Search

As traditional energy structures transition to new sources, hydrogen is receiving significant research attention owing to its potential as a clean energy source. The most significant problem with electrochemical hydrogen evolution is the need for highly efficient catalysts to drive the overpotential required to generate hydrogen gas by electrolyzing water. Experiments have shown that the addition of appropriate materials can reduce the energy required for hydrogen production by electrolysis of water and enable it to play a greater catalytic role in these evolution reactions. Therefore, more complex material compositions are required to obtain these high-performance materials. This study investigates the preparation of hydrogen production catalysts for cathodes. First, rod-like NiMoO4/NiMo is grown on NF (Nickel Foam) using a hydrothermal method. This is used as a core framework, and it provides a higher specific surface area and electron transfer channels. Next, spherical NiS is generated on the NF/NiMo4/NiMo, thus ultimately achieving efficient electrochemical hydrogen evolution. The NF/NiMo4/NiMo@NiS material exhibits a remarkably low overpotential of only 36 mV for the hydrogen evolution reaction (HER) at a current density of 10 mA·cm−2 in a potassium hydroxide solution, indicating its potential use in energy-related applications for HER processes. [ABSTRACT FROM AUTHOR]

Herein, we have demonstrated Lewis acid Fe(III)-assisted hydroxylation of ZIF-67 to form FexCo-layered double hydroxide (LDH) nanosheets. The catalyst Fe0.4Co-LDH produced an excellent water oxidation activity to reach a current density of 20 mA cm−2 at only 190 mV overpotential, superior to that of hydrothermally synthesized LDH with a similar composition. [ABSTRACT FROM AUTHOR]

Developing a robust and highly efficient electrocatalyst for the oxygen evolution reaction (OER) is required, due to its sluggish mechanism and high overpotential. Here, we present the Ti 3 C 2 T x and ZIF-67 composites (MXene/ZIF-67) for an efficient OER. The MXene/ZIF-67_1:10 exhibits an overpotential of 366 mV, which is better than MXene (548 mV) and RuO 2 (395 mV). Moreover, it shows improved electrochemical stability at 20 mA·cm− 2 with only a 0.2% increase in potential after 5 h, while RuO 2 with an overpotential loss of 3.5%. After an increase in the current density of 10–20 mA cm−2 the potential increase by 7.4%, while in RuO 2 by 25.3%. To reveal the observed performance, the composite's robustness and explain each component's role. Moreover, a detailed OER mechanism is discussed. It was realized via in situ Raman microscopy and XRD which allowed the revealing of the active species responsible for boosting OER. • MXene/ZIF-67 composite was designed for OER. • MXene/ZIF-67 presented outstanding electrocatalytic activity in OER. • MXene/ZIF-67 structures exhibit robust stability at high current density for a long time. • In situ Raman and XRD were applied to revile the mechanism of OER. [ABSTRACT FROM AUTHOR]

Transition metal-based nanomaterials exhibit promising potential as highly active and low-cost electrocatalysts for alkaline water splitting, which can be achieved via elaborating compositional modulation and structural manipulation. This, however, normally involves multiple or even complex synthetic procedures. Herein, we report a simple one-step sulfidation of FeMnZn multi-metal skeletons for the preparation of highly efficient electrocatalysts. The incorporation of Mn and Zn induced a hierarchical nano/micro sheet-to-sheet morphology supported on an open porous skeleton (FeMnZn/Mn-FeS, FMZS2), which not only facilitates electron/ion transport but also expands the accessible surface. Meanwhile, Mn is introduced to optimize the adsorption/desorption ability of intermediates on the S sites in FeS. The resultant effect leads to remarkable electrocatalytic performance with good durability. Notably, the optimized FMZS2 delivers 20 mA cm−2 at a low overpotential of 118 mV for the HER and 100 mA cm−2 at an overpotential of 390 mV for the OER, outperforming Pt/C and IrO2 catalysts, respectively. Moreover, the assembled alkaline electrolyzer also has good overall water splitting capability, which is better than that of the noble metal ones. [ABSTRACT FROM AUTHOR]

The sluggish de‐solvation kinetics and uneven Zn2+ transport behavior at the Zn anode are undesirable for commercialization of zinc ion batteries. To address these issues, a periodically alternating electric field is introduced on the Zn anode by constructing a laponite nano‐clay layer with unique electric field separation properties. This layer exhibits negative and positive electric fields together in the same space but in different directions (negative electric field in the normal direction while the positive electric field is in the radial direction); thus, achieving both homogeneous Zn2+ transport and an effective de‐solvation effect. The laponite film (LAP@Zn) as a multifunctional artificial layer can induce Zn2+ nucleation for preferential orientation growth of Zn along the (002) planes, thereby suppressing dendrite growth on the Zn anode. Consequently, the LAP@Zn symmetric cells exhibit an ultralow overpotential (12 mV) and cycle smoothly over 1100 h at 0.5 mA cm−2. Even at an ultrahigh current density of 40 mA cm−2, the cell still operates stably for 500 h. More encouragingly, the effectiveness is also convincing in MnO2‐based full cells with excellent rate performance and cycle stability. The periodically alternating electric field strategy provides an effective path toward high‐performance and dendrite‐free Zn‐based storage systems. [ABSTRACT FROM AUTHOR]

For flexible solid‐state electronics, it is essential to accelerate the transition to renewable materials and environmentally friendly manufacturing procedures. Symmetric supercapacitors (SCs) have a limited voltage window and capacity, hampering their use in practical applications such as portable electronics, hybrid vehicles, and transportation. To improve the energy density of supercapacitors, the strategy of using an advanced pseudo‐capacitive electrode in an asymmetric device configuration is feasible and effective. Here, we report on the design and synthesis of hierarchical honeycomb‐like morphology with controlled Ni/Co molar ratios of NiCo2O4 (NCO) coatings on flexible stainless‐steel substrates utilizing high cathodic overpotential deposition. The NCO electrode retains 90.5% of the three‐electrode capacitance (911 F g−1, or 594 C g−1) even after increasing the current density to 10 A g−1 (∼10 times). Furthermore, we have fabricated a 1.5 V asymmetric supercapacitor (ASC, NCO//AC); such a device delivers maximum specific energy and specific power of 76.8 Wh kg−1 and 16858 W kg−1 in 2 M KOH electrolyte and excellent cycling stability (∼88% retention after 5000 cycles). [ABSTRACT FROM AUTHOR]

