Overpotential Of Reaction Research Articles

Revealing Relationship Between In Situ Impedance and Lithium Plating Onset Based on Lithium–Graphite Half-Cells

Lithium plating may occur during charging, especially at high rates or overcharging conditions for lithium-ion batteries (LIBs), which would cause battery capacity degradation and even trigger thermal runaway. Thus, it is essential to detect lithium plating onset during the charging processes. Electrochemical impedance can reveal the dynamic electrode properties of the battery, which is promising for use in battery management systems for the online detection of lithium plating onset. In this article, the impedance at 1 Hz is measured during the over-discharge and fast discharge processes using lithium–graphite half-cells. For half-cells, the variation in graphite electrode potential vs. Li/Li+ during discharging is directly recorded. An equivalent circuit model is proposed and adopted to estimate the real lithium plating reaction overpotential, which is deemed the thermodynamic indicator of lithium plating and is used as validation for the detection of lithium plating onset. Through the auxiliary validation of the estimation of lithium plating overpotential and the shape of incremental capacity curves, the relationship between impedance changes at specific frequency and the lithium plating onset is revealed. The results lay a good foundation for proposing the online diagnostic method of lithium plating onset based on the in situ impedance.

Polymer Networks Assembled by Ruthenium Catalysts for Enhanced Water Splitting Performance in Calixarene Dye-Sensitized Photoelectrochemical Cells.

Metal-free photosensitizers for the construction of low-cost and eco-friendly dye-sensitized photoelectrochemical cells (DSPECs) have recently been greatly improved, but the optimization of water oxidation catalysts (WOCs) used in DSPECs based on metal-free dyes has received little attention. Herein, a series of polymer networks (RuTPA, RuCz, RuPr and RuTz) assembled by ruthenium WOCs (RuCHO) with various organic donors are constructed and combined with calixarene dyes to prepare DSPEC devices. The FTO|TiO2|C4BTP+RuTPA photoanode shows the best performance with 85% Faraday efficiency for oxygen production and 477 μA cm-2 photocurrent density after 200 s chopping irradiation at 0 V vs. Ag/AgCl, one of the highest records among other reported dye-sensitized photoanodes. Compared to monomeric RuCHO, Ru-based polymers with lower Ru content have higher activity and stability due to their rapid electron transfer and anti-aggregation ability. Meanwhile, RuTPA loaded electrodes show better performance due to the lower overpotential of the water oxidation reaction caused by the higher electron donating ability of its donor. This pioneering work incorporates Ru polymer networks as WOCs into the calixarene-sensitized DSPEC system, which has significant potential as a highly efficient and stable photoelectrochemical water splitting device.

Application and performance Enhancement of acetic acid-Regulated ligand defect engineering in NiMOF electrocatalysts

Introducing organic ligands into metal-organic frameworks (MOFs) is an effective method for preparing defective MOFs. This approach enables the fabrication of cost-effective, efficient, highly conductive, and richly active-site electrocatalysts. Herein, the defective NiMOF is synthesized via a straightforward one-pot solvothermal method by partially substituting phthalic acid (PTA) ligands with acetic acid (HOAc), which effectively regulates the micro-morphology and electronic structure of the NiMOF nanoflowers, thus creating abundant electrochemical active sites, significantly improving electronic conductivity and promoting rapid charge transfer. The resulting DE-NiMOF-0.5 nanoflowers, prepared with HOAc substitution, demonstrate excellent electrochemical performance at a current density of 10 mA cm−2, the hydrogen evolution reaction (HER) overpotential is 188 mV (Tafel slope of 175 mV dec−1), while the oxygen evolution reaction (OER) overpotential is 205 mV (Tafel slope of 37 mV dec−1). The introduction of acetic acid ligands in DE-NiMOF-0.5 not only constructs the ligand defects within the catalyst, but also increases the abundant active sites, enhancing the hydrophilicity of the catalyst and facilitating electronic transfer between the catalyst surface and the electrolyte. This study explores a strategy for preparing defective MOF catalysts through introducing modulators, providing an economically viable material pathway for electrocatalysis and opening new possibilities for designing and synthesizing efficient electrocatalysts in future research endeavors.

