Electrochemical hydrogenation and oxidation of organic species involving water

Interfacial molybdate-enabled electric field deconfinement to passivate water oxidation for wide-potential biomass electrooxidation

The priority adsorption of OH- in the anodic refining process typically compromises the accessibility of organic reactants and propels their competing oxygen evolution reaction (OER), inevitably generating inactive areas of organics electrooxidation. In this work, an electric field deconfinement strategy enabled by self-originated MoO42- was unveiled to confine the mass diffusion of OH- over a Mo-modulated Ni-based electrode (NiMoOx/NF). The reconstructable NiMoOx/NF catalyst was high-efficiency for selective electrooxidation of various biomass derivatives, especially for electrocatalytic 5-hydroxymethylfurfural (HMF) oxidation reaction (e-HMFOR) to afford 2,5-furanedicarboxylic acid (FDCA, a versatile bioplastic monomer). In-situ tests and finite element analyses evidenced that NiOOH-MoO42- in-situ reconstructed from NiMoOx/NF is responsible for e-HMFOR, where the surface-adsorbed MoO42- can trigger a negative electric field to restrict OH- affinity by electrostatic repulsion but facilitate HMF adsorption, thereby leading to the deteriorated OER and enhanced e-HMFOR. Theoretical calculations further elaborated that introduced MoO42- boosts HMF adsorption to accelerate the reaction kinetics but elevates the energy barrier of O* coupling into OOH* to passivate OER. As a result, a wide potential interval (1.35-1.55 VRHE) was applicable to produce FDCA via e-HMFOR with admirable productivity (95.4-97.8% faradaic efficiencies), rivaling the state-of-the-art Ni-based electrodes. In addition, the established membrane electrode assembly electrolyzer could be operated stably for 40 h at least, with high efficiency in electrosynthesis of gram-grade FDCA. This study underlines the viability and criticality of electric field deconfinement for manipulating the OH- adsorption to facilitate organics electrooxidation and biorefinery while getting rid of competing reactions.

Enhanced oxygen diffusion and catalytic performance of self-breathing CB/CNT cathodes for high-efficiency H2O2 production (in dual-chamber reactors)

A novel self-breathing gas diffusion electrode was developed by loading carbon nanotubes (CNTs) and carbon black (CB) onto the surface of graphite felt through vacuum filtration. This electrode features a well-structured mesoporous network and a stable three-phase interface, which enable efficient oxygen mass transfer and enhance the self-breathing capability. The incorporation of carbon nanotubes and carbon black significantly boosts the electrode's catalytic performance. In a dual-chamber reactor operating at a current density of 12 mA/cm2 and an initial pH of 3, the system achieved an H2O2 concentration of 4691 mg/L within 1 h, with an energy consumption of 6.58 kWh/kg H2O2 substantially outperforming conventional gas diffusion electrodes. The dynamic pH regulation in the dual-chamber system optimizes the 2e- ORR pathway, leading to corresponding changes in proton transfer pathways and adsorbed species within the Helmholtz plane. Additionally, the presence of reactive hydrogen (H∗) enhances the chemisorption of O2 and facilitates its hydrogenation to form the ∗OOH intermediate. The electrode exhibited excellent stability, maintaining H2O2 yields above 4000 mg/L over 5 cycles and nearly complete degradation of the simulated contaminants within 30 min in an electro-Fenton system application. These results highlight the electrode's potential for efficient H2O2 synthesis and environmental remediation.

Electrohydrogenation of Benzonitrile into Benzylamine under Mild Aqueous Conditions

The electrohydrogenation of benzonitrile to benzylamine was investigated by using copper and copper-silver electrodes under mild conditions and moderate current density. In this study, we optimized several reaction parameters, including solvent, current density applied, electrolyte effect, and substrate concentration. The results reveal that the best performance in terms of yield, conversion, and faradaic efficiency was obtained at -20 mA·cm-2, using copper-silver electrodes, at neutral pH (0.5 M KCl). Our study highlights the potential of electrochemistry to enhance reduction reactions by electrohydrogenation using only water as the proton source and demonstrates the potential of copper-silver electrodes for efficient and environmentally friendly electrochemical hydrogenation at neutral pH. Additionally, our research aims to emphasize the capability of electrocatalysis to undergo reversible electrohydrogenation/dehydrogenation transformations using the nitrile/amine pair as a promising candidate in the field of hydrogen storage as liquid organic hydrogen carriers. This study not only provides insights into the possibility of sustainable hydrogenation processes but also contributes to further exploration of electrocatalytic systems for scalable, efficient, and environmentally friendly hydrogen storage solutions, such as the nitrile/amine pair.

Ternary PtCoSn Catalyst with Regulated Intermediates Adsorption for Efficient Ammonia Electrolysis

Ammonia electrolysis represents a green and economical strategy for hydrogen production, yet the progress is hindered by the lack of efficient catalyst to boost the kinetically sluggish ammonia oxidation reaction (AOR). Herein, ternary PtCoSn/C catalyst prepared by a facile wet-chemical reduction method is applied for AOR, which exhibits a specific activity of 0.87 mA cmECSA -2, 3 times that of Pt/C. The highly enhanced activity is derived from the regulated intermediates adsorption on the PtCoSn/C surface, which is evidenced by in situ attenuated total reflection Fourier transform infrared measurements. The co-alloying of Co and Sn with Pt not only contributes to the weakened binding strength of *OH and *H species on Pt surface, enhancing the adsorption of NH3 and the related intermediates, but also facilitates the supply of OH- to Pt sites, compensating for the fast consumption of OH- in the double layer during AOR. Benefiting from its high activity for hydrogen evolution reaction, PtCoSn/C can be used as a bifunctional catalyst for ammonia electrolysis in a two-electrode system, which only requires 0.78 V to drive a current density of 10 mA cm-2. This work sheds light on developing efficient AOR catalysts, promoting hydrogen production from ammonia electrolysis.

