Next Article in Journal
Rescaling Flow Curves of Protein-Stabilized Emulsions
Previous Article in Journal
High-Speed All-Optical Encoder and Comparator at 120 Gb/s Using a Carrier Reservoir Semiconductor Optical Amplifier
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nanomaterials
Volume 15
Issue 9
10.3390/nano15090648
nanomaterials-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Electrolyte Effect on Electrocatalytic CO2 Reduction

by
Jiandong Zhang
1,*,
Ziliang Zhang
2,
Tianye Chen
3,
Jiayi Zhang
3 and
Yu Zhang
1,*
1
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
2
School of Electro-Mechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China
3
Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo 315211, China
*
Authors to whom correspondence should be addressed.
Nanomaterials 2025, 15(9), 648; https://doi.org/10.3390/nano15090648
Submission received: 22 March 2025 / Revised: 16 April 2025 / Accepted: 23 April 2025 / Published: 25 April 2025
(This article belongs to the Section Energy and Catalysis)
Browse Figures
Versions Notes

Abstract

Electrocatalytic CO2 reduction reaction shows great potential for converting CO2 into high-value chemicals and fuels at normal temperature and pressure, combating climate change and achieving carbon neutrality goals. However, the complex reaction pathways involve the transfer of multiple electrons and protons, resulting in poor product selectivity, and the existence of competitive hydrogen evolution reactions further increases the associated difficulties. This review illustrates the research progress on the micro mechanism of electrocatalytic CO2 reduction reaction in the electrolyte environment in recent years. The reaction pathways of the products, pH effects, cation effects and anion effects were systematically summarized. Additionally, further challenges and difficulties were also pointed out. Thus, this review provides a theoretical basis and future research direction for improving the efficiency and selectivity of electrocatalytic CO2 reduction reaction.

1. Introduction

Electrocatalytic CO2 reduction reaction (CO2RR) has exhibited immense potential as a promising solution to address climate change by converting CO2 into high-value chemicals and fuels, a process that can be carried out under ambient temperature and pressure with adjustable reactants and driven by renewable energy sources such as wind and solar power [1,2,3,4]. Nevertheless, the reduction pathways are intricate and involve multiple electron (i.e., e−) and proton (i.e., H+) transfers, leading to low selectivity. Additionally, the competing hydrogen evolution reaction (HER) presents a significant challenge in realizing high local current density and faradaic efficiency (FE) [5,6]. Thus, the development of efficient electrocatalytic reduction technologies is of great practical significance.
The electrocatalytic CO2RR occurs within the electrical double layer (EDL) at the electrode–electrolyte interface (EEI), so its efficiency relies not only on the electrode materials (i.e., catalysts) but also on the electrolyte. Previous studies have primarily concentrated on the optimization of catalysts, such as enhancing catalytic performance through morphology and facet engineering [7,8], vacancy steering [9], doping modification [10,11], alloying [12] and single-atom sites [13,14,15]. These strategies increase the number of active sites on the catalyst surface, alter the material electronic structure and local charge polarization or realize synergistic effects between multiple components, optimizing the adsorption or desorption reactions of intermediates and charge transfer process. Despite advancements, only Cu-based catalysts have been proven to reduce CO2 to multi-carbon products, but the activity remains low [16,17,18]. Consequently, merely depending on catalyst optimization may not fully resolve the challenges faced by CO2RR. In this context, as an indispensable part of the reaction, the electrolyte has also gained much attention, not only providing protons but also directly affecting the formation of intermediates and the reaction pathway [19,20,21,22,23]. As outlined in Figure 1, the variation of the reaction pathway is first summarized to understand how the electrolyte influences product selectivity, then the electrolyte’s effects are extensively studied, including pH effects [24,25,26], cation effects [27,28,29,30,31], and anion effects [32,33,34]. Nevertheless, despite immense achievements, the specific effect may differ across studies, resulting in limited consensus. For instance, due to the coexistence of cations and anions at the EEI, multi-interactions overcomplicate related research. Buffer ions are generally introduced to control pH, which leads to confusion between the effects of pH and ions, making it challenging to isolate their individual contributions [23]. Thus, this field lacks a critical and systemic synthesis to summary conflicting observations and the underlying causes of discrepancies in electrolyte effects.
Unlike previous reviews that primarily catalog electrolyte effects [35,36,37], this work critically examines the contradictions among existing studies and identifies key factors (e.g., interfacial field screening, buffer-induced artifacts, and ion cooperativity) that lead to divergent conclusions. By establishing a mechanistic framework that disentangles these complexities, this work provides not only a unified perspective but also practical guidelines for future experimental design—a step toward resolving long-standing debates in CO2RR electrolyte engineering.
Nanomaterials 15 00648 g001
Figure 1. The overview diagram of the content of the review. The variation of the reaction pathway is first summarized to understand how the electrolyte influences product selectivity. Then, the effects of pH, cations and anions are reviewed. Note, the red “?” represents the possible reaction pathways.
Figure 1. The overview diagram of the content of the review. The variation of the reaction pathway is first summarized to understand how the electrolyte influences product selectivity. Then, the effects of pH, cations and anions are reviewed. Note, the red “?” represents the possible reaction pathways.
Nanomaterials 15 00648 g001

2. Reaction Pathway

Proton-coupled electron transfer (PCET) processes occur in CO2RR,* and the number of electrons involved in the reaction may vary depending on the catalyst and reaction conditions, typically ranging from 2e−, 4e−, 6e−, and 8e− to 12e− or even more [23]. The difference in electron number directly determines the type of reduced products [18], as shown in Table 1. The products of CO2RR include carbon monoxide (CO), formic acid (HCOOH) and formate (HCOO−), oxalic acid (H2C2O4) and oxalate (C2O42−), methane (CH4), formaldehyde (CHOH), methanol (CH3OH), ethylene (C2H4) and ethanol (C2H5OH) [7,38,39,40,41]. All products begin with the adsorption of CO2 on the catalyst surface to *CO2 intermediate (* indicates an active site), and the configuration of *CO2 largely determines the reaction pathway. As shown in Figure 2a, the proton–electron transfer occurs via two pathways [42]. The blue arrow represents the sequential proton–electron transfer (SPET), where the *CO2 first accepts an electron to form *CO2− with the carbon coordinated to the catalyst, and then accepts a proton to form *COOH (a key precursor to *CO). The green arrow represents the concerted proton–electron transfer (CPET), where the *CO2 directly gains both a proton and an electron to form *COOH [43]. *CO can desorb from the catalyst surface to generate CO (Product I), so the pathway can be described as follows: *CO2→*COOH→*CO→CO. Apart from *COOH, based on the *CO2 configuration, CO2 can also be hydrogenated to HCOO*, ultimately generating HCOOH (Product II) or HCOO− (Product III) [44]. Other product pathways are depicted in Figure 2b. HCHO (Product IV), CH3OH (Product V) and CH4 (Product VI) are also common C1 products, which involve 4e−, 6e−, and 8e− electron transfer. Intricately, competing reactions exist between different products, such as the intermediates for HCHO and CH3OH being *CHO. The intermediates also vary depending on the catalyst surface and reaction conditions. For instance, Shi et al. [42] described that *COH can directly dehydrate to *C, then be further hydrogenated to CH4. However, other studies suggest that *COH first combines with H to *CHOH, which then undergoes dehydration to form *CH, followed by proton coupling to generate CH4 [45,46].
Multi-carbon products involve more proton–electron transfer and follow complex reaction pathways. Figure 2b summarizes a series of possible multi-carbon products, including C2H4, CH3CH2OH, ethane (C2H6), ethylene glycol (C2H6O2), acetic acid (CH3COOH) and propanol (C3H7OH) [42,46,47,48,49,50]. *CO is considered a key intermediate for C2 products, and the C-C coupling is the RLS [51]. The widely accepted pathway is that *CO undergoes C-C coupling to generate C2 products (e.g., *CO + *CO→*OCCO). Taking the generation pathway of C2H4 as an example, Qiu et al. [52] proposed that C2H4 formation requires combining CO and *CHO to create *COCHO, then the two carbon atoms hydrogenate and deoxygenate to *CCH, which is further hydrogenated to form C2H4. However, an alternative view is that *CO and *CO directly undergo C-C coupling to form *OCCO [53]. In this pathway, the coupled C atoms undergo hydrogenation and deoxygenation to form *CCO, which then proceeds through PCET steps to generate CHCO, CHCHO, CH2CHO, and ultimately C2H4. Thus, exploring the universality of reaction pathways remains a critical focus, and studies on the mechanisms of multi-carbon products are still limited, requiring further exploration and validation.

