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Review

Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions

by
Yuanping Guo
1,2,
Chenghao Yang
2,3,
Jianli Yang
1,
Xin Xiao
2,
Maofei Ran
1,* and
Jing Li
2,*
1
College of Chemistry and Environment Protection, Southwest University for Nationalities, Chengdu 610041, China
2
College of Carbon Neutrality Future Technology, Sichuan University, Chengdu 610065, China
3
College of Materials and Chemistry and Chemical Engineering, Chengdu University of Technology, Chengdu 610065, China
*
Authors to whom correspondence should be addressed.
Energies 2025, 18(12), 3016; https://doi.org/10.3390/en18123016
Submission received: 20 April 2025 / Revised: 30 May 2025 / Accepted: 3 June 2025 / Published: 6 June 2025
(This article belongs to the Special Issue Advances in Electrocatalysis, Electrosynthesis, and Electrochemical Applications)
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Abstract

:
Electrolysis of abundant seawater resources is a promising approach for hydrogen production. However, the high-concentration chloride ion in seawater readily induces the chlorine evolution reaction (CER), resulting in catalyst degradation and decreased electrolysis efficiency. In recent years, the electrooxidation of small organic molecules (e.g., methanol), biomass-derived compounds (e.g., 5-hydroxymethylfurfural), and plastic monomers (e.g., ethylene glycol) has been seen to occur at lower potentials to substitute for the traditional oxygen evolution reaction (OER) and CER. This alternative approach not only significantly reduces energy consumption for hydrogen production but also generates value-added products at the anode. This review provides a comprehensive summary of research advancements in value-added electrooxidation reaction-assisted seawater hydrogen production technologies and emphasizes the underlying principles of various reactions and catalyst design methodologies. Finally, the current challenges in this field and potential future research directions are systematically discussed.

1. Introduction

Hydrogen is a versatile carrier widely used in chemical engineering, construction, transportation, and power generation [1]. Currently, 96% of hydrogen production relies on fossil fuels, such as steam methane reforming and coal gasification, leading to substantial carbon emissions [1,2]. To address the concerns of energy scarcity and environmental degradation, the search for clean and sustainable energy alternatives to fossil fuels has become increasingly urgent. Governments and academic communities are increasingly focused on developing sustainable hydrogen production methods. Among these, water electrolysis (WE) driven by renewable electricity (e.g., solar, wind, and hydro energy) has emerged as a promising alternative [3]. Water electrolysis consists of the hydrogen evolution reaction (HER, the cathodic half-reaction) and the OER (the anodic half-reaction) [4,5]. Many studies have focused on hydrogen production from freshwater resources [6,7,8,9,10] (Figure 1a). However, given the scarcity of fresh water and the abundance of seawater, which constitutes 96.5% of Earth’s water resources, seawater electrolysis has garnered increasing attention in recent years [11,12,13,14] (Figure 1b). Nevertheless, the high concentration of chloride ions (19,000 mg/L–21,000 mg/L) [15] in seawater poses significant challenges to hydrogen production technologies. Theoretically, the theoretical potential of CER is 1.36 V (vs. RHE), while that of OER is 1.23 V (vs. RHE) [16,17]. Although OER is thermodynamically more favorable than CER, CER has a kinetic advantage due to its two-electron process compared to the sluggish four-electron process of OER [18,19]. Under high current densities, CER and OER can easily compete, with only a 480 mV difference (Figure 2a), diminishing the thermodynamic advantage of OER and reducing the efficiency and stability of electrolysis [20]. Competing reactions can produce by-products (e.g., Cl2 and ClO−) with negative environmental impacts [21]. Chloride ions can also react with anode materials to form corrosive by-products (e.g., Cl2 and ClO−), which attack the catalyst lattice atoms and cause catalyst degradation and electrode corrosion [21].
To address the challenges posed by CER, several strategies have been proposed in previous studies: (1) Constructing chloride ion barriers [22]. For example, Vos et al. developed MnOx/IrOx composite catalysts in which the non-catalytic MnOx coating effectively blocks chloride ion diffusion to the underlying IrOx surface, thereby minimizing chloride ion contact with the catalyst. (2) Optimizing the electrolysis system design [20]. Veroneau et al. [23] developed a single device that integrates water purification and water splitting using a forward osmosis membrane. The semipermeable membrane selectively rejects ions during the forward osmosis process, preventing anions and cations from seawater from entering the water electrolysis chamber [23]. (3) Adding electrolyte additives [24]. Some anions, (e.g., sulfate ions) preferentially adsorb onto the anode surface, forming a negatively charged layer that repels chloride ions and significantly reduces chloride-induced corrosion. (4) Using the principle of vapor pressure difference [11]. Xie et al. [11] introduced an innovative phase-change migration mechanism to address chloride oxidation and corrosion at the anode. (5) Constructing Lewis acid layers [12]. Guo et al. [12] introduced a Cr2O3 layer on the catalyst surface to capture OH− ions, thereby inhibiting chloride oxidation/corrosion and achieving efficient, stable direct seawater electrolysis for hydrogen production. (6) Constructing buffer pairs [25]. Zhuang et al. [25] introduced lattice chloride ions as structural buffers to enhance OER selectivity and reduce chlorine gas formation. Despite this progress, few studies can fundamentally eliminate the occurrence of CER and catalyst corrosion.
Recent studies have explored an alternative strategy for hydrogen production using freshwater as a reactant, namely OER-substituted water electrolysis that has a lower thermodynamic voltage [3,26,27,28,29,30]. Inspired by this, researchers have proposed utilizing the electrooxidation of other molecules in seawater to replace OER and CER [3,21,31] (Figure 1c). In spite of the increasing reports in this field, there is still not a timely summarization on alternative anodic oxidation processes in seawater. The advantage of this alternative is that these molecular oxidation reactions proceed at lower thermodynamic potentials (Figure 2b), reducing energy consumption for hydrogen production, avoiding CER and corrosion, and improving electrolysis efficiency and stability. Additionally, valuable chemical products (e.g., formic acid, acetone, and 2,5-furan-dicarboxylic acid) rather than low-value oxygen can be generated at the anode, potentially improving the economic viability of the whole electrolysis system.
Herein, we review and summarize the relevant studies conducted in seawater media over the past few years (Table 1). Table 1 compares performance parameters under different anodizing reactions, summarizing the key parameters (e.g., reactants, catalysts, electrolytes, cell voltages, current densities, and main products). The field of organic coupling with seawater-assisted hydrogen production is still in its nascent stage, with limited publications available. Consequently, most studies are categorized primarily by reaction type. In this review, we classify anodic oxidation reactions into three categories based on application methods: the oxidation of organic small molecules (e.g., methanol), biomass oxidation (e.g., 5-hydroxymethylfurfural), and the oxidation of plastic monomers (e.g., ethylene glycol) (Figure 3). For each category, we discuss catalyst design strategies, including doping engineering and alloying engineering. These approaches can modulate the surface properties of the catalysts, optimizing the adsorption energies of intermediates on the electrocatalytic sites and enhancing water electrolysis performance. With regard to catalyst architecture, we categorize them into one-dimensional (1D) nanorods, two-dimensional (2D) nanosheets, and three-dimensional (3D) nanoflowers. These catalysts, with different dimensions and high specific surface areas, provide abundant active sites that facilitate reactant adsorption and reaction progression. The study emphasizes the principles of oxidation reactions, catalyst design, and catalytic performance. These reactions can replace OER and CER, enabling hydrogen production at the cathode and value-added product generation at the anode. This provides theoretical guidance for resource recycling and efficient, clean hydrogen production from seawater.
For clarity and ease of reference, a comprehensive list of terms and abbreviations used in this review is provided in Term List Table [Appendix A].