The ultimate objective of this research work is to design a sensitive and selective electrochemical sensor for the efficient detection of ascorbic acid (AA), a vital antioxidant found in blood serum that may serve as a biomarker for oxidative stress. To achieve this, we utilized a novel Yb2O3.CuO@rGO nanocomposite (NC) as the active material to modify the glassy carbon working electrode (GCE). The structural properties and morphological characteristics of the Yb2O3.CuO@rGO NC were investigated using various techniques to ensure their suitability for the sensor. The resulting sensor electrode was able to detect a broad range of AA concentrations (0.5–1571 µM) in neutral phosphate buffer solution, with a high sensitivity of 0.4341 µAµM−1cm−2 and a reasonable detection limit of 0.062 µM. The sensor's great sensitivity and selectivity allowed it to accurately determine the levels of AA in human blood serum and commercial vitamin C tablets. It demonstrated high levels of reproducibility, repeatability, and stability, making it a reliable and robust sensor for the measurement of AA at low overpotential. Overall, the Yb2O3.CuO@rGO/GCE sensor showed great potential in detecting AA from real samples. [ABSTRACT FROM AUTHOR]

BACKGROUND: A microbial electrolysis cell (MEC) is a bio‐hydrogen production device that uses electrochemically active bacteria on the anode combined with applied voltage to break down organic matter. However, the effects of element content on cathode reduction and cathode catalysts on bioanode activity remain unknown. RESULTS: MEC cathodes with different content of Na2MoO4·2H2O (i.e. 0 g L−1 (Ni), 12.5 g L−1 (Ni–Mo 1), 25 g L−1 (Ni–Mo 2) and 37.5 g L−1 (Ni–Mo 3)) were fabricated by normal pulse voltammetry to evaluate the cathode performance. Nanoparticles of Ni electrode are crystalline NiO on the carbon fiber surface. Compared with the Ni electrode, the catalysts of Ni–Mo electrodes are composed of smaller crystalline NiO and amorphous Mo oxides. The results of electrochemical analysis confirmed that Ni–Mo 1 exhibited low exchange transfer resistance (148.72 Ω), high electrochemically active surface area and strong conductivity, resulting in optimal electrocatalysis performance. The newly fabricated electrodes are applied as cathodes in single‐chamber MEC reactors and inoculated with activated sludge from a municipal wastewater treatment plant. High peak current density determined using cyclic voltammetry of the bioanode indicated the strong electrochemical activity of electroactive bacteria in the bioanode of Ni–Mo 1. This is because the low resistance in the MECs could accelerate electron transfer and boost electrochemical reaction. CONCLUSIONS: The performance of cathodes with different Ni and Mo content in terms of electrochemical activity was evaluated. Consequently, the optimal cathode electrode in MECs was Ni–Mo 1. The obtained results reveal that the cathode affects the bioanode activity in MECs. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Improving kinetics of solid‐state sulfide conversion in sulfur cathodes can enhance sulfur utilization of metal‐sulfur batteries. However, fundamental understanding of the solid‐state conversion remains to be achieved. Here, taking potassium‐sulfur batteries as a model system, we for the first time report the reducing overpotential of solid‐state sulfide conversion via the meta‐stable S32− intermediates on transition metal single‐atom sulfur hosts. The catalytic sulfur host containing Cu single atoms demonstrates high capacities of 1595 and 1226 mAh g−1 at current densities of 335 and 1675 mA g−1, respectively, with stable Coulombic efficiency of ≈100 %. Combined spectroscopic characterizations and theoretical computations reveal that the relatively weak Cu‐S bonding results in low overpotential of solid‐state sulfide conversion and high sulfur utilization. The elucidation of solid‐state sulfide conversion mechanism can direct the exploration of highly efficient metal‐sulfur batteries. [ABSTRACT FROM AUTHOR]

Herein, layered porous nitrogen-doped carbon sheets (LPNCS) prepared from waste plastics are employed as an electrocatalytic carrier for the HER under alkaline conditions. The N-doped coral-like nanostructure with abundant meso- and macropores would shorten the proton diffusion pathway, reduce the mass transfer resistance and promote Ru dispersion. The prepared Ru/LPNCS shows an excellent performance with an overpotential of 15 mV at 10 mA cm−2, even lower than that of most reported Ru-based catalysts and the commercial Pt/C catalyst (17 mV), which provides a potential application for converting waste plastics into highly efficient HER catalysts. [ABSTRACT FROM AUTHOR]

An in situ electrochemical reduction strategy is proposed to avoid the aggregation of nano-Ru in lithium batteries for the first time. The high-dispersion face-centered cubic (fcc) nano-Ru is successfully synthesized with an average diameter of 2.0 nm, and the asassembled lithium–oxygen batteries deliver an excellent cycling performance of 185 cycles and an ultralow overpotential of only 0.20 V at 100 mA g-1. [ABSTRACT FROM AUTHOR]

The electrochemical oxygen evolution reaction (OER) is a key process in many renewable energy systems. The development of low‐cost, long‐lasting alternatives to precious‐metal catalysts, particularly functional electrocatalysts with high activity for OER processes, is crucial for reducing the operating expense and complexity of renewable energy generating systems. This work describes a concise method for generating marigold flower‐like metal–organic frameworks (MOFs) aided manganese vanadium oxide via a hydrothermal procedure for increased OER activity. As synthesized MOF MnV oxide has a higher surface area due to the 3D flower‐like structure, which is reinvented with enhanced electrocatalytic active sites. These distinctive structural features result in remarkable catalytic activity for MOF MnV oxide microflowers towards OER with a low overpotential of 310 mV at 50 mA cm−2 and a Tafel slope with only 51.4 mV dec−1 in alkaline conditions. This study provides a concise method for developing an optimized catalytic material with greater morphology and beneficial features for potential energy and environmental applications. [ABSTRACT FROM AUTHOR]

The development of a simple and effective strategy for designing a highly efficient oxygen evolution electrocatalyst is more important to speed up the efficiency-limiting step involved in water electrolysis. The high efficiency of the oxygen evolution reaction (OER) is directly correlated with the class of electrode materials employed. This work reports a series of Co3S4 nanoparticles (Co3S4-2h, Co3S4-3h, and Co3S4-4h) derived from a metal–organic framework (MOF) via a single-step annealing strategy with varying reaction times for the study of OER. During the annealing process, the MOF precursor [Co3(tiron-bpy)2(bpy)-(H2O)8]·(H2O)2 termed as Co-T-BPY directly converted to cobalt sulfide (Co3S4) nanoparticles, along with additional support of the N-doped carbon moiety. Interestingly, variation of reaction time in a fixed temperature condition played a decisive role in optimizing the surface area with huge active sites of the derived products. The optimized Co3S4-3h product needed an overpotential of 285 mV to reach 10 mA cm–2 current density and an acceptable Tafel value (109 mV dec–1) with excellent 14 h of stability performance under harsh alkaline conditions. The OER results are attributed to the combined effect of the Co3S4 phase and N-doped carbon matrix, resulting in substantial stability and high conductivity. Therefore, we believe that the time variation strategy for the preparation of a cobalt-based non-precious electrode material can pave the way in search of an OER-efficient electrocatalyst. [ABSTRACT FROM AUTHOR]