3. pH Effects

The selectivity of CO2RR is significantly influenced by the electrolyte pH, with the main difference between acidic and neutral/alkaline electrolytes being the proton source. As shown in Table 1, in acidic media, hydrated hydrogen ions (H3O+) act as the proton source, while water molecules serve as proton donors in neutral/alkaline electrolytes [54,55]. Typically, CO2RR is conducted in neutral or alkaline electrolytes, since a higher pH helps suppress the competing HER [26,56]. However, some studies indicate that HER at the reversible hydrogen electrode (RHE) is independent of pH, as it can be driven by the reduction of water molecules [18,57,58]. In an alkaline environment, CO2 can not only be directly reduced on the electrode surface but may also react with OH− ions to form carbonates (CO32−) or bicarbonates (HCO3−). Specifically, CO2 + 2OH−→CO32− + H2O and CO2 + OH−→HCO3−, both of which cannot directly participate in the reduction reaction, leading to carbon loss and low conversion efficiency [59,60,61].
To address the above issue, acidic electrolytes have become an emerging area of interest in CO2RR, effectively avoiding the CO32− and HCO3−, while a higher H+ concentration makes HER more kinetically favorable. To suppress HER, researchers have proposed various strategies. For example, Bondue et al. [62] studied CO2RR on gold electrodes under mild acidic conditions and found that the rates of CO and OH− generation must be sufficiently high to effectively suppress HER. Huang et al. [24] reported that adding high concentrations of alkaline metal cations (AMCs) to acidic electrolytes can enhance the local pH or electric field, effectively increasing the current density. Additionally, active site engineering has been applied to adjust the interaction between key intermediates like *COOH, *OCOH, and *OCCO with the catalyst surface. However, the stability of CO2RR in acidic electrolytes is much lower than that in basic ones, as the higher H+ concentration and the lack of HCO3−/CO32− ions hinder stable progression. Meanwhile, the acidic environment leads to the dissolution of many metal or metal oxide catalysts, and the degradation is uncontrollable [63,64,65,66,67].
Apart from bulk pH, the local pH at the EEI significantly affects catalytic selectivity and product distribution. Hori et al. [68] were the first to propose that local pH could alter the reaction pathways of CO2RR. The local pH is related to the formation of key intermediates, primarily because it can determine proton transfer or rate-limiting steps (RLSs), as shown in Figure 3. Specifically, H+ can couple to generate H2 or undergo PCET with the *CO to generate *CHO (a key reaction step for CH4). In contrast, for multi-carbon products like C2H4, the RLS involves C-C coupling, which is less dependent on proton transfer and pH [69]. Notably, increasing the local pH helps reduce the overpotential of C-C coupling at RHE and enhance the selectivity for multi-carbon products [35]. Furthermore, both CH4 and C2H4 formation share the common *CO intermediate, while both CH4 and H2 formation involve the common *H, suggesting that the formation of C1 products is closely related to changes in pH [25,70]. Table 2 compares the FE of various CO2 reduction products in both alkaline and acidic electrolytes, encompassing both previous and recent advances. The comparative analysis demonstrates that product selectivity depends not only on catalyst composition but is also significantly influenced by key electrolyte parameters, particularly pH and ion effects (cations/anions). These electrolyte-mediated controls have enabled progressive improvements in CO2 conversion across different reaction pathways.
In summary, pH regulates proton availability and the reaction pathways of intermediates, determining the product distribution. Acidic electrolytes help prevent carbonate/bicarbonate formation but may promote HER. Alkaline electrolytes help suppress HER while leading to lower conversion efficiency. At the EEI, local pH changes can influence proton transfer and RLS, which controls the product reaction pathway. Consequently, optimizing pH can effectively enhance CO2RR efficiency, especially for multi-carbon products.
Nanomaterials 15 00648 g003
Figure 3. The mechanism model for C1, C2+ and H2 evolution [35]. Copyright 2022, American Chemical Society.
Figure 3. The mechanism model for C1, C2+ and H2 evolution [35]. Copyright 2022, American Chemical Society.
Nanomaterials 15 00648 g003

4. Cation Effects

Cations in the electrolyte are considered to be critical factors influencing the kinetics and product selectivity of electrocatalytic CO2RR, and their interactions with the electrode include specific adsorption and electrostatic adsorption (long-range interactions) [84,85]. According to the classical theory of the EDL, particularly the Gouy–Chapman–Stern (GCS) model [86,87], the specifically adsorbed species reside at the inner Helmholtz plane (IHP), while the electrostatically adsorbed species are located at the outer Helmholtz plane (OHP), as illustrated in Figure 4a. In the GCS model, there is no potential gradient along the planes parallel to the electrode surface, and the potential only varies in the direction perpendicular to the electrode surface. Murata et al. [88] first demonstrated that the activity and selectivity of CO2RR are influenced by AMCs, such as Li+, Na+, K+, Cs+, in the electrolyte on Cu catalysts. Based on the EDL structure, the larger the size of the AMCs (Li+ < Na+ < K+ < Cs+), the smaller the degree of hydration, with the hydration thickness following the order Cs+ + nH2O < K+ + nH2O < Na+ + nH2O < Li+ + nH2O [89], as shown in Figure 4b. Hydrated cations are generally adsorbed at the OHP rather than directly on the electrode surface, with their hydration shells interacting with the negative charges on the cathode [90,91,92]. Although various studies have been conducted on cations and proposed thorites to elucidate these effects, the cations mechanisms remain multifaceted. Typically, the role of cations in CO2RR can be categorized into three aspects: (1) modulating the interfacial electric field through non-covalent interactions; (2) controlling local CO2 concentration by buffering the interfacial pH; and (3) stabilizing intermediates through electric field–dipole interactions [92,93,94].
Non-covalent interactions, such as electrostatic interactions, lead cations to accumulate at the OHP, thereby altering the activity and selectivity of CO2RR [95]. The strength of the interfacial electric field (IEF) is the primary reason for the gradual increase in CO2RR reactivity from Li+ to Cs+ [96]. Figure 4c illustrates that, at −0.7 V, when the cation in the electrolyte is replaced from Li+ to Cs+, the current densities of C2+ and H2 significantly increase, while CH4 becomes a minor product for all cations. The trend of CO2RR reactivity in the presence of different AMCs is generally consistent with that in HCO3− electrolytes reported by Resasco [93]. DFT calculations also confirm the value of the electrostatic stabilization. As shown in Figure 4d, during the electrochemical reduction of CO on Cu (100), the size of the AMCs affects the local current at the same potential. Similarly, the partial currents of HCOO−, C2H4, and C2H5OH generated on the Cu (111) surface also increase with the size of the cation. Nevertheless, Resasco suggest that the generation rates of H2 and CH4 are less influenced by cation size, which may be due to the absence of a dipole in the hydrogen ion or the presence of distinct counter-ions in the electrolyte (e.g., OH− and HCO3−). Additionally, AMCs adsorbed at the OHP can suppress HER by altering the distribution of the IEF, limiting the migration of hydrated hydrogen ions to the cathode surface [97]. In comparison, the electric field of cations is more likely to stabilize CO rather than *CHO (the intermediate of CH4), which affects the formation of C1 products [93]. These trends are consistent with previous studies [92,98]. Hydrated cations with smaller sizes have larger surface charges and interfacial fields, thus requiring a smaller driving force for CO2RR at specific potentials. Therefore, cations are considered a necessary condition for promoting the CO2RR reaction.
Another theory posits that hydrated AMCs undergo hydrolysis reactions, acting as buffering agents to regulate the local pH and CO2 concentration at the EEI [92]. The O–H bonds within the hydration shells exhibit enhanced polarization through interactions with the negatively charged cathode, thereby facilitating the adsorption performance. This phenomenon shifts the OHP potential more negative, and increases the hydrogen ion concentration at the EEI and lower the local pH. In contrast to HER, a low-pH environment favors CO2RR, as the efficiency of CO2RR can be enhanced under elevated CO2 concentrations compared to HER, which is predominantly affected by a low pH [92]. Ayemoba et al. [99] and Zhang [100] independently determined the local pH of different AMCs during CO2RR using in-site surface-enhanced infrared absorption spectroscopy (SEIRAS) and rotating ring-disk electrode (RRDE) techniques, respectively. The results propose that the local pH follows the trend Li+ > Na+ > K+ > Cs+ (Figure 4e), consistent with conclusions of Murata [88]. However, direct experimental validation of the interfacial CO2 concentration trends under varying cations in CO2RR conditions remains lacking [101]. Contrary to the cation-buffering hypothesis, Malkani et al. [101] employed SEIRAS to probe the interfacial CO2 concentration dependence on cation size for a Au electrode under −0.8 V, revealing that larger AMCs correlate with lower interfacial CO2 concentrations (Figure 4f). Although the cation hydrolysis theory was developed based on Ag and Cu surfaces, which differ from Au in their potential of zero charge, the cation-buffering effect on interfacial CO2 concentration exhibits similar trends across Au, Ag, and Cu surfaces [99]. This study, combining reaction activity and spectroscopic results, demonstrates that interfacial CO2 concentration is primarily governed by reaction kinetics rather than cation-buffering capacity.
Nanomaterials 15 00648 g004
Figure 4. (a) Schematic diagram of the electric double layer. (b) The radius of the hydrated alkali metal cation [89]. (c) Current density on carbon paper supported Cu microparticles at −0.7 V [96]. Copyright 2020, American Association for the Advancement of Science. (d) Average current densities obtained during bulk electrolysis on Cu (100) as a function of metal cation at different potentials [93]. (e) Steady-state pH at different metal−electrolyte interfaces at −1 V vs. RHE [99]. (f) Tracking the interfacial CO2 concentration for the different alkali metal bicarbonate electrolytes by normalizing to the band area with Li [101]. All figures (b,d–f) are adapted from the American Chemical Society, Copyright 2017–2024.
Figure 4. (a) Schematic diagram of the electric double layer. (b) The radius of the hydrated alkali metal cation [89]. (c) Current density on carbon paper supported Cu microparticles at −0.7 V [96]. Copyright 2020, American Association for the Advancement of Science. (d) Average current densities obtained during bulk electrolysis on Cu (100) as a function of metal cation at different potentials [93]. (e) Steady-state pH at different metal−electrolyte interfaces at −1 V vs. RHE [99]. (f) Tracking the interfacial CO2 concentration for the different alkali metal bicarbonate electrolytes by normalizing to the band area with Li [101]. All figures (b,d–f) are adapted from the American Chemical Society, Copyright 2017–2024.
Nanomaterials 15 00648 g004
In the third theoretical framework, cations can influence CO2RR by inducing interactions between the electric field within the EDL and intermediates with large dipole moments, such as *CO2, *CO, and *OCCO. Specifically adsorbed AMCs at the electrode surface significantly modulate the binding strength or coverage of these intermediates [24,85]. Resasco et al. [93] propose that pronounced dipole interactions exist between adsorbed intermediates and hydrated cations, with interaction strengths following the order Cs+ > Rb+ > K+ > Na+ > Li+. According to density functional theory (DFT) calculations, this trend arises from the higher concentration of larger cations at the OHP. Further studies corroborate this theory; for instance, Ovalle et al. [102] utilized SEIRAS to investigate the displacement effects of tetramethylammonium (Me4N+) against AMCs, revealing an adsorption sequence of Li+ < Na+ < K+ < Cs+. Additionally, Monteiro et al. [103] demonstrated that CO2 cannot be reduced to CO on Au, Ag, or Cu electrodes in the absence of AMCs, thereby ruling out the influence of cation-mediated electric fields and pH buffering on CO2RR. Based on these studies, the authors propose three cation effects: (1) stabilizing intermediates via short- and medium-range interactions; (2) activating CO2 by reducing the O–C–O bond angle; and (3) enhancing electron transfer rates from the electrode surface to CO2. Furthermore, Monteiro et al. [31] explored the impact of cations with varying valences (e.g., Cs+, Ba2+, Nd3+) on CO2RR the HER. They argue that +3-valent cations have stronger acidity and higher hydrolysis propensity and can promote HER. Specifically, strongly acidic Nd3+ facilitates hydrolysis, leading to water reduction even at low overpotentials. In contrast, Cs+ and Ba2+ exhibit slower hydrolysis kinetics, thereby favoring CO2RR.
In summary, cation size significantly impacts CO2RR performance, with larger AMCs generally enhancing C2+ production while suppressing CH4. This occurs through three key mechanisms: (1) stronger interfacial electric fields that stabilize *CO intermediates, (2) local pH buffering that increases CO2 concentration, and (3) dipole interactions with key intermediates. Faradaic efficiency for C2+ products improves with cation size (up to ∼60% for Cs+), while current densities increase due to enhanced electric fields. However, trivalent cations (e.g., Nd3+) favor HER through acidic hydrolysis. These effects collectively demonstrate how cation selection can tune product selectivity.

