Search

Sodium‐carbon dioxide (Na‐CO2) batteries are regarded as promising energy storage technologies because of their impressive theoretical energy density and CO2 reutilization, but their practical applications are restricted by uncontrollable sodium dendrite growth and poor electrochemical kinetics of CO2 cathode. Constructing suitable multifunctional electrodes for dendrite‐free anodes and kinetics‐enhanced CO2 cathodes is considered one of the most important ways to advance the practical application of Na‐CO2 batteries. Herein, RuO2 nanoparticles encapsulated in carbon paper (RuCP) are rationally designed and employed as both Na anode host and CO2 cathode in Na‐CO2 batteries. The outstanding sodiophilicity and high catalytic activity of RuCP electrodes can simultaneously contribute to homogenous Na+ distribution and dendrite‐free sodium structure at the anode, as well as strengthen discharge and charge kinetics at the cathode. The morphological evolution confirmed the uniform deposition of Na on RuCP anode with dense and flat interfaces, delivering enhanced Coulombic efficiency of 99.5% and cycling stability near 1500 cycles. Meanwhile, Na‐CO2 batteries with RuCP cathode demonstrated excellent cycling stability (>350 cycles). Significantly, implementation of a dendrite‐free RuCP@Na anode and catalytic‐site‐rich RuCP cathode allowed for the construction of a symmetric Na‐CO2 battery with long‐duration cyclability, offering inspiration for extensive practical uses of Na‐CO2 batteries. [ABSTRACT FROM AUTHOR]

This study reports the selective hydroxylation of macroscopic carbon surfaces that renders initially hydrophobic carbon fiber paper hydrophilic for more than one year (62 weeks) so far. This long time of sustained hydrophilicity is unprecedented and transforms the utility of macroscopic carbon materials. Quantification of surface oxygenates of a systematic series of 13 chemical treatments reveals that surface hydroxyls are predictors of long‐lasting hydrophilicity. The rapid, mild, acid‐free, transition‐metal‐free treatment does not leave surface residues, inhibits overoxidation of graphitic carbon beyond hydroxyls, and introduces the highest edge density on carbon surfaces, without altering the mesostructure of carbon fiber network architectures and without lowering the flexural strength of carbon fiber paper. Graphitic edges are required for enhanced stability of surface oxygenates that retain a threshold amount of adsorbed water, which is necessary for keeping carbon fiber paper hydrophilic. Application of hydrophilic carbon fiber paper as high‐surface‐area working electrode supports for alkaline water oxidation catalyzed by [NiFe]‐layered double hydroxide nanosheets demonstrates a factor of 60 higher mass activity compared to catalysis on flat basal‐plane highly ordered pyrolytic graphite electrodes. [ABSTRACT FROM AUTHOR]

The fabrication of flexible catalytic films with isolated single/dual‐atomic sites and their integration in wearable electronics is challenging. Herein, an efficient method to prepare atomically dispersed binary Ni/Co‐decorated flexible carbon nanofiber (NiCo‐CNF) film using formamide‐derived cyano‐specific NiCo‐NC as nanofillers was developed. The optimized Ni1Co1‐CNF catalytic film, having large‐area, high density of adjacent Ni‐N4 and Co‐N4 active sites, and good mechanical properties under repeated bending and release conditions, possessed high catalytic activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The ORR/OER potential difference (ΔE10) for Ni1Co1‐CNF at 10.0 mA cm−2 was highly comparable with the Pt/C+RuO2 mixture. In addition, flexible Ni1Co1‐CNF‐assembled Zn‐air battery displayed very good mechanical robustness and cycling stability. Our work may inspire the fabrication of other atomic metal‐decorated films for membrane electrocatalysis. [ABSTRACT FROM AUTHOR]

Electrochemical lactate biosensors based on lactate oxidase (LOx) are used for diagnostics, sports medicine, and the food industry. However, samples from these sectors may have acidic levels at which the biocatalytic activity of LOx may be diminished. In this work, the enhancement of the bio‐electrocatalytic activity of LOx at low pH by pKa modulation of its catalytic His265 was studied by rational engineering of lactate oxidase from Aerococcus viridans (AvLOx). Several candidates based on interactions with His265 were selected by in silico structural analysis. The designed variants were heterologously produced, and the S175A mutant showed considerable improvement over its wild‐type counterpart, showing 157 % of the enzymatic activity found in the wild‐type at pH 5. Bioelectrodes were assembled based on Prussian‐blue‐modified carbon paper mediator system. The electrocatalytic performance of the amperometric biosensors of S175A variant at pH 5 exhibited a linear range of 0.2–2 mM measured at 0 V vs SCE, a sensitivity of −17.52 μA/mM ⋅ cm2, representing 240 % of the sensitivity found in the wild‐type biosensor, and a limit of detection of 38 μM, lower than observed with the wild‐type enzyme. These results show that the mutant obtained offers a significant improvement in lactate biosensing at low pH. [ABSTRACT FROM AUTHOR]

Amorphous Fe−Co−P−C films supported on carbon fiber paper were prepared by using an inexpensive conventional magnetron co‐sputtering technique, and the effects of the Co content on electrocatalytic performance were assessed. These Fe80-x CoxP13C7 (x=20, 40 or 60) films performed well as electrocatalysts and exhibited good durability during the oxygen evolution reaction in 1.0 M KOH. Increases in the Co concentration improved the electrocatalytic activity, and the Fe20Co60P13C7 film produced a low overpotential of approximately 310 mV at 10 mA cm−2, with a low Tafel slope of approximately 31 mV dec−1. This material also maintained a constant overpotential for at least 20 h. Based on the results of this study, these materials represent a new approach to the development of highly efficient, inexpensive catalysts for water electrolysis. [ABSTRACT FROM AUTHOR]

Efficient and durable catalysts for the oxygen evolution reaction (OER) are of great importance for energy storage and conversion devices. However, an objective evaluation and fair comparison of different catalysts remain challenging due to the different catalyst loadings and substrates for OER measurements. In this work, we investigated NiFe layer double hydroxide and commercial Ni/NiO catalysts with different loadings and substrates of glassy carbon (GC), porous nickel foam (NF), and carbon paper (CP). The activity, cycling stability, and potentiostatic stability of the catalysts are compared with respect to the loading and substrate. Catalyst loading exhibits a volcano trend with OER activity, while it has little impact on stability. The 3D substrates NF and CP significantly improved the OER activity of the catalysts compared to GC, especially at higher loadings. The consistent degradation trend of the catalysts confirms the validity of using NF or CP as substrates for the stability test. [ABSTRACT FROM AUTHOR]