Adsorption Configuration and H* Flux Modulation Enable Electrocatalytic Semihydrogenation of Alkynes with Group Tolerance in a Palladium Membrane Reactor

Ineffective control of alkene adsorption on a palladium membrane (PM) and the flux of active hydrogen (H*) diffusing from the aqueous side to the organic side through the PM cause low selectivity and Faradaic efficiency (FE) of alkynes to alkenes in a PM reactor. Here, a PM with a phenylthiolate-modified palladium sulfide thin layer coupled with pulsed electrolysis is reported to enable alkyne-to-alkene electrosynthesis with up to 98% selectivity and 80% FE. Electrochemical in situ Raman spectra reveal weak alkene adsorption and specific σ-alkynyl adsorption rather than flat adsorption of alkynes on the modified PM, accounting for the high alkene selectivity and functional group tolerance. Pulsed electrolysis causes reduced H* generation and restricted H* diffusion to the organic side, which better balances the generation and utilization of H*, suppresses H2 evolution, and improves the FE. The high alkene selectivity and FE in a wide potential and current range, over 50 examples of (deuterated) alkenes with functional group tolerance and deuterated drug applications (d2-naftifine, d2-cinarizine, d2-bucinnazine, d2-artemisinin derivative, and d2-estradiol derivative), and scalable electrosynthesis of deuterated styrene for deuterated polystyrene with improved thermal stability demonstrate potential utility.

High-Entropy Environments Enable Metal Surface-Catalyzed Nucleophilic Electrooxidation

Electrochemical biomass conversion offers a sustainable route to diverse products, minimizing environmental impact. However, conventional 5-hydroxymethylfurfural electrooxidation (HMFOR) catalysts such as Ni(OH)₂ and NiS suffer from low conductivity, poor stability, and limited active sites. This work introduces a CoNiMnMoPd high entropy alloy (HEA) to address these limitations by simultaneously maintaining high conductivity, stability, and a high Ni oxidation state, enabling nucleophilic dehydrogenation. The HEA catalyst achieved a 92.5% 2,5-furandicarboxylic acid (FDCA) Faradaic efficiency, 89.5% HMF conversion, and 95.8% FDCA selectivity, maintaining performance for over 100 h. Experimental and theoretical investigations revealed that the multielement composition of the HEA enabled Ni sites to maintain a high-valence state, serving as the primary adsorption sites for HMF, and the dehydrogenation reaction occurs preferentially at non-Ni sites within the HEA. Compared to monometallic Ni, the d-band center shift and reduced antibonding filling contributed to a decrease in the energy barrier for the rate-determining step (RDS) in the HMF-to-FDCA conversion, from 0.770 to 0.567 eV. This work offers novel insights for the development of Ni-based HEA catalysts for biomass valorization.

Atomic Scale Engineering of Multivalence-State Palladium Photocatalyst for Transfer Hydrogenation with Water as a Proton Source

Hydrogenation reactions are fundamental in the fine chemical, pharmaceutical, and petrochemical industries, however heavily relying on H2 gas at high temperatures and pressures, incurring large energy and carbon costs. Photocatalytic transfer hydrogenation, using water as a proton source, offers a greener alternative, but existing photocatalysts often suffer from modest yields, limited selectivity, and narrow substrate scope. Additionally, they often require co-activation, such as Mg-activated water or non-sustainable hydrogen feeds. Here, a photocatalyst is introduced that offers high yields and selectivities across a broad spectrum of organic compounds. The developed photocatalyst is a multivalence palladium superstructure with ultrasmall Pd0 nanoparticles enveloped by isolated Pd2+/Pd4+ atoms within a carbon-nitride matrix. Mechanistic studies reveal that the redox-flexible Pd single atoms, with triethylamine as an electronic modulator, attract photogenerated holes for water oxidation, while Pd0 nanoparticles facilitate hydrogen transfer to the unsaturated bonds of the organic molecules. The cooperative and dynamic behavior of Pd centers during catalysis, involving transitions among Pd+2, Pd+3, and Pd+4 states, is validated using operando electron paramagnetic resonance spectroscopy. This multivalent palladium catalyst represents a conceptual advance in photocatalytic transfer hydrogenation with water as a hydrogen source, holding promise for sustainable hydrogenation processes in the chemical industry.

Boosted high-throughput D⁺ transfer from D₂O to unsaturated bonds via Pdδ+ cathode for solvent-free deuteration

Deuterated organic compounds have gained significant attention due to their diverse applications, including reaction mechanism studies, probes for metabolism and pharmacokinetics, and raw materials for labeled compounds and polymers. Conventional reductive deuteration methods are limited by the high cost of deuterium sources (e.g., D₂ gas) and challenges in product separation and D₂O recycling. Electrochemical deuteration using D₂O is promising, but existing methods still suffer from low Faradaic efficiency (FE) and high separation costs. Herein, we report a deuterium ion diffusion-based all-solid electrolyser, featuring a RuO₂ anode for D+ generation from pure D2O and a Pd/nitrogen-doped carbon-based liquid diffusion cathode (Pdδ+/NC LDC) with tunable electron deficiencies Pdδ+/NC to enhance selective deuteration. This system achieves over 99% selectivity for deuterated benzyl alcohol with a FE of 72%, and demonstrates broad applicability for the deuteration of aldehydes, ketones, imines, and alkenes with high FE and selectivity. Moreover, the Pdδ+/NC-based electrolyser can achieve ten-gram-scale production of deuterated benzyl alcohol over 500 hours, showcasing its potential for high-throughput, solvent-free deuteration reactions in practical applications.

Facet-Engineered Copper Electrocatalysts Enable Sustainable NADH Regeneration with High Efficiency

Electrochemical regeneration of the nicotinamide cofactor (NADH) provides a sustainable approach to enzymatic reactions. However, the low productivity and selectivity of bioactive 1,4-NADH limit its broad applications. The hydrogenation of NAD+ to 1,4-NADH at the electrode surface is strongly coupled to the conformation of adsorbed NAD*, the formation of adsorbed hydrogen (Had), and the Had transfer to NAD*. Therefore, searching for materials with a suitable NAD* conformation, low Had formation energy, and rapid NAD* hydrogenation becomes a key task for the research. In this study, the (111) facet of Cu was found to exhibit a higher 1,4-NADH selectivity of 86.4%, compared to 50.4% and 57.4% for (100) and (110) facets, respectively. Density functional theory (DFT) calculations revealed that the high selectivity of Cu(111) stemmed from the favorable conformation of adsorbed NAD* and the reduced hydrogenation barrier. Subsequently, a Cu nanowire electrode with a (111)-dominant surface and abundant grain boundaries, Cugb(111), was constructed. Electrochemical kinetic analysis and DFT calculations demonstrated that the grain boundaries reduce the reaction barrier of Had formation. A record-high 1,4-NADH productivity of 73.5 μmol h-1 cm-2 was achieved by Cugb(111), while the 1,4-NADH selectivity was well-maintained at 84.7%. This study elucidates the effects of crystal facets and grain boundaries on regulating the selectivity and productivity of 1,4-NADH, providing a pathway for renewable energy-powered, high-efficiency green biomanufacturing.

