Reduction in Alkaline Electrolyte. J. Am. Chem. Soc. 2020, 142, 15438–15444. [Google Scholar] [CrossRef] [PubMed]
  55. Ren, W.H.; Xu, A.N.; Chan, K.R.; Hu, X.L. A Cation Concentration Gradient Approach to Tune the Selectivity and Activity of CO2 Electroreduction. Angew. Chem.-Int. Edit. 2022, 61, 6. [Google Scholar] [CrossRef] [PubMed]
  56. Liu, B.C.; Guo, W.X.; Gebbie, M.A. Tuning Ionic Screening To Accelerate Electrochemical CO2 Reduction in Ionic Liquid Electrolytes. ACS Catal. 2022, 12, 9706–9716. [Google Scholar] [CrossRef]
  57. Tan, Y.; Wang, X.Q.; Liao, X.Q.; Chen, Q.; Li, H.M.; Liu, K.; Fu, J.W.; Liu, M. Near-Electrode Concentration Gradients of Bicarbonate and pH within Porous Gas Diffusion Electrode for Optimized Selective CO2 Electroreduction to C2+ Products. Nano Lett. 2024, 24, 12163–12170. [Google Scholar] [CrossRef]
  58. Varela, A.S.; Kroschel, M.; Reier, T.; Strasser, P. Controlling the selectivity of CO2 electroreduction on copper: The effect of the electrolyte concentration and the importance of the local pH. Catal. Today 2016, 260, 8–13. [Google Scholar] [CrossRef]
  59. Gebbie, M.A.; Liu, B.C.; Guo, W.X.; Anderson, S.R.; Johnstone, S.G. Linking Electric Double Layer Formation to Electrocatalytic Activity. ACS Catal. 2023, 13, 16222–16239. [Google Scholar] [CrossRef]
  60. Möller, T.; Ngo Thanh, T.; Wang, X.; Ju, W.; Jovanov, Z.; Strasser, P. The product selectivity zones in gas diffusion electrodes during the electrocatalytic reduction of CO2. Energy Environ. Sci. 2021, 14, 5995–6006. [Google Scholar] [CrossRef]
  61. Garg, S.; Li, M.R.; Wu, Y.M.; Idros, M.N.; Wang, H.M.; Yago, A.J.; Ge, L.; Wang, G.G.X.; Rufford, T.E. Understanding the Effects of Anion Interactions with Ag Electrodes on Electrochemical CO2 Reduction in Choline Halide Electrolytes. ChemSusChem 2021, 14, 2601–2611. [Google Scholar] [CrossRef]
  62. Fu, Z.Z.; Ouyang, Y.X.; Wu, M.L.; Ling, C.Y.; Wang, J.L. Mechanism of surface oxygen-containing species promoted electrocatalytic CO2 reduction. Sci. Bull. 2024, 69, 1410–1417. [Google Scholar] [CrossRef]
  63. Guo, W.X.; Liu, B.C.; Gebbie, M.A. Suppressing Co-Ion Generation via Cationic Proton Donors to Amplify Driving Forces for Electrochemical CO2 Reduction. J. Phys. Chem. C 2023, 127, 14243–14254. [Google Scholar] [CrossRef]
  64. Ovalle, V.J.; Waegele, M.M. Understanding the Impact of N-Arylpyridinium Ions on the Selectivity of CO2 Reduction at the Cu/Electrolyte Interface. J. Phys. Chem. C 2019, 123, 24453–24460. [Google Scholar] [CrossRef]
  65. Monteiro, M.C.O.; Dattila, F.; López, N.; Koper, M.T.M. The Role of Cation Acidity on the Competition between Hydrogen Evolution and CO2 Reduction on Gold Electrodes. J. Am. Chem. Soc. 2022, 144, 1589–1602. [Google Scholar] [CrossRef]
  66. Parada, W.A.; Sajevic, U.; Mammadzada, R.; Nikolaienko, P.; Mayrhofer, K.J.J. Tethered Alkylammonium Dications as Electrochemical Interface Modifiers: Chain Length Effect on CO2 Reduction Selectivity at Industry-Relevant Current Density. ACS Appl. Mater. Interfaces 2024, 16, 30107–30116. [Google Scholar] [CrossRef] [PubMed]
  67. Vichou, E.; Adjez, Y.; Li, Y.; Gömez-Mingot, M.; Fontecave, M.; Sánchez-Sánchez, C.M. Smart Electrode Surfaces by Electrolyte Immobilization for Electrocatalytic CO2 Conversion. J. Am. Chem. Soc. 2024, 146, 2824–2834. [Google Scholar] [CrossRef]