Increasing world energy demands and crises led to alternative energy production methods, such as fuel cells using hydrogen gas which is the half electrochemical reaction of water splitting process. Herein, we synthesize polyvinylpyrrolidone coated Pd, Co and Pd x Co 1-x (x: 0.5, 0.12, 0.23, 0.49, 0.55, 0.62) metallic and bimetallic nanoparticles (NPs) via polyol process alternative to Pt-based catalysts for hydrogen evolution reaction (HER). Detailed structural analyses of Pd, Co and Pd x Co 1-x NPs revealed that fcc-Pd, fcc/hcp-Co and fcc-PdCo NPs crystal structures, and the lattice parameters were calculated as 3.5358 Å for Co NPs and 3.9777 Å for Pd NPs. The average size confirmed below 9 nm via TEM imaging and XPS data confirmed the formation of a bimetallic PdCo structure. Although Pd catalyst is mostly responsible for HER process, Pd 62 Co 38 catalysts reduced the onset potential to about 197 mV and provided greater current density. Although E a values were slightly higher against the Pt/C (20 wt %) benchmark which is reported as 16 kJ mol−1, PdCo NPs provided considerably reduced activation energy (E a) values compared to Pd/C catalyst of 31 kJ mol−1. The best onset potential was recorded for Pd 62 Co 38 catalysts for HER activity which is 16 mV higher compared to commercially available Pt/C catalyst. • Multiphase oxide-free fcc-PdCo, fcc-Co, and hcp-Co phases synthesized with a size of below 9 nm via modified polyol process. • Pd plays important role on HER activity and addition of Co increase the activity. • The activation energy of PdCo NPs is slightly higher than commercially available Pt/C. • Pd 62 Co 38 catalysts exhibited the best performance for HER activity which is 16 mV higher compared to Pt/C catalyst. [ABSTRACT FROM AUTHOR]

A cost-effective, efficient and stable electrocatalyst is a remarkable and significant prospect for hydrogen evolution reaction. By adjusting the copper contents, the Hexagonal and Tetragonal phases of the copper selenide have been synthesized using the solvo-hydrothermal process. Hexagonal phased-based copper selenide has exhibited a greater current density than the Tetragonal phase. However, the augmented structure, lower Gibbs Free energy, greater electrical conductivity and electrochemical surface promoted the electrocatalytic behavior of Hexa-CuSe-1.04 nanosheets. Hexa-CuSe-1.04 nanosheets exhibit a good overpotential of 61 mV at the state of art current density of 10 mAcm−2 along with Tafel slope of 59 mV dec−1 in 1 M KOH, which is better than the other Hexagonal phase structure, Hexa-CuSe-1.67 nanosheets and Tetra-Cu 2 Se-1.30 phase of the copper selenides. The electrocatalyst Hexa-CuSe-1.04 maintains the current density for a long duration and exhibits a similar linear sweep voltammetry curve in 1 M KOH during the chronoamperometry test. Moreover, Hexa-CuSe-1.04 nanosheets show a good Tafel slope of 26 mV dec−1 with a good turnover frequency of 72.40 m s−1 in 0.5 M H 2 SO 4 and follow the Tafel phenomenon. Optimized density functional theory reveals that Hexa-CuSe-1.04 exhibits the lower Gibbs of 1.04 eV, free energy, which promotes the desorption and recombination process of the active hydrogen atoms at the active sites and enhanced the hydrogen evolution process. All results indicate the leading potential application of the Hexagonal phase of Hexa-CuSe-1.04 for hydrogen evolution reaction. [Display omitted] 1. Copper contents significantly influenced the growth process. 2. Intrinsic features depend significantly on the crystal structural phases. 3. Hexa-CuSe-1.04 exhibits greater electrical conductivity and low Gibbs Free energy. 4. Hexa-CuSe-1.04 exhibits a good overpotential of 61 mV in 1 M KOH. 5. Electrocatalyst, Hexa-CuSe-1.04 shows a Tafel slope of 26 mV dec−1 in M H 2 SO 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • HER thermodynamics and kinetics is evaluated on V 2 C (0001) MXene by density functional theory. • While –OH surface termination is less relevant for HER, the reaction is facile on -H termination. • The reaction switches from Volmer-Heyrovsky to Volmer-Tafel depending when increasing the overpotential. • V2C MXene features HER reaction similarities to Pt-based electrocatalysts. Both experimentally and theoretically, the MXene family has shown promising hydrogen evolution reaction (HER) capabilities. However, so far, the theoretical approach has been relying on the well-known thermodynamic descriptor, Δ G H , whereas experimental studies report Tafel plots, containing kinetic rather than thermodynamic information. Aiming to link theory to experiments, the present study explores five different HER pathways over the exemplary V 2 C (0001) MXene by density functional theory calculations. While the surface coverage under HER conditions (with either H* or OH* adsorbates) is extracted from a Pourbaix diagram, we determine the energetics of the reaction intermediates and transition states for both surface species as active sites. This enables the construction of free-energy diagrams for the Volmer-Heyrovsky and Volmer-Tafel mechanisms and allows for the simulation of Tafel plots by a rigorous microkinetic framework. While the active-site motif V 2 C-OH seems to be less relevant for the HER under typical reaction conditions, we demonstrate that the HER is kinetically facile on the V 2 C-H surface. For this surface termination, we report a potential-depending switching of the preferred mechanism from the Volmer-Heyrovsky to the Volmer-Tafel description with increasing overpotential while encountering similarities to the HER over Pt. [ABSTRACT FROM AUTHOR]

High cost and restricted activity of electrocatalysis are the major challenges for hydrogen generation and biosensors. In this work, we provided a one-pot synthesis of CuxPdy alloy nanoparticles (NPs) with controllable atomic ratio and "clean surface". Benefiting from the preferable d-band structure, the Cu62Pd38 NPs exhibited a lower overpotentials in the hydrogen evolution reaction (HER) over the full pH range. In the acidic media, Cu62Pd38 NPs achieved a low overpotential of 28.12 mV for HER, which was 25.73% of Pd NPs. In the neutral solution, the overpotential by Cu62Pd38 NPs is only 41.71% for that by uncleaned CuPd NPs. In alkaline media, the overpotential by Cu62Pd38 NPs was declined from 38.01 to 20.20 mV after 720 min yielding hydrogen, which was only 53.14% for the initial overpotential. As applied in biosensor, the synergistic effect of Cu and Pd accelerated the kinetics of electrocatalytic process, resulting in an enhanced performance. The glucose sensor constructed by Cu67Pd33 exhibited a wider detection range up to 100.0 mM. And the sensitivity is 379.4 µA/(mM·cm2), which is ca. 4.63 and 14.09 folds for that by pure Cu NPs and Pd NPs, respectively. An optimal atomic percent would be conducive to optimize electrocatalytic activity of CuxPdy alloy. The volcano plots for CuxPdy would open up a new avenue for designing electrocatalysis with rationalized cost and optimized performance. [ABSTRACT FROM AUTHOR]