Electrochemical Oxidative Reassembly of 1,3-Diketones with Aryl Alkenes and Water via Carbon-Carbon Bond Cleavage Rearrangement

We report the electrochemical cleavage and reassembly of 1,3-diketones with aryl alkenes and water for the synthesis of 1,4-ketoalcohol derivatives. This approach represents the first example of formal carbon-carbon cleavage of 1,3-diketones and alkene insertion via electro-oxidation, enabling the direct synthesis of diverse 1,4-ketoalcohol derivatives in good to high yields. The developed strategy employs an electrochemical approach using inexpensive commercial carbon electrodes in an undivided cell under mild and operationally simple conditions.

Electrochemical Cascade Reactions of 1,2,3-Benzotriazinones with Alkynes to Assemble 3,4-Dihydroisoquinolin-1(2H)-ones

An unexpected electrochemical cascade reaction of 1,2,3-benzotriazinones with alkynes to assemble 3,4-dihydroisoquinolin-1(2H)-ones has been developed, which avoids the use of pressurized H2, any metal catalysts, and stoichiometric redox agents. This route tolerates a wide range of functional groups in both reactants and can be performed under an air atmosphere. The process of continuous cathodic reduction was demonstrated by control experiments and cyclic voltammograms. Moreover, the gram-scale reaction confirmed the potential of this environmentally benign method for practical applications.

Electrocatalytic Hydrogenation of Olefins

Electrochemical synthesis offers a powerful and sustainable alternative to conventional chemical manufacturing techniques. The direct and selective electrohydrogenation of olefins has enormous potential applicability; however, this reactivity has not been sufficiently demonstrated. Herein, we show that an efficient Pt-based electrocatalyst from commercially available PtCl2 can promote such transformations. This approach enables olefins to be electrohydrogenated (often below -3.0 V vs. Ag/AgCl) at high current density (JGeo up to 133 mA cm-2) using protons and electrons as the hydrogen source. This reaction exhibits broad functional group compatibility, requires low catalyst loading, and affords a diverse series of valuable molecules (more than 60 examples) with high chemoselectivity. In addition, highly regioselective electrocatalytic hydrogenation of olefins (r.r. > 19:1) is demonstrated using PtCl2 and 2,2'-bipyridine.

Production of High-Purity 2,5-Furandicarboxylic Acid through Electrocatalytic Oxidation of 2,5-Bis(hydroxymethyl)furan over Reconstructed Ni2P/NF

The generation of high-valence surface active species (such as CoOOH and NiOOH) determines the crucial oxidation rates and stabilities in the electrocatalytic reactions. Herein, a unique Ni2P/NF catalyst is designed using a chemical vapor deposition method along with a rapid reconstruction (Ni2+ → Ni3+) rate, stably achieving ≈90% FDCA yields from BHMF electron-oxidation after 10 cycles at a formation rate of 218 μmolFDCA cm-2 h-1 (seven times higher than data in reported literature). The abundance of available electrons near the Ni-3d Fermi level, together with the reduced NiP bond strength and the lowest electronegativity of Ni2P, accelerates surface NiOOH species formation. In addition, the electrocatalytic oxidation of BHMF offers a more stable furan-based substrate, while also prolonging the residence time of the oxidative intermediate HMF. This mitigates humin formation, thereby enabling the synthesis of high-purity FDCA (>99%) at high concentrations (100 mmol L-1), making it a promising approach for efficient FDCA synthesis.

Water in Electrocatalysis

Renewable electricity-powered electrocatalysis technologies occupy a central position in clean energy conversion and the pursuit of a net-zero carbon emission future. Water can serve multiple roles in electrocatalytic reactions, for instance, as a reaction medium, reactant, modifier, promoter, etc. This significantly influences the mass transport, active site, intermediate adsorption and reaction kinetics, ultimately determining the electrocatalytic performance (e.g., activity, selectivity, and stability) as well as device efficiency. As the heart location where electrocatalytic reactions occur, the typical electrical-double layer is established at a water-electrode interface. Therefore, the comprehension and regulation of water are crucial topics in electrocatalysis, which encourages us to organize this review. We begin with the fundamental understanding on structure of water and its behavior under electrochemical conditions. Subsequently, we delve into the "water effect" by elucidating specific functions of water in electrocatalysis. Recent advances in manipulating water to enhance electrocatalytic efficiency of representative reactions such as hydrogen evolution/oxidation, oxygen evolution/reduction, CO2 reduction, N2 reduction and organic electrosynthesis, are also highlighted. We finally discuss the remaining challenges and future opportunities in this field.

Homonuclear/Heteronuclear Bimetallic Conjugated Coordination Polymers with Customized Oxygen Evolution Pathway

The reasons for the generally superior performance of synergistic effects in bimetallic catalysts in the oxygen evolution reaction (OER) are not fully understood, largely due to the complexity of catalyst structures and the challenges associated with synthesizing long-range atomic ordering catalysts. In this study, we present a series of two-dimensional (2D) conjugated bimetallic coordination polymers (c-CPs) involving Co or Ni with unambiguous and nearly identical geometry structures for the electrocatalysis of OER, which are highly suitable for discussions on structure-property correlations. The heteronuclear CoNi-PI unexpectedly alters the OER catalytic mechanisms from adsorbate evolution mechanism those observed in homonuclear CoCo-PI and NiNi-PI to the kinetically faster oxide path mechanism, exhibiting high stability and an ultralow overpotential of 282 mV even at 100 mA cm-2 with a Tafel slope of approximately 42 mV dec-1. This study presents an extremely rare crystalline heteronuclear bimetallic catalyst with excellent catalytic properties, promising significant influences in catalyst development research.