  68. Li, Y.F.; Calvinho, K.U.D.; Dhiman, M.; Laursen, A.B.; Gu, H.F.; Santorelli, D.; Clifford, Z.; Dismukes, G.C. Tunable product selectivity on demand: A mechanism-guided Lewis acid co-catalyst for CO2 electroreduction to ethylene glycol. EES Catal. 2024, 2, 823–833. [Google Scholar] [CrossRef]
  69. Li, T.; Lees, E.W.; Goldman, M.; Salvatore, D.A.; Weekes, D.M.; Berlinguette, C.P. Electrolytic conversion of bicarbonate into CO in a flow cell. Joule 2019, 3, 1487–1497. [Google Scholar] [CrossRef]
  70. Li, Y.G.C.; Lee, G.; Yuan, T.G.; Wang, Y.; Nam, D.H.; Wang, Z.Y.; de Arquer, F.P.G.; Lum, Y.; Dinh, C.T.; Voznyy, O.; et al. CO2 Electroreduction from Carbonate Electrolyte. ACS Energy Lett. 2019, 4, 1427–1431. [Google Scholar] [CrossRef]
  71. Chen, B.Y.; Rong, Y.W.; Li, X.; Sang, J.Q.; Wei, P.F.; An, Q.D.; Gao, D.F.; Wang, G.X. Molecular Enhancement of Direct Electrolysis of Dilute CO2. ACS Energy Lett. 2024, 9, 911–918. [Google Scholar] [CrossRef]
  72. Tian, D.; Wang, Q.; Qu, Z.G.; Zhang, H.J. Enabling direct flue gas electrolysis by clarifying impurity gas effects on CO2 electroreduction. Nano Energy 2025, 134, 12. [Google Scholar] [CrossRef]
  73. Cui, G.K.; Zheng, J.J.; Luo, X.Y.; Lin, W.J.; Ding, F.; Li, H.R.; Wang, C.M. Tuning Anion-Functionalized Ionic Liquids for Improved SO2 Capture. Angew. Chem. Int. Edit. 2013, 52, 10620–10624. [Google Scholar] [CrossRef] [PubMed]
  74. Vos, J.; Ramírez, A.; Pérez-Fortes, M. Learning from the past: Limitations of techno-economic assessments for low-temperature CO2 electrolysis. Renew. Sust. Energ. Rev. 2025, 213, 115454. [Google Scholar] [CrossRef]
  75. Villadsen, S.N.B.; Kaab, M.A.; Nielsen, L.P.; Moller, P.; Fosb, P.L. New electroscrubbing process for desulfurization. Sep. Purif. Technol. 2022, 278, 119552. [Google Scholar] [CrossRef]
  76. Shijian, L.; Yuping, G.; Ling, L.; Guojun, K.; Xi, C.; Miaomiao, L.; Juanjuan, Z.; Feng, W. Research status and future development direction of CO2 absorption technology for organic amine. Clean Coal Technol. 2022, 28, 44–54. [Google Scholar] [CrossRef]
  77. Zhao, K.; Liu, Z.; Qiu, X.T.; Ju, C.; Xia, R.K.; Tan, A.D.; Xu, C.; Liu, J.G. Study of dynamic thermal behavior and control strategies for membrane electrode assembly of proton exchange membrane water electrolysis. Int. J. Hydrogen Energy 2025, 102, 482–489. [Google Scholar] [CrossRef]
  78. Wack, Y.; Sollich, M.; Salenbien, R.; Diriken, J.; Baelmans, M.; Blommaert, M. A multi-period topology and design optimization approach for district heating networks. Appl. Energy 2024, 367, 123380. [Google Scholar] [CrossRef]
  79. Gao, T.Q.; Xia, B.K.; Yang, K.; Li, D.; Shao, T.Y.; Chen, S.; Li, Q.; Duan, J.J. Techno-economic Analysis and Carbon Footprint Accounting for Industrial CO2 Electrolysis Systems. Energy Fuels 2023, 37, 17997–18008. [Google Scholar] [CrossRef]
  80. Li, A.C.; Liu, R.; Yi, S.J. Integrating communication networks with reinforcement learning and big data analytics for optimizing carbon capture and utilization strategies. Alex. Eng. J. 2024, 108, 937–951. [Google Scholar] [CrossRef]
Figure 1. Solubility (mol/L) and relative solubility values of alkali metal derivatives in 1 L of water at 20 °C (adapted with permission from [6], Energy Environ. Sci., 2023).