Metal‐organic frameworks (MOFs) have been widely studied for electrochemical CO2 reduction reaction (CO2RR). However, the application of negative potential tends to trigger its structural reconstruction and component alteration. It is of great significance to study the relationship between the structural evolution of MOF‐derived materials and product selectivity under the reaction conditions. Herein, we fabricate a HKUST‐1 thin film on carbon fiber paper by a facile electrodeposition approach to investigate the variation of CO2RR activity with HKUST‐1 structural reconstruction. During the CO2RR process, the HKUST‐1 reconstructs into two structures successively over time: 3D nanospheres composed of numerous small fragments and 3D nano‐network composed of cross‐linked nanobelts in different directions. The former shows a better catalytic activity due to more active sites, lower charge transfer resistance and higher Cu+/Cu0 ratio. The optimum Faradaic efficiency (FE) of C2 products (ethylene and ethanol) reaches 58.6 % at −0.98 V versus reversible hydrogen electrode (RHE). [ABSTRACT FROM AUTHOR]

Homogeneous, aqueous solutions of the natural compound riboflavin were investigated for their electrocatalytic oxygen to hydrogen peroxide (H2O2) reduction performance using cyclic voltammetry and electrolysis. In addition to pH dependencies, interestingly the choice of carbon‐based electrode material had a strong impact on the electrocatalytic performance. Therefore, the three electrode materials, glassy carbon, carbon paper (CP), and carbon felt were electrochemically compared and afterwards investigated with scanning electron microscopy. Attributed to the deprotonation of riboflavin, pH = 13 was identified as the best performing condition. Using CP at pH = 13, the addition of riboflavin enhanced the H2O2 production by a factor of 14 up to 355 μmol after 6 h at an average faradaic efficiency of around 80%. [ABSTRACT FROM AUTHOR]

A series of surface‐functionalized gold nanocatalysts are synthesized. Through diazonium chemistry, calix[4]arene molecules are grafted at the gold surface. Sharing the same anchoring function and a common backbone, the calix[4]arene ligands possess distinct terminal chemical functions where the length, hydrophobic nature, and oxygen affinity are varied. Thanks to the versatility of the calix[4]arene platform, this paper only focuses on the molecular tuning of the solid/liquid interface through the change of the tail groups while electronic effects that are regulated by the anchoring function will be similar for all catalysts. Electrocatalytic tests demonstrate the influence of the tails group on the oxygen reduction reaction performances, including efficiency, selectivity, and durability. Beyond a pure geometric steric effect, it is shown that chemical properties of the ligands can effectively tune the interactions between the metallic catalyst and the electrolyte and reactants. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the core reactions of a series of advanced modern energy and conversion technologies, such as fuel cells and metal–air cells. Among all kinds of oxygen electrocatalysts that have been reported, single‐atom catalysts (SACs) offer great development potential because of their nearly 100% atomic utilization, unsaturated coordination environment, and tunable electronic structure. In recent years, numerous SACs with enriched active centers and asymmetric coordination have been successfully constructed by regulating their coordination environment and electronic structure, which has brought the development of atomic catalysts to a new level. This paper reviews the improvement of SACs brought by atom‐level interface engineering. It starts with the introduction of advanced techniques for the characterizations of SACs. Subsequently, different design strategies that are applied to adjust the metal active center and first coordination sphere of SACs and then enhance their oxygen electrocatalysis performance are systematically illustrated. Finally, the future development of SACs toward ORR and OER is discussed and prospected. [ABSTRACT FROM AUTHOR]

Solution precursor plasma spraying is used to produce catalytic trimetallic coatings containing Ni, Fe and Mo directly onto stainless‐steel mesh, Ni foam and carbon paper. The resulting material is mostly comprised of face centered cubic FeNi3 alloy forming a highly porous coating with nanostructured features. The addition of Mo (up to ≈14 at%) generates no new crystal phases but only an increase in the lattice parameter, indicating the formation of FeNi3Mox solid solutions. The FeNi3Mox solid solutions are used as electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media. The addition of Mo increases the HER activity significantly reaching an optimum performance at ≈9 at% Mo (FeNi3Mo0.40) with an overpotential at −10 mA cm−2 of 112 mV and a Tafel slope of 109 mV dec−1. The enhanced HER activity is attributed to the formation of a FeNi3Mox solid solution with an increased work function that is correlated to smaller hydrogen adsorption energies. Theoretical activity maps reveal that sites near superficial Mo atoms forms catalytic hot spots and are responsible for the observed activity. [ABSTRACT FROM AUTHOR]

Converting CO2, a major component of greenhouse gas in the atmosphere, into value‐added fine chemicals is beneficial from environmental and economic aspects. Except for various methods for CO2 reduction such as thermal catalysis, photocatalysis, electrocatalysis and biological reduction, hydrothermal reduction of CO2 to organics is becoming a novel and promising strategy. The hydrogen formed in situ from high‐temperature water could avoid the serious issues of hydrogen storage and transportation. This paper summarizes the recent advances on CO2 conversion to formic acid with metal‐ and biomass‐based compounds under hydrothermal conditions mainly focusing on the role of high‐temperature water, autocatalysis mechanism of metal reductants, and interfacial catalysis mechanism of metal/metal oxides. The effects of several experimental variables including temperature, reaction time and pH of the solution on formic acid yield are systematically illustrated as well. Finally, future efforts for fundamental researches and industrial applications of hydrothermal CO2 reduction are discussed. [ABSTRACT FROM AUTHOR]

In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N2 reduction (Li-N2R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N2R, the formation of Li metal, LiOH and Li2O as well as a peak consistent with the a-phase of Li3N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems. [ABSTRACT FROM AUTHOR]