5. Anion Effects

Anions, as an indispensable component of the electrolyte, are also crucial for CO2RR. Current research primarily focuses on specifically adsorbed anions, which chemically interact with the electrode substrate or undergo chemisorption with other electrolyte species. This interaction can dramatically alter reaction rates and selectivity by modulating the local pH at the EEI via buffering capacity, restructuring the catalyst surface, and affecting the adsorption/desorption of intermediates [85,104]. In the electrocatalytic process, anions are able to occupy active sites, leading to catalyst poisoning and hindering the adsorption of reactants or intermediates, thereby slowing down reaction kinetics [33]. Contrary to this conclusion, some studies have proposed that certain anions can enhance reaction kinetics, and the coverage of adsorbed anions should not be excessive [34,105].
The protons transfer near the electrode generates a large amount of OH−. Acting as a proton donor, phosphate ions (H2PO4−) can neutralize OH− to buffer the interfacial pH to maintain a low value [106,107]. In contrast, anions such as perchlorate (ClO4−), sulfate (SO42−), and halides (e.g., Cl−, Br−, I−) may elevate the local pH due to the lack of effective neutralizing species, which inhibits the formation of certain products [108,109,110,111,112]. Dunwell et al. [59] proposed that most CO2(aq) in the electrolyte originates from the equilibrium with HCO3− rather than the diffusion of CO2(g). In other words, HCO3− serves as a carbon source to promote CO generation on Au electrodes, although it does not directly participate in the RLS of the CO formation [113]. Instead, it acts as a proton donor for both CO2RR and HER in the electrolyte, as shown in Figure 5a, complicating the role of HCO3−. Previous studies have compared the buffering effects of several anions on local pH using pKa (Figure 5b), revealing the following order of pH increase: H2PO4− < HCO3− < ClO4−. Although ClO4− can suppress HER, the slower kinetics result in a lower selectivity at higher potentials [114]. As a supplement, the buffering capacity of KHCO3, KCl and phosphate electrolytes on the CO2RR rate and local pH were explored [106]. Under CO2-limiting conditions, the CO2 consumption rate (Jlim) in KHCO3 solutions is notably higher than that in KCl solutions (Figure 5c). Specifically, at higher CO2 pressures (PCO2), Jlim exhibits nearly linear growth in KCl solutions, whereas it exhibits a nonlinear increase in KHCO3 solutions. Consequently, the CO2RR is not only influenced by KHCO3 concentration but is also closely related to its excellent buffering capacity. The simulation results in Figure 5d further demonstrate that KHCO3 can maintain a relatively stable pH at the EEI, preventing excessive alkalinity in the local environment. On the contrary, KCl electrolytes lack buffering capacity, causing a pronounced pH increase at the electrode surface.
Halide ions (e.g., Br−, I−, Cl−) can promote CO2RR, especially on Cu electrodes. On Cu (100) surfaces, halide ions enhance the FE of C2 products while reducing H2 [111]. At −1.23 V, the FE of C2H4 in KI electrolyte reaches 50.3%, which is higher than the 30.6% observed in the KClO4 electrolyte. Similarly, the FE of C2H5OH increases from 7.1% to 16.4%, while that of CO rises from 11.8% to 22.8%. These results indicate that I− can alter the electronic environment of *CO, enhancing its adsorption strength and surface coverage, and effectively lowering the energy barrier for C–C coupling. Also, halide ions are crucial in restructuring the catalyst surface, leading to the formation of highly rough surfaces that provide more active sites [34]. For instance, Garg et al. [115] investigated the effects of different halide ions in choline-based electrolytes on reducing CO2 to CO on the Ag electrode. They illustrated that the FE of CO follows the order Cl− > Br− > I−. At more negative potentials, halide ions promote the dissolution and redeposition of Ag electrodes, forming high-index crystal facets, such as (220), (311) (222). Beyond restructuring catalyst surface, halide ions also modulate the formation of key intermediates in the reaction pathway. Their charge-enabling properties facilitate the formation of *COOH, not only reducing the overpotential but also increasing the number of adsorbed CO species available for coupling [111,116]. Wang et al. [4] studied the effects of three different anions (F−, Cl−, HCO3−) on CO2RR and proposed an anion enrichment strategy to regulate ion adsorption and desorption. By periodically applying positive potentials to the cathode during pulsed electrolysis, anions can be adsorbed in the IHP, increasing the local anion concentration (Figure 5f). The results show that KF, KCl, and KHCO3 electrolytes exhibit the highest selectivity for CO, C2+ and CH4, respectively, as illustrated in Figure 5e. The strong electronegativity of F− enables it to strongly adsorb on the electrode surface, inhibiting further reduction of *CO. The moderate adsorption strength of Cl− favors C–C coupling between *CO species. For HCO3−, its strong proton-donating ability promotes the hydrogenation of *CO, enhancing CH4 selectivity. A key advantage of this strategy is that pulsed electrolysis periodically pushes protons away from the electrode surface, reducing the proton source and significantly suppressing HER.
Organic anions primarily influence CO2RR by restructuring the electrode surface. For instance, under −0.8 V vs. RHE, propionate (C3H5CO2−) increases the FE of CO to 98.7%, far exceeding the 80% achieved with HCO3− [114]. Molecular dynamics simulations reveal that carboxylate form a suitable interfacial water structure through weak adsorption on the electrode surface, promoting CO2 reduction while inhibiting HER. Additionally, Ge et al. [110] investigated the effects of different anionic surfactants, including sodium dodecylbenzene sulfonate (SDS), sodium lauryl sulfate (SLS), sodium monolauryl phosphate (SMP), and sodium laurate (SL), in KHCO3 electrolyte. They found that these additives significantly improved the FE of CO at −1.2 V vs. RHE, reaching 89.7%, 97.5%, 98.4%, and 98.9%, respectively, far exceeding the 53.1% FE observed in the absence of surfactants. Simultaneously, the FE of H2 significantly decreased. These results demonstrate that surfactants not only enhance CO selectivity but also suppress HER. In-site attenuated total reflection surface-enhanced infrared spectroscopy (ATR-SEIRAS) analysis revealed that surfactants strengthen the H-bond network of interfacial water molecules, promoting proton-coupled reactions and inhibiting HER. DFT calculations further support these anions in improving water structure, showing that SL and SMP exhibit a stronger H-bond than SDS and SLS. The organic compound dodecyl phosphate (DDPA) also can restructure the H-bond network at the EEI, increasing the proportion of free water [117]. DDPA increases the FE of CO from 70% to 98% at −1.0 V vs. RHE, maintaining over 90% efficiency for 8 h in flow electrolysis, demonstrating a significant enhancement in CO2 reduction performance.
In summary, anions have remarkable effects on CO2RR performance through multiple mechanisms: (1) pH regulation via buffering capacity (e.g., H2PO4− maintains a low pH while ClO4− elevates it), (2) surface restructuring (halides create rough surfaces and high-index facets), and (3) intermediate stabilization (I− enhances *CO adsorption for C–C coupling). These effects lead to distinct product distributions—halides boost C2+ Faradaic efficiency, while F− favors CO and HCO3− promotes CH4. Organic anions like carboxylates and surfactants further enhance CO selectivity (up to 98.9% FE) by optimizing interfacial water structure. Current density variations arise from altered reaction kinetics, with buffering anions sustaining higher CO2 consumption rates than non-buffering ones. The interplay between anion-specific adsorption strength and proton management ultimately dictates reaction pathway length, with moderately adsorbing species favoring multi-carbon products while strongly adsorbing ones that terminate at CO.
Nanomaterials 15 00648 g005
Figure 5. (a) Schematic diagram of the equilibrium conversion mechanism between CO2 and bicarbonate, and (b) the effect of the buffering capacity of anions on local pH [85]. Copyright 2024, John Wiley and Sons Ltd. (c) CO2 pressure (PCO2) dependence of the limiting rate of mass transport of CO2 (Jlim) in 0.5 M KHCO3 and 0.5 M KCl solutions, and (d) pH within the 100 μm boundary layer at PCO2 of 2 atm [106]. (e) The selectivity of CO, CH4, and C2 as a function of anions, and (f) schematic illustrations for the structures of an electric double layer under pulsed CP mode [4]. (g) FE of CO at different potentials [117]. Copyright 2018, 2023, and 2024. American Chemical Society.
Figure 5. (a) Schematic diagram of the equilibrium conversion mechanism between CO2 and bicarbonate, and (b) the effect of the buffering capacity of anions on local pH [85]. Copyright 2024, John Wiley and Sons Ltd. (c) CO2 pressure (PCO2) dependence of the limiting rate of mass transport of CO2 (Jlim) in 0.5 M KHCO3 and 0.5 M KCl solutions, and (d) pH within the 100 μm boundary layer at PCO2 of 2 atm [106]. (e) The selectivity of CO, CH4, and C2 as a function of anions, and (f) schematic illustrations for the structures of an electric double layer under pulsed CP mode [4]. (g) FE of CO at different potentials [117]. Copyright 2018, 2023, and 2024. American Chemical Society.
Nanomaterials 15 00648 g005