Figure 1. Solubility (mol/L) and relative solubility values of alkali metal derivatives in 1 L of water at 20 °C (adapted with permission from [6], Energy Environ. Sci., 2023).
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Figure 2. The schematic of a zero-gap AEM-based CO2 electrolyzer showing (1) cation (M+) movement to the cathode surface via electrostatic attraction, (2) diffusion of anionic species (OH/HCO3/CO32−) through the anion exchange membrane, and (3) how salt formation occurs at the cathode (reproduced with permission from [6], Energy Environ. Sci., 2023).
Figure 2. The schematic of a zero-gap AEM-based CO2 electrolyzer showing (1) cation (M+) movement to the cathode surface via electrostatic attraction, (2) diffusion of anionic species (OH/HCO3/CO32−) through the anion exchange membrane, and (3) how salt formation occurs at the cathode (reproduced with permission from [6], Energy Environ. Sci., 2023).
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Figure 3. The rapid equilibrium reaction between HCO3 and CO2 on the electrode plate (adapted with permission from [30], J. Am. Chem. Soc., 2017).
Figure 3. The rapid equilibrium reaction between HCO3 and CO2 on the electrode plate (adapted with permission from [30], J. Am. Chem. Soc., 2017).
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Figure 4. Quantification relationship among ammonia slip, ammonia concentration, and CO2 removal efficiency under Aspen Plus simulation data replotted from Zhang (2016) Master’s Thesis (Beijing University of Chemical Technology) with modifications: (i) added trendline fitting using Origin 2021, (ii) normalized to 1 atm conditions, and (iii) incorporated comparative data from [31]. Original copyright remains with the author.
Figure 4. Quantification relationship among ammonia slip, ammonia concentration, and CO2 removal efficiency under Aspen Plus simulation data replotted from Zhang (2016) Master’s Thesis (Beijing University of Chemical Technology) with modifications: (i) added trendline fitting using Origin 2021, (ii) normalized to 1 atm conditions, and (iii) incorporated comparative data from [31]. Original copyright remains with the author.
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Figure 5. The coupling process of amine-based sorbents in carbon capture and carbon absorption (adapted with permission from [7], Nat. Commun., 2024).
Figure 5. The coupling process of amine-based sorbents in carbon capture and carbon absorption (adapted with permission from [7], Nat. Commun., 2024).
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Figure 6. The competitive effect of the copper electrode surface and weak surface interaction on the lead electrode (adapted with permission from [7], Nat. Commun., 2024).
Figure 6. The competitive effect of the copper electrode surface and weak surface interaction on the lead electrode (adapted with permission from [7], Nat. Commun., 2024).
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Figure 7. (a) The FECO and (b) partial current density of Ag@Naf and Ag@Sus electrodes. Data replotted from [34], Li (2023) Master’s Thesis (Chongqing University, Figure 3.7), with identical datasets but modified visual presentation: (i) color scheme adjusted and (ii) layout reorganized using Microsoft Visio 2021. Original data copyright remains with the author.
Figure 7. (a) The FECO and (b) partial current density of Ag@Naf and Ag@Sus electrodes. Data replotted from [34], Li (2023) Master’s Thesis (Chongqing University, Figure 3.7), with identical datasets but modified visual presentation: (i) color scheme adjusted and (ii) layout reorganized using Microsoft Visio 2021. Original data copyright remains with the author.
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Figure 8. CO2, C2H4, C2H6, CH4, Ar, and O2 solubility in [bmim][PF6] at 25 °C (reproduced with permission from [38], J. Phys. Chem. B, 2002).
Figure 8. CO2, C2H4, C2H6, CH4, Ar, and O2 solubility in [bmim][PF6] at 25 °C (reproduced with permission from [38], J. Phys. Chem. B, 2002).