In this paper, Ti4O7/g‐C3N4 nanocomposites are successfully prepared by hydrothermal and carbothermal reduction reaction. It shows large specific surface area and electrochemical active surface area (ECSA = 187.82 cm2) and can act as an oxidation reduction reaction catalyst. Compared with commercial Pt/C catalyst, Ti4O7/g‐C3N4 nanocomposites show good catalytic activity in alkaline medium. The peak potential, onset potential, and half‐wave potential are 0.74 (versus RHE), 0.96 (versus RHE), and 0.74 V (versus RHE), respectively. It is worth mentioning that Ti4O7/g‐C3N4 catalyst shows better methanol tolerance and cycle stability than commercial Pt/C catalyst. The relative current density attenuation is less than 30% after a long cycle of 24 h. [ABSTRACT FROM AUTHOR]

The field of electrochemical CO2 reduction has been transitioning to industrially relevant scales by changing the architecture of the electrochemical cells and moving away from the traditional aqueous H‐cells to membrane electrode assemblies (MEA). The reaction environments in MEAs vary drastically from that of aqueous H‐cells, which could result in significantly different catalytic activity. In this paper, we test AgPd alloys, one of the most promising CO producing catalysts reported, at industrially relevant scales (50 to 200 mA/cm2) in a MEA configuration. We report that, with increasing Pd composition in the electrode, the CO selectivity reduces from 99 % for pure Ag to 73 % for pure Pd at 50 mA/cm2. The MEA configuration helps attain a high CO partial current density of 123 mA/cm2. We find that catalytic activity reported in aqueous H‐Cells does not translate at higher current densities and that cell architecture must play an important role in benchmarking catalytic activity. [ABSTRACT FROM AUTHOR]

A table of contents for the journal is presented.

Monitoring the surface dynamics of catalysts under working conditions is important for a deep understanding of the underlying electrochemical mechanisms towards efficient energy conversion and storage. Fourier transform infrared (FTIR) spectroscopy with high surface sensitivity has been considered as a powerful tool for detecting surface adsorbates, but it faces a great challenge when being adopted in surface dynamics investigations during electrocatalysis due to the complication and influence of aqueous environments. This work reports a well designed FTIR cell with tunable micrometre-scale water film over the surface of working electrodes and dual electrolyte/gas channels for in situ synchrotron FTIR tests. By coupling with a facile single-reflection infrared mode, a general in situ synchrotron radiation FTIR (SR-FTIR) spectroscopic method is developed for tracking the surface dynamics of catalysts during the electrocatalytic process. As an example, in situ formed key *OOH is clearly observed on the surface of commercial benchmark IrO2 catalysts during the electrochemical oxygen evolution process based on the developed in situ SRFTIR spectroscopic method, which demonstrates its universality and feasibility in surface dynamics studies of electrocatalysts under working conditions. [ABSTRACT FROM AUTHOR]

Invited for this issue's Front Cover is the group of Prof. Dr. Gilberto Maia. The cover picture schematically illustrates ways to optimize graphene nanoribbons for use in energy‐related electrocatalytic processes, specifically in the oxygen reduction reaction (ORR). Emphasis is placed on the interplay between edge defects, oxygenated groups inherited from the CNT opening process, and their collective influence on the N‐ and P‐doping process. This modulation affects the ORR performance and H2O2 selectivity for specific conditions. Read the full text of the Research Article at 10.1002/celc.202300505. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage and conversion systems (EESCSs), including batteries, supercapacitors, fuel cells, and water electrolysis technologies, enabling the direct conversion between chemical and electrical energies. They are key to the flexible storage and utilization of renewable energy and play an important role in future energy technologies. The physical and chemical properties of electrode materials significantly influence the performance of EESCSs, necessitating the development of materials with both high cost‐effectiveness and superior electrochemical storage and catalytic capabilities. Layered double hydroxides (LDHs), due to their unique properties as high surface area, evenly distributed active sites, and tunable compositions, makes themselves and the derivatives have become focal points in the EESCSs. This review summarizes recent advances of LDH and their derivates for diverse EESCSs applications, aims to elucidate the modification strategies of LDH materials and provide valuable insights for exploring LDH‐derived materials in various electrochemical devices, offering interdisciplinary perspectives for the rational design of LDH‐based materials. [ABSTRACT FROM AUTHOR]

Copper‐based bimetallic heterojunction catalysts facilitate the deep electrochemical reduction of CO2 (eCO2RR) to produce high‐value‐added organic compounds, which hold significant promise. Understanding the influence of copper interactions with other metals on the adsorption strength of various intermediates is crucial as it directly impacts the reaction selectivity. In this review, an overview of the formation mechanism of various catalytic products in eCO2RR is provided and highlight the uniqueness of copper‐based catalysts. By considering the different metals' adsorption tendencies toward various reaction intermediates, metals are classified, including copper, into four categories. The significance and advantages of constructing bimetallic heterojunction catalysts are then discussed and delve into the research findings and current development status of different types of copper‐based bimetallic heterojunction catalysts. Finally, insights are offered into the design strategies for future high‐performance electrocatalysts, aiming to contribute to the development of eCO2RR to multi‐carbon fuels with high selectivity. [ABSTRACT FROM AUTHOR]

Hydrogen absorption in transition metals has received enormous attention for applications such as the hydrogen storage, sensing and corrosion. In particular, the Pd‐H system is a simple and classical metal hydride system that serves as a platform for a deeper understanding of hydrogen behavior. In the past few years, Pd‐H has been reported as electrocatalyst in multiple reactions, whereas the impact of hydrogen absorption/desorption in electrocatalytic applications remains unclear. Therefore, in this concept, factors influencing the hydrogen adsorption/desorption of palladium in the gas phase, such as facet engineering, ligand effects, and alloying effects, are summarized. Subsequently, in the context of electrocatalysis, factors affecting electrochemical hydrogen adsorption/desorption are outlined. Particularly, prospects for the further investigation of electrochemical hydrogen adsorption/desorption in catalysis are discussed. [ABSTRACT FROM AUTHOR]

Hydrogen evolution and oxidation reactions (HER/HOR) are the most fundamental reactions in electrocatalysis. Despite the practical significance, the mechanisms of HER/HOR in aqueous solutions are still elusive. Various theories have been proposed to rationalize the pH effect, cation effect, and structure effect of HER/HOR but none of them can explain all observations. In this review, we discuss four schools of thought for the HER/HOR, focusing on the strengths and shortcomings of each hypothesis and highlighting the magnitude of electrochemical interface structure in hydrogen electrocatalysis. [ABSTRACT FROM AUTHOR]