6. Summary and Outlook

This review summarizes the critical role of the electrolyte in electrochemical CO2RR, including the effects of pH, cations, and anions on reaction pathways, activity, and selectivity. The research shows the following findings:
  • The configuration of reaction intermediates significantly influences the product formation, and exploring the universality of pathways remains a key focus.
  • The local pH of the electrolyte not only affects the source of protons but also regulates intermediates.
  • Cations significantly affect the kinetics and selectivity of CO2RR through non-covalent interactions, buffering the interface pH, and stabilizing intermediates.
  • Anions alter the reaction rate and product distribution by regulating local pH, catalyst surface reconstruction, and the adsorption/desorption processes of intermediates.
Although numerous studies have highlighted the critical role of the electrolyte environment in CO2RR, several key challenges and unresolved questions remain. Addressing these challenges will be essential for advancing the field and improving the efficiency and selectivity of CO2RR.
  • The interaction mechanisms between the effects of cations and anions are not yet fully understood, particularly in complex electrolyte systems, making it difficult to isolate and analyze individual contributions.
  • The stability of CO2RR in acidic electrolytes remains a significant issue, as catalyst dissolution and dynamic changes in the local microenvironment require further investigation.
  • The formation pathways of multi-carbon products are intricate, necessitating a combination of advanced experimental techniques and theoretical calculations to elucidate the underlying reaction mechanisms.

Author Contributions

Conceptualization, J.Z. (Jiandong Zhang) and Z.Z.; methodology, J.Z. (Jiandong Zhang) and Z.Z.; investigation, J.Z. (Jiandong Zhang), Z.Z., T.C., J.Z. (Jiayi Zhang) and Y.Z.; writing—original draft preparation, J.Z. (Jiandong Zhang) and Z.Z.; writing—review and editing, J.Z. (Jiandong Zhang), Z.Z., T.C., J.Z. (Jiayi Zhang) and Y.Z., J.Z. (Jiandong Zhang) and Z.Z. are co-first authors. J.Z. (Jiandong Zhang) played a leading role in the literature review and paper writing. Z.Z. provided important support in the data analysis and chart production. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partly supported by the Student Innovation and Entrepreneurship Training Program of China (Project Nos.xj2024118450017).