Electrochemical hydrogenative coupling of nitrobenzene into azobenzene over a mesoporous palladium-sulfur cathode

Azobenzene (AZO) and its derivatives are of great importance in the dyestuff and pharmaceutical industries; however, their sustainable synthesis is much slower than expected due to the lack of high-performance catalysts. In this work, we report a robust yet highly efficient catalyst of PdS mesoporous nanospheres (MNSs) with confined mesostructures and binary elemental composition that achieved sustainable electrosynthesis of value-added AZO by selective hydrogenative coupling of nitrobenzene (NB) feedstocks in H2O under ambient conditions. Using a renewable electricity source and H2O, binary PdS MNSs exhibited a remarkable NB conversion of 95.4%, impressive AZO selectivity of 93.4%, and good cycling stability in selective NB hydrogenation reaction (NBHR) electrocatalysis. Detailed mechanism studies revealed that the confined mesoporous microenvironment of PdS MNSs facilitated the hydrogenative coupling of key intermediates (nitrosobenzene and phenylhydroxylamine) into AZO and/or azoxybenzene (AOB), while their electron-deficient S sites stabilized the Pd-spillovered active H* and inhibited the over-hydrogenation of AZO/AOB into AN. By coupling with the anodic methanol oxidation reaction (MOR), the (-)NBHR‖MOR(+) two-electrode system exhibits much better NB-to-AZO performance in a sustainable and energy-efficient manner. This work thus paves the way for designing functional mesoporous metal alloy electrocatalysts applied in the sustainable electrosynthesis of industrial value-added chemicals.

CeO2 Modification Promotes the Oxidation Kinetics for Adipic Acid Electrosynthesis from KA Oil Oxidation at 200 mA cm-2

Electrocatalytic oxidation of cyclohexanol/cyclohexanone in water provides a promising strategy for obtaining adipic acid (AA), which is an essential feedstock in the polymer industry. However, this process is impeded by slow kinetics and limited Faradaic efficiency (FE) due to a poor understanding of the reaction mechanism. Herein, NiCo2O4/CeO2 is developed to enable the electrooxidation of cyclohexanol to AA with a 0.0992 mmol  h-1 cm-2 yield rate and 87 % Faradaic efficiency at a lower potential. Mechanistic investigations demonstrate that cyclohexanol electrooxidation to AA is a gradual oxidation process involving the dehydrogenation of cyclohexanol to cyclohexanone, the generation of 2-hydroxy cyclohexanone, and subsequent C-C cleavage. Theoretical calculations reveal that electronic interactions between CeO2 and NiCo2O4 decrease the energy barrier of cyclohexanone oxidation to 2-hydroxy cyclohexanone and inhibit the *OH to *O step, leading to AA electrosynthesis with a high yield rate and FE. Kinetic analysis further elucidates the effect of CeO2 on promoting cyclohexanone adsorption and activation on the electrode surface, thus facilitating the reaction kinetics. Moreover, a two-electrode flow reactor is constructed to produce 72.1 mmol AA and 10.4 L H2 by using KA oil as the anode feedstock at 2.5 A (200 mA cm-2), demonstrating promising potential.

Mesoporous Cu Nanoplates with Exposed Cu+ Sites for Efficient Electrocatalytic Transfer Semi-Hydrogenation of Alkynes

Electrocatalytic transfer alkyne semi-hydrogenation with H2O as hydrogen source is industrially promising for selective electrosynthesis of high value-added alkenes while inhibiting byproduct alkanes. Although great achievements, their development has remarkably restricted by designing atomically sophisticated electrocatalysts. Here, we reported single-crystalline mesoporous copper nanoplates (meso-Cu PLs) as a robust yet highly efficient electrocatalyst for selective alkene electrosynthesis from transfer semi-hydrogenation reaction of alkyne in H2O. Anisotropic meso-Cu PLs were prepared through a facile epitaxial growth strategy with functional C22H45N(CH3)2-C3H6-SH as concurrent mesopore-forming and structure-controlled surfactant. Different to nonporous Cu counterparts with flat surface, meso-Cu PLs with spherical mesopores exposed abundant Cu+ sites, which not only stabilized active H* radicals from electrocatalytic H2O splitting without coupling into molecular H2 but also accelerated kinetically the desorption of semi-hydrogenated alkenes. With 4-aminophenylacetylene (4-AP) as the substrate, anisotropic meso-Cu PLs delivered superior electrocatalytic transfer semi-hydrogenation performance with up to 99 % of 4-aminostyrene selectivity and 100 % of 4-AP conversion as well as good cycle stability. Meanwhile, meso-Cu PLs were electrocatalytically applicable for transfer semi-hydrogenation of various alkynes. This work thus paved an alternative paradigm for designing robust mesoporous metal electrocatalysts with structurally functional metal sites applied in the selective electrosynthesis of industrially value-added chemicals in H2O.

Surface Coverage Tuning for Suppressing Over-Oxidation: A Case of Photoelectrochemical Alcohol-to-Aldehyde/Ketone Conversion

Suppressing over-oxidation is a crucial challenge for various chemical intermediate synthesis in heterogeneous catalysis. The distribution of oxidative species and the substrate coverage, governed by the direction of electron transfer, are believed to influence the oxidation extent. In this study, we presented an experimental realization of surface coverage modulation on a photoelectrode using a photo-induced charge activation method. Through the surface coverage modulation, both pre-oxidized alcohol substrates and surface coverage were increased, which not only improved the reaction kinetics but also suppressed the over-oxidation of the generated aldehydes/ketones. As a demonstration, the Faradaic efficiency for the conversion of glycerol to dihydroxyacetone increased from 31.8 % to 46.8 % (with selectivity rising from 47.6 % to 71.3 %), from 73.4 % to 87.8 % for benzyl alcohol to benzyl aldehyde (selectivity increasing from 76.7 % to 92.4 %) and from 4.2 % to 53.6 % for ethylene glycol to glycolaldehyde (selectivity increasing from 6.2 % to 62.7 %). Our findings offer a promising strategy for the production of high-value carbon products in heterogeneous catalysis.