Electrocatalysis plays a pivotal role in energy conversion and holds significant promise for the development of new energy sources. Understanding the intricate atomic‐level interplay between active sites and electrocatalytic activity is essential for comprehending catalytic behavior and advancing high‐performance catalysts. In this review, an overview of the recent advances in X‐ray absorption fine structure (XAFS) is provided for deciphering the local environment of electrocatalytic metal sites. The application of XAFS in disclosing the electronic interaction and coordination environment of metal sites is summarized, offering insights into the correlation between ligand arrangement and catalytic activity. Special attention is given to advanced XAFS techniques for exploring active species, including determining the actual active sites, monitoring the local structure transformation, and deciphering metal sites–catalysis relationship. The limitations of traditional XAFS have naturally prompted the development of high‐spatiotemporal‐resolution and high‐energy‐resolution techniques as well as in‐situ/operando methods to better understand the entire catalytic process. This review is anticipated to provide a comprehensive understanding of the capabilities of XAFS in exploring the fine structure of electrocatalysts, with implications for the design of advanced catalytic materials. [ABSTRACT FROM AUTHOR]

N‐coordinated Ni sites (NiNx) are effective catalysts for the electrochemical reduction of CO2 to CO. In most researches, modulating the coordination environment of Ni atoms is focused on to improve electrochemical CO2 reduction (ECR) performance. However, the influence of the carbon substrate's structure on the intrinsic activity of NiNx is seldom investigated. The highly curved surface of carbon nanotubes (CNT) may provide a unique curvature effect on NiNx. It is found that the Ni residues in CNT can be atomized to form NiNx sites on the surface of CNT (Ni‐N/CNT@covalent triazine framework [CTF]) through high‐temperature pyrolysis, using a soluble CTF nanosheet as N precursor. The π‐conjugated and ultrathin 2D structure of CTF enables closer interfacial contact between CTF and CNT, which avoids the formation of a thick carbon layer to maximize the curvature effect. Theoretical data reveal that the NiN3 configuration may act as a highly active ECR site, and the curvature effect from CNT can further tune the electronic structure of NiN3, thus improving the ECR kinetics. The Ni‐N/CNT@CTF‐based flow‐cell electrolyzer exhibits a jCO of 201 mA cm−2 at −0.9 V with a high FECO of 98%. [ABSTRACT FROM AUTHOR]

B Contributing to the field b : With this Special Collection, the aim is to transcend the barriers of geography and highlight the recent work of Latin American Electrochemists around the world. Especially in the last few decades, in which time electrochemistry has become popular in diverse areas of research in science and engineering, including material science, energy applications, organic synthesis, and medicine. These talented researchers, many of whom were educated in Latin America, are also contributing to electrochemistry research in diverse areas. [Extracted from the article]

The differential XAFS technique holds promise for detecting surface changes, which benefits many chemical applications. Phase-sensitive detection (PSD) analysis based on modulated excitation spectroscopy experiments is expected to obtain a high-quality difference spectrum, while the mathematical relationship and experiment parameters remain to be discussed. In this article, an approach to obtaining the difference spectrum from the PSD demodulated spectrum is described and its applicability in different experiment settings is discussed. The results indicate that the demodulated spectrum is almost equal to the difference spectrum when the modulating period is 20 times larger than the relaxation time constant. This approach was subsequently applied to an electrochemical modulation experiment and the demodulated spectrum was analyzed. A reversible lattice shrinking is observed via the fitting of demodulated spectra, which is proportional to the charge amount on the electrode. This approach could be used to quantitatively analyze the modulated excitation XAS data and holds promise for a wide range of electrochemical studies. [ABSTRACT FROM AUTHOR]

MoS2, as a catalyst, has attracted broad attention in recent years due to its high catalytic activity and low cost. However, MoS2 stacks readily, especially the one synthesized by calcination which is close to bulk, so it limits the number of exposed active site. Carbon materials possess excellent electrical conductivity and large surface area. In this paper, N‐doped hollow carbon sphere coated MoS2 (NHCS@MoS2) nanocomposites are synthesized via one‐step calcination treatment of the polypyrrole@(NH4)2MoS4 core shell structure directly. Compared with bare MoS2, the NHCS@MoS2 shows remarkably high electrocatalytic activity for hydrogen evolution with the overpotential of 190 mV to reach the current density of 10 mA cm−2. Both small tafel slope and Rct suggest that NHCS@MoS2 has a high hydrogen dissociation rate. Furthermore, it also exhibits excellent stability. Nanocomposites consisting of N‐doped hollow‐carbon‐sphere‐coated MoS2 (NHCS@MoS2) are successfully synthesized via one‐step calcination of the polypyrrole@(NH4)2MoS4 core‐shell structure. The NHCS@MoS2 material shows a remarkably high electrocatalytic activity for the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