The application of slurry electrolysis for high-arsenic antimony–gold concentrate treatment provides several benefits, including a short treatment process, complete separation of antimony and gold, and low environmental impact. A key process in slurry electrolysis is the anodic reaction. In this study, pure stibnite was used as raw material and linear sweep voltammetry was adopted to investigate the anodic process with the introduction of the Fe(III)/Fe(II) redox couple. The results indicated that the anodic polarization curve comprised three distinct regions: a low potential region (0.47–0.65 V), where the reaction rate was controlled by the electrochemical reaction; a medium potential region (0.65–0.90 V), where the electrochemical reaction was accelerated with an increase in overpotential, and the diffusion of Fe(II) gradually became the rate-controlling step; and a high potential region, where the reaction reached a stable state in which Fe(II) diffusion controlled the rate, and the polarization current density changed minimally with an increase in potential. The effects of particle size, liquid–solid ratio, stirring speed, temperature, and iron ion concentration were also investigated. The introduction of Fe(III)/Fe(II) considerably improved the oxidative leaching rate and significantly reduced the power consumption of electrolysis, offering the possibility of using slurry electrolysis in industrial applications. [ABSTRACT FROM AUTHOR]

Sandwich polyoxometalate [WCo3(H2O)2(CoW9O34)2]12− (Co-WCo3) heterogenized with poly(vinyl butyl imidazolium) cations (PVIM+) acts as a stable electrochemical water oxidation catalyst in 1 M KOH with 0.28 V@10 mA cm−2 overpotential and TOF of 6.16 s−1. Various in situ spectroelectrochemical studies and control experiments provide the details of the catalytic activities and long-term stability of the catalyst. [ABSTRACT FROM AUTHOR]

Theoretical calculation results unveil that the reconstructed Co(Ni)OOH on FeNiCo-MOF during OER processes is beneficial to improve the OER activity. Experimentally, to achieve 2D trimetallic FeNiCo-MOF nanosheets, a facile room-temperature dispersion approach is employed. Such 2D nanosheets reveal an OER overpotential as low as 239 mV at 10 mA cm−2 and excellent long-term stability in 1M KOH. Undoubtedly, this work highlights the great potential of directly utilizing MOF nanosheets as OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Molecular electrocatalysts for CO2‐to‐CO conversion often operate at large overpotentials, due to the large barrier for C−O bond cleavage. Illustrated with ruthenium polypyridyl catalysts, we herein propose a mechanistic route that involves one metal center that acts as both Lewis base and Lewis acid at different stages of the catalytic cycle, by density functional theory in corroboration with experimental FTIR. The nucleophilic character of the Ru center manifests itself in the initial attack on CO2 to form [Ru‐CO2]0, while its electrophilic character allows for the formation of a 5‐membered metallacyclic intermediate, [Ru‐CO2CO2]0,c, by addition of a second CO2 molecule and intramolecular cyclization. The calculated activation barrier for C−O bond cleavage via the metallacycle is decreased by 34.9 kcal mol−1 as compared to the non‐cyclic adduct in the two electron reduced state of complex 1. Such metallacyclic intermediates in electrocatalytic CO2 reduction offer a new design feature that can be implemented consciously in future catalyst designs. [ABSTRACT FROM AUTHOR]

Highly efficient and stable Earth abundant transition metal electrocatalysts are in great demand for the oxygen evolution reaction (OER), a bottleneck process involved in the water splitting reaction and metal–air batteries. Herein, we have demonstrated a single step direct fabrication of cobalt hydroxide (Co(OH)2) nanowires doped with vanadium(V) in a less stable +4 oxidation state and fluoride (F) ions (V–Co(OH)2) on a carbon cloth electrode that showed highly enhanced OER activity under alkaline conditions. V–Co(OH)2 nanowires synthesized under the optimized conditions produced excellent OER activity with an ultralow overpotential of 136 mV at 10 mA cm−2 (scan rate 1 mV s−1), a small Tafel slope (51.6 mV dec−1) and good stability over 72 h. To the best of our knowledge, this is the lowest overpotential reported for cobalt-based electrocatalysts to achieve a geometric current density of 10 mA cm−2. The controlled synthesis and HR-TEM studies revealed the formation of hybrid nanostructures (nanowires along with spherical assembly of nanoparticles) and codoping of V and F ions played an important role in enhancing the OER activity. The detailed chemical composition and oxidation state analysis by X-ray photoelectron spectroscopy (XPS) confirmed the doping of V4+ and ionic F in V–Co(OH)2 with mixed valence states of Co2+/Co3+ and a higher Co2+ ratio. The outstanding OER activity of V–Co(OH)2 is attributed to the formation of a spherical assembly of nanoparticles with nanowires, which provided a high number of catalytically active sites with enhanced charge transport, and doping of higher valence V4+ and strongly electronegative F in V–Co(OH)2 with a higher ratio of Co2+/Co3+ promoted OOH* intermediate generation and significantly boosted the OER activity. Overall, the present work highlights the possibility of achieving highly active Earth abundant OER electrocatalysts by controlling the mixed oxidation state of Co with a judicious choice of dopants along with maintaining optimal nanostructure morphologies. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable Mg batteries (ARMBs) usually fail from severe anode passivation, alternatively, executing quasi‐underpotential Mg plating/stripping chemistry (UPMC) on a proper heterogeneous metal substrate is a crucial remedy. Herein, a stable UPMC on Zn substrate is initially achieved in new hydrated eutectic electrolytes (HEEs), delivering an ultralow UPMC overpotential and high energy/voltage plateau of ARMBs. The unique eutectic property remarkably expands the lower limit of electrochemical stability window (ESW) of HEEs and undermines the competition between hydrogen evolution/corrosion reactions and UPMC, enabling a reversible UPMC. The UPMC is carefully revealed by multiple characterizations, which shows a low overpotential of 50 mV at 0.1 mA cm−2 over 550 h. With sulfonic acid‐doped polyaniline (SPANI) cathodes, UPMC‐based full cells show high energy/power densities of 168.6 Wh kg−1/2.1 kWh kg−1 and voltage plateau of 1.3 V, far overwhelming conventional aqueous systems. [ABSTRACT FROM AUTHOR]