2. Anodic Oxidation Reaction

2.1. Oxidation of Organic Small Molecules

2.1.1. Oxidation of Methanol (MOR)

Methanol is the simplest alcohol that is widely used as a fuel in the automotive industry. Furthermore, methanol is a key precursor for chemicals such as formaldehyde and formic acid. The electrochemical oxidation of methanol to formic acid (HCOOH) has potential value in the energy and chemical industries. In the leather industry, formic acid is used for tanning and dye fixation [45]. In the rubber industry, formic acid is widely used in rubber latex processing to enhance its performance and stability [46]. Formic acid can inhibit harmful bacteria and promote lactic acid bacteria growth as a feed additive. It is also used to synthesize formate salts and pesticides, such as glyphosate [47]. In different electrolyte concentrations, methanol can be selectively oxidized to formaldehyde and then to formic acid (CH3OH + 2OH− → HCHO + 2H2O + 2e−, CH3OH + 4OH− → HCOOH + 3H2O + 4e−). Studies have shown that at low electrolyte concentrations, the reaction tends to proceed via a direct dehydrogenation pathway, forming formaldehyde. Conversely, at high electrolyte concentrations, the reaction mechanism favors further oxidation, leading to the formation of formic acid. This may be due to the more reactive environment at the electrode surface under high electrolyte concentrations, which promotes the oxidation of reaction intermediates [48]. Overall, understanding the reaction mechanisms and their influencing factors is essential for optimizing electrochemical processes, particularly in energy-related applications like hydrogen production.
Methanol electrooxidation has a low thermodynamic oxidation potential 0.103 V vs RHE) [49], making it highly promising for energy-efficient hydrogen production [50]. Several electrocatalysts have been developed to promote H2 production in seawater splitting. For example, Du et al. prepared a NiFe2O4/NF catalyst using the hydrothermal synthesis method (Figure 4a) [32]. As shown in Figure 4b, NiFe2O4 nanoparticles are uniformly deposited on the macroporous 3D nickel foam framework. The two-electrode NiFe2O4/NF || NiFe2O4/NF cell in methanol-containing seawater achieves a current density of 100 mA cm−2 at 1.74 V (Figure 4c). At a cell voltage of 2.0 V, the current density reached 700 mA cm−2 and remained stable for 6 h (Figure 4d). The addition of methanol markedly enhances the rate of hydrogen production, which is significantly higher than that without introducing methanol. (Figure 4e). These phenomena can be attributed to the synergy effect of nickel (Ni) and iron (Fe) sites in the spinel structure of NiFe2O4, which respectively activate methanol and hydroxyl groups (OH) and thus significantly enhance the overall reaction.
The three-dimensional porous foam structure provides shorter diffusion pathways for ion and mass transfer, facilitating seawater infiltration. Faiza et al. synthesized porous NiCo-loaded nickel foam (pNiCo@NF) using a combination of electro-deposition and the dynamic hydrogen bubble template (DHBT) method, enhancing methanol oxidation performance for hydrogen production in seawater (Figure 5a,b) [34]. As shown in Figure 5c, in 1 M KOH + 0.5 M NaCl, the potential required to achieve a current density of 100 mA cm−2 was 200 mV lower in the presence of 2 M methanol than that without methanol. Moreover, in seawater containing methanol, the initial oxidation potential for methanol on the pNiCo@NF catalyst (1.3 V) was lower than that on the NiFe2O4/NF catalyst (1.5 V). The pNiCo@NF electrode maintained a constant potential of 1.38 V at a current density of 50 mA cm−2 for over 70 h (Figure 5d). These improvements are attributed to the strong interfacial interactions between the electrode and electrolyte, established by the bubble template electro-deposition technique, which ensures excellent mechanical stability.
Element doping is considered an effective strategy to enhance reaction kinetics for seawater electrolysis [51]. Xiang et al. [33] introduced a solution containing platinum ions into the OV Co3O4 NS catalyst with oxygen vacancies, reducing platinum ions to metallic platinum via electrodeposition. This process established the Pt-Co3O4 NS catalyst with the nanosheet structure, enhancing its activity for methanol coupling with seawater electrolysis for hydrogen evolution (Figure 6a,b) [33]. As shown in Figure 6c, in alkaline simulated seawater, the onset potential of the Pt–Co3O4/CP electrocatalyst decreased significantly to 0.555 V at 10 mA cm−2 with the addition of 2.0 M methanol. In the presence of methanol, the Faradaic efficiency for hydrogen generation reached approximately 100% at each cell voltage (Figure 6d). At a cell voltage of 1.0 V, the current density remained stable for a 20 h test (Figure 6e). These phenomena can be attributed to the nanosheet structure of Pt-Co3O4 and its abundant nanopores, which significantly increase the catalyst’s specific surface area. This structure provides more active sites for electrochemical reactions, thereby promoting reaction kinetics. Furthermore, the uniform dispersion of Pt on Co3O4 and the intimate interfacial contact between Pt and Co3O4 nanosheets enhance the catalyst’s long-term stability during operation.