Electrocatalytic Biomass Oxidation via Acid-Induced In Situ Surface Reconstruction of Multivalent State Coexistence in Metal Foams

Electrocatalytic biomass conversion offers a sustainable route for producing organic chemicals, with electrode design being critical to determining reaction rate and selectivity. Herein, a prediction-synthesis-validation approach is developed to obtain electrodes for precise biomass conversion, where the coexistence of multiple metal valence states leads to excellent electrocatalytic performance due to the activated redox cycle. This promising integrated foam electrode is developed via acid-induced surface reconstruction to in situ generate highly active metal (oxy)hydroxide or oxide (MOxHy or MOx) species on inert foam electrodes, facilitating the electrooxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). Taking nickel foam electrode as an example, the resulting NiOxHy/Ni catalyst, featuring the coexistence of multivalent states of Ni, exhibits remarkable activity and stability with a FDCA yields over 95% and a Faradaic efficiency of 99%. In situ Raman spectroscopy and theoretical analysis reveal an Ni(OH)2/NiOOH-mediated indirect pathway, with the chemical oxidation of 5-HMF as the rate-limiting step. Furthermore, this in situ surface reconstruction approach can be extended to various metal foams (Fe, Cu, FeNi, and NiMo), offering a mild, scalable, and cost-effective method for preparing potent foam catalysts. This approach promotes a circular economy by enabling more efficient biomass conversion processes, providing a versatile and impactful tool in the field of sustainable catalysis.

Manipulating hydrogenation pathways enables economically viable electrocatalytic aldehyde-to-alcohol valorization

Electrocatalytic reduction (ECR) of furfural represents a sustainable route for biomass valorization. Unfortunately, traditional Cu-catalyzed ECR suffers from diversified product distribution and industrial-incompatible production rates, mainly caused by the intricate mechanism-performance relationship. Here, we manipulate hydrogenation pathways on Cu by introducing ceria as an auxiliary component, which enables the mechanism switching from proton-coupled electron transfer to electrochemical hydrogen-atom transfer (HAT) and thus high-speed furfural-to-furfuryl alcohol electroconversion. Theoretical and kinetic analyses show that oxygen-vacancy-rich ceria delivers an efficient formation-diffusion-hydrogenation chain of H* by diminishing H* adsorption. Spectroscopic characterizations indicate that Cu/ceria interfacial perimeter enriches the local furfural, synergistically lowering the barrier of the rate-determining HAT step across the perimeter. Our Cu/ceria catalyst realizes high-rate HAT-dominated ECR for electrosynthesis of single-product furfuryl alcohol, achieving a high production rate of 19.1 ± 0.4 mol h-1 m-2 and a Faradaic efficiency of 97 ± 1% at an economically viable partial current density of over 0.1 A cm-2. Our results demonstrate a highly efficient route for biofeedstock valorization with enhanced techno-economic feasibility.

Electrochemical epoxidation enhanced by C2H4 activation and hydroxyl generation at the Ag/SnO2 interface

Direct electrochemical ethylene (C2H4) epoxidation with water (H2O) represents a promising approach for the production of value-added ethylene oxide (EO) in a sustainable way. However, the activity remains limited due to the sluggish activation of C2H4 and the stiff formation of *OH intermediate. This paper describes the design of a Ag/SnO2 electrocatalyst to achieve efficient electrochemical C2H4 epoxidation with a high faradaic efficiency of 39.4% for EO and a high selectivity of 91.5% at 25 mA/cm2 in a membrane electrode assembly. Results of in situ attenuated total reflection infrared spectra characterizations and computational calculations reveal that the Ag/SnO2 interface promotes C2H4 adsorption and activation to obtain *C2H4. Moreover, electrophilic *OH is generated on the catalyst surface through H2O dissociation, which further reacts with *C2H4 to facilitate the formation of *C2H4OH, contributing to the enhanced electrochemical epoxidation activity. This work would provide general guidance for designing catalysts for electrochemical olefin epoxidation through interface engineering.

Mechanisms of electrochemical hydrogenation of aromatic compound mixtures over a bimetallic PtRu catalyst

Efficient electrochemical hydrogenation (ECH) of organic compounds is essential for sustainability, promoting chemical feedstock circularity and synthetic fuel production. This study investigates the ECH of benzoic acid, phenol, guaiacol, and their mixtures, key components in upgradeable oils, using a carbon-supported PtRu catalyst under varying initial concentrations, temperatures, and current densities. Phenol achieved the highest conversion (83.17%) with a 60% Faradaic efficiency (FE). In mixtures, benzoic acid + phenol yielded the best performance (64.19% conversion, 74% FE), indicating a synergistic effect. Notably, BA consistently exhibited 100% selectivity for cyclohexane carboxylic acid (CCA) across all conditions. Density functional theory (DFT) calculations revealed that parallel adsorption of BA on the cathode (-1.12 eV) is more stable than perpendicular positioning (-0.58 eV), explaining the high selectivity for CCA. These findings provide a foundation for future developments in ECH of real pyrolysis oil.

Substrate diffusion electrodes allow for the electrochemical hydrogenation of concentrated alkynol substrate feeds

Electrosynthesis has the potential to revolutionize industrial organic synthesis sustainably and efficiently. However, high cell voltages and low stability often arise due to solubility issues with organic solvents, while protic electrolytes restrict substrate options. We present a three-layered electrode design that enables the use of concentrated to neat substrate feeds. This design separates the organic substrate from the aqueous electrolyte using layers with varying porosity and hydrophilicity, ensuring precise reactant transport to the catalyst layer while minimizing substrate and electrolyte crossover. We demonstrate its effectiveness by semi-hydrogenating three alkynols with different hydrophobicities. For the semi-hydrogenation of 3-methyl-1-pentyn-3-ol in pure form, we achieved 65% faradaic efficiency at 80 mA cm-2. Additionally, semi-hydrogenation of neat 2-methyl-3-butyn-2-ol on palladium showed a faradaic efficiency for semi-hydrogenation of 36%, that was stable for 22 h. This design could be pioneering the electrochemical valorization of neat substrates, reducing the need for extensive downstream processing.