The electrochemical performance of solid oxide cells (SOCs) is investigated under both fuel cell and electrolyzer operations to understand their asymmetric behavior between the two operation modes. The current–voltage and electrochemical impedance characteristics of a hydrogen-electrode-supported cell are experimentally analyzed. Also, a numerical model is developed to reproduce the cell performance and to understand the internal resistances of the cell. Partial pressures of supplied gas and load current are varied to evaluate their effects on the cell performance. The gas partial pressures of hydrogen and steam supplied to the hydrogen electrode are kept equivalent so that the cell performance can be fairly compared between the two operation modes when the same current is applied. It is found that the origin of the asymmetry is mostly from the hydrogen electrode; both activation and concentration overpotentials show asymmetric behavior particularly at high current densities. A numerical experiment is also conducted by deliberately changing parameters in the model. Asymmetry in the activation overpotential is found to be originated from the non-identical charge-transfer coefficients in the Butler–Volmer equation and also from the non-uniform gas concentration formed in the hydrogen electrode under current-biased conditions. On the other hand, asymmetry in the concentration overpotential is associated with the non-equimolar counter diffusion of hydrogen and steam caused by the effect of Knudsen diffusion. Therefore, enhancing gas transport in the hydrogen electrode and reducing the contribution of Knudsen diffusion are effective approaches to reduce asymmetry not only in the concentration overpotential but also in the activation overpotential. • Performance of solid oxide cell is evaluated in fuel cell and electrolysis modes. • Numerical simulation is performed to understand the overpotential components. • Asymmetric behavior is observed between the two operation modes. • Asymmetry is caused by activation and diffusion resistances in hydrogen electrode. • Numerical experiment is conducted to identify physicochemical origin of asymmetry. [ABSTRACT FROM AUTHOR]

Single‐atom Fe‐N‐C (denoted as Fe1‐N‐C) catalysts exhibit inadequate bifunctional activities to conquer the sluggish oxygen reduction and evolution reaction (ORR/OER), hindering their practical applications in rechargeable Zn‐air batteries (ZABs). Here, by employing Fe1‐N‐C hollow nanorods as ORR‐active support, OER‐active NiFe‐layered double hydroxide (NiFe‐LDH) nanodots are evenly decorated through a spatially confined process to form NiFe‐LDH/Fe1‐N‐C heterostructure hollow nanorods with abundant accessible catalytic sites. The NiFe‐LDH/Fe1‐N‐C heterostructure not only enhances the ORR activity of pristine Fe1‐N‐C but also realizes efficient bifunctional ORR/OER activity in one monolithic catalyst. Theoretical calculations reveal that introducing NiFe‐LDH nanodots results in donation of electrons to the Fe1‐N‐C matrix and thus lowers the Fe‐d band center of the Fe‐N4 sites, dramatically narrowing the energy barriers of the ORR rate‐limiting steps. As a result, NiFe‐LDH/Fe1‐N‐C nanorods deliver remarkable ORR activity with a half‐wave potential of 0.90 V versus reversible hydrogen electrode, surpassing bare Fe1‐N‐C and commercial Pt/C. Impressively, the integrated NiFe‐LDH/Fe1‐N‐C catalysts show outstanding bifunctional performance with a small overpotential gap of only 0.65 V. The liquid‐state ZABs with NiFe‐LDH/Fe1‐N‐C as an air‐cathode catalyst deliver a peak power density of 205 mW cm−2 and long‐term cycling stability of up to 400 h. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is a well-sought method for the production of renewable energy due to its low cost, high efficiency, ease of operation, availability of a variety of catalysts, and green approach. In this research, an amine-functionalized Ce-MOF loaded on nickel foam (NF) presented as Ce-MOF-NH2/NF electrocatalyst is prepared by a simple hydrothermal method. Prepared material is characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) to confirm morphological and structural properties. The synthesized catalyst is used for electrochemical OER in a 1M KOH solution. Ce-MOF-NH2/NF demonstrated onset potential, Tafel slope, and overpotential of 1.49 V, 69 mV/dec, and 328 mV, respectively. For comparison, Ce-MOF is also prepared and employed for OER under the same conditions and it exhibited onset potential, Tafel slope, and overpotential 1.5 V, 89 mV/dec, and 348 mV, indicating the superior performance of functionalized MOF. The obtained results reveal the promising overpotential of the Ce-MOF-NH2/NF -based electrocatalyst for green energy production via electrochemical water splitting.

Abstract Aprotic lithium–oxygen batteries (LOBs) have been recognized as novel energy storage devices for their outstanding specific energy density, while the large discharge/charge overpotential is a tough barrier to be overcome. Here, hetero‐structured MoS2/ZnIn2S4 nanosheets have been prepared to capture visible light and the generated charge carriers are utilized for promoting both the oxygen reduction reaction and the oxygen evolution reaction. With the light illumination in the discharge process, the abundant photo‐inspired electrons serve as the reaction sites to promote the reduction of O2 into LiO2 which is finally deposited as Li2O2. On the contrary, the generated holes in the valence band can contribute to the low oxidization potential of Li2O2 during the charge process. It delivers a low charge potential of 3.29 V, with an excellent resulting energy efficiency of 96.7%, much superior to that of 69.2% in the dark condition. It is noted that the involvement of photoelectrons has influenced the growth of Li2O2 films on the MoS2/ZnIn2S4 nanosheets through the surface‐adsorption pathway. The insights from the theoretical calculation confirm that the photoelectrons favor the absorption of LiO2 and the formation of the Li2O2 film through the surface route. Therefore, this paper provides a deeper understanding of the mechanism of photo‐inspired charge carriers in LOBs and will enable further exploration of photo‐involved energy storage systems.

A binder-free, self-supporting and substrate-rejuvenating electrocatalytic electrode based on nonnoble elements is widely acknowledged as the most potential candidate for feasible water splitting. Through the consecutive surface treatment including Fe-leaching in a simple KSCN solution, anodic polarization and chronopotentiometric aging in KOH solution, a commercially available 4J40 INVAR alloy was adopted in this work to fabricate an anode for oxygen evolution in alkaline media. Featuring all above advantages over most state-of-the-art OER electrocatalysts, the 4J40 electrode after being stabilized by CP-aging needs an overpotential of only 241 mV to achieve the current density of 10 mA cm−2 in 1 M KOH, in addition to its stability tested at the lower and higher current densities, respectively. The controlling OER mechanisms were discussed accordingly, with the Fe-doped nickel-based oxyhydroxide and the nickel peroxide being considered correspondingly as the main OER-enhancing species before and after CP-aging. [Display omitted] • 4J40 INVAR alloy was Fe-leached in KSCN solution to modulate Ni/Fe ratio. • OER-active (oxy)hydroxides were obtained on alloy surface by LSV polarizations. • Anode based on this alloy was stabilized by CP-aging for efficient and stable OER. • Oxyhydroxide and peroxide are OER-enhancing respectively before and after CP-aging. • Current density of 10 mA cm−2 was attained at overpotential of 241 mV in 1 M KOH. [ABSTRACT FROM AUTHOR]