Data Availability Statement

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. DuanMu, J.-W.; Gao, F.-Y.; Gao, M.-R. A Critical Review of Operating Stability Issues in Electrochemical CO2 Reduction. Sci. China Mater. 2024, 67, 1721–1739. [Google Scholar] [CrossRef]
  2. Zhu, Y.-Z.; Wang, K.; Zheng, S.-S.; Wang, H.-J.; Dong, J.-C.; Li, J.-F. Application and development of electrochemical spectroscopy methods. Acta Phys.-Chim. Sin. 2024, 40, 2304040. [Google Scholar] [CrossRef]
  3. Chen, Y.; Chen, C.; Cao, X.; Wang, Z.; Zhang, N.; Liu, T. Recent Advances in Defect and Interface Engineering for Electroreduction of CO2 and N2. Acta Phys. Chim. Sin. 2023, 39, 2210053. [Google Scholar] [CrossRef]
  4. Wang, J.; Qin, Y.; Jin, S.; Yang, Y.; Zhu, J.; Li, X.; Lv, X.; Fu, J.; Hong, Z.; Su, Y.; et al. Customizing CO2 Electroreduction by Pulse-Induced Anion Enrichment. J. Am. Chem. Soc. 2023, 145, 26213–26221. [Google Scholar] [CrossRef]
  5. Chen, S.; Liu, J.; Zhang, Q.; Teng, F.; McLellan, B.C. A Critical Review on Deployment Planning and Risk Analysis of Carbon Capture, Utilization, and Storage (CCUS) toward Carbon Neutrality. Renew. Sustain. Energy Rev. 2022, 167, 112537. [Google Scholar] [CrossRef]
  6. Dutta, N.; Bagchi, D.; Chawla, G.; Peter, S.C. A Guideline to Determine Faradaic Efficiency in Electrochemical CO2 Reduction. ACS Energy Lett. 2024, 9, 323–328. [Google Scholar] [CrossRef]
  7. Jiao, J.; Kang, X.; Yang, J.; Jia, S.; Chen, X.; Peng, Y.; Chen, C.; Xing, X.; Chen, Z.; He, M.; et al. Lattice Strain Engineering Boosts CO2 Electroreduction to C2+ Products. Angew. Chem. Int. Ed. 2024, 63, e202409563. [Google Scholar] [CrossRef]
  8. Li, H.; Jiang, Y.; Li, X.; Davey, K.; Zheng, Y.; Jiao, Y.; Qiao, S.-Z. C2+ Selectivity for CO2 Electroreduction on Oxidized Cu-Based Catalysts. J. Am. Chem. Soc. 2023, 145, 14335–14344. [Google Scholar] [CrossRef]
  9. Ma, L.; Zhao, W.; Wang, B.; Ling, L.; Zhang, R. CO2 Activation and Conversion on Cu Catalysts: Revealing the Role of Cu Surface Defect Types in Tuning the Activity and Selectivity. Fuel 2022, 313, 122686. [Google Scholar] [CrossRef]
  10. Song, X.; Xiong, W.; He, H.; Si, D.; Lü, L.; Peng, Y.; Jiang, Q.; Wang, Y.; Zheng, Y.; Nan, Z.-A.; et al. Boosting CO2 Electrocatalytic Reduction to Ethylene via Hydrogen-Assisted C-C Coupling on Cu2O Catalysts Modified with Pd Nanoparticles. Nano Energy 2024, 122, 109275. [Google Scholar] [CrossRef]
  11. Zhu, W.; Liu, S.; Zhao, K.; Su, Y.; Yang, Y.; Huang, K.; He, Z. Activating *CO by Strengthening Fe–CO Π-backbonding to Enhance Two-carbon Products Formation toward CO2 Electroreduction on Fe–N4 Sites. Adv. Funct. Mater. 2024, 34, 2402537. [Google Scholar] [CrossRef]
  12. Su, S.; Zhou, Y.; Xiong, L.; Jin, S.; Du, Y.; Zhu, M. Structure-activity Relationships of the Structural Analogs Au8Cu1 and Au8Ag1 in the Electrocatalytic CO2 Reduction Reaction. Angew. Chem. Int. Ed. 2024, 136, e202404629. [Google Scholar] [CrossRef]
  13. Li, Y.; Wei, Z.; Sun, Z.; Zhai, H.; Li, S.; Chen, W. Sulfur Modified Carbon-based Single-atom Catalysts for Electrocatalytic Reactions. Small 2024, 20, 2401900. [Google Scholar] [CrossRef]
  14. Yuan, F.; Wang, X.; Ma, T.; Fan, J.; Lai, X.; Liu, Y. Enhanced Conversion of CO2 into C2H4 on Single Atom Cu-Anchored Graphitic Carbon Nitride: Synergistic Diatomic Active Sites Interaction. J. Colloid Interface Sci. 2024, 667, 291–302. [Google Scholar] [CrossRef] [PubMed]
  15. Hung, S.-F.; Xu, A.; Wang, X.; Li, F.; Hsu, S.-H.; Li, Y.; Wicks, J.; Cervantes, E.G.; Rasouli, A.S.; Li, Y.C.; et al. A Metal-Supported Single-Atom Catalytic Site Enables Carbon Dioxide Hydrogenation. Nat. Commun. 2022, 13, 819. [Google Scholar] [CrossRef] [PubMed]
  16. Yang, H.; Li, S.; Xu, Q. Efficient Strategies for Promoting the Electrochemical Reduction of CO2 to C2+ Products over Cu-Based Catalysts. Chin. J. Catal. 2023, 48, 32–65. [Google Scholar] [CrossRef]
  17. Liu, C.; Gong, J.; Gao, Z.; Xiao, L.; Wang, G.; Lu, J.; Zhuang, L. Regulation of the Activity, Selectivity, and Durability of Cu-Based Electrocatalysts for CO2 Reduction. Sci. China Chem. 2021, 64, 1660–1678. [Google Scholar] [CrossRef]
  18. Nitopi, S.; Bertheussen, E.; Scott, S.B.; Liu, X.; 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]
  19. Chu, M.; Chen, C.; Wu, Y.; Yan, X.; Jia, S.; Feng, R.; Wu, H.; He, M.; Han, B. Enhanced CO2 Electroreduction to Ethylene via Strong Metal-Support Interaction. Green Energy Environ. 2022, 7, 792–798. [Google Scholar] [CrossRef]
  20. Liu, Y.; Song, Y.; Huang, L.; Su, J.; Li, G.; Zhang, Q.; Xin, Y.; Cao, X.; Guo, W.; Dou, Y.; et al. Constructing Ionic Interfaces for Stable Electrochemical CO2 Reduction. ACS Nano 2024, 18, 14020–14028. [Google Scholar] [CrossRef]
  21. Hou, J.; Xu, B.; Lu, Q. Influence of Electric Double Layer Rigidity on CO Adsorption and Electroreduction Rate. Nat. Commun. 2024, 15, 1926. [Google Scholar] [CrossRef]
  22. Gebbie, M.A.; Liu, B.; Guo, W.; Anderson, S.R.; Johnstone, S.G. Linking Electric Double Layer Formation to Electrocatalytic Activity. ACS Catal. 2023, 13, 16222–16239. [Google Scholar] [CrossRef]
  23. Xu, A.; Govindarajan, N.; Kastlunger, G.; Vijay, S.; Chan, K. Theories for Electrolyte Effects in CO2 Electroreduction. Acc. Chem. Res. 2022, 55, 495–503. [Google Scholar] [CrossRef] [PubMed]
  24. Huang, J.E.; Li, F.; Ozden, A.; Sedighian Rasouli, A.; García De Arquer, F.P.; Liu, S.; Zhang, S.; Luo, M.; Wang, X.; Lum, Y.; et al. CO2 Electrolysis to Multicarbon Products in Strong Acid. Science 2021, 372, 1074–1078. [Google Scholar] [CrossRef]
  25. Schreier, M.; Yoon, Y.; Jackson, M.N.; Surendranath, Y. Competition between H and CO for Active Sites Governs Copper-mediated Electrosynthesis of Hydrocarbon Fuels. Angew. Chem. Int. Ed. 2018, 57, 10221–10225. [Google Scholar] [CrossRef] [PubMed]
  26. Wu, T.; Bu, H.; Tao, S.; Ma, M. Determination of Local pH in CO2 Electroreduction. Nanoscale 2024, 16, 3926–3935. [Google Scholar] [CrossRef] [PubMed]
  27. Shin, S.-J.; Choi, H.; Ringe, S.; Won, D.H.; Oh, H.-S.; Kim, D.H.; Lee, T.; Nam, D.-H.; Kim, H.; Choi, C.H. A Unifying Mechanism for Cation Effect Modulating C1 and C2 Productions from CO2 Electroreduction. Nat. Commun. 2022, 13, 5482. [Google Scholar] [CrossRef]
  28. Xu, Y.; Xia, Z.; Gao, W.; Xiao, H.; Xu, B. Cation Effect on the Elementary Steps of the Electrochemical CO Reduction Reaction on Cu. Nat. Catal. 2024, 7, 1120–1129. [Google Scholar] [CrossRef]
  29. Qin, X.; Vegge, T.; Hansen, H.A. Cation-Coordinated Inner-Sphere CO2 Electroreduction at Au–Water Interfaces. J. Am. Chem. Soc. 2023, 145, 1897–1905. [Google Scholar] [CrossRef]
  30. Dong, Y.; Ma, M.; Jiao, Z.; Han, S.; Xiong, L.; Deng, Z.; Peng, Y. Effect of Electrolyte Cation-Mediated Mechanism on Electrocatalytic Carbon Dioxide Reduction. Chin. Chem. Lett. 2024, 35, 109049. [Google Scholar] [CrossRef]
  31. 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] [PubMed]
  32. Hsieh, Y.-C.; Senanayake, S.D.; Zhang, Y.; Xu, W.; Polyansky, D.E. Effect of Chloride Anions on the Synthesis and Enhanced Catalytic Activity of Silver Nanocoral Electrodes for CO2 Electroreduction. ACS Catal. 2015, 5, 5349–5356. [Google Scholar] [CrossRef]
  33. Tripkovic, D.V.; Strmcnik, D.; Van Der Vliet, D.; Stamenkovic, V.; Markovic, N.M. The Role of Anions in Surface Electrochemistry. Faraday Discuss. 2009, 140, 25–40. [Google Scholar] [CrossRef]