2.1.2. Oxidation Reaction of Ethanolamine

Ethanolamine is a key raw material for synthesizing detergents and emulsifiers and serves as an intermediate in the production of anti-tumor drugs and antibiotics [52]. The electrooxidation of ethanolamine produces glycine and formic acid (HOCH2CH2NH2 + 2H2O → NH2CH2COOH + 4H+ + 4e−, HOCH2CH2NH2 + 2H2O → HCOOH + 2H+ + 2e−).
Glycine serves as a flavoring agent, humectant, and pH regulator and is used in organic synthesis and polymer processing. Recent studies indicate that in saline systems, anodic electrocatalytic oxidation can remove ethanolamine pollutants, generate value-added by-products, and achieve energy-efficient hydrogen production. For example, Zhao et al. synthesized a heterogeneous Ni@Ni3S2/CNT catalyst for hydrogen generation via the electrolysis of saline water, which was prepared by the in situ growth of Ni@Ni3S2 core@shell nanoparticles within a cross-linked three-dimensional CNT network using a one-pot thermal injection method (Figure 7a) [35]. Compared to Ni@Ni3S2m/CNTs, Ni@Ni3S2, and CNTs, the Ni@Ni3S2/CNT catalyst demonstrated superior electrocatalytic activity (Figure 7b). Ethanolamine has a lower oxidation potential than the OER and CER. In a sodium chloride solution containing ethanolamine, its oxidation can replace the OER/CER, thereby inhibiting CER and preventing the formation of corrosive chlorinated oxides. In the presence of ethanolamine, the energy required to produce the same amount of hydrogen gas (e.g., 1 mmol H2) is significantly reduced [35]. As shown in Figure 7c, in a 0.5 M ethanolamine-containing electrolyte, a potential of 1.63 V was required to achieve a current density of 10 mA cm−2, higher than that without ethanolamine. Chronopotentiometry (CP) measurements showed that ethanolamine oxidation could be stably sustained for 20 h at current densities of 10 mA cm−2, 50 mA cm−2, and 100 mA cm−2 (Figure 7d). However, in the absence of ethanolamine, the activity of the catalyst continuously decreases. The excellent performance is attributed to Ni@Ni3S2 nanocrystals with the core–shell structure that was closely attached to CNTs, which would be favorable for rapid electron transport. Ni@Ni3S2 nanocrystals are uniformly dispersed within the carbon nanotube (CNT) network. The CNT network prevents the aggregation of nanocrystals, thereby enhancing the stability of the catalyst [53,54].

2.1.3. Isopropanol Oxidation Reaction (IPAOR)

Isopropanol (IPA) is an excellent solvent that is widely used in the pharmaceutical industry as a solvent and additive [55]. Isopropanol can be oxidized to acetone (CH3CH(OH)CH3 + 2OH− → CH3COCH3 + 2H2O + 2e−), a higher-value compound that can be used to dissolve plastics, fibers, and resins, and as a precursor for synthesizing methyl methacrylate and bisphenol A.
Isopropanol exhibits a relatively low oxidation potential (0.1–0.8 vs. RHE) [56]. Studies have shown that among Rh, Pt, Pd, and Au, only Pd is active in the oxidation of isopropanol to acetone in acidic electrolytes. In alkaline media, the C−C bond of isopropanol remains intact on the catalyst surface at lower potentials, leading to highly selective acetone formation without CO2 production [56]. However, at elevated temperatures, acetone selectivity decreases while CO2 selectivity increases [57]. By replacing the OER and CER with isopropanol oxidation, energy-saving hydrogen production is achieved in seawater. For example, Liu et al. prepared thin PdIr bimetallic nanorods (PdIr BNRs) with rich defects via a one-pot wet chemical strategy (Figure 8a,b) [36]. Similar defect-rich catalysts have also been shown to be effective for hydrogen production in numerous studies [58,59,60]. Compared to other catalysts (such as RuO2 or Pt/C), the prepared PdIr BNRs catalysts with a high density of defects can provide a larger active surface area, thereby enhancing the electrocatalytic performance of isopropanol oxidation in seawater or potassium hydroxide solution (Figure 8c). Moreover, the introduction of the metal iridium optimizes the electronic structure of the palladium surface, facilitating the desorption of hydrogen and the release of active sites, which enables the catalyst to achieve efficient hydrogen evolution at a lower applied voltage (Figure 8c). As shown in Figure 8d, the system achieved a current density of 10 mA cm−2 at 0.38 V in 1 M KOH with 1 M isopropanol. The overpotential required by the dual-electrode system composed of PdIr BNRs is significantly lower than that of RuO|| Pt/C under a current density of 10 mA cm−2. The current density of PdIr BNRs remained stable during the 15 h test, both with and without seawater (Figure 8e).

2.2. Oxidation of Biomass

2.2.1. Oxidation of 5-Hydroxymethylfurfural (HMF)

The substance 5-Hydroxymethylfurfural (HMF) is an important biomass-derived platform compound [61]. It is used as a food additive and flavoring agent in candies and beverages. However, the application scope of HMF itself is relatively limited. Its primary value lies in its transformation into other chemicals as an intermediate. For example, HMF can be oxidized to 2,5-furan-dicarboxylic acid (FDCA), an important monomer for synthesizing bio-based polyesters and producing biodegradable polyester fibers and plastics [62,63]. Apart from FDCA, other intermediate oxidation products, such as 5-hydroxymethyl-2-furoic acid (HMFCA), 2,5-furan-dialdehyde (DFF), and 5-formyl-2-furoic acid (FFCA), can also be obtained via HMF electrooxidation (Figure 9a).
HMF electrooxidation has been extensively reported in freshwater splitting to produce value-added FDCA coupled with H2 production [64,65,66,67,68], but the studies of HMF electrooxidation in seawater are still in their infancy stage. Lin et al. prepared a FeCoNi-S@NF catalyst with 3D nanoflower structures using a simple solution impregnation and hydrothermal method (Figure 9b) [37]. The FeCoNi-S@NF catalyst achieved a current density of 44.4 mA cm−2 at 1.45 V and outperformed the CoS@NF, FeCo-S@NF, and CoNi-S@NF catalysts (Figure 9c). In 1 M KOH, FeCoNi-S@NF achieved a current density of 10 mA cm−2 at 1.38 V. At the same time, the addition of HMF lowers the oxidation potential, thereby enabling energy-efficient hydrogen production (Figure 9d). At an applied potential of 1.45 V, the HMF conversion rate reached 95.68%, and the FDCA yield of 94.83% (Figure 9e). At a current density of 10 mA cm−2 in 1.0 M KOH, the overpotential required in simulated seawater was 234 mV, significantly lower than that (296 mV) required in alkaline water (Figure 9f).
To further improve the catalytic performance of HMF-coupled seawater hydrogen production, Guo et al. synthesized a heterostructure CuO@NiCo-LDH catalyst consisting of copper oxide nanowires and nickel–cobalt layered double hydroxide nanosheets via impregnation and electrodeposition (Figure 10a) [38]. As shown in Figure 10b, CuO@NiCo-LDH exhibited superior performance compared to other catalysts, achieving a current density of 100 mA cm−2 at a potential of only 1.37 V under the same conditions. Under 1.0 M KOH conditions with 50 mM HMF present, CuO@NiCo-LDH achieved a current density of 30 mA cm−2 at a potential of only 1.30 V (Figure 10c). In alkaline seawater, the yield of FDCA remained approximately 70% after five consecutive cycles at a potential of 1.4 V (Figure 10d). The CuO@NiCo-LDH catalyst with a core–shell structure increases the number of active sites and facilitates electron transfer through its layered structure. Additionally, the heterostructure formed at the interface between CuO and NiCo-LDH regulates electron distribution and transfer, thereby enhancing the electrochemical performance of the catalyst.