Cuδ+ Site-Enhanced Adsorption and Crown Ether-Reconfigured Interfacial D2O Promote Electrocatalytic Dehalogenative Deuteration

Electrocatalytic dehalogenative deuteration is a sustainable method for precise deuteration, whereas its Faradaic efficiency (FE) is limited by a high overpotential and severe D2 evolution reaction (DER). Here, Cuδ+ site-adjusted adsorption and crown ether-reconfigured interfacial D2O are reported to cooperatively increase the FE of dehalogenative deuteration up to 84% at -100 mA cm-2. Cuδ+ sites strengthen the adsorption of aryl iodides, promoting interfacial mass transfer and thus accelerating the kinetics toward dehalogenative deuteration. The crown ethers disrupt the hydration effect of K·D2O and reconstruct the hydrogen bond with the interfacial D2O, lowering the content K·D2O of the electric double layer and hindering the interaction between D2O and the cathode, thus inhibiting the kinetics of the competitive DER. A linear relationship between the matched sizes of crown ethers and alkali metal cations is demonstrated for universally increasing FEs. This method is also suitable for the deuteration of various halides with high easily reducible functional group compatibility and improved FEs at -100 mA cm-2.

Electrosynthesis of Organonitrogen Compounds via Hydroxylamine-Mediated Cascade Reactions

Hydroxylamine (NH2OH) is a key intermediate in the formation of numerous high value-added organonitrogen compounds. The traditional synthesis of NH2OH requires the use of precious metals under high temperature conditions, which leads to high cost, high energy consumption, and environmental pollution. The NH2OH-mediated cascade reaction integrates the electrochemical synthesis of NH2OH and the chemical synthesis of organonitrogen compounds, offering a facile, green, and efficient alternative. This review presents the recent advances on electrosynthesis of high value-added organonitrogen compounds by NH2OH-mediated cascade reactions. We present key concepts and the transformation process of different N-species to NH2OH, discuss suitable substrates and electrocatalysts, and elucidate the reaction mechanisms involved in generating compounds such as amino acids, cyclohexanone oxime, urea, amine, etc.. Finally, we address current challenges and future directions in this emerging field to encourage further research effort and the development of NH2OH-mediated cascade reaction.

Dynamic restructuring of electrocatalysts in the activation of small molecules: challenges and opportunities

Electrochemical activation of small molecules plays an essential role in sustainable electrosynthesis, environmental technologies, energy storage and conversion. The dynamic structural changes of catalysts during the course of electrochemical reactions pose challenges in the study of reaction kinetics and the design of potent catalysts. This short review aims to provide a balanced view of in situ restructuring of electrocatalysts, including its fundamental thermodynamic origins and how these compare to those in thermal and photocatalysis, and highlighting both the positive and negative impacts of in situ restructuring on the electrocatalyst performance. To this end, examples of in situ electrocatalyst restructuring within a focused scope of reactions (i.e. electrochemical CO2 reduction, hydrogen evolution, oxygen reduction and evolution, and dinitrogen and nitrate reduction) are used to demonstrate how restructuring can benefit or adversely affect the desired process outcome. Prospects of manipulating in situ restructuring towards an energy-efficient and durable electrocatalytic process are discussed. The practicality of pulse electrolysis on an industrial scale is questioned, and the need for genius schemes, such as self-healing catalysis, is emphasized.

Atomically Asymmetrical Ir-O-Co Sites Enable Efficient Chloride-Mediated Ethylene Electrooxidation in Neutral Seawater

The chloride-mediated ethylene oxidation reaction (EOR) of ethylene chlorohydrin (ECH) via electrocatalysis is practically attractive because of its sustainability and mild reaction conditions. However, the chlorine oxidation reaction (COR), which is essential for the above process, is commonly catalyzed by dimensionally stable anodes (DSAs) with high contents of precious Ru and/or Ir. The development of highly efficient COR electrocatalysts composed of nonprecious metals or decreased amounts of precious metals is highly desirable. Herein, we report a modified Co3O4 with a single-atom Ir substitution (Ir1/Co3O4) as a highly efficient COR electrocatalyst for chloride-mediated EOR to ECH in neutral seawater. Ir1/Co3O4 achieves a Faradaic efficiency (FE) of up to 94.8 % for ECH generation and remarkable stability. Combining experimental results and density functional theory (DFT) calculations, the unique atomically asymmetrical Ir-O-Co configuration with a strong electron coupling effect in Ir1/Co3O4 can accelerate electron transfer to increase the reaction kinetics and maintain the structural stability of Co3O4 during COR. Moreover, a coupling reaction system integrating the anodic chloride-mediated and cathodic H2O2-mediated EOR show a total FE of ~170 % for paired electrosynthesis of ECH and ethylene glycol (EG) using ethylene as the raw material. The technoeconomic analysis highlights the promising application prospects of this system.

Phase Engineering Facilitates O-O Coupling via Lattice Oxygen Mechanism for Enhanced Oxygen Evolution on Nickel-Iron Phosphide

Nickel-iron-based catalysts are recognized for their high efficiency in the oxygen evolution reaction (OER) under alkaline conditions, yet the underlying mechanisms that drive their superior performance remain unclear. Herein, we revealed the molecular OER mechanism and the structure-intermediate-performance relationship of OER on a phosphorus-doped nickel-iron nanocatalyst (NiFeP). NiFeP exhibited exceptional activity and stability with an overpotential of only 210 mV at 10 mA cm-2 in 1 M KOH and a cell voltage of 1.68 V at 1 A cm-2 in anion exchange membrane water electrolyzers. The evolution of active sites and intermediates during OER on NiFeP was in situ probed and correlated using shell-isolated nanoparticle-enhanced Raman spectroscopy, complemented by differential electrochemical mass spectrometry and density functional theory. These results provide direct evidence that OER proceeds via the lattice oxygen-mediated mechanism. Remarkably, phosphorus doping plays a critical role in stabilizing the active β-Ni(Fe)OOH phase, which facilitates the *OH deprotonation and the subsequent O-O coupling to form *OO intermediates. Our findings offer a deeper understanding of the OER mechanism, providing a clear pathway for designing next-generation OER catalysts with improved efficiency and durability.