The present paper describes the electrochemical activity of a Ni(II)‐Schiff base metallopolymer electrode for the oxidation of ethanol in alkaline media. The scanning electron microscope results show that the metallopolymer at the glassy carbon surface has a nanoflake‐like lamellar structure, and there is no molecular structural change after treatment with NaOH. Voltammetry measurements indicate that the metallopolymer acts as efficient material for the electrocatalytic oxidation of ethanol, where a high‐valent nickel(IV) was revealed as the reactive intermediate during the anodic scan. An isopotential point can be observed in rotating disk electrode voltammetry for ethanol oxidation. The electrode surface may be considered to consist of two independent electrochemical regions, one corresponding to the ethanol electro‐oxidation by nickel(IV) and the second corresponding to water oxidation. The Tafel slopes were found to be 246 mV dec−1 at low overpotentials and 44 mV dec−1 at high overpotentials, which suggest that the first electron transfer step is the rate controlling step. The specific activity of the metallopolymer‐modified electrode for the ethanol electro‐oxidation reaction was 6.66 mA cm−2 for 0.130 μmol cm−2 of electroactive species of metallopolymer at 0.6 V vs. SCE. The activity of a Ni(II)‐Schiff base metallopolymer electrodes for ethanol oxidation is investigated in alkaline media. Tafel slopes of 246 mV dec−1 at low overpotentials and 44 mV dec−1 at high overpotentials are found, suggesting that the first electron transfer step is rate controlling. An isopotential point is observed, revealing that the electrode surface may be considered to consist of two independent electrochemical regions. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen production plays a major role in technologies for renewable energy storage. Water and urea electrolysis (WE, UE) are promising processes in this regard. The oxygen evolution reaction (OER) and urea oxidation reaction (UOR), respectively, are limiting the efficiency of the overall process. As catalysts for these reactions, metal‐organic frameworks (MOF) have gained increasing attention due to their combinations and co‐existence of metal and organic moiety properties. Here, we investigated the catalytic behavior of Ni MOF (1,3,5‐Benzenetricarboxylic acid (BTC)) towards OER and UOR in alkaline medium on carbon paper (CP) as a support. The Ni MOF exhibits 346 mV overpotential (η) at a current density of 10 mA cm−2, 79.03 A g−1 specific‐mass activity at 400 mV of η than compared to wet chemically prepared (WCP) NiO and RuO2 for OER in 1 M KOH. Meanwhile, ≈230 mV of η at 10 mA cm−2 current density with appreciable stability for 12 hours for Ni MOF in 30 % KOH was also observed. For UOR in UE, Ni MOF shows an onset potential of 1.34 V vs. RHE and 63.15 mA cm−2 current density at 1.5 V vs RHE in 1 M KOH in the presence of 1 M urea. The observed results of OER and UOR catalytic behavior are better than wet chemically prepared (WCP) NiO and noble benchmark RuO2 catalyst under identical conditions. The results suggested that the MOF plays a major role in enhancing the catalytic activity by the facile formation of Ni(OH)2/NiOOH, stability and electronic properties due to their porous and interconnected structure. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the rational design of Fe‐N‐, Fe‐S‐, and Fe‐N‐S‐based model catalysts for oxygen reduction reaction (ORR), developed using task‐specific hypercrosslinked polymers as precursors is presented. Based on the model catalysts, atom‐induced differences in ORR performance are carefully examined. In the S‐doped carbons, Fe1−xS forms the metal nanoparticles, while the N sourced together with FeCl3 ensures the uniform distribution of Fe3O4. Obtained results indicate that N/Fe3O4 acts as the higher catalytic active site, whereas the S/Fe1−xS deteriorates the ORR catalytic activity. However, due to the synergistic effect between Fe1−xS /Fe3O4 and N, the S‐doped carbons can substantially enhance the ORR performance. Hence, this work provides guidance for the efficient design of Fe‐N‐S‐based catalysts for ORR. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron oxygen reduction reaction (2e− ORR) has emerged as an efficient route to generate hydrogen peroxide (H2O2) under ambient conditions, being a promising alternative to the traditional energy‐intensive anthraquinone process and direct synthesis route using H2 and O2. However, this 2e− ORR process still requires highly efficient electrocatalysts to adsorb and activate O2 with two‐electron reaction pathway. Among all investigated 2e− ORR electrocatalysts to date, non‐noble metal single atom catalysts (SACs) with tunable electronic structure and different coordination structures manifest great potential in controlling ORR pathway to obtain high‐efficiency H2O2 production. In this review, recent advances and achievements in tuning non‐noble metal SACs for selective 2e− ORR to H2O2 are systematically summarized. Especially, the strategies to effectively regulate the catalytic active sites of non‐noble metal SACs for optimizing the binding strength of key oxygenated intermediates during 2e− ORR are emphatically exhibited and reviewed. Finally, we also point out the challenges and outlooks about the development of non‐noble metal SACs in H2O2 electrosynthesis and the diverse utilization of in‐situ formed H2O2 for biomass upgrading. This review would be helpful to guide the design and development of efficient SACs for electrochemical 2e− ORR to H2O2 under ambient conditions. [ABSTRACT FROM AUTHOR]

The electrocatalytic synthesis of C–N coupling compounds from CO2 and nitrogenous species not only offers an effective avenue to achieve carbon neutrality and reduce environmental pollution, but also establishes a route to synthesize valuable chemicals, such as urea, amide, and amine. This innovative approach expands the application range and product categories beyond simple carbonaceous species in electrocatalytic CO2 reduction, which is becoming a rapidly advancing field. This review summarizes the research progress in electrocatalytic urea synthesis, using N2, NO2−, and NO3− as nitrogenous species, and explores emerging trends in the electrosynthesis of amide and amine from CO2 and nitrogen species. Additionally, the future opportunities in this field are highlighted, including electrosynthesis of amino acids and other compounds containing C–N bonds, anodic C–N coupling reactions beyond water oxidation, and the catalytic mechanism of corresponding reactions. This critical review also captures the insights aimed at accelerating the development of electrochemical C–N coupling reactions, confirming the superiority of this electrochemical method over the traditional techniques. [ABSTRACT FROM AUTHOR]

Conductive metal–organic frameworks (c‐MOFs) have aroused extensive attention due to their excellent properties by integrating the features of both conductive and porous crystalline materials. Recent investigations in miniaturization of c‐MOFs into nanostructured conductive MOFs (nc‐MOFs) endow them with additional advantages such as reduced diffusion distance, accelerated mass/electron transfer, enhanced active site exposure, and accessibility, further widening their applications with reinforced performances compared to the conventional bulk counterparts. Herein, a timely review on the latest achievements in the field of nc‐MOFs is provided. First, we systematically introduce the synthetic strategies for producing nc‐MOFs with controllable morphologies and compositions. Second, the enhanced performance of nc‐MOFs in electrocatalysis, supercapacitors, batteries, sensors, and photocatalysis is highlighted. Finally, a discussion on the challenges and opportunities of the synthesis and applications of nc‐MOFs is presented. It is expected that this review will shed light on the future development of nc‐MOFs with promising application potential. [ABSTRACT FROM AUTHOR]