2.2.2. Oxidation Reaction of Glycerol (GOR)

Glycerol is a low-cost by-product of biodiesel production. Through electrooxidation [69], glycerol can be converted into value-added chemicals, such as formic acid (C3H8O3 + 8OH−→ 3HCOOH + 5H2O + 8e−) [70]. High-entropy alloys refer to alloys composed of five or more elements, with each element present in relatively high concentrations (5–35 at%) [71,72]. Recent studies have shown that high-entropy alloy catalysts can significantly enhance the electrocatalytic activity for hydrogen evolution in seawater electrolysis [73,74,75], especially in biomass-coupled seawater systems. For example, Song et al. successfully synthesized a FeCoNiCuP high-entropy alloy with an ultrathin, corrugated nanosheet array structure on a carbon cloth substrate via electrochemical deposition (Figure 11a) [39]. This alloy was employed for hydrogen production and the generation of value-added formate. The GOR-coupled electrolyzer (Figure 11b) using FeCoNiCuP HEANAs/CC as both cathode and anode exhibits almost unchanged activity in the presence of simulated/real seawater (Figure 11c). As illustrated in Figure 11d, the electrolyzer only requires a voltage of 1.54 V to achieve current densities of 60 mA cm−2. At 1.40 V, the FE of formic acid remains stable at around 80% (Figure 11e). The system can operate stably for 10 h at 1.40 V (Figure 11f). This is attributed to the FeCoNiCuP HEANAs catalyst ultrathin structure, which has a large specific surface area and provides more active sites and enhanced electrical conductivity. The synergistic effects of the multi-element composition of the catalyst optimize its electronic structure, thereby enhancing its electrocatalytic activity.
Element doping is also used to produce hydrogen by oxidation in a glycerol-coupled seawater system. It is considered an effective strategy to modulate electron density and thus enhance reaction kinetics for seawater electrolysis [76,77]. The metal dopants can regulate the bonding energy of OH intermediates (*OH) and H intermediates (*H), accelerate charge transfer, and enhance electrocatalytic performance [78,79,80]. For instance, Deng et al. prepared a Ru-doped Ru-CoP2 catalyst via the hydrothermal method (Figure 12a) [40]. in 1.0 M KOH + 0.1 M glycerol solution. This catalyst exhibits superior catalytic activity compared to several others (Figure 12b). In the presence of 0.1 M glycerol, a-Ru-CoP2 shows a relatively low glycerol oxidation reaction (GOR) potential of 1.27 V to reach current densities of 100 mA cm−2 (Figure 12c). Coupling glycerol with alkaline natural seawater required a voltage of 1.43 V to achieve a current density of 100 mA cm−2 (Figure 12d). In 0.1 M glycerol-containing alkaline seawater, the system maintained in stable operation for 50 h (Figure 12e). The excellent performance of the Ru-CoP2 catalyst is attributed to Ru doping, which triggered a deep structural reconstruction of CoP2. This reconstruction increased the number of active sites on the catalyst surface and optimized its electronic structure. Additionally, Ru-CoOOH has stronger adsorption energies for both OH* and CH2OHCHOHCH2OH* than CoOOH, which is conducive to the initial adsorption and activation of glycerol.

2.2.3. Xylose Oxidation Reaction (XOR)

Xylose is a major component of hemicellulose and is particularly abundant in agricultural by-products such as corn cobs and sugarcane bagasse. Despite its low value as a raw material, xylose can be selectively oxidized to produce a highly valuable product formic acid (C5H10O5 + 5H2O → 5HCOOH + 20H+ + 20e−).
Yang et al. prepared a nanorod NiCoP catalyst by the hydrothermal method (in Figure 13a) [81]. Compared to other catalysts, the NiCoP catalyst exhibited lower potential and higher current density in 1.0 M KOH electrolyte (Figure 13b). As shown in Figure 13c, in the presence and absence of xylose, NiCoP required the overpotentials of the catalyst to be 1.57 and 1.86 to achieve a current density of 100 mA cm−2, respectively. Using 1.0 M KOH seawater as the electrolyte and NiCoP as the bifunctional electrode, the hydrogen production rate in the presence of xylose is higher than that in the absence of xylose (Figure 13d). The formic acid (FA) selectivity was retained as high as 94.6% (Figure 13e). The excellent performance of the NiCoP catalyst is attributed to its nanorod array structure, which provides a large surface area and abundant active sites, facilitating reactant adsorption and reaction progress.