Synergistic enhancement of electrochemical alcohol oxidation by combining NiV-layered double hydroxide with an aminoxyl radical

Electrochemical alcohol oxidation (EAO) represents an effective method for the production of high-value carbonyl products. However, its industrial viability is hindered by suboptimal efficiency stemming from low reaction rates. Here, we present a synergistic electrocatalysis approach that integrates an active electrode and aminoxyl radical to enhance the performance of EAO. The optimal aminoxyl radical (4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl) and Ni0.67V0.33-layered double hydroxide (LDH) are screen as cooperative electrocatalysts by integrating theoretical predictions and experiments. The Ni0.67V0.33-LDH facilitates the adsorption and activation of N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)acetamide (ACTH) via interactions with ketonic oxygen, thereby improving selectivity and yield at high current densities. The electrolysis process is scaled up to produce 200 g of the steroid carbonyl product 8b (19-Aldoandrostenedione), achieving a yield of 91% and a productivity of 243 g h-1. These results represent a promising method for accelerating electron transfer to enhance alcohol oxidation, highlighting its potential for practical electrosynthesis applications.

Promoting Water Dissociation and Weakening Active Hydrogen Adsorption to Boost the Hydrogen Transfer Reaction over a Cu-Ag Superlattice Electrocatalyst

The prerequisite for electrocatalytic hydrogenation reactions (EHRs) is H2O splitting to form surface hydrogen species (*H), which occupy catalytic sites and lead to mismatched coverage of *H and reactants, resulting in unsatisfactory activity and selectivity. Thus, modulating the splitting pathway of H2O is significant for optimizing the EHR process. Herein, a Cu-Ag alloy with a superlattice structure of staggered-ordered Cu and Ag is theoretically predicted and experimentally proven to undergo a pathway for H2O splitting called the hydrogen transfer reaction (HTR) in the water layer, which involves the formation of *H, the capture of *H by a water cluster to form H*(H2O)x and subsequent hydrogenation reactions by H*(H2O)x. Taking acetylene hydrogenation as a model case, the as-proposed HTR pathway could lead to a relaxation hydrogenation process to modulate the matching degree of C2H2 and *H, thus enabling a 91.2 % C2H4 Faradaic efficiency at a partial current density of 0.38 A cm-2, greatly outperforming its counterpart without a superlattice structure.

Evaluation of Active Oxygen Species Derived from Water Splitting for Electrocatalytic Organic Oxidation

Active oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high-value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au-based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d-band center of Au-based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

Investigation of Electron Transfer Properties on Silicalite-1 Zeolite for Potential Electrocatalytic Applications

To develop high-performance electrocatalysts is critical to sustainable conversion and storage of renewable energy. Silicalite-1 (S-1) zeolite is considered promising for constructing electrocatalysts featuring uniform and precise porosity and a stable structural skeleton even at extreme potentials. However, its electrochemical properties remain poorly understood, particularly regarding the roles of internal pore channels. Herein, inner- and outer-sphere electron transfer (ISET/OSET) routes on the S-1 zeolite were investigated by classical redox probes. The results for the first time revealed that the ISET kinetics inside the pores of S-1 zeolite is more rapid than that on external surfaces, optimized by microporous scale channels and terminated hydroxyl groups. Conversely, the kinetics of the OSET did not closely depend on the porosity and surface properties of the S-1 zeolite. These electrochemical insights further initiated a lithium-ion-incorporated S-1 zeolite with rapid ISET kinetics for electrocatalysis of oxygen reduction. It demonstrated a high performance of 85% selectivity for H2O2 production in a neutral solution and a yield of 9.2 mol gcat-1 h-1 when configured in a flow cell.

Mn and Mo co-doped NiS nanosheets induce abundant Ni3+-O bonds for efficient electro-oxidation of biomass

MnMo-NiS were synthesized for electro-oxidizing ethylene glycol (EG), glycerol (GLY), and 5-hydroxymethylfurfural (HMF), achieving faradaic efficiencies of 97.5%, 98.6%, and 99.2%, and yield rates of 615.7, 475.5, and 333.9 μmol h-1 cm-2. In situ Raman spectroscopy and multi-step chronoamperometry reveal that Ni3+-O is the active site.

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon-6 Precursor

Coupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon-6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h-1 gcat -1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high-performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

A Stepwise Electrochemical Baeyer-Villiger Oxidation with Water as the Oxygen Source

Baeyer-Villiger oxidation is a method with a 125-year history that produces lactones through a synergistic mechanism by reaction with stoichiometric peracids. Therefore, substituted lactones can be obtained from only substituted cyclic ketones. In this context, an electrochemical Baeyer-Villiger oxidation was developed using a CeO2@PbO2@Ti electrode, which produces substituted lactones through a stepwise mechanism. PbO2, in combination with a benzoic acid molecular catalyst, can generate and utilize reactive oxygen species from electrochemical water splitting to serve as the oxidant. CeO2 is designed to promote the stepwise mechanism while suppressing the synergistic mechanism. Therefore, substituted lactone can be produced from unsubstituted cyclic ketone with high selectivity (77%) and yield (20 mM) through a carbocation rearrangement process. The developed stepwise electrochemical Baeyer-Villiger oxidation, using water as the oxygen source, offers a new green approach to organic synthesis.

Practical electrochemical hydrogenation of nitriles at the nickel foam cathode

We report a scalable hydrogenation method for nitriles based on cost-effective materials in a very simple two-electrode setup under galvanostatic conditions. All components are commercially and readily available. The method is very easy to conduct and applicable to a variety of nitrile substrates, leading exclusively to primary amine products in yields of up to 89% using an easy work-up protocol. Importantly, this method is readily transferable from the milligram scale in batch-type screening cells to the multi-gram scale in a flow-type electrolyser. The transfer to flow electrolysis enabled us to achieve a notable 20 g day-1 productivity of phenylethylamine at a geometric current density of 50 mA cm-2 in a flow-type electrolyser with 48 cm2 electrodes. It is noteworthy that this method is sustainable in terms of process safety and reusability of components.