  34. Masana, J.J.; Peng, B.; Shuai, Z.; Qiu, M.; Yu, Y. Influence of Halide Ions on the Electrochemical Reduction of Carbon Dioxide over a Copper Surface. J. Mater. Chem. A 2022, 10, 1086–1104. [Google Scholar] [CrossRef]
  35. Deng, B.; Huang, M.; Zhao, X.; Mou, S.; Dong, F. Interfacial Electrolyte Effects on Electrocatalytic CO2 Reduction. ACS Catal. 2022, 12, 331–362. [Google Scholar] [CrossRef]
  36. Lv, J.; Yin, R.; Zhou, L.; Li, J.; Kikas, R.; Xu, T.; Wang, Z.; Jin, H.; Wang, X.; Wang, S. Microenvironment Engineering for the Electrocatalytic CO2 Reduction Reaction. Angew. Chem. 2022, 134, e202207252. [Google Scholar] [CrossRef]
  37. Peng, L.; Zhang, Y.; He, R.; Xu, N.; Qiao, J. Research advances in electrocatalysts, electrolytes, reactors and membranes for the electrocatalytic carbon dioxide reduction reaction. Acta Phys. Chim. Sin. 2023, 10, 2302037. [Google Scholar] [CrossRef]
  38. Chen, B.; Jiang, Y.-F.; Xiao, H.; Li, J. Selective CO2-to-HCOOH Electroreduction on Graphdiyne-Supported Bimetallic Single-Cluster Catalysts. ACS Catal. 2024, 14, 10510–10518. [Google Scholar] [CrossRef]
  39. Guan, A.; Chen, Z.; Quan, Y.; Peng, C.; Wang, Z.; Sham, T.-K.; Yang, C.; Ji, Y.; Qian, L.; Xu, X.; et al. Boosting CO2 Electroreduction to CH4 via Tuning Neighboring Single-Copper Sites. ACS Energy Lett. 2020, 5, 1044–1053. [Google Scholar] [CrossRef]
  40. Sebastián-Pascual, P.; Escudero-Escribano, M. Addressing the Interfacial Properties for CO Electroreduction on Cu with Cyclic Voltammetry. ACS Energy Lett. 2020, 5, 130–135. [Google Scholar] [CrossRef]
  41. Li, S.; Guan, A.; Yang, C.; Peng, C.; Lv, X.; Ji, Y.; Quan, Y.; Wang, Q.; Zhang, L.; Zheng, G. Dual-Atomic Cu Sites for Electrocatalytic CO Reduction to C2+ Products. ACS Mater. Lett. 2021, 3, 1729–1737. [Google Scholar] [CrossRef]
  42. Shi, X.; Shi, L.; Wang, J.; Zhou, Y.; Zhao, S. Defect Engineering of Nanomaterials for Selective Electrocatalytic CO2 Reduction. Matter 2024, 7, 4233–4259. [Google Scholar] [CrossRef]
  43. Birdja, Y.Y.; Pérez-Gallent, E.; Figueiredo, M.C.; Göttle, A.J.; Calle-Vallejo, F.; Koper, M.T.M. Advances and Challenges in Understanding the Electrocatalytic Conversion of Carbon Dioxide to Fuels. Nat. Energy 2019, 4, 732–745. [Google Scholar] [CrossRef]
  44. Dong, J.; Liu, Y.; Pei, J.; Li, H.; Ji, S.; Shi, L.; Zhang, Y.; Li, C.; Tang, C.; Liao, J.; et al. Continuous Electroproduction of Formate via CO2 Reduction on Local Symmetry-Broken Single-Atom Catalysts. Nat. Commun. 2023, 14, 6849. [Google Scholar] [CrossRef] [PubMed]
  45. Huang, B.; Wu, Y.; Luo, Y.; Zhou, N. Double Atom-Anchored Defective Boron Nitride Catalyst for Efficient Electroreduction of CO2 to CH4: A First Principles Study. Chem. Phys. Lett. 2020, 756, 137852. [Google Scholar] [CrossRef]
  46. Dong, H.; Li, Y.; Jiang, D. First-Principles Insight into Electrocatalytic Reduction of CO2 to CH4 on a Copper Nanoparticle. J. Phys. Chem. C 2018, 122, 11392–11398. [Google Scholar] [CrossRef]
  47. Ali, S.A.; Sadiq, I.; Ahmad, T. Deep Insight of CO2 Reduction Reaction Mechanism through Experimental and Theoretical Anticipations. Mater. Today Sustain. 2023, 24, 100587. [Google Scholar] [CrossRef]
  48. Du, P.; Ding, J.; Liu, C.; Li, P.; Liu, W.; Yan, W.; Pan, Y.; Hu, J.; Zhu, J.; Li, X.; et al. Interface-engineering-induced C−C Coupling for C2H4 Photosynthesis from Atmospheric-concentration CO2 Reduction. Angew. Chem. 2024, 137, e202421353. [Google Scholar] [CrossRef]
  49. Lei, Y.; Wang, Z.; Bao, A.; Tang, X.; Huang, X.; Yi, H.; Zhao, S.; Sun, T.; Wang, J.; Gao, F. Recent Advances on Electrocatalytic CO2 Reduction to Resources: Target Products, Reaction Pathways and Typical Catalysts. Chem. Eng. J. 2023, 453, 139663. [Google Scholar] [CrossRef]
  50. Wang, Y.; Chen, E.; Tang, J. Insight on Reaction Pathways of Photocatalytic CO2 Conversion. ACS Catal. 2022, 12, 7300–7316. [Google Scholar] [CrossRef]
  51. Zhang, Y.-C.; Zhang, X.-L.; Wu, Z.-Z.; Niu, Z.-Z.; Chi, L.-P.; Gao, F.-Y.; Yang, P.-P.; Wang, Y.-H.; Yu, P.-C.; Duanmu, J.-W.; et al. Facet-Switching of Rate-Determining Step on Copper in CO2 -to-Ethylene Electroreduction. Proc. Natl. Acad. Sci. USA 2024, 121, e2400546121. [Google Scholar] [CrossRef] [PubMed]
  52. Qiu, X.-F.; Zhu, H.-L.; Huang, J.-R.; Liao, P.-Q.; Chen, X.-M. Highly Selective CO2 Electroreduction to C2H4 Using a Metal–Organic Framework with Dual Active Sites. J. Am. Chem. Soc. 2021, 143, 7242–7246. [Google Scholar] [CrossRef]
  53. Meng, D.; Zhang, M.; Si, D.; Mao, M.; Hou, Y.; Huang, Y.; Cao, R. Highly Selective Tandem Electroreduction of CO2 to Ethylene over Atomically Isolated Nickel–Nitrogen Site/Copper Nanoparticle Catalysts. Angew. Chem. Int. Ed. 2021, 60, 25485–25492. [Google Scholar] [CrossRef]
  54. Kastlunger, G.; Wang, L.; Govindarajan, N.; Heenen, H.H.; Ringe, S.; Jaramillo, T.; Hahn, C.; Chan, K. Using pH Dependence to Understand Mechanisms in Electrochemical CO Reduction. ACS Catal. 2022, 12, 4344–4357. [Google Scholar] [CrossRef]
  55. Li, P.; Jiang, Y.; Hu, Y.; Men, Y.; Liu, Y.; Cai, W.; Chen, S. Hydrogen Bond Network Connectivity in the Electric Double Layer Dominates the Kinetic pH Effect in Hydrogen Electrocatalysis on Pt. Nat. Catal. 2022, 5, 900–911. [Google Scholar] [CrossRef]
  56. Chen, C.; Li, Y.; Yang, P. Address the “Alkalinity Problem” in CO2 Electrolysis with Catalyst Design and Translation. Joule 2021, 5, 737–742. [Google Scholar] [CrossRef]
  57. Ooka, H.; Figueiredo, M.C.; Koper, M.T.M. Competition between Hydrogen Evolution and Carbon Dioxide Reduction on Copper Electrodes in Mildly Acidic Media. Langmuir 2017, 33, 9307–9313. [Google Scholar] [CrossRef] [PubMed]
  58. Grozovski, V.; Vesztergom, S.; Láng, G.G.; Broekmann, P. Electrochemical Hydrogen Evolution: H+ or H2 O Reduction? A Rotating Disk Electrode Study. J. Electrochem. Soc. 2017, 164, E3171–E3178. [Google Scholar] [CrossRef]
  59. Dunwell, M.; Lu, Q.; Heyes, J.M.; Rosen, J.; Chen, J.G.; Yan, Y.; Jiao, F.; Xu, B. 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]
  60. Wuttig, A.; Yoon, Y.; Ryu, J.; Surendranath, Y. Bicarbonate Is Not a General Acid in Au-Catalyzed CO2 Electroreduction. J. Am. Chem. Soc. 2017, 139, 17109–17113. [Google Scholar] [CrossRef]
  61. Marcandalli, G.; Goyal, A.; Koper, M.T.M. Electrolyte Effects on the Faradaic Efficiency of CO2 Reduction to CO on a Gold Electrode. ACS Catal. 2021, 11, 4936–4945. [Google Scholar] [CrossRef] [PubMed]
  62. Bondue, C.J.; Graf, M.; Goyal, A.; Koper, M.T.M. Suppression of Hydrogen Evolution in Acidic Electrolytes by Electrochemical CO2 Reduction. J. Am. Chem. Soc. 2021, 143, 279–285. [Google Scholar] [CrossRef] [PubMed]
  63. Shen, H.; Jin, H.; Li, H.; Wang, H.; Duan, J.; Jiao, Y.; Qiao, S.-Z. Acidic CO2-to-HCOOH Electrolysis with Industrial-Level Current on Phase Engineered Tin Sulfide. Nat. Commun. 2023, 14, 2843. [Google Scholar] [CrossRef]
  64. Ling, N.; Zhang, J.; Wang, M.; Wang, Z.; Mi, Z.; Bin Dolmanan, S.; Zhang, M.; Wang, B.; Ru Leow, W.; Zhang, J.; et al. Acidic Media Impedes Tandem Catalysis Reaction Pathways in Electrochemical CO2 Reduction. Angew. Chem. Int. Ed. 2023, 62, e202308782. [Google Scholar] [CrossRef] [PubMed]