Here, a dual functional Nb 2 CT x @Pt nanocomposite has been synthesized by in situ reduction method. The Pt loading in the composite has been optimized to get minimum overpotential (141 mV at 10 mA/cm2) for hydrogen evolution reaction (HER) along with a promising Tafel slope of 46.3 mV/dec, while Pt/C shows an overpotential and Tafel slope of 104 mV and 32.4 mV/dec, respectively. The Pt mass activity for Nb 2 CT x @Pt3.8 composite at 100 mV overpotential was 3.44 A g−1 while the Pt mass activity for conventional Pt/C was 0.7 A g−1, which shows that the activity of Nb 2 CT x @Pt3.8 composite is approximately 5 times higher than Pt/C. In addition, the catalyst was found to be stable for continuous 500 cycles without any binder molecules. The oxygen reduction reaction (ORR) capability of the material was also evaluated and found that the catalyst exhibited a current density of −4.28 mA/cm2 in the diffusion limiting region in comparison with the current density of −5.82 mA/cm2 for Pt/C at 2600 revolutions per minute (RPM). The Pt mass activity of Nb 2 CT x @Pt3.8 composite for ORR is approximately 10 times higher than Pt/C. The Nb 2 CT x @Pt3.8 composite was able to reduce O 2 completely using the 4-electron pathway with very little peroxide production. From these results, the dual functionality of the Nb 2 CT x @Pt3.8 composite for both HER and ORR has been established. [Display omitted] • A dual functional Nb 2 CT x @Pt (with 3.8% atomic ratio) nanocomposite has been synthesized. • The Nb 2 CT x @Pt3.8 catalyst was able to get an overpotential of 141 mV at 10 mA/cm2 with a Tafel slope of 46.3 mV/dec. • The Pt mass activity for Nb 2 CT x @Pt3.8 composite approximately 5 times higher than Pt/C at 100 mV overpotential. • The Pt mass activity of Nb 2 CT x @Pt3.8 composite for ORR is approximately 10 times higher than Pt/C. [ABSTRACT FROM AUTHOR]

Highly active, robust and easy-to-get electrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an in situ electrochemical approach to synthesize metal (Co, Ni) oxide decorated MoS2 nanosheets for water splitting. The CoO/MoS2/CC exhibits an overpotential of 93 mV for hydrogen evolution and 210 mV for oxygen evolution at 10 mA cm−2 with a Tafel slope value of 57.9 mV dec−1 and 282 mV dec−1. Moreover, we achieve 10 mA cm−2 at 1.65 V for 12 h in basic alkaline electrolyte for overall water splitting. The results presented here offer a simple method to fabricate effective non-noble-metal electrode materials for overall water splitting. [ABSTRACT FROM AUTHOR]

The study of reversible and irreversible heat generation of lithium-ion batteries at different C rates is important for designing thermal management system. Galvanostatic intermittent titration technique is used to determine the overpotential of different SOC (state of charge) or SOD (state of discharge) of commercial lithium iron phosphate pouch cells. The reversible and irreversible heat generation of the battery is calculated based on the entropy change and overpotential. It is found that when the lithium iron phosphate battery is charged, reversible heat first manifests itself as heat absorption, and then soon as exotherm after around 30% SOC, while the reverse for discharge. The total heat generation of lithium iron phosphate batteries during charging is higher than that during discharging. The relative contribution of irreversible and reversible heat generation at low and high rates are different. At 0.1 C rate, the maximum proportion of qrev is about 70%, while at 1 C rate, the maximum proportion of qrev is about 25%. [ABSTRACT FROM AUTHOR]

The nickel sulfide phase-heterostructure (r-NiS/h-NiS) was constructed between r-NiS and h-NiS. The r-NiS/h-NiS (1.25) displayed the excellent HER performance with low overpotential (101 ± 1 mV@10 mA cm−2) and small Tafel slope (62.10 ± 0.1 mV dec−1), which were superior to the pure phase r-NiS and h-NiS. [Display omitted] • r-NiS/h-NiS catalysts with the NiS phase-heterostructure have been successfully fabricated by a simple one pot method. • r-NiS/h-NiS (1.25) displayed the outstanding HER performance with low overpotential (101 ± 1 mV@10 mA cm−2) and small Tafel slope (62.10 ± 0.1 mV dec−1). • Improved HER activity was attributed to the dense coupling interfaces between r-NiS and h-NiS. Constructing transition metal sulfides (TMSs) heterostructure is an effective strategy to optimize the catalytic performance for hydrogen evolution reaction (HER) in alkaline medium. Herein, the rhombohedral nickel sulfide/hexagonal nickel sulfide (r-NiS/h-NiS) catalysts with the NiS phase-heterostructure were successfully fabricated by a simple one pot method. The r-NiS/h-NiS (1.25) (1.25 means the theoretical mole ratio of S and Ni added to reaction) displayed the excellent HER performance with low overpotential (101 ± 1 mV@10 mA cm−2) and small Tafel slope (62.10 ± 0.1 mV dec−1), which were superior to the pure phase r-NiS and h-NiS. In this work, the improved HER catalytic performances were attributed to the dense coupling interfaces between the r-NiS and h-NiS. This work shows the feasibility of construction NiS phase-heterostructure and provides a novel strategy for the application of NiS for water splitting. [ABSTRACT FROM AUTHOR]

Sulfur-nitrogen doped porous carbon (SNPC) material was first synthesized by the hydrothermal method and high-temperature carbonization. Then, the three-dimensional cube SNPC-Ni-metal organic frameworks (SNPC-Ni-MOF) composite was finally synthesized by hydrothermal method and applied in oxygen evolution reaction (OER). BET analysis proved the porosity and higher specific surface area of SNPC. FTIR analysis implied that the coordination of trimesic acid with metal ions was successful. SEM images showed that the as-synthesized carbon materials presented beautiful spherical. The overpotential of the as-synthesized composite was conducted by the LSV test, and it was found that the SNPC-Ni-MOF composite exhibited the lower overpotential (400 mV). Electrochemical impedance spectroscopy showed the SNPC-Ni-MOF had the smaller Rct value (1.744 Ω cm−2). Tafel plot indicated that the doping of sulfur and nitrogen improved the electrochemical properties of carbon materials to some extent. The cyclic voltammetry test illustrated that the electrochemical active surface area of SNPC-Ni-MOF was 48.75 cm2. The turnover frequency ​​for OER was 0.016 s−1. In addition, the i-t curve test indicated that the SNPC-Ni-MOF composite possessed better stability, the retention rate reaches 96.7% after 20,000 cycles. All results illustrate that the OER performance of the as-prepared SNPC-Ni-MOF composite has been improved and can be used as electro-catalysts for water splitting. [ABSTRACT FROM AUTHOR]