2.3. Oxidation Reactions of Plastics

Polyethylene terephthalate (PET) is a widely used plastic material, the waste of which can be repurposed through chemical recycling methods [82]. Under alkaline conditions, PET can be hydrolyzed into ethylene glycol (EG) [82]. The electrochemical oxidation of PET-derived EG in seawater produces glycolic acid, a monomer for biodegradable plastics [83].
The dimensional regulation of catalysts, including 0D single atoms [84,85,86], 1D nanorods [87,88,89], 2D nanosheets [90,91], and 3D frameworks [92], has been reported to enhance seawater electrolysis activity for HER. Liu et al. developed a Pd-CuCo2O4 catalyst with a 1D nanorod structure using the hydrothermal method (Figure 14a) [44]. This catalyst enabled chlorine-free hydrogen production and glycolic acid (GA) generation at low voltages (Figure 14b). In an integrated seawater electrolyzer (ISE), a current density of 200 mA cm−2 was achieved at a low cell voltage of 1.11 V (Figure 14b,c). Under industrial-scale current conditions, the system demonstrated stable electrolysis for over 100 h in both alkaline simulated seawater (ASS) and natural seawater electrolytes (Figure 14d). Between the potentials of 0.7 and 1.1 V vs. RHE, the Faradaic efficiency of glycolic acid increases with the increase in potential, reaching a maximum Faradaic efficiency of 96.1% at 0.9 V. Under this potential condition, the yield of glycolic acid reaches as high as 90.2% [44]. The excellent performance of the Pd-CuCo2O4 catalyst is attributed to the CuCo2O4 effectively mitigating Pd poisoning by CO. The downward shift of the d-band center in Pd-CuCo2O4 weakens the Pd’s adsorption capacity for reaction intermediates, accelerating product desorption (e.g., glycolic acid). Additionally, CuCo2O4 nanorods grown on nickel foam provide a large specific surface area, facilitating reactant adsorption and product desorption. Scaling up this process to an industrial level requires high current densities to enhance production efficiency, yet this can exacerbate side reactions. For instance, during ethylene glycol oxidation, high current densities may trigger OER, which not only reduce product selectivity but also degrade the catalyst. Moreover, efficient separation techniques are needed to isolate the product, glycolic acid, from the electrolyte.
Mao et al. prepared a hydroxylated Rh/RhOOH metallene catalyst with a 2D ultrathin nanosheet structure via the hydrothermal method (Figure 15a) [41]. The Rh/RhOOH metallene achieves a current density of 10 mA/cm2 at a low cell voltage of 0.678 V, significantly lower than the 1.548 V required for traditional water splitting (HER-OER) (Figure 15b). The Rh/RhOOH metallene catalyst exhibits excellent electrolytic performance in KOH + EG solution, with or without the addition of seawater (Figure 15c). As shown in Figure 15d, in 1 M KOH + 6 M EG + seawater solution, stable operation is maintained for 20 h. At a current density of 20 mA/cm2, the experimentally produced H2 volume approaches the theoretical value. Similarly, Patil et al. prepared the 2D-CoFe@OF/NF catalyst via the hydrothermal method (Figure 16a) [43]. The 2D-CoFe@OF/NF electrode achieved the current density of 10 mA cm−2 at 1.42 V in a 1.0 M KOH alkaline seawater electrolyte containing 0.5 M EG (Figure 16b). When 0.5 M EG was added to the 2.0 M KOH seawater electrolyte, the CoFe@OF/NF anode exhibited high durability after 50 h of electrolysis at current densities of 10 mA cm−2 and 100 mA cm−2 (Figure 16c). The Faradaic efficiency for hydrogen evolution was nearly 100% at 150 mA cm−2 (Figure 16d). The excellent performance of the Rh/RhOOH catalyst and CoFe@OF/NF catalyst is primarily attributed to their 2D nanosheet structure and the lattice vacancies of Rh/RhOOH metallene, which offer a high specific surface area and provide more active sites, accelerate the surface charge transfer, and facilitate mass diffusion. The introduction of fluoride significantly enhanced the charge transfer characteristics of the 2D-CoFe@OF/NF catalyst.
Additionally, Zhang et al. synthesized A-CoFeNi and Pt-CoFeNi catalysts with 3D structures using a one-pot simulated seawater corrosion technology (Figure 17a) [42]. They employed A-CoFeNi and Pt-CoFeNi as the electrode system and achieved current densities of 10 mA cm−2 at 1.38 V and 100 mA cm−2 at 1.56 V in a 1 M KOH + 0.3 M EG seawater electrolyte (Figure 17b). Additionally, the formate value-added product was continuously obtained with a Faradaic efficiency (FE) ranging from 90.2% to 80.3% (Figure 17c). The Faraday efficiency for hydrogen evolution reaches nearly 100% (Figure 17d). The excellent performance of the catalysts in this system can be attributed to the unique 3D nanoflower-like structure of the A-CoFeNi catalyst, which provides a large number of active sites that facilitate reactant adsorption and reaction progress. Synergistic interactions among these metals contribute to the performance. For instance, Fe significantly enhances the charge transfer capability of the catalyst, while Co plays a crucial role in the ethylene glycol oxidation reaction (EGOR).

3. Conclusions and Outlook

This review summarizes recent advances in electrooxidation-assisted hydrogen production from seawater, focusing on the principles, catalyst design, and performance of various anodic oxidation reactions, including the oxidation of organic small molecules, biomass, and plastics. These oxidation reactions proceed at lower potentials, reducing the energy consumption of seawater electrolysis for hydrogen production and generating high-value-added chemicals (e.g., 2,5-furan-dicarboxylic acid), thereby achieving efficient energy and resource utilization. The electrochemical characteristics of these oxidation reactions, the relationship between catalyst structure and activity, and their stability in seawater environments were analyzed. This approach not only avoids CER but also underscores the importance of the catalyst design, with the structure and composition of catalysts being decisive for anodic oxidation reaction performance. For example, structures such as core–shell, porous nanosheets, nanorod arrays, and high-entropy alloys can provide abundant active sites, enhance electron transfer efficiency, and optimize the adsorption and desorption of reaction intermediates, thereby improving seawater hydrogen production efficiency. Alternative oxidation reactions can partially prevent chlorine evolution and the subsequent catalyst corrosion caused by chlorinated oxides. However, under high industrial current densities, competition between these reactions reduces electrolysis efficiency. Additionally, the presence of multiple oxidation products complicates the separation and purification of the main product. To surmount these challenges and facilitate the large-scale industrial implementation of seawater electrolysis, future research directions may encompass the following: (1) The development of highly efficient catalysts. For instance, constructing catalysts that feature a Lewis acid layer and a protective layer capable of promoting the adsorption of substrate while utilizing electrostatic effects to repel chloride ions, thereby enhancing the activity of the anodic oxidation reaction and the stability of the catalyst. (2) The separation and purification of products. The separation and purification could exploit the differences in physical properties (such as boiling points) between the target product and other components in the post-reaction mixture. Future research should consider the efficiency, cost, and feasibility of a large-scale application of the separation methods. (3) Operation at industrial current densities. While significant research has been conducted on H-cells, studies on flow cells under high industrial current densities are still limited.
Density functional theory (DFT) calculations elucidated the interaction mechanisms between active sites and reaction intermediates to guide the accurate design of the well-defined catalyst, while the integration of theoretical calculations, experimental research, and industrial applications will further accelerate the advancement of anode oxidation reaction (AOR)-assisted seawater hydrogen production technologies.
In summary, organic matter-coupled seawater oxidation for assisted hydrogen production is of significant research significance, and its broad application prospects—with the continuous optimization of catalyst design and reaction systems enabling efficient and clean hydrogen production—offer novel solutions to address global energy demands.

Funding

This work is supported by the National Natural Science Foundation of China (grant No. 22402135), Chengdu Science and Technology Bureau (grant No. 2024-YF05-00689-SN), and the Natural Science Foundation of Sichuan Province (grant No. 2025ZNSFSC0896).

Conflicts of Interest

Jing Li serves as the Guest Editor of this special issue. The peer-review process was managed independently by another editor to ensure objectivity. No other competing interests are reported.

Appendix A

Term List Table
Molecular Formula/Structural FormulaFull Name of the SubstanceAcronym
—oxygen evolution reactionOER
—chlorine evolution reactionCER
—anodic oxidation reactionsAOR
—hydrogen evolution reactionHER
—water electrolysisWE
CH3OHmethanolMeOH
—oxidation of methanolMOR
HCOOHformic acidFA
—dynamic hydrogen bubble templateDHBT
—nanosheetNS
HOCH2CH2NH2ethanolamineETA
—the carbon nanotubeCNT
—chronopotentiometryCP
CH3CH(OH)CH3isopropanolIPA
—isopropanol oxidation reactionIPAOR
—PdIr bimetallic nanorodsPdIr BNRs
C6H6O35-hydroxymethylfurfuralHMF
C6H6O45-hydroxymethyl-2-furoic acidHMFCA
C6H4O32,5-furan-dialdehydeDFF
C6H4O45-formyl-2-furoic acidFFCA
C6H4O52,5-furan-dicarboxylic acidFDCA
CH2OHCHOHCH2OHglycerolGly
—oxidation reaction of glycerolGOR
—high-entropy alloy nanoparticlesHEANAs
—glycerol-coupled electrolysisGOE
C5H10O5xyloseXyl
—xylose oxidation reactionXOR
CH3CH(OH)COOHlactic acidLA
CH3COOHacetic acidAA
(CH8O4)npolyethylene terephthalatePET
HOCH2CH2OHethylene glycolEG
—ethylene glycol oxidation reactionEGOR
HOCH2COOHglycolic acidGA
—nickel FoamNF
—integrated seawater electrolyzerISE
—faradaic efficiencyFE
—density functional theoryDFT