Sustainable energy development can no longer be met by fossil fuels alone. Hence, electrochemical water splitting containing oxygen and hydrogen evolution reactions is appealing as a clean energy pathway. As respects the water splitting efficiency which is largely determined by the selectivity, durability, and intrinsic activity of the electrocatalysts, one of the most challenging questions when studying these materials is "which category of electrocatalysts will show the best performance in this issue?" The best electrocatalysts for water splitting still come from noble metals. Although these materials show particularly good efficiency, but due to the scarce resources their massive use is limited. Therefore, the noble metal‐free materials due to their stability, efficiency, abundance and variety of reaction sites were introduced as an interesting candidate for electrochemical water splitting reactions. In this review, based on the important above‐mentioned points, our attention was focused on key categories based on transition metals (TMs), metal organic framework derived (MOF‐derived), carbon‐based hybrids, graphitic carbon nitride (g‐C3N4) hybrids, and bio‐assisted electrocatalysts. These compounds have shown significant activity and stability for broad electrocatalysis applications in water splitting reactions and displaying remarkable potential to replace with noble metal‐based catalysts. This comprehensive review identifies rational strategies for designing and synthesizing high‐performance novel noble metal‐free electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

The development of cost‐effective and stable electrocatalysts that can replace the prevailing Pt‐based and Ir‐based catalysts for water splitting remains a formidable challenge. The electrocatalytic performance of a catalyst depends on its chemical composition and environment during catalysis. Herein, a Ru–Mo composite is used as an example to highlight the significance of tailoring the chemical environments of the active‐sites. This customization enhances the cathodic and anodic reactions involved in water splitting, ultimately leading to an improved full reaction efficiency. Specifically, the chemically reduced state of Ru–Mo demonstrates promising hydrogen evolution activity and exhibits low overpotentials of 48 and 34 mV at the current density of 10 mA cm−2 in acidic and alkaline electrolytes, respectively. The chemically oxidized state of Ru–Mo, derived from the same precursor, demonstrates proficient oxygen evolution activity and exhibits low overpotentials of 260 and 270 mV at 10 mA cm−2 in acidic and alkaline electrolytes, respectively. Additionally, in both cases, the Ru–Mo composites exhibit significantly improved stability under typical water‐splitting conditions. Despite the close chemical compositions of these two catalysts, they show poor performance in the counter electrode reactions, demonstrating the importance of establishing a suitable chemical environment for efficient electrocatalysis. [ABSTRACT FROM AUTHOR]

The development of precious‐metal‐free catalysts with bifunctional activities for both oxygen reduction and evolution reactions (ORR/OER) is crucial for the advancement of regenerative fuel cells and rechargeable metal−air batteries. Manganese oxides (MnOx) have emerged as promising bifunctional catalysts. However, MnOx electrodes typically exhibit poor ORR/OER cycling stability owing to polarization‐induced MnOx redox reactions and phase transition. To address this issue, we developed metallic cation (i. e., Co2+, Ni2+, Cu2+, or Bi3+) doped MnOx/carbon electrodes using potentiodynamic, potentiostatic and galvanostatic methods. Among the explored dopant cations Ni2+ intercalated into MnOx under acidic conditions using a slow‐scan cyclic voltammetry method, significantly enhanced the ORR/OER activity and stability of MnOx. Alongside electrochemical doping, MnOx also underwent redox reactions leading to changes in Mn valence and phase transitions. The Ni‐incorporated MnOx gas diffusion electrode (GDE) demonstrated exceptional stability for over 120 accelerated OER and ORR cycles at ±10 mA cm−2 in 5 M KOH, surpassing the performance of the Pt/C−IrO2 benchmark. Furthermore, it achieved OER current densities of approximately 22 mA cm−2 at 1.65 VRHE, which was twice as high as that of Pt/C−IrO2. [ABSTRACT FROM AUTHOR]

Electrochemical ammonia oxidation reaction (eAOR) regains interest due to ammonia being an interesting alternative to hydrogen for fuel cell technologies. In the present review, we first discuss some of the most important findings on eAOR with solid catalysts, including mechanistic and feasibility aspects for practical implementation. We then examine the reports on molecular catalysis of eAOR that have recently emerged. We finally discuss immobilization strategies of these molecular catalysts, and discuss intrinsic advantages of those strategies, so as to guide the design of efficient catalytic systems able to compete with heterogeneous, solid catalysts. [ABSTRACT FROM AUTHOR]

This paper describes the preparation and electrocatalytic activity of nanocomposites composed of reduced graphene oxide and Au25 clusters. Well-defined nanocomposites are prepared by coating the surface of reduced graphene oxide with multiple layers of Au25 film, the thickness of which can be precisely controlled according to the preparation conditions. The electrocatalytic activity of the nanocomposites are examined for the reduction of [Ru(NH3)6]3+ and in the oxygen reduction reaction by chronoamperometry and electrochemical impedance spectroscopy as a function of Au25 thickness. Whereas the catalytic rate constants obtained for the reduction of [Ru(NH3)6]3+ are found to be rather constant with varying Au25 thickness, those for the oxygen reduction reaction increased drastically with an increasing number of Au25 layers. This increase can be ascribed to the porous structures generated in the nanocomposites. The porous channels generated in the nanocomposites offer confined space surrounded by electrified surface, greatly enhancing the electrocatalytic activity for the oxygen reduction reaction. Additional rotating disk electrode and rotating ring-disk electrode voltammetry show that the nanocomposites support an efficient four-electron reduction of oxygen. [ABSTRACT FROM AUTHOR]