Bismuth‐based electrocatalysts are promising candidates for electrochemical CO2 reduction to formate attributing to the accelerated formation of *OCHO intermediate, while the high‐energy consumption remains a major challenge for practicability. Herein, we present the ultrathin Bi2O2CO3 nanosheets with abundant oxygen vacancy (Vo‐BOC‐NS) reconstructed from S, N‐co‐doped bismuth oxides that can act as durable electrocatalyst for CO2‐to‐formate conversion with faradic efficiency (FEformate) of >95%, partial current density of 286 mA cm−2 with energy efficiency of 73.8% at −0.62 V (vs. RHE) and low overpotential of 200 mV in a flow electrolyzer. The theoretical calculations decipher that the oxygen vacancy can optimize *OCOH adsorption/desorption for the accelerated conversion kinetics. The pair‐electrosynthesis tactic of formate co‐production can enable a superior FEformate of >90% at wide cell voltage of 2–3.3 V and total yield rate of 3742 μmol cm−2 h−1 at 3.3 V, suggesting great potential for future industrialization. [ABSTRACT FROM AUTHOR]

Numerous clean energy systems rely on the oxygen evolution process (OER), which takes place during water splitting reaction. For this purpose, transition-metal oxides have garnered considerable attentions as a prominent OER electrocatalysts. In present study, we fabricate the nanosheet arrays of metal oxide/carbon (MOx/C; M = Fe, Ag, and Mn) fabricated via hydrothermal route. As templates, this approach employs the covered 2-dimensional (2D) metal-organic frameworks (2D-MOFs), and these MOx/C arrays made from 2D MOFs exhibit significant electrocatalytic activity and durability. Among all, Ag 2 O/C showed the overpotentials of 270 mV at a current density (j) of 10 mA cm−2, while the tafel slope is 45 mV dec−1, that is lower than other metal oxide-based catalysts like MnO/C, and Fe 2 O 3 /C. It also shows 48 h high stability due to the conductive nature, larger surface area and the presence of carbon cage for easy transfer of electrons. The conceptual framework and synthetic strategy employed in this study can be applied to create more multi-metal oxide anchoring Ag 2 O carbon matrix-based electrocatalysts that are extremely efficient, affordable, and perform significantly better in OER and other future applications. [ABSTRACT FROM AUTHOR]

A pyrazole‐based ligand substituted with terpyridine groups at the 3 and 5 positions has been synthesized to form the dinuclear cobalt complex 1, that electrocatalytically reduces carbon dioxide (CO2) to carbon monoxide (CO) in the presence of Brønsted acids in DMF. Chemical, electrochemical and UV‐vis spectro‐electrochemical studies under inert atmosphere indicate pairwise reduction processes of complex 1. Infrared spectro‐electrochemical studies under CO2 and CO atmosphere are consistent with a reduced CO‐containing dicobalt complex which results from the electroreduction of CO2. In the presence of trifluoroethanol (TFE), electrocatalytic studies revealed single‐site mechanism with up to 94 % selectivity towards CO formation when 1.47 M TFE were present, at −1.35 V vs. Saturated Calomel Electrode in DMF (0.39 V overpotential). The low faradaic efficiencies obtained (<50 %) are attributed to the generation of CO‐containing species formed during the electrocatalytic process, which inhibit the reduction of CO2. [ABSTRACT FROM AUTHOR]

Co3ZnC can efficiently boost the activity of Co@N, O co-doped carbons for hydrogen evolution. The results show that moderate Co3ZnC plays key roles in achieving an appropriate weighted Co 3d band centre, enhancing charger transfer and thus optimizing the electrochemical active surface area. Thus, a low overpotential of ∼219 mV can drive a high current density of 1000 mA cm−2 under the favourable condition of moderate Co3ZnC. [ABSTRACT FROM AUTHOR]

Co3ZnC can efficiently boost the activity of Co@N, O co-doped carbons for hydrogen evolution. The results show that moderate Co3ZnC plays key roles in achieving an appropriate weighted Co 3d band centre, enhancing charger transfer and thus optimizing the electrochemical active surface area. Thus, a low overpotential of ∼219 mV can drive a high current density of 1000 mA cm−2 under the favourable condition of moderate Co3ZnC. [ABSTRACT FROM AUTHOR]

A hybrid protective layer containing a Li3N and Li–Bi alloy is fabricated on a Li-metal anode as an artificial SEI layer to guide dendrite-free Li deposition. Noteworthily, the hybrid interface could not only facilitate homogeneous Li plating but also provide rapid Li+ transportation, enabling a long-term stability of ∼2400 h at 0.5 mA cm−2 with a low steady overpotential of 10 mV. [ABSTRACT FROM AUTHOR]

Zn metal anode has drawn tremendous attention owing to its low cost and high volumetric capacity advantages. However, the commercial application of zinc‐based batteries is greatly deterred by Zn dendrite and severe side reactions. Interface modification is one of the most effective strategies to solve these issues. Herein, a facile iodine etching strategy to in situ construct a film‐coated 3D porous Zn anode is first proposed, which significantly reduces the nucleation overpotential of Zn while suppressing side reactions, thus resulting in uniform Zn deposition. Benefiting from the dual protection of surface coating and 3D porous Zn anode, the symmetric cell displays a long lifespan of over 5000 h at 1 mA cm–2, ≈40 times of bare Zn anode. The asymmetric cell with modified Zn anode also delivers excellent cycling stability for over 2000 cycles to achieve a high average Coulombic efficiency of 99.87%. Moreover, the capacity retention of a full battery coupled with ammonium vanadate cathode after 5000 cycles is up to 97.3%, which is much more stable than the bare Zn anode under the same condition (20%). Such a novel interfacial modification method provides a new perspective for the realization of stable metal electrodes. [ABSTRACT FROM AUTHOR]

The performance of an anion exchange membrane-based direct urea/O 2 fuel cell (AEM-DUFC) is analyzed via a mathematical model based on mass/charge transport and electrochemical reactions. The present model is verified using published experimental data, featuring a good accuracy with high R2 of 0.989 for polarization curve. The cell performances are evaluated in terms of voltage losses at anode/cathode, ohmic voltage loss in membrane, and urea crossover. The voltage losses in electrodes are dominant at a low current density; however, that in membrane is the highest at a high current density. The mathematical analysis results indicate that the structural design parameters (membrane thickness, porosity, and thickness of diffusion layers) and the operating parameters (urea fuel concentration and flow rate, O 2 /air, KOH feed concentration, and temperature) are important factors for high performance of AEM-DUFC. Urea and KOH concentrations exhibit optimum levels because of their composite effect. Overall, improve AEM-DUFC performance mainly depends on the structure and operating parameters of anode side. [Display omitted] • An analytical model for anion exchange membrane based direct urea/O 2 fuel cell. • The model predicts voltage losses in electrodes and membrane and urea crossover. • The cell performance mainly depends on the parameters of anode side. • The mode is used for the optimization of the cell design. [ABSTRACT FROM AUTHOR]