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Figure 9. The schematic representation of CO2 electroreduction with the assistance of the novel superbasic IL [Bmim][124Triz] (adapted with permission from [39], ChemSusChem, 2018).
Figure 9. The schematic representation of CO2 electroreduction with the assistance of the novel superbasic IL [Bmim][124Triz] (adapted with permission from [39], ChemSusChem, 2018).
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Figure 10. The mechanism of CO2 electrochemical reduction in 0.1 M Bu4NClO4/PC containing 0.4 M [Bmim][Cl] (reproduced with permission from [42], ChemElectroChem, 2018).
Figure 10. The mechanism of CO2 electrochemical reduction in 0.1 M Bu4NClO4/PC containing 0.4 M [Bmim][Cl] (reproduced with permission from [42], ChemElectroChem, 2018).
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Figure 11. The mechanism of CO2 electroreduction to oxalic acid on Pb electrode in the [TEA][4-MF-PhO] (0.9 m)-AcN electrolyte (adapted with permission from [8], ChemSusChem, 2020).
Figure 11. The mechanism of CO2 electroreduction to oxalic acid on Pb electrode in the [TEA][4-MF-PhO] (0.9 m)-AcN electrolyte (adapted with permission from [8], ChemSusChem, 2020).
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Figure 12. The performance of ZnO(OH)/CP-600 catalysts in [Bmim]PF6/acetonitrile/H2O electrolytes with different contents of [Bmim]PF6 (a) and H2O (b) at −2.0 V versus Ag/Ag+. Data were obtained with 20 sccm CO2 stream with 2 h electrolysis at ambient temperature and pressure (reproduced with permission from [47], ChemCatChem, 2021).
Figure 12. The performance of ZnO(OH)/CP-600 catalysts in [Bmim]PF6/acetonitrile/H2O electrolytes with different contents of [Bmim]PF6 (a) and H2O (b) at −2.0 V versus Ag/Ag+. Data were obtained with 20 sccm CO2 stream with 2 h electrolysis at ambient temperature and pressure (reproduced with permission from [47], ChemCatChem, 2021).
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Figure 13. (a,b) Faradic Efficiency for H2, C1, and C2+ product formation using (a) the unmodified electrode or (b) the CuNP-EMIM electrode and (c) the C2+/C1 ratio as a function of applied current density. CO2RR performed in an acidic catholyte (0.05 M H2SO4 + 3 M KCl, pH = 0.89) under a CO2 flow of 10 mL·min–1 at different current densities for 30 min each (reproduced with permission from [18], Chem. Mater., 2023).
Figure 13. (a,b) Faradic Efficiency for H2, C1, and C2+ product formation using (a) the unmodified electrode or (b) the CuNP-EMIM electrode and (c) the C2+/C1 ratio as a function of applied current density. CO2RR performed in an acidic catholyte (0.05 M H2SO4 + 3 M KCl, pH = 0.89) under a CO2 flow of 10 mL·min–1 at different current densities for 30 min each (reproduced with permission from [18], Chem. Mater., 2023).
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Figure 14. (a) The FE of gaseous electrolysis products under an applied potential of −1.27 V vs. RHE at 3.0 C in a CO2-purged 0.5 mol/dm3 aqueous KHCO3 solution (pH ≈ 8.75) over a Cu foil and electrodeposited Cu with and without amino acids: electrodeposited with 1.0 mmol/dm3. (b) The FE of produced CO during CO2 electrolysis under an applied potential of −0.77 V vs. RHE at 3.0 C in a CO2-purged 0.5 mol/dm3 aqueous KHCO3 solution over electrodeposited Cu with and without amino acids (reproduced with permission from [49], J. Electrochem. Soc., 2024).
Figure 14. (a) The FE of gaseous electrolysis products under an applied potential of −1.27 V vs. RHE at 3.0 C in a CO2-purged 0.5 mol/dm3 aqueous KHCO3 solution (pH ≈ 8.75) over a Cu foil and electrodeposited Cu with and without amino acids: electrodeposited with 1.0 mmol/dm3. (b) The FE of produced CO during CO2 electrolysis under an applied potential of −0.77 V vs. RHE at 3.0 C in a CO2-purged 0.5 mol/dm3 aqueous KHCO3 solution over electrodeposited Cu with and without amino acids (reproduced with permission from [49], J. Electrochem. Soc., 2024).