In this work, a new polymeric binder (polymer of intrinsic microporosity, PIM‐1) has been investigated and discussed to prepare and characterize composite materials for the cathodic oxygen reduction reaction. The new binder is a polymer of intrinsic microporosity, a family of organic compounds with molecularly rigid (glassy) structure, good mechanical and chemical stability. Their influence on the electrocatalytic behaviour of a commercial electrocatalyst during the oxygen reduction reaction in acidic and alkaline media has been investigated, discussed and compared to the behaviour of common cationic and anionic polymer binders, using rotating disk electrode (RDE) techniques. Polymers of intrinsic microporosity perform similarly well, and sometimes better (due to rigidity and gas permeation) when compared to commercial binders. Thus, herein, we showed that PIMs do represent a very promising and versatile alternative as binders in electrocatalysis. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of complicated multiphase conversions and the severe shuttling effect of lithium polysulfides (LiPSs) significantly hinder the applications of Li‐S battery, which is one of the most promising candidates for the next‐generation energy storage system. Herein, a bifunctional electrocatalyst, indium phthalocyanine self‐assembled with carbon nanotubes (InPc@CNT) composite material, is proposed to promote the conversion kinetics of both reduction and oxidation processes, demonstrating a bidirectional catalytic effect on both nucleation and dissolution of Li2S species. The theoretical calculation shows that the unique electronic configuration of InPc@CNT is conducive to trapping soluble polysulfides in the reduction process, as well as the modulation of electron transfer dynamics also endows the dissolution of Li2S in the oxidation reaction, which will accelerate the effectiveness of catalytic conversion and facilitate sulfur utilization. Moreover, the InPc@CNT modified separator displays lower overpotential for polysulfide transformation, alleviating polarization of electrode during cycling. The integrated spectroscopy analysis, HRTEM, and electrochemical study reveal that the InPc@CNT acts as an efficient multifunctional catalytic center to satisfy the requirements of accelerating charging and discharging processes. Therefore, the Li–S battery with InPc@CNT‐modified separator obtains a discharge‐specific capacity of 1415 mAh g−1 at a high rate of 0.5 C. Additionally, the 2 Ah Li–S pouch cells deliver 315 Wh kg−1 and achieved 80% capacity retention after 50 cycles at 0.1 C with a high sulfur loading of 10 mg cm−2. Our study provides a practical method to introduce bifunctional electrocatalysts for boosting the electrochemical properties of Li–S batteries. [ABSTRACT FROM AUTHOR]

How to put together a comprehensive water oxidation design is the long‐term problem for the generation of sustainable fuels. In nature, plants are equipped with a complex mechanism (the Calvin cycle) in the stroma that, over the billions of years, efficiently takes CO2 and converts it to sugar. This reductive process needs electrons from an oxygen‐evolving complex (OEC) in the core of photosystem II, where a water oxidation reaction (WOR) releases molecular oxygen. The initial function of proton relays in natural WOR happens when Tyrosine Yz is oxidized by light harvested P680 through a proton‐coupled electron transfer reaction. The second and main one, is composed of water‐included polypeptide channels from and to CaMn4O5. These channels were created utilizing hydrogen‐bonded networks (HBN). HBN is crucial in providing water substrate and removing the released protons to prevent the accumulation of protons and preserve the stability of the catalytic center. This concept summarizes the challenges in employing biomimicry to create artificial leaves from the viewpoint of proton relays, with the main purpose being providing structural functionality to assist the quick proton hopping. [ABSTRACT FROM AUTHOR]

Thermochemical conversion of fossil resources into fuels, chemicals, and materials has rapidly increased atmospheric CO2 levels, hindering global efforts toward achieving carbon neutrality. With the increasing push for sustainability, utilizing electrochemical technology to transform CO2 or biomass into value‐added chemicals and to close the carbon cycle with sustainable energy sources represents a promising strategy. Expanding the scope of electrosynthesis technology is a prerequisite for the electrification of chemical manufacturing. To this end, constructing the C─N bond is considered a priority. However, a systematic review of electrocatalytic processes toward building C─N bonds using CO2 and biomass as carbon sources is not available. Accordingly, this review highlights the research progress in the electrosynthesis of organic nitrogen compounds from CO2 and biomass by C─N coupling reactions in view of catalytic materials, focusing on the enlightenment of traditional catalysis on C─N coupling and the understanding of the basis of electrochemical C─N coupling. The possibility of C─N bond in electrocatalysis is also examined from the standpoints of activation of substrates, coupling site, mechanism, and inhibition of hydrogen evolution reaction (HER). Finally, the challenges and prospects of electrocatalytic C─N coupling reactions with improved efficiency and selectivity for future development are discussed. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) high‐entropy alloys (HEAs) have emerged as promising electrocatalysts due to the benefits of polymetallic coordination and robust electrical conductivity. However, the multiple elements in 2D HEAs pose challenges in achieving a uniform composition and maintaining a 2D limit morphology, complicating their structural characterization. Furthermore, even minor adjustments to the composition can significantly alter the properties of 2D HEAs, underscoring the need for a deeper understanding of their structure–property relationships to advance synthesis and application. Therefore, this review critically examines the intrinsic factors influencing synthesis methods and the practical applications of 2D HEAs in electrocatalysis for sustainable energy conversion. The urgency is emphasized for developing new synthesis techniques, enhancing advanced characterization methods, and gaining profound insights into the functional mechanisms of 2D HEAs. [ABSTRACT FROM AUTHOR]

Pd‐based nanostructures are endowed with impressive catalytic features for alcohol‐based fuel cells, however, their poisoning by carbon monoxide (CO) is a great barrier to large‐scale utilization of such fuel cells as alternative power sources. The need to optimize the electrochemical CO oxidation (COOxid) of Pd‐based nanostructures in various electrolytes has attracted much attention in the last decade, so it is important to provide a timely update on this area of research. This mini‐review highlights the most recent advances in controlling some synthesis methods of Pd‐based nanostructures and their morphologies for enhanced electrocatalytic COOxid in different electrolyte conditions in the last three years. Finally, the main challenges for commercially viable Pd‐based nanostructures for electrochemical COOxid are discussed, highlighting the future perspectives and providing promising solutions for practical COOxid application. [ABSTRACT FROM AUTHOR]