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Figure 1. Schematic models of different electrolysis systems. (a) Traditional freshwater electrolysis. (b) Traditional seawater electrolysis. (c) Value-added electrooxidation reaction assisted seawater electrolysis.
Figure 1. Schematic models of different electrolysis systems. (a) Traditional freshwater electrolysis. (b) Traditional seawater electrolysis. (c) Value-added electrooxidation reaction assisted seawater electrolysis.
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Figure 2. (a) Pourbaix diagram of redox couples for OER and chlorine chemistry in saline electrolytes, including H2O/O2 and Cl−/Cl2/HOCl/ClO− [17]. (b) Comparison of CER, OER, and OER-substituted seawater splitting.
Figure 2. (a) Pourbaix diagram of redox couples for OER and chlorine chemistry in saline electrolytes, including H2O/O2 and Cl−/Cl2/HOCl/ClO− [17]. (b) Comparison of CER, OER, and OER-substituted seawater splitting.
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Figure 3. Various molecules are used for electrooxidation in seawater electrolysis for hydrogen production.
Figure 3. Various molecules are used for electrooxidation in seawater electrolysis for hydrogen production.
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Figure 4. NiFe2O4/NF catalyst for methanal-assisted seawater electrolysis [32]. (a) Schematic illustration of the synthesis of the NiFe2O4/NF catalyst. (b) Scanning electron microscopy (SEM) images of NiFe2O4/NF. (c) Polarization curves of NiFe2O4/NF for hydrogen evolution reaction—selective methanol oxidation reaction (HER-SMOR) electrolysis in seawater. (d) Chronoamperometric curves at 2.0 V. (e) Comparison of H2 and O2 production rates for HER-SMOR and HER-OER at 2.0 V.
Figure 4. NiFe2O4/NF catalyst for methanal-assisted seawater electrolysis [32]. (a) Schematic illustration of the synthesis of the NiFe2O4/NF catalyst. (b) Scanning electron microscopy (SEM) images of NiFe2O4/NF. (c) Polarization curves of NiFe2O4/NF for hydrogen evolution reaction—selective methanol oxidation reaction (HER-SMOR) electrolysis in seawater. (d) Chronoamperometric curves at 2.0 V. (e) Comparison of H2 and O2 production rates for HER-SMOR and HER-OER at 2.0 V.
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Figure 5. Three-dimensional porous pNiCo@NF catalyst [34]. (a) Schematic illustration of the synthesis of pNiCo@NF electrocatalyst using the DHBT method. (b) Scanning electron microscopy (SEM) image of pNiCo@NF. (c) Linear sweep voltammograms (LSVs) under different conditions. (d) Chronopotentiometric experiment at a current density of 50 mA cm−2.
Figure 5. Three-dimensional porous pNiCo@NF catalyst [34]. (a) Schematic illustration of the synthesis of pNiCo@NF electrocatalyst using the DHBT method. (b) Scanning electron microscopy (SEM) image of pNiCo@NF. (c) Linear sweep voltammograms (LSVs) under different conditions. (d) Chronopotentiometric experiment at a current density of 50 mA cm−2.
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Figure 6. Pt-Co3O4 nanosheet (NS) catalyst for methanol-coupled seawater hydrogen production [33]. (a) SEM images of Pt–Co3O4/CP. (b) Schematic illustration of the preparation of Pt-Co3O4 catalyst assisted by oxygen vacancies. (c) Linear sweep voltammograms (LSV) of the Pt-Co3O4/CP catalyst in alkaline simulated seawater with and without the addition of 2.0 M methanol. (d) Faradaic efficiency of hydrogen gas at different cell voltages with and without the addition of 2.0 M methanol. (e) Stability test of the Pt-Co3O4/CP catalyst for electrocatalytic hydrogen evolution reaction (HER) coupled with methanol oxidation at 1.0 V.
Figure 6. Pt-Co3O4 nanosheet (NS) catalyst for methanol-coupled seawater hydrogen production [33]. (a) SEM images of Pt–Co3O4/CP. (b) Schematic illustration of the preparation of Pt-Co3O4 catalyst assisted by oxygen vacancies. (c) Linear sweep voltammograms (LSV) of the Pt-Co3O4/CP catalyst in alkaline simulated seawater with and without the addition of 2.0 M methanol. (d) Faradaic efficiency of hydrogen gas at different cell voltages with and without the addition of 2.0 M methanol. (e) Stability test of the Pt-Co3O4/CP catalyst for electrocatalytic hydrogen evolution reaction (HER) coupled with methanol oxidation at 1.0 V.
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Figure 7. Ni@Ni3S2/CNTs catalyst with nano-heterostructure for the electrocatalytic removal of ethanolamine pollutant via electrooxidation in saline water [35]. (a) TEM image of Ni@Ni3S2/CNTs nano-heterostructured electrode. (b) LSV curves of different catalysts in 1.0 M saline solution + 0.5 M ethanolamine electrolyte. (c) LSV curves of Ni@Ni3S2/CNTs in saline electrolyte with and without ethanolamine. (d) Chronopotentiometry (CP) curves for ethanolamine electrooxidation at different current densities.
Figure 7. Ni@Ni3S2/CNTs catalyst with nano-heterostructure for the electrocatalytic removal of ethanolamine pollutant via electrooxidation in saline water [35]. (a) TEM image of Ni@Ni3S2/CNTs nano-heterostructured electrode. (b) LSV curves of different catalysts in 1.0 M saline solution + 0.5 M ethanolamine electrolyte. (c) LSV curves of Ni@Ni3S2/CNTs in saline electrolyte with and without ethanolamine. (d) Chronopotentiometry (CP) curves for ethanolamine electrooxidation at different current densities.
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Figure 8. PdIr bimetallene nanoribbons (PdIr BNRs) catalyst [36]. (a) Schematic illustration of the preparation of the PdI BNRs catalyst. (b) Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM) of PdIr BNRs. (c) LSV curves of different catalysts in 1 M KOH + 1 M isopropanol. (d) LSV curves of various catalysts in 1 M KOH + 1M isopropanol in a two-electrode system. (e) Chronopotentiometric curves at a constant current density of 10 mA cm−2.
Figure 8. PdIr bimetallene nanoribbons (PdIr BNRs) catalyst [36]. (a) Schematic illustration of the preparation of the PdI BNRs catalyst. (b) Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM) of PdIr BNRs. (c) LSV curves of different catalysts in 1 M KOH + 1 M isopropanol. (d) LSV curves of various catalysts in 1 M KOH + 1M isopropanol in a two-electrode system. (e) Chronopotentiometric curves at a constant current density of 10 mA cm−2.
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Figure 9. HMF electrooxidation in seawater using the FeCoNi-S@NF catalyst [37]. (a) The reaction pathway of HMF oxidation. (b) Schematic of the synthesis process of the FeCoNi-S@NF catalyst. (c) The current density of different catalysts at 1.45 V. (d) LSV curves of the FeCoNi-S@NF catalyst with and without the addition of HMF. (e) HMF conversion rate, FDCA yield, and Faradaic efficiency of FDCA for the FeCoNi-S@NF electrode at different potentials. (f) Overpotential of FeCoNi-S@NF at 10 mA cm−2 and 50 mA cm−2 under different electrolytes.
Figure 9. HMF electrooxidation in seawater using the FeCoNi-S@NF catalyst [37]. (a) The reaction pathway of HMF oxidation. (b) Schematic of the synthesis process of the FeCoNi-S@NF catalyst. (c) The current density of different catalysts at 1.45 V. (d) LSV curves of the FeCoNi-S@NF catalyst with and without the addition of HMF. (e) HMF conversion rate, FDCA yield, and Faradaic efficiency of FDCA for the FeCoNi-S@NF electrode at different potentials. (f) Overpotential of FeCoNi-S@NF at 10 mA cm−2 and 50 mA cm−2 under different electrolytes.
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Figure 10. HMF electrooxidation in seawater using a CuO@NiCo-LDH heterostructure catalyst [38]. (a) Schematic illustration of the synthesis of the CuO@NiCo-LDH catalyst. (b) LSV curves of CuO@NiCo-LDH, CuO, NF@NiCo-LDH, and CF catalysts. (c) LSV curves of CuO@NiCo-LDH with and without 50 mM HMF in 1.0 M KOH electrolyte. (d) Yield of FDCA and Faradaic efficiency during five consecutive cycles of HMFOR in alkaline seawater.
Figure 10. HMF electrooxidation in seawater using a CuO@NiCo-LDH heterostructure catalyst [38]. (a) Schematic illustration of the synthesis of the CuO@NiCo-LDH catalyst. (b) LSV curves of CuO@NiCo-LDH, CuO, NF@NiCo-LDH, and CF catalysts. (c) LSV curves of CuO@NiCo-LDH with and without 50 mM HMF in 1.0 M KOH electrolyte. (d) Yield of FDCA and Faradaic efficiency during five consecutive cycles of HMFOR in alkaline seawater.
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Figure 11. Glycerol electrooxidation over the FeCoNiCuP HEANAs/CC catalyst in seawater [39]. (a) Schematic illustration of the synthesis of FeCoNiCuP high-entropy alloy nanoparticles (HEANAs) catalyst. (b) Schematic diagram of the GOR (glycerol oxidation reaction)-coupled electrolysis cell. (c) Polarization curves of GOR in real seawater and simulated seawater. (d) Voltage profiles of glycerol-coupled electrolysis (GOE-HER) and traditional electrolysis (OER-HER) under different current densities. (e) Faradaic efficiency (FE) of formate production during five consecutive cycles of electrolysis at 1.40 V in 1.0 M KOH and 0.1 M glycerol. (f) Chronopotentiometric curve of the GOR-coupled electrolysis cell at a current density of 10 mA cm−2.
Figure 11. Glycerol electrooxidation over the FeCoNiCuP HEANAs/CC catalyst in seawater [39]. (a) Schematic illustration of the synthesis of FeCoNiCuP high-entropy alloy nanoparticles (HEANAs) catalyst. (b) Schematic diagram of the GOR (glycerol oxidation reaction)-coupled electrolysis cell. (c) Polarization curves of GOR in real seawater and simulated seawater. (d) Voltage profiles of glycerol-coupled electrolysis (GOE-HER) and traditional electrolysis (OER-HER) under different current densities. (e) Faradaic efficiency (FE) of formate production during five consecutive cycles of electrolysis at 1.40 V in 1.0 M KOH and 0.1 M glycerol. (f) Chronopotentiometric curve of the GOR-coupled electrolysis cell at a current density of 10 mA cm−2.
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Figure 12. Glycerol electrooxidation over Ru-CoP2 catalyst in seawater [40]. (a) Schematic illustration of the preparation of Ru-doped CoP2 catalyst. (b) Linear sweep voltammograms (LSV) of different catalysts in 1.0 M KOH + 0.1 M glycerol solution. (c) Comparison of LSV curves in 1.0 M KOH with and without 0.1 M glycerol. (d) Potential values correspond to different electrolytes at various current densities. (e) Chronopotentiometric curves at a constant current density in 1 L of electrolyte solution.
Figure 12. Glycerol electrooxidation over Ru-CoP2 catalyst in seawater [40]. (a) Schematic illustration of the preparation of Ru-doped CoP2 catalyst. (b) Linear sweep voltammograms (LSV) of different catalysts in 1.0 M KOH + 0.1 M glycerol solution. (c) Comparison of LSV curves in 1.0 M KOH with and without 0.1 M glycerol. (d) Potential values correspond to different electrolytes at various current densities. (e) Chronopotentiometric curves at a constant current density in 1 L of electrolyte solution.
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Figure 13. Xylose electrooxidation over NiCoP catalyst in seawater [81]. (a) Schematic illustration of the preparation of NiCoP electrocatalyst and the corresponding SEM images of nickel foam, NiCoOH, and NiCoP samples. (b) LSV curves of different catalysts in 1.0 M KOH electrolyte. (c) LSV curves of NiCoP electrocatalyst in 1.0 M KOH seawater with and without 100 mM xylose. (d) Yield of H2 and O2 at 1.9 V with and without 100 mM xylose. (e) Selectivity tests of formic acid (FA), lactic acid (LA), and acetic acid (AA) products.
Figure 13. Xylose electrooxidation over NiCoP catalyst in seawater [81]. (a) Schematic illustration of the preparation of NiCoP electrocatalyst and the corresponding SEM images of nickel foam, NiCoOH, and NiCoP samples. (b) LSV curves of different catalysts in 1.0 M KOH electrolyte. (c) LSV curves of NiCoP electrocatalyst in 1.0 M KOH seawater with and without 100 mM xylose. (d) Yield of H2 and O2 at 1.9 V with and without 100 mM xylose. (e) Selectivity tests of formic acid (FA), lactic acid (LA), and acetic acid (AA) products.
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Figure 14. Electrooxidation of PET-derived EG over Pd–CuCo2O4 catalyst in seawater [44]. (a) Schematic illustration of the synthesis of Pd–CuCo2O4. (b) Schematic diagram of chlorine-free seawater splitting coupled with electrochemical glycerol oxidation reaction (EGOR) for the production of H2 and glyceric acid (GA) under low potential. (c) Comparison of linear sweep voltammograms (LSV) using alkaline seawater as the electrolyte. (d) Durability tests of the integrated system (ISE) in artificial seawater (ASS) and alkaline seawater at a cell voltage of 1.4 V.
Figure 14. Electrooxidation of PET-derived EG over Pd–CuCo2O4 catalyst in seawater [44]. (a) Schematic illustration of the synthesis of Pd–CuCo2O4. (b) Schematic diagram of chlorine-free seawater splitting coupled with electrochemical glycerol oxidation reaction (EGOR) for the production of H2 and glyceric acid (GA) under low potential. (c) Comparison of linear sweep voltammograms (LSV) using alkaline seawater as the electrolyte. (d) Durability tests of the integrated system (ISE) in artificial seawater (ASS) and alkaline seawater at a cell voltage of 1.4 V.
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Figure 15. Electrooxidation of PET-derived EG over Rh/RhOOH metalene catalyst [41]. (a) Schematic illustration of the synthesis process of Rh/RhOOH metalene. (b) Linear sweep voltammograms (LSV) in 1 M KOH with and without the addition of ethylene glycol (EG) solution. (c) LSV curves in 1 M KOH + 6 M EG with and without the addition of seawater. (d) Chronopotentiometric curves at a current density of 10 mA cm−2 and the theoretical and experimental values of H2 evolution over 20 h in 1 M KOH + 6 M EG + seawater solution.
Figure 15. Electrooxidation of PET-derived EG over Rh/RhOOH metalene catalyst [41]. (a) Schematic illustration of the synthesis process of Rh/RhOOH metalene. (b) Linear sweep voltammograms (LSV) in 1 M KOH with and without the addition of ethylene glycol (EG) solution. (c) LSV curves in 1 M KOH + 6 M EG with and without the addition of seawater. (d) Chronopotentiometric curves at a current density of 10 mA cm−2 and the theoretical and experimental values of H2 evolution over 20 h in 1 M KOH + 6 M EG + seawater solution.
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Figure 16. Electrooxidation of PET-derived EG over 2D-CoFe@OF/NF catalyst [43]. (a) Schematic illustration of the preparation process of 2D@CoFeOF/NF and its application in ethylene glycol oxidation. (b) Distribution of potential and current density under different electrolytes. (c) Stability testing of the electrolyzer at various current densities. (d) Faradaic efficiency of H2 at a current density of 150 mA cm−2.
Figure 16. Electrooxidation of PET-derived EG over 2D-CoFe@OF/NF catalyst [43]. (a) Schematic illustration of the preparation process of 2D@CoFeOF/NF and its application in ethylene glycol oxidation. (b) Distribution of potential and current density under different electrolytes. (c) Stability testing of the electrolyzer at various current densities. (d) Faradaic efficiency of H2 at a current density of 150 mA cm−2.
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Figure 17. Electrooxidation of PET-derived EG over A-CoFeNi and Pt-CoFeNi catalyst [42]. (a) Schematic illustration of the preparation of A-CoFeNi catalyst. (b) Linear sweep voltammetry (LSV) tests under different electrolytes and various potentials. (c) Faradaic efficiency for formic acid production. (d) Comparison between the experimental and theoretical volumes of hydrogen.
Figure 17. Electrooxidation of PET-derived EG over A-CoFeNi and Pt-CoFeNi catalyst [42]. (a) Schematic illustration of the preparation of A-CoFeNi catalyst. (b) Linear sweep voltammetry (LSV) tests under different electrolytes and various potentials. (c) Faradaic efficiency for formic acid production. (d) Comparison between the experimental and theoretical volumes of hydrogen.
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Table 1. Performance comparison of the hybrid seawater electrolysis based on the anodic oxidation reaction coupling with cathodic hydrogen production reported recently in the literature.
Table 1. Performance comparison of the hybrid seawater electrolysis based on the anodic oxidation reaction coupling with cathodic hydrogen production reported recently in the literature.
Substance ClassReactantCatalystElectrolytePotential (vs. RHE)/Cell Voltage (V)Current Density (mA cm−2)Main ProductRefs.
small organic moleculemethanolNiFe2O4/NFSeawater + methanol1.74100formate[32]
methanolPt–Co3O41.0 M NaOH + 3.5%NaCl + 2.0 Mmethanol.0.53310formate[33]
methanolPt–Co3O41.0 M NaOH + 3.5% NaCl + 2.0 M methanol.0.64750formate[33]
methanolpNiCo@NF1.0 M KOH + 0.5NaCl + 2.0 M methanol1.3850formate[34]
ethanolamineNi@Ni3S2/CNT1.0 M NaCl + 0.5M ethanolamine1.6310glycinate[35]
ethanolamineNi@Ni3S2/CNT1.0 M NaCl + 0.5M ethanolamine2.13100glycinate[35]
IsopropanolPdIr BNRsSeawater + isopropanol0.3810acetone[36]
biomassHMFFeCoNi-S@NF1 M KOH HMF + 0.5 M NaCl1.710FDCA[37]
HMFCuO@NiCo-LDH1.0 M KOH + 0.5 M NaCl + 50 Mm HMF1.4133.4FDCA[38]
glycerolFeCoNiCuP HEANAs1.0 M KOH + 0.1 M1.410formate[39]
Glycerol + 0.6NaCl
glycerolRu-CoP2seawater + 1 M glycerol1.43100formate[40]
xylose.NiCoP1.0 M KOH seawater+1.57100Formic acid[35]
100 mM xylose.
plastic monomerethylene glycolRh/RhOOH metallene1 M KOH seawater + 6 M EG0.67810glycolate[41]
ethylene glycolA-CoFeNi1 M KOH + 0.3 M EG + seawater1.3810formate[42]
ethylene glycolA-CoFeNi1 M KOH + 0.3 M EG + seawater1.56100formate[42]
ethylene glycol2DCoFe@OF/NFalkaline seawater + EG1.4210formate[43]
ethylene glycol2DCoFe@OF/NFalkaline seawater + EG1.48100formate[43]
ethylene glycolPd-CuCo2O4alkaline seawater + EG0.68100glycolate[44]
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Guo, Y.; Yang, C.; Yang, J.; Xiao, X.; Ran, M.; Li, J. Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions. Energies 2025, 18, 3016. https://doi.org/10.3390/en18123016

AMA Style

Guo Y, Yang C, Yang J, Xiao X, Ran M, Li J. Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions. Energies. 2025; 18(12):3016. https://doi.org/10.3390/en18123016

Chicago/Turabian Style

Guo, Yuanping, Chenghao Yang, Jianli Yang, Xin Xiao, Maofei Ran, and Jing Li. 2025. "Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions" Energies 18, no. 12: 3016. https://doi.org/10.3390/en18123016

APA Style

Guo, Y., Yang, C., Yang, J., Xiao, X., Ran, M., & Li, J. (2025). Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions. Energies, 18(12), 3016. https://doi.org/10.3390/en18123016

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