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Figure 15. Schematic diagrams of CCU and ICCU systems: (a) CCU system and (b) ICCU system.
Figure 15. Schematic diagrams of CCU and ICCU systems: (a) CCU system and (b) ICCU system.
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Table 1. The total current density and FEs of all carbon-containing products over Cu electrode at −2.5 V vs. Ag/Ag+ in different electrolytes (reproduced with permission from [48], J. Am. Chem. Soc., 2023).
Table 1. The total current density and FEs of all carbon-containing products over Cu electrode at −2.5 V vs. Ag/Ag+ in different electrolytes (reproduced with permission from [48], J. Am. Chem. Soc., 2023).
EntryElectrolytesj (mA·cm−2)FECO (%)FEHCOOH (%)
10.3 M BminBF4/0.2 M C12minBF4/MeCN (1)83.6 ± 1.399.5 ± 0.20
20.5 M C12minBF4/MeCN (2)48.3 ± 2.699.2 ± 0.40
30.5 M BminBF4/MeCN (3)63.2 ± 3.278.2 ± 1.33.6 ± 2.6
40.4 M BminBF4/0.1 M C12minBF4/MeCN77.8 ± 1.598.3 ± 0.81.0 ± 0.5
50.2 M BminBF4/0.3 M C12minBF4/MeCN72.4 ± 1.098.8 ± 0.20
60.1 M BminBF4/0.4 M C12minBF4/MeCN66.5 ± 3.198.3 ± 0.50
Table 2. Performance comparison of electrolyte systems for CO2 electroreduction.
Table 2. Performance comparison of electrolyte systems for CO2 electroreduction.
Electrolyte TypeAdvantagesLimitations
Bicarbonates
  • Fast reaction kinetics and high CO2 absorption efficiency [21,22]
  • Easy CO2 desorption and absorbent regeneration
  • Superior eCO2RR selectivity (e.g., CsHCO3 [6])
  • Highly corrosive (equipment challenges)
  • Environmental risks if leaked
  • Metal deposition issues (e.g., Li+) [6]
Amines
  • Mature technology (e.g., MEA) with high CO2 capture efficiency [33]
  • Direct carbon source for eCO2RR
  • Primary formate production [7]
  • High regeneration energy
  • Competitive adsorption on electrodes (e.g., Cu [7])
  • High reaction barriers
ILs
  • Negligible volatility and thermal stability
  • High CO2 affinity/selectivity
  • Tunable product distribution (HCOOH [39]/CO [42])
  • HER suppression
  • High viscosity limits mass/charge transfer
  • Prohibitive costs
  • Moderate CO2 capacity
  • Complex synthesis
Emerging Systems
  • Ternary electrolytes (e.g., IL mixtures) enhance current density/selectivity (FECO ≈ 100%) [48]
  • Amino acid salts: eco-friendly, low-energy
  • Requires precise composition tuning [48]
  • Complex amino acid–electrode interactions [49]
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You, G.; Li, Y.; Dong, L.; Li, Y.; Zhang, Y. Research on the Characteristics of Electrolytes in Integrated Carbon Capture and Utilization Systems: The Key to Promoting the Development of Green and Low-Carbon Technologies. Energies 2025, 18, 3039. https://doi.org/10.3390/en18123039

AMA Style

You G, Li Y, Dong L, Li Y, Zhang Y. Research on the Characteristics of Electrolytes in Integrated Carbon Capture and Utilization Systems: The Key to Promoting the Development of Green and Low-Carbon Technologies. Energies. 2025; 18(12):3039. https://doi.org/10.3390/en18123039

Chicago/Turabian Style

You, Guoqing, Yunzhi Li, Lihan Dong, Yichun Li, and Yu Zhang. 2025. "Research on the Characteristics of Electrolytes in Integrated Carbon Capture and Utilization Systems: The Key to Promoting the Development of Green and Low-Carbon Technologies" Energies 18, no. 12: 3039. https://doi.org/10.3390/en18123039

APA Style

You, G., Li, Y., Dong, L., Li, Y., & Zhang, Y. (2025). Research on the Characteristics of Electrolytes in Integrated Carbon Capture and Utilization Systems: The Key to Promoting the Development of Green and Low-Carbon Technologies. Energies, 18(12), 3039. https://doi.org/10.3390/en18123039

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