Identifying Highly Active and Selective Cobalt X-Ides for Electrocatalytic Hydrogenation of Quinoline

Earth-abundant Co X-ides are emerging as promising catalysts for the electrocatalytic hydrogenation of quinoline (ECHQ), yet challenging due to the limited fundamental understanding of ECHQ mechanism on Co X-ides. This work identifies the catalytic performance differences of Co X-ides in ECHQ and provides significant insights into the catalytic mechanism of ECHQ. Among selected Co X-ides, the Co3O4 presents the best ECHQ performance with a high conversion of 98.2% and 100% selectivity at ambient conditions. The Co3O4 sites present a higher proportion of 2-coordinated hydrogen-bonded water at the interface than other Co X-ides at a low negative potential, which enhances the kinetics of subsequent water dissociation to produce H*. An ideal 1,4/2,3-H* addition pathway on Co3O4 surface with a spontaneous desorption of 1,2,3,4-tetrahydroquinoline is demonstrated through operando tracing and theoretical calculations. In comparison, the Co9S8 sites display the lowest ECHQ performance due to the high thermodynamic barrier in the H* formation step, which suppresses subsequent hydrogenation; while the ECHQ on Co(OH)F and CoP sites undergo the 1,2,3,4- and 4,3/1,2-H* addition pathway respectively with the high desorption barriers and thus low conversion of quinoline. Moreover, the Co3O4 presents a wide substrate scope and allows excellent conversion of other quinoline derivatives and N-heterocyclic substrates.

Electricity-driven organic hydrogenation using water as the hydrogen source

Hydrogenation is a pivotal process in organic synthesis and various catalytic strategies have been developed in achieving effective hydrogenation of diverse substrates. Despite the competence of these methods, the predominant reliance on molecular hydrogen (H2) gas under high temperature and elevated pressure presents operational challenges. Other alternative hydrogen sources such as inorganic hydrides and organic acids are often prohibitively expensive, limiting their practical utility on a large scale. In contrast, employing water as a hydrogen source for organic hydrogenation presents an attractive and sustainable alternative, promising to overcome the drawbacks associated with traditional hydrogen sources. Integrated with electricity as the sole driving force under ambient conditions, hydrogenation using water as the sole hydrogen source aligns well with the environmental sustainability goals but also offers a safer and potentially more cost-effective solution. This article starts with the discussion on the inherent advantages and limitations of conventional hydrogen sources compared to water in hydrogenation reactions, followed by the introduction of representative electrocatalytic systems that successfully utilize water as the hydrogen source in realizing a large number of organic hydrogenation transformations, with a focus on heterogeneous electrocatalysts. In summary, transitioning to water as a hydrogen source in organic hydrogenation represents a promising direction for sustainable chemistry. In particular, by exploring and optimizing electrocatalytic hydrogenation systems, the chemical industry can reduce its reliance on hazardous and expensive hydrogen sources, paving the way for safer, greener, and less energy-intensive hydrogenation processes.

Ethylene electrosynthesis from low-concentrated acetylene via concave-surface enriched reactant and improved mass transfer

Electrocatalytic semihydrogenation of acetylene (C2H2) provides a facile and petroleum-independent strategy for ethylene (C2H4) production. However, the reliance on the preseparation and concentration of raw coal-derived C2H2 hinders its economic potential. Here, a concave surface is predicted to be beneficial for enriching C2H2 and optimizing its mass transfer kinetics, thus leading to a high partial pressure of C2H2 around active sites for the direct conversion of raw coal-derived C2H2. Then, a porous concave carbon-supported Cu nanoparticle (Cu-PCC) electrode is designed to enrich the C2H2 gas around the Cu sites. As a result, the as-prepared electrode enables a 91.7% C2H4 Faradaic efficiency and a 56.31% C2H2 single-pass conversion under a simulated raw coal-derived C2H2 atmosphere (~15%) at a partial current density of 0.42 A cm-2, greatly outperforming its counterpart without concave surface supports. The strengthened intermolecular π conjugation caused by the increased C2H2 coverage is revealed to result in the delocalization of π electrons in C2H2, consequently promoting C2H2 activation, suppressing hydrogen evolution competition and enhancing C2H4 selectivity.

Correlating Substrate Reactivity at Electrified Interfaces with the Electrolyte Structure in Synthetically Relevant Organic Solvent/Water Mixtures

Optimizing electrosynthetic reactions requires fine tuning of a vast chemical space, including charge transfer at electrocatalyst/electrode surfaces, engineering of mass transport limitations, and complex interactions of reactants and products with their environment. Hybrid electrolytes, in which supporting salt ions and substrates are dissolved in a binary mixture of organic solvent and water, represent a new piece of this complex puzzle as they offer a unique opportunity to harness water as the oxygen or proton source in electrosynthesis. In this work, we demonstrate that modulating water-organic solvent interactions drastically impacts the solvation properties of hybrid electrolytes. Combining various spectroscopies with synchrotron small-angle X-ray scattering (SAXS) and force field-based molecular dynamics (MD) simulations, we show that the size and composition of aqueous domains forming in hybrid electrolytes can be controlled. We demonstrate that water is more reactive for the hydrogen evolution reaction (HER) in aqueous domains than when strongly interacting with solvent molecules, which originates from a change in reaction kinetics rather than a thermodynamic effect. We exemplify novel opportunities arising from this new knowledge for optimizing electrosynthetic reactions in hybrid electrolytes. For reactions proceeding first via the activation of water, fine tuning of aqueous domains impacts the kinetics and potentially the selectivity of the reaction. Instead, for organic substrates reacting prior to water, aqueous domains have no impact on the reaction kinetics, while selectivity may be affected. We believe that such a fine comprehension of solvation properties of hybrid electrolytes can be transposed to numerous electrosynthetic reactions.

Microenvironment regulation breaks the Faradaic efficiency-current density trade-off for electrocatalytic deuteration using D2O

The high Faradaic efficiency (FE) of the electrocatalytic deuteration of organics with D2O at a large current density is significant for deuterated electrosynthesis. However, the FE and current density are the two ends of a seesaw because of the severe D2 evolution side reaction at nearly industrial current densities. Herein, we report a combined scenario of a nanotip-enhanced electric field and surfactant-modified interface microenvironment to enable the electrocatalytic deuteration of arylacetonitrile in D2O with an 80% FE at -100 mA cm-2. The increased concentration with low activation energy of arylacetonitrile due to the large electric field along the tips and the accelerated arylacetonitrile transfer and suppressed D2 evolution by the surfactant-created deuterophobic microenvironment contribute to breaking the trade-off between a high FE and large current density. Furthermore, the application of our strategy in other deuteration reactions with improved Faradaic efficiencies at -100 mA cm-2 rationalizes the design concept.