  65. Li, X.; Zhang, P.; Zhang, L.; Zhang, G.; Gao, H.; Pang, Z.; Yu, J.; Pei, C.; Wang, T.; Gong, J. Confinement of an Alkaline Environment for Electrocatalytic CO2 Reduction in Acidic Electrolytes. Chem. Sci. 2023, 14, 5602–5607. [Google Scholar] [CrossRef]
  66. Lai, W.; Qiao, Y.; Wang, Y.; Huang, H. Stability Issues in Electrochemical CO2 Reduction: Recent Advances in Fundamental Understanding and Design Strategies. Adv. Mater. 2023, 35, 2306288. [Google Scholar] [CrossRef]
  67. Nie, W.; Heim, G.P.; Watkins, N.B.; Agapie, T.; Peters, J.C. Organic Additive-derived Films on Cu Electrodes Promote Electrochemical CO2 Reduction to C2+ Products under Strongly Acidic Conditions. Angew. Chem. Int. Ed. 2023, 62, e202216102. [Google Scholar] [CrossRef]
  68. Hori, Y.; Murata, A.; Takahashi, R. Formation of Hydrocarbons in the Electrochemical Reduction of Carbon Dioxide at a Copper Electrode in Aqueous Solution. J. Chem. Soc. Faraday Trans. 1 1989, 85, 2309. [Google Scholar] [CrossRef]
  69. Sargeant, E.; Rodriguez, P.; Calle-Vallejo, F. Cation Effects on the Adsorbed Intermediates of CO2 Electroreduction Are Systematic and Predictable. ACS Catal. 2024, 14, 8814–8822. [Google Scholar] [CrossRef]
  70. Raciti, D.; Mao, M.; Wang, C. Mass Transport Modelling for the Electroreduction of CO2 on Cu Nanowires. Nanotechnology 2018, 29, 044001. [Google Scholar] [CrossRef]
  71. Pan, B.; Fan, J.; Zhang, J.; Luo, Y.; Shen, C.; Wang, C.; Wang, Y.; Li, Y. Close to 90% Single-Pass Conversion Efficiency for CO2 Electroreduction in an Acid-Fed Membrane Electrode Assembly. ACS Energy Lett. 2022, 7, 4224–4231. [Google Scholar] [CrossRef]
  72. Qin, H.-G.; Du, Y.-F.; Bai, Y.-Y.; Li, F.-Z.; Yue, X.; Wang, H.; Peng, J.-Z.; Gu, J. Surface-Immobilized Cross-Linked Cationic Polyelectrolyte Enables CO2 Reduction with Metal Cation-Free Acidic Electrolyte. Nat. Commun. 2023, 14, 5640. [Google Scholar] [CrossRef]
  73. Su, J.; Pan, D.; Dong, Y.; Zhang, Y.; Tang, Y.; Sun, J.; Zhang, L.; Tian, Z.; Chen, L. Ultrafine Fe2 C Iron Carbide Nanoclusters Trapped in Topological Carbon Defects for Efficient Electroreduction of Carbon Dioxide. Adv. Energy Mater. 2023, 13, 2204391. [Google Scholar] [CrossRef]
  74. Jiang, M.; Zhu, M.; Wang, H.; Song, X.; Liang, J.; Lin, D.; Li, C.; Cui, J.; Li, F.; Zhang, X.L.; et al. Rapid and Green Electric-Explosion Preparation of Spherical Indium Nanocrystals with Abundant Metal Defects for Highly-Selective CO2 Electroreduction. Nano Lett. 2023, 23, 291–297. [Google Scholar] [CrossRef] [PubMed]
  75. Yan, T.; Pan, H.; Liu, Z.; Kang, P. Phase-inversion Induced 3D Electrode for Direct Acidic Electroreduction CO2 to Formic Acid. Small 2023, 19, 2207650. [Google Scholar] [CrossRef]
  76. Liu, X.; Zheng, H.; Sun, Q.; He, J.; Yao, X.; Sun, C.; Shan, G.; Zhang, M.; Zhu, C.; Su, Z.; et al. Mastering the Lattice Strain in Bismuth-based Electrocatalysts for Efficient CO2-to-formate Conversion. Adv. Funct. Mater. 2024, 34, 2400928. [Google Scholar] [CrossRef]
  77. Sun, B.; Li, Z.; Xiao, D.; Liu, H.; Song, K.; Wang, Z.; Liu, Y.; Zheng, Z.; Wang, P.; Dai, Y.; et al. Unveiling pH-dependent Adsorption Strength of *CO2− Intermediate over High-density Sn Single Atom Catalyst for Acidic CO2-to-HCOOH Electroreduction. Angew. Chem. Int. Ed. 2024, 63, e202318874. [Google Scholar] [CrossRef] [PubMed]
  78. Zhu, J.; Wang, Y.; Zhi, A.; Chen, Z.; Shi, L.; Zhang, Z.; Zhang, Y.; Zhu, Y.; Qiu, X.; Tian, X.; et al. Cation-deficiency-dependent CO2 Electroreduction over Copper-based Ruddlesden–Popper Perovskite Oxides. Angew. Chem. Int. Ed. 2022, 61, e202111670. [Google Scholar] [CrossRef]
  79. Kash, B.C.; Gomes, R.J.; Amanchukwu, C.V. Mitigating Electrode Inactivation during CO2 Electrocatalysis in Aprotic Solvents with Alkali Cations. J. Phys. Chem. Lett. 2023, 14, 920–926. [Google Scholar] [CrossRef]
  80. Fan, M.; Huang, J.E.; Miao, R.K.; Mao, Y.; Ou, P.; Li, F.; Li, X.-Y.; Cao, Y.; Zhang, Z.; Zhang, J.; et al. Cationic-Group-Functionalized Electrocatalysts Enable Stable Acidic CO2 Electrolysis. Nat. Catal. 2023, 6, 763–772. [Google Scholar] [CrossRef]
  81. Zhang, J.; Wang, Y.; Li, Z.; Xia, S.; Cai, R.; Ma, L.; Zhang, T.; Ackley, J.; Yang, S.; Wu, Y.; et al. Grain Boundary-derived Cu+ /Cu0 Interfaces in CuO Nanosheets for Low Overpotential Carbon Dioxide Electroreduction to Ethylene. Adv. Sci. 2022, 9, 2200454. [Google Scholar] [CrossRef] [PubMed]
  82. Wang, Z.; Li, Y.; Zhao, X.; Chen, S.; Nian, Q.; Luo, X.; Fan, J.; Ruan, D.; Xiong, B.-Q.; Ren, X. Localized Alkaline Environment via in Situ Electrostatic Confinement for Enhanced CO2 -to-Ethylene Conversion in Neutral Medium. J. Am. Chem. Soc. 2023, 145, 6339–6348. [Google Scholar] [CrossRef] [PubMed]
  83. Yang, R.; Wu, M.; Huang, D.; Yang, Y.; Liu, Y.; Zhang, L.; Lai, F.; You, B.; Fang, J.; Liu, T.; et al. Which Dominates Industrial–Current–Density CO2 -to-C2+ Electroreduction: Cuδ+ or the Microenvironment? Energy Environ. Sci. 2024, 17, 2897–2907. [Google Scholar] [CrossRef]
  84. Chen, W.; Zhang, L.-L.; Wei, Z.; Zhang, M.-K.; Cai, J.; Chen, Y.-X. The Electrostatic Effect and Its Role in Promoting Electrocatalytic Reactions by Specifically Adsorbed Anions. Phys. Chem. Chem. Phys. 2023, 25, 8317–8330. [Google Scholar] [CrossRef]
  85. Ma, M.; Seger, B. Rational Design of Local Reaction Environment for Electrocatalytic Conversion of CO2 into Multicarbon Products. Angew. Chem. Int. Ed. 2024, 63, e202401185. [Google Scholar] [CrossRef]
  86. Grahame, D.C. The Electrical Double Layer and the Theory of Electrocapillarity. Chem. Rev. 1947, 41, 441–501. [Google Scholar] [CrossRef]
  87. Devanathan, M.A.V.; Tilak, B.V.K.S.R.A. The Structure of the Electrical Double Layer at the Metal-Solution Interface. Chem. Rev. 1965, 65, 635–684. [Google Scholar] [CrossRef]
  88. 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]
  89. Li, Z.; Wang, L.; Sun, L.; Yang, W. Dynamic Cation Enrichment during Pulsed CO2 Electrolysis and the Cation-Promoted Multicarbon Formation. J. Am. Chem. Soc. 2024, 146, 23901–23908. [Google Scholar] [CrossRef]
  90. Waegele, M.M.; Gunathunge, C.M.; Li, J.; Li, X. How Cations Affect the Electric Double Layer and the Rates and Selectivity of Electrocatalytic Processes. J. Chem. Phys. 2019, 151, 160902. [Google Scholar] [CrossRef]
  91. Moura De Salles Pupo, M.; Kortlever, R. Electrolyte Effects on the Electrochemical Reduction of CO2. ChemPhysChem 2019, 20, 2926–2935. [Google Scholar] [CrossRef] [PubMed]
  92. Singh, M.R.; Kwon, Y.; Lum, Y.; Ager, J.W.; Bell, A.T. Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO2 over Ag and Cu. J. Am. Chem. Soc. 2016, 138, 13006–13012. [Google Scholar] [CrossRef] [PubMed]
  93. Resasco, J.; Chen, L.D.; Clark, E.; Tsai, C.; Hahn, C.; Jaramillo, T.F.; Chan, K.; Bell, A.T. Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide. J. Am. Chem. Soc. 2017, 139, 11277–11287. [Google Scholar] [CrossRef]
  94. Chen, L.D.; Urushihara, M.; Chan, K.; Nørskov, J.K. Electric Field Effects in Electrochemical CO2 Reduction. ACS Catal. 2016, 6, 7133–7139. [Google Scholar] [CrossRef]
  95. 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, 3001–3014. [Google Scholar] [CrossRef]
  96. Malkani, A.S.; Li, J.; Oliveira, N.J.; He, M.; Chang, X.; Xu, B.; Lu, Q. Understanding the Electric and Nonelectric Field Components of the Cation Effect on the Electrochemical CO Reduction Reaction. Sci. Adv. 2020, 6, eabd2569. [Google Scholar] [CrossRef] [PubMed]