The electrochemical conversion of CO2 into value-added chemicals is a promising approach for addressing environmental and energy supply problems. In this study, electrochemical CO2 catalysis to ethanol is achieved using incorporated Cu/CuxO nanoparticles into nitrogenous porous carbon cuboids. Pyrolysis of the coordinated Cu cations with nitrogen heterocycles allowed Cu nanoparticles to detach from the coordination complex but remain dispersed throughout the porous carbon cuboids. The heterogeneous composite Cu/CuxO-PCC-0h electrocatalyst reduced CO2 to ethanol at low overpotential in 0.5 M KHCO3, exhibiting maximum ethanol faradaic efficiency of 50% at −0.5 V vs. reversible hydrogen electrode. Such electrochemical performance can be ascribed to the synergy between pyridinic nitrogen species, Cu/CuxO nanoparticles, and porous carbon morphology, together providing efficient CO2 diffusion, activation, and intermediates stabilization. This was supported by the notably high electrochemically active surface area, rich porosity, and efficient charge transfer properties. [ABSTRACT FROM AUTHOR]

[Display omitted] Non-precious metals have been considered as suitable alternatives for high-performance hydrogen evolution reactions (HER). Although the incorporation of carbon substances is shown to improve the number of active sites, electron transfer pathways, and long-term stability, there have been rare reports on their single-step scalable production. Herein, we realize free-standing two-dimensional (2D) carbon sheets heterostructured with nickel (Ni) nanocatalysts by pyrolyzing ultrathin layers of acetate tetrahydrate (i.e. the single precursor for both Ni and C sources) over water-soluble salt crystals. Such a salt-templated methodology is environmentally friendly and readily scalable without the implementation of sophisticated equipment. The resulting 2D carbon sheets exhibit an average small thickness of ∼ 3 nm and lateral dimensions with tens of micrometers, where a large number of nano-sized Ni particles with an average diameter of 14 nm are uniformly dispersed. Such 2D Ni-C sheets demonstrate a small overpotential of 111 mV at 10 mA/cm2 and a low Tafel slope of 86 mV/dec for HER in 1 M KOH, which is significantly improved over those of reported non-precious metals composited with carbon substances. This work offers new insight into the design and practical production of non-precious metal matrixes for economical HER. [ABSTRACT FROM AUTHOR]

Artificial redox catalysts are typically limited by unfavorable scaling relations of reaction intermediates leading to a significant overpotential in multi‐electron redox reactions such as for example the oxygen reduction reaction (ORR). The multicopper oxidase laccase is able to catalyze the ORR in nature. In particular the high‐potential variants show a remarkably low overpotential for the ORR and apparently do not suffer from such unfavorable scaling relations. Although laccases are intensively studied, it is presently unknown why the overpotential for ORR is so low and a clear description regarding the thermodynamics of the catalytic cycle and the underlying design principles is lacking. In order to understand the laccase catalyzed ORR from an electrochemical perspective, elucidation of the free energy scheme would be of high value. This article reviews the energetics of the proposed laccase catalyzed ORR mechanisms based on experimental and computational studies. However, there are still remaining challenges to overcome to elucidate the free energy scheme of laccase. Obtaining thermodynamic data on intermediates is hard or even impossible with analytical techniques. On the other hand, several computational studies have been performed with significantly different parameters and conditions, thus making a direct comparison difficult. For these reasons, a consensus on a clear free energy scheme is still lacking. We anticipate that ultimately conquering these challenges will result in a better understanding of laccase catalyzed ORR and will allow for the design of low overpotential redox catalysts. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) poisoning of polymer electrolyte membrane fuel cells (PEMFCs) remains a challenge for their deployment, and a deeper understanding of the spatiotemporal dynamics involved is needed to develop effective mitigation strategies. In this work, localised reference electrodes were used to measure the anode overpotential at three locations across the active area of a galvanostatically operated cell (0.3 A cm−2) exposed to 100 ppm CO/H 2. The anode region closest to the inlet was poisoned more rapidly than the rest of the cell, following a sigmoidal variation, and presented a higher CO coverage. The varying CO concentration, combined with local operating conditions, had a direct impact on the distribution of CO coverage. Additionally, complex self-sustained oscillations of the cell voltage and the anode overpotential were observed and correlated with the rate of CO oxidation in the overall cell. The coexistence of a dominant mean-field coupling area closer to the anode inlet, and a dominant migration coupling region closer to the outlet was identified, consistent with reported modelling predictions for a single straight channel cell. Finally, the cell recovery with pure H 2 was shown to be a faster process than the CO adsorption, which follows first-order kinetics and is affected by local conditions. • In situ measurements of anode overpotential performed in the presence of CO. • Local operating conditions had an impact on distribution of adsorbed CO. • Spatiotemporal dynamics observed, including self-sustained potential oscillations. • Coexistence of dominant mean-field and migration coupling areas identified. [ABSTRACT FROM AUTHOR]

Here, this work reports an innovative strategy for the synthesis of chemically robust metal–organic frameworks (MOFs), and applies them as catalysts for the electrocatalytic oxygen evolution reaction (OER). A bimetallic squarate‐based MOF (Sq‐MOF) with a zbr topology serves as an excellent platform for electrocatalytic OER owing to its open porous structure, high affinity toward water, and presence of catalytically active 1D metal hydroxide strips. By regulating the Ni2+ content in a bimetallic squarate MOF system, the electrochemical structural stability toward OER can be improved. The screening of various metal ratios demonstrates that Ni3Fe1 and Ni2Fe1 Sq‐zbr‐MOFs show the best performance for electrocatalytic OER in terms of catalytic activity and structural stability. Ni2Fe1 Sq‐zbr‐MOF shows a low overpotential of 230 mV (at 10 mA cm−2) and a small Tafel slope of 37.7 mV dec−1, with an excellent long‐term electrochemical stability for the OER. Remarkably, these overpotential values of Ni2Fe1 Sq‐zbr‐MOF are comparable with those of the best‐performing layered double hydroxide (LDH) systems and outperforms the commercially available noble‐metal‐based RuO2 catalyst for OER under identical operational conditions. [ABSTRACT FROM AUTHOR]

In the electrochemical reduction of CO2 to CO, controlling the binding of the *COOH intermediate is key to adjusting the selectivity and catalytic activity of the CO product. Herein, we report that CN vacancies were used to control the binding of the *COOH intermediate on a Co PBA-VCN catalyst treated by H2 cold plasma bombardment to improve the CO2RR into CO. The CN vacancies can tune the local electronic structure and coordination environment of CoIII-CN-CoII (Co-PBA-VCN) with a high CO faradaic efficiency close to 100% with remarkable durability (>87 h), and a low onset overpotential of 0.17 V in CO2RR. The steric effects of the VCN can decrease the free energy barrier of the rate limiting step for the formation of *COOH which can further crack into *CO on the active site of the Co near the VCN. This work provides a new strategy to tune the binding of the *COOH intermediate on the catalyst surface by new vacancies of VCN to enhance the CO2RR into a single product. [ABSTRACT FROM AUTHOR]