The electrocatalytic conversion of nitrate (NO3‾) to NH3 (NO3RR) offers a promising alternative to the Haber–Bosch process. However, the overall kinetic rate of NO3RR is plagued by the complex proton‐assisted multiple‐electron transfer process. Herein, Ag/Co3O4/CoOOH nanowires (i‐Ag/Co3O4 NWs) tandem catalyst is designed to optimize the kinetic rate of intermediate reaction for NO3RR simultaneously. The authors proved that NO3‾ ions are reduced to NO2‾ preferentially on Ag phases and then NO2‾ to NO on Co3O4 phases. The CoOOH phases catalyze NO reduction to NH3 via NH2OH intermediate. This unique catalyst efficiently converts NO3‾ to NH3 through a triple reaction with a high Faradaic efficiency (FE) of 94.3% and a high NH3 yield rate of 253.7 μmol h−1 cm−2 in 1 M KOH and 0.1 M KNO3 solution at ‒0.25 V versus RHE. The kinetic studies demonstrate that converting NH2OH into NH3 is the rate‐determining step (RDS) with an energy barrier of 0.151 eV over i‐Ag/Co3O4 NWs. Further applying i‐Ag/Co3O4 NWs as the cathode material, a novel Zn‐nitrate battery exhibits a power density of 2.56 mW cm−2 and an FE of 91.4% for NH3 production. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of sulfur conversions have long been hindering the implementation of fast and efficient sulfur electrochemistry in lithium–sulfur (Li–S) batteries. In this regard, herein the unique chromium boride (CrB) is developed via a well‐confined mild‐temperature thermal reaction to serve as an advanced sulfur electrocatalyst. Its interstitial‐alloy nature features excellent conductivity, while the nano‐lamination architecture affords abundant active sites for host‐guest interactions. More importantly, the CrB nanocatalyst demonstrates a dual sulphophilicity with simultaneous Cr─S and B─S bondage for establishing strong interactions with the intermediate polysulfides. As a result, significant stabilization and promotion of sulfur redox behavior can be achieved, enabling an excellent Li–S cell cyclability with a minimum capacity fading rate of 0.0176% per cycle over 2000 cycles and a favorable rate capability up to 7 C. Additionally, a high areal capacity of 5.2 mAh cm−2, and decent cycling and rate performances are still attainable under high sulfur loading and low electrolyte dosage. This work offers a facile approach and instructive insights into metal boride sulfur electrocatalyst, holding a good promise for pursuing high‐efficiency sulfur electrochemistry and high‐performance Li–S batteries. [ABSTRACT FROM AUTHOR]

The electrochemical N2 reduction reaction (ENRR), driven by renewable electricity and run under ambient conditions, offers a promising sustainable avenue for carbon‐neutral NH3 production. Yet, to efficiently bind and activate the inert N2 remains challenge. Herein, effective and stable electrochemical NH3 synthesis on Sm(OH)3 via enhanced adsorption of hydrogen and dinitrogen by dual integration of sulfur dopants and oxygen vacancies (VO) is reported. The resulting S‐doped lanthanide electrocatalyst attains both a good NH3 yield rate, exceeding 21 μgNH3 h−1 mgcat.−1, and an NH3 faradaic efficiency of over 29% at −0.3 V (vs reversible hydrogen electrode) in an H‐type cell using a neutral electrolyte, figures of merit that are largely maintained after 2 days of consecutive polarization. Density functional theory calculations show that the adsorption energy barrier of N2 on S‐Sm(OH)3(VO) is greatly lowered by the introduction of VO. In addition, the S sites improve the adsorption of hydrogen produced via the Volmer reaction, which is conducive to the formation of the *N–NH intermediate (i.e., the potential determining step, PDS) on adjacent Sm sites, and thereby significantly promotes the reaction kinetics of ENRR. The PDS free energy for the catalyst is comparable with the values at the peak of the ENRR volcano plots of leading transition metal catalyst surfaces. [ABSTRACT FROM AUTHOR]

The presence of nitrate in industrial, domestic and agricultural wastewater has a detrimental impact on both ecosystem and human health, as remediation and purification efforts are slow, challenging and difficult, given the high solubility and stability of this pollutant. Taking nitrate into high value‐added ammonia by electrochemical reduction can overcome high pollution and energy consumption limit of Haber‐Bosch process with long‐term significance of environmental protection and energy saving. This review summarized the research progress on the electrocatalytic reduction of nitrate to ammonia, with a focus on the reaction mechanisms, influencing factors, product detection methods, performance evaluation methods and the research status of electrocatalysts up to now. The review reported the latest strategies employed to design efficient electrocatalysts, such as pore structure regulation, alloying, heterostructure construction, defect and interface engineering, crystal surface regulation and microenvironment modulation of single‐atom catalysts. It highlights critical factors that determin the performance in terms of nitrate adsorption, exposed active sites, mass transfer rate, intermediates barrier and side reactions, as well as the stability of electrocatalysts and recovery of ammonia. In addition, the future direction of technology for electrocatalytic reduction of nitrate to ammonia has also been proposed. [ABSTRACT FROM AUTHOR]

The scarcity of inexpensive and efficient electrocatalyst for acid water oxidation to molecular oxygen presents the development of nonprecious catalysts for water oxidation a scientific priority. For water splitting, transition-metal dichalcogenides have attracted great interest as advanced catalysts for hydrogen evolution reaction, but there has been no sincere attention to generate significant anodic current density of oxygen evolution reaction (OER) with these materials. Addressing this unmet need, here, the outstanding catalytic performance of MoS2 and TaS2 in OER is demonstrated. Chemically exfoliated 2D thin sheets of MoS2 and TaS2, in both of their 1T and 2H polymorph, have been employed for OER catalysis in acid medium. The best performance for oxygen evolution, which is also comparable to benchmark IrO2, comes out from 1T-MoS2 followed by 1T-TaS2, 2H-MoS2, and 2H-TaS2. Theoretical study reveals that the dominant catalytic activity is on edge sites instead of surface and corroborates the experimental results of polymorphic dependence of electrocatalytic activity. The materials have also shown moderate durability in the harsh acidic medium. The study brings up new set of electrocatalyst for oxygen evolution in acid regime that hitherto has remained largely unrevealed. [ABSTRACT FROM AUTHOR]

Palladium has been proved to be an effective catalyst for CO2 electrocatalytic reduction. In this paper, nanostructured Pd particles fixed on polyaniline-covered MWNTs surfaces (Pd-PANI/CNT) were synthesized using an in situ method by reducing H2PdCl4 in a mixture of MWNTs and aniline with sodium citrate as protective stabilizer. TEM micrographs indicate that the addition of sodium citrate optimizes the size and distribution of the nanoparticles. In a 3-electrode system, both catalysts exhibit efficient and sustainable CO2 conversion towards formate but the one with sodium citrate addition is even better. The highest faradaic efficiency happens at −0.8 V vs. SCE and can be as high as 83 %. Based on the experiments, we put forward a mechanism of Pd-catalyzed CO2 electroreduction in aqueous solution in which Pd forms a PdH x hybrid that is involved in the reduction process with Pd. [ABSTRACT FROM AUTHOR]