  97. Gu, J.; Liu, S.; Ni, W.; Ren, W.; Haussener, S.; Hu, X. Modulating Electric Field Distribution by Alkali Cations for CO2 Electroreduction in Strongly Acidic Medium. Nat. Catal. 2022, 5, 268–276. [Google Scholar] [CrossRef]
  98. Thorson, M.R.; Siil, K.I.; Kenis, P.J.A. Effect of Cations on the Electrochemical Conversion of CO2 to CO. J. Electrochem. Soc. 2013, 160, F69–F74. [Google Scholar] [CrossRef]
  99. 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]
  100. Zhang, Z.-M.; Wang, T.; Cai, Y.-C.; Li, X.-Y.; Ye, J.-Y.; Zhou, Y.; Tian, N.; Zhou, Z.-Y.; Sun, S.-G. Probing Electrolyte Effects on Cation-Enhanced CO2 Reduction on Copper in Acidic Media. Nat. Catal. 2024, 7, 807–817. [Google Scholar] [CrossRef]
  101. Malkani, A.S.; Anibal, J.; Xu, B. Cation Effect on Interfacial CO2 Concentration in the Electrochemical CO2 Reduction Reaction. ACS Catal. 2020, 10, 14871–14876. [Google Scholar] [CrossRef]
  102. Ovalle, V.J.; Hsu, Y.-S.; Agrawal, N.; Janik, M.J.; Waegele, M.M. Correlating Hydration Free Energy and Specific Adsorption of Alkali Metal Cations during CO2 Electroreduction on Au. Nat. Catal. 2022, 5, 624–632. [Google Scholar] [CrossRef]
  103. Monteiro, M.C.O.; Dattila, F.; Hagedoorn, B.; García-Muelas, R.; López, N.; Koper, M.T.M. Absence of CO2 Electroreduction on Copper, Gold and Silver Electrodes without Metal Cations in Solution. Nat. Catal. 2021, 4, 654–662. [Google Scholar] [CrossRef]
  104. Chen, W.; Du, X.; Tao, S.; Lin, B.; Tranca, I.; Tielens, F.; Ma, M.; Liu, Z. Electrolyte Effects on Reaction Kinetics in Electrochemical CO2 Reduction: The Roles of pH, Cations, and Anions. Chem. Phys. Rev. 2025, 6, 011302. [Google Scholar] [CrossRef]
  105. Gao, D.; Sinev, I.; Scholten, F.; Arán-Ais, R.M.; Divins, N.J.; Kvashnina, K.; Timoshenko, J.; Roldan Cuenya, B. Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte-driven Nanostructuring. Angew. Chem. Int. Ed. 2019, 58, 17047–17053. [Google Scholar] [CrossRef]
  106. Hashiba, H.; Weng, L.-C.; Chen, Y.; Sato, H.K.; Yotsuhashi, S.; Xiang, C.; Weber, A.Z. Effects of Electrolyte Buffer Capacity on Surface Reactant Species and the Reaction Rate of CO2 in Electrochemical CO2 Reduction. J. Phys. Chem. C 2018, 122, 3719–3726. [Google Scholar] [CrossRef]
  107. Resasco, J.; Lum, Y.; Clark, E.; Zeledon, J.Z.; Bell, A.T. Effects of Anion Identity and Concentration on Electrochemical Reduction of CO2. ChemElectroChem 2018, 5, 1064–1072. [Google Scholar] [CrossRef]
  108. Tomisaki, M.; Kasahara, S.; Natsui, K.; Ikemiya, N.; Einaga, Y. Switchable Product Selectivity in the Electrochemical Reduction of Carbon Dioxide Using Boron-Doped Diamond Electrodes. J. Am. Chem. Soc. 2019, 141, 7414–7420. [Google Scholar] [CrossRef]
  109. Moradzaman, M.; Mul, G. Optimizing CO Coverage on Rough Copper Electrodes: Effect of the Partial Pressure of CO and Electrolyte Anions (pH) on Selectivity toward Ethylene. J. Phys. Chem. C 2021, 125, 6546–6554. [Google Scholar] [CrossRef]
  110. Ge, W.; Zhu, Y.; Wang, H.; Jiang, H.; Li, C. Anionic Surfactant-Tuned Interfacial Water Reactivity Promoting Electrocatalytic CO2 Reduction. ACS Catal. 2024, 14, 18156–18166. [Google Scholar] [CrossRef]
  111. Huang, Y.; Ong, C.W.; Yeo, B.S. Effects of Electrolyte Anions on the Reduction of Carbon Dioxide to Ethylene and Ethanol on Copper (100) and (111) Surfaces. ChemSusChem 2018, 11, 3299–3306. [Google Scholar] [CrossRef] [PubMed]
  112. Gao, D.; Arán-Ais, R.M.; Jeon, H.S.; Roldan Cuenya, B. Rational Catalyst and Electrolyte Design for CO2 Electroreduction towards Multicarbon Products. Nat. Catal. 2019, 2, 198–210. [Google Scholar] [CrossRef]
  113. Wuttig, A.; Yaguchi, M.; Motobayashi, K.; Osawa, M.; Surendranath, Y. Inhibited Proton Transfer Enhances Au-Catalyzed CO2 -to-Fuels Selectivity. Proc. Natl. Acad. Sci. USA 2016, 113, E4585–E4593. [Google Scholar] [CrossRef]
  114. Yoo, J.M.; Ingenmey, J.; Salanne, M.; Lukatskaya, M.R. Anion Effect in Electrochemical CO2 Reduction: From Spectators to Orchestrators. J. Am. Chem. Soc. 2024, 146, 31768–31777. [Google Scholar] [CrossRef] [PubMed]
  115. Garg, S.; Li, M.; Wu, Y.; Nazmi Idros, M.; Wang, H.; 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] [PubMed]
  116. Gao, D.; Scholten, F.; Roldan Cuenya, B. Improved CO2 Electroreduction Performance on Plasma-Activated Cu Catalysts via Electrolyte Design: Halide Effect. ACS Catal. 2017, 7, 5112–5120. [Google Scholar] [CrossRef]
  117. Yuan, X.; Ge, W.; Zhu, Y.; Dong, L.; Jiang, H.; Li, C. Anionic Surfactant–Tailored Interfacial Microenvironment for Boosting Electrochemical CO2 Reduction. ACS Appl. Mater. Interfaces 2024, 16, 38083–38091. [Google Scholar] [CrossRef]
Nanomaterials 15 00648 g002
Figure 2. (a) Two pathways of electron transfer, and (b) overview of reaction pathways for CO2RR towards different products [42]. Copyright 2024, Elsevier.
Figure 2. (a) Two pathways of electron transfer, and (b) overview of reaction pathways for CO2RR towards different products [42]. Copyright 2024, Elsevier.
Nanomaterials 15 00648 g002
Table 1. The reactions of CO2RR and HER [18]. Copyright 2019, American Chemical Society.
Table 1. The reactions of CO2RR and HER [18]. Copyright 2019, American Chemical Society.
ReactionPotential (V vs. RHE)
x CO2 + n H+ + n e−→product + y H2O
CO2 + 2H+ + 2e−→CO (g) + H2O−0.10
CO2 + 2H+ + 2e−→HCOOH (aq)−0.12
CO2 + 4H+ + 4e−→C (s) + 2H2O0.21
CO2 + 6H+ + 6e−→CH3OH (aq) + H2O0.03
CO2 + 8H+ + 8e−→CH4 (aq) + 2H2O0.17
2CO2 + 8H+ + 8e−→CH3COOH (aq) + 2H2O0.11
2CO2 + 10H+ + 10e−→CH3CHO (aq) + 3H2O0.06
2CO2 + 12H+ + 12e−→C2H4 (q) + 4H2O0.08
2CO2 + 12H+ + 12e−→C2H5COOH (aq) + 3H2O 0.09
2CO2 + 14H+ + 14e−→C2H6 (g)+ 4H2O0.14
3CO2 + 16H+ + 16e−→C2H5CHO (aq) + 5H2O0.09
3CO2 + 18H+ + 18e−→C3H7OH (aq) + 5H2O0.10
H3O+→H+ + H2O-
2H+ + 2e−→H20
2H2O + 2e−→H2 + 2OH−-
Table 2. Comparative analysis of electrolyte effects in CO2RR.
Table 2. Comparative analysis of electrolyte effects in CO2RR.
ParametersPrevious StudiesRecent Advances
CO FE~80% (H2SO4 + Cs2SO4, Ag) [71]95% (K2SO4, Ag@C) [65]
95% (H2SO4, c-PDDA-Ag) [72]
97.1% (KHCO3, Fe2C-Cs@DC) [73]
HCOOH FE80% (KHCO3, In NCs) [74]
89.2% (Na2SO4, Porous Bi) [75]		90.15% (KOH, BOC/Bi-3) [76]
90.8% (K2SO4 + H2SO4, Sn-SAC) [77]
93% (K2SO4, r-Pb) [77]
CH4 FE~57% (KOH, La2−x CuO4−δ) [78]80% (DMSO, Cu) [79]
71% (H2SO4, EDTA-Cu) [80]
C2H4 FE26% (H3PO4 + KCl, CAL-Cu) [24]
~63% (KOH, CuO-160W) [81]		70% (K2SO4 + H2SO4, C/Cu/PTFE) [82]
74% (KOH, Dendritic CuO) [83]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zhang, J.; Zhang, Z.; Chen, T.; Zhang, J.; Zhang, Y. Electrolyte Effect on Electrocatalytic CO2 Reduction. Nanomaterials 2025, 15, 648. https://doi.org/10.3390/nano15090648

AMA Style

Zhang J, Zhang Z, Chen T, Zhang J, Zhang Y. Electrolyte Effect on Electrocatalytic CO2 Reduction. Nanomaterials. 2025; 15(9):648. https://doi.org/10.3390/nano15090648

Chicago/Turabian Style

Zhang, Jiandong, Ziliang Zhang, Tianye Chen, Jiayi Zhang, and Yu Zhang. 2025. "Electrolyte Effect on Electrocatalytic CO2 Reduction" Nanomaterials 15, no. 9: 648. https://doi.org/10.3390/nano15090648

APA Style

Zhang, J., Zhang, Z., Chen, T., Zhang, J., & Zhang, Y. (2025). Electrolyte Effect on Electrocatalytic CO2 Reduction. Nanomaterials, 15(9), 648. https://doi.org/10.3390/nano15090648

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop