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Review

Recent Advances of the Electrochemical Hydrogenation of Biofuels and Chemicals from Furfural

by
Huiyi Liang
1,
Ke Liu
1,
Xinghua Zhang
1,
Qi Zhang
1,
Lungang Chen
1,
Yubao Chen
2,*,
Xiuzheng Zhuang
1,* and
Longlong Ma
1
1
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China
2
School of Energy and Environment Science, Yunnan Normal University, Kunming 650500, China
*
Authors to whom correspondence should be addressed.
Energies 2025, 18(12), 3075; https://doi.org/10.3390/en18123075
Submission received: 27 April 2025 / Revised: 26 May 2025 / Accepted: 6 June 2025 / Published: 11 June 2025
(This article belongs to the Special Issue Advances in Bioenergy and Biofuel Conversion: Designs and Optimization)
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Abstract

:
With increasing energy demand and depletion of fossil fuels, the search for renewable energy sources has become imperative. Among them, biomass energy has attracted significant attention as it is clean, renewable, and abundant. This review summarizes recent advances in the electroreduction of the biomass-derived platform compound furfural (FF) for producing high-value fuels and chemicals. First, the principles and mechanisms of electrocatalysis are introduced, followed by a detailed analysis of reaction pathways for electrocatalytic hydrogenation, hydrogenolysis, and dimerization. Subsequently, the review highlights the research progress on the electrochemical reduction of FF to hydrofuroin (HDF, a precursor for jet fuel), analyzing its reaction mechanisms and summarizing the effects of catalytic materials and reaction conditions on product selectivity and faradaic efficiency. Additionally, it provides an overview of catalyst selection for both hydrogenation and hydrogenolysis processes. Studies indicate that Cu-based catalysts exhibit superior performance in hydrogenation and hydrogenolysis, with the latter being more favorable under low pH. In contrast, metal-doped carbon catalysts demonstrate enhanced activity in dimerization reactions. Reaction conditions also significantly influence product distribution, with lower reduction potentials generally favoring dimerization. Finally, the challenges and future directions in FF electroreduction are discussed, including the need for deeper understanding of competing pathways, improved electrode stability, and scalable reactor design. The integration of electrocatalytic with renewable energy offers a green and sustainable approach for the efficient utilization of biomass-derived compounds, holding substantial research significance and application potential.

1. Introduction

With the continuous growth of the global population, the improvement of living standards, and rapid industrial development, the world’s energy demand and the consumption of energy have shown sustained increasing trends [1,2]. Currently, fossil fuels remain extensively utilized as the primary energy, accounting for approximately 80% of the global energy mix in 2022 [3]. The extensive consumption of fossil fuels not only leads to resource depletion but also causes severe environmental issues. Furthermore, the extraction and utilization of fossil fuels generate harmful gases such as sulfur oxides and nitrogen oxides, resulting in environmental problems, including acid rain and smog [4,5]. Numerous alternatives have been developed, including wind, solar, tidal, and geothermal energy [6]. However, these energies cannot provide carbon sources for producing high-value chemicals and fuels [4]. From this perspective, the further exploration of carbon-based renewable energy has become an imperative task. Biomass energy has attracted widespread attention because it is renewable and clean [7]. Biofuels are important products of biomass conversion including biodiesel, bioethanol, and bio-aviation fuels [8]. Compared to fossil fuels, biofuels offer significant environmental advantages: their full life cycle carbon footprint can be reduced by 60~90% [9,10,11,12], their combustion process pro-duces virtually no sulfur oxides or particulate matter emissions, and they possess biodegradable and carbon-neutral characteristics, enabling circular regeneration through sustainable cultivation.
Lignocellulosic biomass is a highly promising feedstock, which is recognized as the most abundant and renewable carbon-neutral organic resource (production reached approximately 62 million tons by 2022 [13]). Its primary components, cellulose (40–50%), hemicellulose (20–35%), and lignin (15–30%), can be obtained from the non-edible parts of plants as shown in Figure 1 [6]. Through hydrolysis reactions, cellulose and hemicellulose can be upgraded into various platform compounds such as levulinic acid (LA), 5-hydroxymethylfurfural (HMF), and furfural (FF), which serve as ideal feedstocks for producing chemicals and fuels [4]. Lignin, a cross-linked phenolic polymer, can be converted into a series of aromatic molecules, including phenol, guaiacol, benzaldehyde, and so on [6]. Among these derivatives, FF is a significant biomass-based compound and was designated by the U.S. Department of Energy as one of the top 30 high-value chemicals in 2004, finding extensive applications across multiple industrial productions [14].
Compared with fossil fuels, biomass and its derivatives exhibit higher oxygen content and lower energy density. Hydrodeoxygenation is required in order to better utilize these renewable resources, with thermal reduction and electrochemical reduction being the main methods currently [15]. Thermal reduction is more mature. Reactants and H2 are adsorbed and activated on catalysts, followed by reactions of the activated intermediates to form target products. However, thermal reduction demands high hydrogen pressure and temperature [1,7]. While using alcohols or acids as hydrogen sources can avoid high pressure, it still cannot avoid high temperature. In contrast, electrochemical reduction has attracted attention due to its ability to proceed under ambient conditions and use H2O as the hydrogen source, aligning with green chemistry principles. The electrochemical upgrading of biomass to biofuels or high-value chemicals primarily focuses on hydrogenation, hydrogenolysis, and dimerization [16,17,18]. Electrocatalysts for these processes are mainly based on noble metals and Cu [19,20,21,22]. Compared to metal oxides (another widely used catalyst which is cheaper), noble metals and Cu typically require lower loading amounts in electrocatalytic systems and exhibit excellent atomic utilization efficiency. In contrast, metal oxide catalysts often require high temperature and high-pressure H2 to achieve high conversion efficiency, leading to increased overall energy consumption costs. Typical modification strategies for enhancing reaction rates and improving selectivity involve tuning electronic structures and optimizing surface morphology. These include single-atom catalysts, alloys [23], multi-site catalysts [24], doped materials [25], and so on. Additionally, electrolyte pH, initial reactant concentration, applied potential, and other operational conditions can significantly influence selectivity.
In current research, Wang et al. [26] systematically summarized recent advances in the electroreduction upgrading of biomass-derived platform compounds, including LA, HMF, and FF (from cellulose and hemicellulose) and phenol, guaiacol, benzaldehyde, acetophenone, and benzoic acid (from lignin). Their work emphasized the interactions between organic substrates and electrolytes as well as the interfacial effects between organic substrates and electrocatalysts. Additionally, they reviewed some promising reactions, such as HMF ring opening, reductive amination, C-C coupling, and ring saturation. But further discussion on reaction mechanisms remains blank. By contrast, Munirathinam et al. [27] narrowed their research scope and focused on furan compounds represented by FF. They examined various catalyst materials for the electrosynthesis under acidic conditions for biofuel production, discussing the effects of noble metals (Pt, Pd, Ag) and non-noble metals (Cu, Ni, Pb) on the electrocatalytic conversion of FF. However, constrained by their research scope, the application of non-metallic materials (particularly carbon-based catalysts) was not thoroughly investigated. With the advancements in characterization techniques, mechanistic studies of FF electroreduction have become increasingly sophisticated. Yang et al. [17] reviewed current research on reaction mechanisms using in situ techniques (including infrared reflection absorption spectroscopy, Raman spectroscopy, and sum frequency generation) and theoretical calculations. Nevertheless, their discussion just focused on the formation of furfuryl alcohol and 2-methylfuran, while paying less attention to the characteristics of hydrofuroin (HDF). Previous studies have generally adopted a macroscopic perspective to systematically summarize the upgrading processes of various biomass platform molecules. However, as a high-value fuel that has recently entered research focus, HDF still faces many critical scientific questions that urgently need to be addressed, for example:
(1)
Current research primarily focuses on the selective control of furfuryl alcohol and 2-methylfuran, lacking systematic understanding of the HDF formation pathways and competitive reaction mechanisms;
(2)
The dynamic interaction mechanisms between catalyst active sites and reaction intermediates are unclear and result in the selectivity toward HDF being below 40%;
(3)
Quantitative models have not yet been established for the influence patterns of operating conditions such as electrolyte pH and applied potential on product distribution, which constrains process optimization.
In recent years, electrocatalyst design has shown two major breakthrough directions: on one hand, constructing active sites through single-atom catalysts and utilizing coordination microenvironments to regulate intermediate adsorption energy, thereby improving selectivity toward target products [28]; on the other hand, non-precious metal catalysts achieve optimization of surface adsorption behavior by adjusting interfacial water structure through crystal phase control [29].
With this background, this work summarizes recent progress in the electroreduction of FF. At first, it outlines fundamental principles of electrocatalysis and analyzes reaction pathways for electrocatalytic hydrogenation, hydrogenolysis, and dimerization. Subsequently, it focuses on the reaction mechanisms for HDF production, summarizing the effects of different catalytic and reaction conditions on selectivity and faradaic efficiency (FE). In addition, the catalyst selection for hydrogenation and hydrogenolysis processes are discussed. Finally, it shows the challenges and future development in FF electroreduction.

2. Overview of Electrocatalysis

Electroreduction proceeds through different pathways in acid and alkali solutions, but both involve the adsorption and desorption of hydrogen ions on the electrode surface, as shown in Figure 2. The first step is the Volmer reaction. Protons or water are electrochemically adsorbed onto the electrode surface to form adsorbed hydrogen (Hads). Hads can participate in the electroreduction of most organic compounds, such as hydrogenolysis and hydrogenation of aldehydes and hydrogenolysis of alcohols. However, the reaction pathway for dimerization is still under investigation. Most studies suggest that the reduction utilizes hydrogen ions (H+) from the solution rather than Hads. Generally, the hydrogen evolution reaction (HER) of water electrolysis [30] is considered a competing reaction with the electroreduction of biomass-derived platform compounds. Because it follows the Volmer reaction, the HER will proceed via the Heyrovsky or Tafel steps, consuming H+ and Hads, reducing FE, and hindering the reduction of organic substrates. Thus, efficient catalysts must suppress the Heyrovsky and Tafel reactions.
The electroreduction of aromatic carbonyl compounds like FF produces different products. The product distribution is usually related to the degree of hydrogenation, which can be divided into dimerization, hydrogenation, and hydrogenolysis. When different types of catalysts are used, the reaction process also varies accordingly, taking Cu as an example (Figure 3). When the degree of hydrogenation is relatively low, the reactant undergoes single-electron reduction via the outer-sphere mechanism. There is no adsorption of reactant on the electrode and electron transfer occurring in the solution. Two reactant radicals cross-couple after obtaining one hydrogen atom and one electron to form dimer products. As the degree of hydrogenation increases, a two-electron reduction step can occur. According to the Langmuir–Hinshelwood mechanism, the reactant forms the corresponding alcohol through a process involving reactant adsorption, diffusion to active sites on the catalyst surface, reaction at active sites to produce adsorbed products, and finally desorption of the product from the catalyst surface. The reaction rate is mainly limited by the second Hads transfer step. When the proton concentration further increases, a four-electron reduction step can take place, cleaving the C-O bond to generate the corresponding alkane. In this case, the C-O bond cleavage is the rate-determining step (RDS) of the reaction.
The competition between dimerization and hydrogenation/hydrogenolysis is essentially a dynamic equilibrium between surface adsorption and solution-phase reactions. Taking copper catalysts as an example, the stronger furan ring adsorption capacity of the (100) crystal facet favors surface-mediated hydrogenation reactions, while the lower adsorption energy of the (111) facet is more conducive to solution-phase radical coupling [31]. Furthermore, applied potential has a nonlinear effect on selectivity: when the potential is below −0.8 V vs. RHE, the strongly reducing environment leads to excessively high Hads coverage, whereas in the −0.4 to −0.6 V range, moderate Hads concentration and adsorption strength can achieve an optimal balance between dimerization and hydrogenation.

3. Research Progress in Electroreduction of Furfural

3.1. Overview of Furfural

Furfural (FF) is an organic compound that is widely used in the chemical and materials fields. It is a commonly used solvent in petroleum refining and can also be used to synthesize resins, electrical insulation materials, nylon, and coatings, as well as for pharmaceutical production and organic synthesis reactions. It can be produced through two common methods: dehydration of pentose sugars or hydrolysis of hemicellulose. Due to its reactive chemical properties, FF is not stable enough to be used directly as fuel or as a component in other high-value chemical products. Therefore, it needs to be converted into more stable and valuable products. The molecular structure of FF contains two main reactive sites: the aldehyde group and the furan ring. The aldehyde group readily undergoes hydrogen addition reactions and can be reduced to a hydroxyl group. And the furan ring contains double bonds that can undergo stepwise hydrogenation to produce partially or fully saturated cyclic structures.
The reduction products of FF are relatively simple, mainly including furfuryl alcohol (FA), hydrofuroin (HDF), 2-methylfuran (2-MF), and tetrahydrofurfuryl alcohol (THFA), as shown in Figure 4. Among these, the formation of HDF involves carbon–carbon coupling, achieving carbon chain extension and obtaining higher energy density. This makes it suitable for producing more valuable jet fuels for heavy-duty applications (such as aviation or maritime fields). The reduction of FF can be accomplished through thermochemical and electrochemical methods. Thermochemical reduction is usually conducted at medium-to-high temperatures and requires specific pressures. The use of different reduction methods leads to variations in the final product distribution. Thermal treatment typically occurs under high temperature and pressure conditions, promoting the reduction of FF to a greater extent, while electrochemical reduction can be carried out at room temperature and atmospheric pressure, making it easier to control the hydrogenation depth and making it favorable for dimer formation.

3.2. Research Progress on the Conversion of Furfural to Hydrofuroin

HDF is produced through the dimerization of FF. Due to the mild degree of hydrogenation, precise control of the reduction conditions is necessary, making conventional thermochemical reduction rarely suitable for HDF production. The development of electrochemical processes promoted related research. A literature search in Web of Science using the keywords “furfural” and “hydrofuroin/furfuryl alcohol/2-methylfuran/tetrahydrofurfuryl alcohol” reveals that studies on the reduction of FF into high-value chemicals and fuels have been increasing year by year, with product diversification becoming a trend, as shown in Figure 5. Among them, HDF is a precursor of jet fuel with high energy density, which has attracted growing attention from researchers. Current mechanistic studies on FF hydrogenation mainly focus on the production of FA and 2-MF. The formation mechanism of HDF remains unclear. The main controversy currently concerns where the coupling process occurs (in solution or on the electrode surface).
(1)
Mechanistic Studies
In 2017, Chadderon et al. [32] first conducted a thorough investigation of the reaction mechanism of FF on Cu electrodes using H2SO4-based electrolytes. They modified the electrode surface with organic thiol self-assembled monolayers (SAMs) to explore the reaction mechanism by blocking direct electrode contact. The study found that SAM modification significantly inhibited the formation of FA and 2-MF, but had no effect on HDF production. This led to the proposal of the HDF formation mechanism: FF forms furfural radicals in the solution through an outer-sphere electron transfer mechanism, followed by self-coupling reactions. Proton transfer occurred in the solution rather than relying on Hads. These results demonstrate that HDF generation is electrode-independent and insensitive to electrode surface properties.
Liu et al. [33] obtained similar results in their study. By controlling the local environment, they investigated the reaction of FF electroreduction products on Pb catalyst surfaces and also concluded that HDF formation occurs through self-coupling in solution, confirming the findings of Chadderon et al. [32]. Recently, Geng et al. [34] conducted experiments that further verified the results of both Chadderon et al. [32] and Liu et al. [33]. They examined the effect of stirring speed on HDF selectivity and observed that as the stirring speed increased, both the FF conversion rate and HDF selectivity increased correspondingly while FA selectivity decreased. From these observations, they inferred that furfural radicals are generated at the electrode surface. The stirring process promotes their diffusion into the solution. Ultimately, two furfural radicals collide in the solution to produce HDF.
Mukadam et al. [7] determined through reaction sequence fitting and DFT calculations that proton-coupled electron transfer (PCET) is the RDS of the reaction, while the coupling of intermediates is an exothermic step that is not difficult to carry out. However, through catalyst design, they achieved a higher yield of one dimer isomer compared to the other, indicating that the coupling may occur on the catalyst surface, which facilitates better control of the coupling products such as regulation of product chirality.
(2)
Catalyst Design
In recent years, catalyst design for the electroreduction of FF to HDF has gradually increased. The performance of these electrocatalysts are summarized in Table 1. Rabet et al. [35] prepared laser-structured Pb electrodes that significantly expanded the current range and reduced the onset overpotential, achieving 28% HDF selectivity with a 75% yield. Compared to pure metal electrodes, carbon-based electrodes more readily exhibit favorable dimerization. For example, Shang et al. [8] used carbon paper and Cu foam as working electrodes, respectively, to conduct the electrochemical dimerization of FF in batch electrolysis cells. By varying the cell voltage under a constant voltage operation mode, they obtained optimal parameters for HDF production in terms of energy efficiency and productivity. At a cell voltage of 2.1 V, the carbon paper electrode achieved 60% and 66% FF conversion rates at pH = 7 and pH = 13, respectively, with corresponding HDF yields of 52% and 66%, FE of 75% and 89%, and HDF selectivity of 86% and 99%. In contrast, the Cu electrode achieved nearly 100% conversion at pH = 13, but the HDF yield was comparable to that of the carbon paper electrode at only 60%. This is because Cu contributed to the high selectivity toward FA.
An increasing number of studies have opted to load metals onto carbon-based electrodes to achieve higher FE, with Cu being a preferred choice. Liu et al. [36] employed an electrodeposition method to load Cu and Sn onto carbon paper. The presence of Sn reduced hydrogen adsorption, thereby suppressing H2 and FA production while promoting the dimerization process. This approach resulted in over 97% FF conversion and greater than 67% HDF selectivity. Mukadam et al. [7] developed Cu phthalocyanine and Co phthalocyanine (Cu/CoPc) catalysts supported on graphene. The weak binding of metal phthalocyanines to FF made them suitable for HDF production. Test results demonstrated that the FE for HDF formation could exceed 60%, and selectivity reached approximately 80%. Geng et al. [34] proposed a highly efficient electrocatalyst, [Cu(pz)]3[PW12O40], synthesized by combining Cu-pz redox catalytic centers, Keggin-type PW12O40, with electron sponge. Under neutral conditions, this catalyst achieved 99% FF conversion and 92.1% HDF selectivity. The incorporation of PW12 not only facilitated electron transfer and improved FF conversion rates but also modified the RDS to favor HDF formation.
(3)
Influence of Reaction Environment
In addition to catalyst design, the applied potential significantly affects product selectivity. Most studies suggest that HDF tends to form at relatively low potentials, as illustrated in Figure 6a–e. However, some researchers have reached contrasting conclusions. Xu et al. [1] investigated the electrochemical hydrogenation of FF on a Cu catalyst supported by N-doped porous carbon. They found that product selectivity was highly sensitive to the applied potential. Using an H-type batch cell with 30 mM FF and 1 M KOH electrolyte, FF conversion reached 93%, and HDF selectivity was 56% after being reacted for 4 h at a potential of −0.45 V vs. RHE. When the potential was shifted to −0.35 V vs. RHE, the HDF yield gradually decreased. This occurs because of the mismatch between adsorbed hydrogen and furfural intermediates on the Cu electrode at higher potentials, reducing FA selectivity while favoring HDF production. Geng et al. [34] further supported this conclusion. At lower potential ranges, FF electroreduction proceeded slowly, generating FA as the primary byproduct. When the potential increased to −0.76 V vs. RHE, selectivity toward HDF reached 92.1%, with only trace amounts of FA produced.
The surface morphology of catalysts significantly influences mass diffusion and electron transfer during reactions. Optimized structures can enhance catalytic performance for higher HDF selectivity. Ma et al. [37] developed a Cu2O nanowire array structure for FF conversion and C-C coupling. In strongly alkaline electrolyte (pH 14), this morphology achieved 83.5% HDF selectivity. Comparative tests showed markedly reduced dimerization selectivity when using foil or foam catalysts instead of nanowire arrays (Figure 7a). The array structure suppresses diffusion of in situ formed radicals, increasing their local concentration to promote radical collision and HDF formation. Another study supports this finding. Huang et al. [5] prepared octahedral and hexagonal MoS2 electrodes on carbon supports using a hydrothermal method, controlling the distribution of structural phases by varying annealing conditions to achieve over 98% FF conversion. The authors observed that the ratio of octahedral and hexagonal structures played a dominant role in reaction selectivity. MoS2 electrodes rich in octahedral structures showed 94.4% selectivity for FA, while those rich in hexagonal structures exhibited 42.7% selectivity for HDF, as shown in Figure 7b.

3.3. Research Progress on Furfural Conversion to Other Products

3.3.1. Furfuryl Alcohol

The electrocatalytic conversion of FF to FA primarily employs Cu-based catalysts, which operate effectively across a wide pH range (6.9–13.6). Liu et al. [38] investigated the electrochemical behavior of various electrodes (Cu, lead, nickel, iron, platinum, titanium, and graphite) in carbonate buffer solution (pH = 10). The overpotential order for the hydrogen evolution reaction (HER) was found to be Pt > C > Ti > Fe > Ni > Cu > Pb, with Pb slightly higher than Cu. However, due to byproducts, the current efficiency was highest on Cu electrodes. Reducing Cu to nanoscale enhances electrocatalytic activity. Yang et al. [39] prepared Cu electrocatalysts with a bicontinuous nanoporous structure and high specific surface area through chemical dealloying of CuAl alloy. The high surface area and porous structure provided sufficient Hads for FF hydrogenation, achieving 95% FE and 96% FA selectivity. Introducing nickel into the nanoporous structure can optimize the electronic structure of Cu. Dixit et al. [40] electrodeposited Cu on optimized nickel foam to prepare a Cu-NPNi/NF catalyst, which achieved 100% FF conversion after 2 h of electrolysis. In addition to metal doping, non-metal doping can also effectively enhance the ECH activity of FF. Zhang et al. [41] prepared Cu3P nanosheets on carbon fiber cloth via a vapor-phase hydrothermal method. This catalyst exhibited high Hads coverage, facilitating hydrogenation reactions and achieving near 100% FA selectivity with 98% FE. Qin et al. [42] developed zinc-manganese bimetallic oxide with surface Zn2+ vacancies supported on carbon nanofibers. This catalyst demonstrated excellent performance in electroreduction of FF (FA production 49,461.1 μmol/g and FE 95.5%). In-depth studies revealed that the carbon nanofibers strongly promoted the generation of Hads, while Zn2+ vacancies significantly reduced the energy barrier for FF reduction to FA. The synergistic effect between carbon nanofibers and zinc-manganese bimetallic oxide likely facilitated the reaction between Hads and furfural radicals, promoting FA formation.

3.3.2. 2-Methylfuran

Liu et al. [38] investigated the reaction mechanism of FF electroreduction on Cu electrodes. The results showed that Cu electrodes can produce both FA and 2-MF with nearly equal activation energies, as these two products have comparable reactivity. Under moderate overpotentials, the second PCET step in the reaction was identified as the RDS for the electrochemical generation of these two main products from FF on Cu. Therefore, the authors recommended selective production of 2-MF under low pH (<1.5) and moderate potentials (approximately 0.5 V vs. SHE). Jung and Biddinger [43] used Cu electrodes in 0.5 M H2SO4 and achieved a maximum 2-MF selectivity of 71%. Bharath and Banat [44] prepared Ru/RGO nanocomposites using a simple microwave irradiation technique and performed paired electrolysis with 2.0 M H2SO4 as the catholyte and KOH as the anolyte for the electroreduction and electrooxidation of 1.0 M FF. The paired electrolytic cell exhibited better catalytic activity than the half-cell, achieving 95% FE and 91% 2-MF yield, as the cathode could more readily obtain electrons from the anode. In addition to coupled electrooxidation strategies, a water–oil biphasic system can be employed to improve reaction efficiency. This is because the conversion of FF to 2-MF occurs in the aqueous phase, while 2-MF has higher solubility in the oil phase, shifting the chemical equilibrium toward the product side. Jiang et al. [45] used a Cu electrode as the working electrode with K2SO4 solution as the electrolyte. After adding cyclohexane, the 2-MF yield and FE increased by 9.7-fold and 18.2-fold, respectively, compared to single-phase aqueous electrolysis.

3.3.3. Tetrahydrofurfuryl Alcohol

Due to the excellent stability of the furan ring, the current research on the conversion of FF to THFA primarily focuses on thermochemical routes, with few reports on electrochemical reduction. Lenk et al. [46] investigated the conversion of FF to THFA on Pd5/Pt electrodes. High Pd content favored THFA formation, while a small amount of Pt enhanced both selectivity and FE. In this system, the selectivity for THFA from FF and FA was 15.3% and 33%, respectively. To further improve THFA selectivity, Delima et al. [47] developed a Pd membrane reactor, successfully converting FF to THFA with a selectivity of up to 98%. The performance of these electrocatalysts are summarized in Table 2.

4. Future Perspectives and Challenges

Currently, thermochemical hydrogenation technology is developing well and has become the dominant industrial method. However, its requirements for high temperatures and large amounts of hydrogen are unfavorable for cost control and sustainability. With advancements in electrochemical hydrogenation reactors and theoretical research, this technology demonstrates significant potential for emission reduction. Currently, the industrialized application of electrochemical hydrogenation is the hydrodimerization of acrylonitrile to adiponitrile, used in nylon production [48]. Notably, Nippon Oil Corporation has implemented a 150 kW reactor for the electrochemical hydrogenation of methylcyclohexane [6]. Nevertheless, the application of electrochemical hydrogenation in biomass valorization remains at the laboratory stage. Research groups worldwide are actively improving reactor designs (e.g., flow cell and batch electrolyzers) and developing electrochemical components (e.g., catalysts, membranes, electrodes) to enhance FE and current density. Under the global climate change and carbon neutrality initiatives, electrochemical hydrogenation presents a promising alternative to traditional thermochemical hydrogenation in organic synthesis. When integrated with renewable electricity, this technology can further amplify its emission reduction potential. The future development of electrochemical hydrogenation hinges on the process optimization, synthesis of high-efficiency catalysts, and design of large-scale reactors.
For bio-based aromatic carbonyl compounds, the previous research primarily focused on electrocatalytic hydrogenation and hydrogenolysis. However, significant progress has recently been made in the electrocatalytic hydrogenation of FF to HDF, exploring new synthetic routes for its valorization. To suppress competing reactions like HER and electrocatalytic hydrogenation during the hydrodimerization, measures need to be taken such as increasing substrate concentration, selecting appropriate cathode materials, and raising solution pH. Specifically, low-cost carbon materials like graphite or carbon paper exhibit high selectivity for hydrodimerization products while effectively suppressing competing reactions like HER and improving the FE of dimerization. Additionally, reactor design can facilitate the industrial application of this technology. Although most studies reported in the literature have been conducted in batch cells in order to achieve high yields, transitioning to flow reactors is necessary for scaling up from the laboratory to the technical process scale. Furthermore, coupling with anodic electrochemical reactions to oxidize bio-based feedstocks into valuable products should be considered to achieve more economical paired electrosynthesis.
In summary, future development of electrochemical reduction will face the following challenges:
(1)
Deeply understand the competitive mechanisms and explore how to achieve targeted product selectivity by modulating reaction conditions.
The electrochemical reduction process involves competition among multiple reaction pathways, including hydrogenation, hydrogenolysis, and dimerization. These reactions occur simultaneously on the electrode surface [32]. The adsorption and dissociation behaviors of various molecules are complex. A strategy combining multi-scale simulation with advanced characterization techniques can be adopted. By developing an in situ Raman spectroscopy–electrochemical mass spectrometry coupled system, the dynamic evolution of intermediates on the electrode surface can be tracked in real time. Combined with DFT calculations, quantitative structure–activity relationships between key intermediate adsorption energies and reaction pathways can be established [49,50].
(2)
Address Electrode Corrosion and Improving Recycling Efficiency in Electrocatalytic Processes.
During the electrochemical reduction processes, particularly under strongly acidic, alkaline, or high-potential conditions, electrode materials face significant corrosion risks [51]. This phenomenon not only reduces electrode service life but may also lead to product contamination and decreased reaction efficiency. To address these challenges, the development of corrosion-resistant materials is essential [52]. Core–shell structured catalysts can be developed, or interface engineering between layered double hydroxides and carbon-based supports can be explored to enhance structural stability by constructing vertical nanosheet arrays.
(3)
Research Potential of Unknown Macromolecules in Electrochemical Hydrogenation.
In electrochemical hydrogenation, many macromolecular substances remain unstudied. Research in this area would help refine the reaction pathways of aldehyde electrochemical reduction systems and expand their application scope, including trimers and polymers, complex cyclic or chain structures formed through C-C coupling, and hybrid macromolecules formed by cross-coupling of aldehydes with other functional groups (such as ketones, alcohols, acids, etc.) [50]. These macromolecules may possess unique physicochemical properties and application potential. An in-depth study of their formation mechanisms, structural characteristics, and potential uses could open new pathways for the development of novel materials, synthesis of drug precursors, and preparation of specialty chemicals.
(4)
Develop modular electrolyzer stack design to advance engineering applications.
An intelligent reactor control system should be established and coupled with renewable energy sources to construct adaptive electrolysis control algorithms under fluctuating voltages. Integrated research should be strengthened between electrochemical systems and downstream separation and purification units, particularly focusing on the development of selective extraction and membrane separation technologies for dimer products.

5. Conclusions

This paper provides a review of the research progress and development trends in the high-value conversion of FF by electrochemical means. As a crucial biomass-derived platform compound, FF electrocatalytic conversion exhibits notable advantages, such as mild reaction conditions, low energy consumption, and environmental friendliness, demonstrating promising application potential. By analyzing research achievements on the conversion of FF into high-value chemicals and fuels, this paper summarizes recent advances in catalyst design, reaction condition optimization, and mechanistic investigations. Studies show that the type and structure of catalysts play a decisive role in product distribution, requiring appropriate catalytic systems to be selected for different products. Additionally, reaction conditions significantly influence the reaction process and product selectivity. Optimizing parameters can effectively improve the selectivity and conversion efficiency of desired products. Although significant progress has been made in the high-value utilization of FF through electrocatalysis, there remain scientific and engineering challenges to be addressed. Future research should focus on developing efficient, stable, and cost-effective catalytic materials, optimizing reaction parameters, deepening mechanistic studies, and enhancing reactor design and scale-up efforts. With continued breakthroughs in key technologies, the high-value conversion of FF is expected to provide innovative pathways for biomass energy development and application, making positive contributions to achieving carbon emission reduction and carbon neutrality goals.

Author Contributions

X.Z. (Xiuzheng Zhuang) and Y.C. supervised and designed the research. H.L. summarized the relevant information and wrote the original paper. K.L. and L.C. assisted with the analysis of data. Q.Z., X.Z. (Xinghua Zhang) and L.M. reviewed and corrected the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported financially by National Natural Science Foundation of China (22469024, 52306232, and 52236010), National Science Foundation for Post-doctoral Scientists of China (2023M740597), Jiangsu Funding Program for Excellent Postdoctoral Talent (2023ZB175), and Fundamental Research Funds for the Central Universities (2242022R10058).

Data Availability Statement

Data supporting the findings of this study are available from the corresponding authors upon reasonable request. Correspondence and requests for materials should be addressed to X.Z. (Xiuzheng Zhuang).

Conflicts of Interest

The authors declare no competing financial interests.

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Figure 1. Electrochemical processes of biomass-derived platform compounds.
Figure 1. Electrochemical processes of biomass-derived platform compounds.
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Figure 2. Schematic diagram of Hads generation process.
Figure 2. Schematic diagram of Hads generation process.
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Figure 3. Schematic illustration of dimerization, hydrogenation, and hydrogenolysis processes for biomass-derived carbonyl compounds (* indicates unused electron pairs).
Figure 3. Schematic illustration of dimerization, hydrogenation, and hydrogenolysis processes for biomass-derived carbonyl compounds (* indicates unused electron pairs).
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Figure 4. Reaction pathways for electroreduction of furfural.
Figure 4. Reaction pathways for electroreduction of furfural.
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Figure 5. Using “furfural” and “hydrofuroin/furfuryl alcohol/2-methylfuran/tetrahydrofurfuryl alcohol” as keywords, Web of Science was searched for research results on different reduction products of furfural during 2015–2024.
Figure 5. Using “furfural” and “hydrofuroin/furfuryl alcohol/2-methylfuran/tetrahydrofurfuryl alcohol” as keywords, Web of Science was searched for research results on different reduction products of furfural during 2015–2024.
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Figure 6. Effect of reduction potential on furfural dimerization. (a) Electrolysis of FF using the MoS2 electrodes in pH 9 buffer solutions with methanol as a cosolvent [5]. Copyright 2022 ACS Catalysis. (b) Faradaic efficiency of ECH at different applied potentials for 1 h electrolysis with 20 mM furfural [33]. Copyright 2022 ACS Catalysis. (c) FF conversion, selectivity, and faradaic efficiency of the corresponding products in the electrocatalytic reduction of FF on the Cu2O-D arrays at different applied potentials [37]. (d) Performance of furfural reduction on Cu−Sn/CP at different voltages for 4 h electrolysis with 20 mM furfural [36]. Copyright 2022 ACS Catalysis. (e) Furfural conversion, hydrofuroin yield, and faradaic efficiency at different applied potentials [8].
Figure 6. Effect of reduction potential on furfural dimerization. (a) Electrolysis of FF using the MoS2 electrodes in pH 9 buffer solutions with methanol as a cosolvent [5]. Copyright 2022 ACS Catalysis. (b) Faradaic efficiency of ECH at different applied potentials for 1 h electrolysis with 20 mM furfural [33]. Copyright 2022 ACS Catalysis. (c) FF conversion, selectivity, and faradaic efficiency of the corresponding products in the electrocatalytic reduction of FF on the Cu2O-D arrays at different applied potentials [37]. (d) Performance of furfural reduction on Cu−Sn/CP at different voltages for 4 h electrolysis with 20 mM furfural [36]. Copyright 2022 ACS Catalysis. (e) Furfural conversion, hydrofuroin yield, and faradaic efficiency at different applied potentials [8].
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Figure 7. Influence of catalyst structure on furfural dimerization. (a) FF conversion, selectivity, and faradaic efficiency after constant-potential electrolysis on Cu2O-D arrays, Cu2O-D foam, and Cu2O-D foil [37]. (b) Performance comparison of the M250, pure 2H-MoS2, and MoO3 catalysts on furfural electrolysis in pH 9 at room temperature [5]. Copyright 2022 ACS Catalysis.
Figure 7. Influence of catalyst structure on furfural dimerization. (a) FF conversion, selectivity, and faradaic efficiency after constant-potential electrolysis on Cu2O-D arrays, Cu2O-D foam, and Cu2O-D foil [37]. (b) Performance comparison of the M250, pure 2H-MoS2, and MoO3 catalysts on furfural electrolysis in pH 9 at room temperature [5]. Copyright 2022 ACS Catalysis.
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Table 1. Typical cases of furfural electrochemical dimerization.
Table 1. Typical cases of furfural electrochemical dimerization.
ElectrolyteCatalystsF.E/%Conv./%Yield/%Sel./%PotentialRefs.
1/Pb///28−0.985 R[35]
20.1 M KOHC89666699−1.4 R[8]
30.1 M KOHCu/10060/−1.4 R[8]
4phosphate bufferCu-Sn8097.3/67−0.5 R[36]
50.1 M carbonate bufferCu6017/80−0.6 R[7]
60.4 M phosphate buffer + wood spiritCu/999092.1−0.76 R[34]
71 M KOHN-Cu/935256−0.45 R[1]
81 M KOHCu2O5090/83.5−0.176 R[37]
90.4 M borate buffer + wood spiritMoS215.498742.7−1.0 A[5]
Note: R, VRHE; A, VAg/AgCl.
Table 2. Typical cases of furfural electrochemical hydrogenation and hydrogenolysis.
Table 2. Typical cases of furfural electrochemical hydrogenation and hydrogenolysis.
ElectrolyteCatalystProductF.E/%Conv./%Yield/%Sel./%PotentialRefs.
10.1 M carbonate bufferCuFA/62%45%87%−1.4 A[38]
2PBS + methanolCu + AlFA9577/96−1.5 A[39]
30.5 M NaOHNi + CuFA/100//−0.45 R[40]
41.0 M KOHCu + PFA9810099100−0.35 R[41]
50.5 M NaOHZn + MnFA96//85−0.5 R[42]
60.5 M H2SO4CuMF15.270%/71%−0.8 R[43]
72.0 M H2SO4RuMF959791/−1.25 A[44]
80.5 M K2SO4 + cyclohexaneCuMF407520/−0.73 R[45]
90.5 M H2SO4Pd + PtTHFA/34/15.3−300 M[46]
101.0 M H2SO4PtTHFA/908898−225 M[47]
Note: R, VRHE; A, VAg/AgCl; M, mA.
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Liang, H.; Liu, K.; Zhang, X.; Zhang, Q.; Chen, L.; Chen, Y.; Zhuang, X.; Ma, L. Recent Advances of the Electrochemical Hydrogenation of Biofuels and Chemicals from Furfural. Energies 2025, 18, 3075. https://doi.org/10.3390/en18123075

AMA Style

Liang H, Liu K, Zhang X, Zhang Q, Chen L, Chen Y, Zhuang X, Ma L. Recent Advances of the Electrochemical Hydrogenation of Biofuels and Chemicals from Furfural. Energies. 2025; 18(12):3075. https://doi.org/10.3390/en18123075

Chicago/Turabian Style

Liang, Huiyi, Ke Liu, Xinghua Zhang, Qi Zhang, Lungang Chen, Yubao Chen, Xiuzheng Zhuang, and Longlong Ma. 2025. "Recent Advances of the Electrochemical Hydrogenation of Biofuels and Chemicals from Furfural" Energies 18, no. 12: 3075. https://doi.org/10.3390/en18123075

APA Style

Liang, H., Liu, K., Zhang, X., Zhang, Q., Chen, L., Chen, Y., Zhuang, X., & Ma, L. (2025). Recent Advances of the Electrochemical Hydrogenation of Biofuels and Chemicals from Furfural. Energies, 18(12), 3075. https://doi.org/10.3390/en18123075

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