Additive manufacturing of multiscale NiFeMn multi-principal element alloys with tailored composition

Abstract Nanostructured multi-principal element alloys (MPEAs) have been explored as next-generation engineering materials due to unique mechanical and functional properties which have significant advantages over traditional dilute alloys. However, the practical applications of nanostructured MPEAs are still limited due to the lack of scalable processing approaches to prepare a large quantity of nanostructured MPEAs, as well as lack of an efficient pathway for high-throughput discovery of better functional nanostructured MPEAs within their vast compositional space. Here we tackle these challenges by presenting an integrated approach by combining direct-ink-writing-based additive manufacturing, solid-state sintering, and chemical dealloying to manufacture hierarchically porous MPEAs. The hierarchical structure is comprised of macro- and micro-scale pores introduced via extrusion printing and polymer decomposition during sintering, as well as nanoscale pores formed via chemical dealloying. The macro- and micro-scale pores allow efficient dealloying of a large mass of material as the diffusion length that the corroding medium must penetrate remains at the scale of the ligaments formed after sintering (∼10 μm), despite the large volume of the 3D-printed samples. In addition, this integrated approach enables versatile control of the alloy composition via precisely tuning the ratio of elemental powders in the starting ink, thus offering a pathway for high-throughput discovery of novel functional MPEAs. As a case study, multiscale macro/micro/nanoporous NiFeMn MPEAs with three different compositions were investigated as catalysts to reduce the overpotential of oxygen evolution reaction (OER), where NiFeMn-based electrocatalysts display composition-dependent performance such that the overpotential measured at a current of 0.5 A g−1 for OER increases in the order of Ni58Fe29Mn13 ⩽ Ni64Fe26Mn10 < Ni76Fe18Mn6. This introduced manufacturing process offers new opportunities for scalable fabrication and rapid screening of nanostructured multi-component complex alloys.

Comparison of oxygen evolution reaction performance for Ni and Co using isostructural trans‐cinnamate complexes

AbstractEfforts are underway to develop highly active catalysts to reduce the high overpotential of the oxygen evolution reaction (OER). Metal–organic frameworks or coordination polymers are promising candidates because of their tunable structures and high surface areas. In this study, Nickel and Cobalt trans‐cinnamate (t‐ca) were synthesized via a hydrothermal method. Their structures were analyzed and found to be isostructural. Both complexes exhibited superior electrocatalytic properties in the OER compared to those of IrO2, with overpotentials of 373 and 390 mV and Tafel slopes of 58 and 66 mV/dec. These excellent characteristics were attributed to the electron delocalization of the metal centers via interactions with π‐π delocalized organic ligands. Ni t‐ca, with stronger ligand interactions, displayed an enhanced OER catalytic performance, emphasizing the importance of metal–ligand interactions and suggesting that further exploration of diverse π–π delocalized organic ligands and metal centers may lead to further advancements in electrocatalytic activity.

Demonstration of Scalable Water Splitting into H2 and O2 by a Flow-Type Photocatalysis-Electrolysis Hybrid System Using a Highly Stable Photocatalyst.

Water splitting via a photocatalysis-electrolysis hybrid system has been investigated as a potentially scalable and economically feasible means of producing renewable H2. However, there are no reports demonstrating a scalable system for stoichiometric water splitting using an efficient and stable photocatalyst, and the key operating conditions for efficiently driving the entire system have not been established. Herein, we address the issues required to efficiently drive the entire system of a Cs+, Fe2+, and H+ ion-modified WO3 (denoted as H-Fe-Cs-WO3) photocatalyst fixed reactor combined with a polymer electrolyte membrane (PEM)-type electrolyzer. In electrochemical H2 production using Fe2+, the current density improved as the concentration of both H+ and Fe2+ increased, and we determined the optimum conditions for a hybrid system using high concentrations of HClO4 and Fe(ClO4)3, which differ from those reported for photocatalysis alone. No performance deterioration of the H-Fe-Cs-WO3 photocatalyst was observed even after light irradiation for more than 10 000 h under strong acidic conditions. The accumulated Fe2+ ions were extremely stable and did not oxidize even when exposed to air for more than two months. As for the stepwise operation that takes advantage of the characteristics of the hybrid system, the contribution factor of the photocatalyst in the photocatalysis-electrolysis hybrid system for H2 evolution (CP@STHap) under an applied bias was estimated to be 0.24%, which is a value comparable to that of the solar-to-chemical (STC) conversion efficiency (0.31%). The efficiency difference (0.07%) corresponds to the overpotential of the electrolytic reaction and indicates that water splitting via the photocatalysis-electrolysis hybrid system proceeds efficiently at a small overpotential of 0.06 V (∼11.6 kJ mol-1).

Nickel-Nitrogen Doped MnO2 as Oxygen Reduction Reaction Catalyst for Aluminum Air Batteries.

Aluminum-air battery has the advantages of high energy density, low cost and environmental protection, and is considered as an ideal next-generation energy storage conversion system. However, the slow oxygen reduction reaction (ORR) in air cathode leads to its unsatisfactory performance. Here, we report an electrode made of N and Ni co-doped MnO2 nanotubes. In alkaline solution, Ni/N-MnO2 has higher oxygen reduction activity than undoped MnO2, with an initial potential of 1.00 V and a half-wave potential of 0.75 V. This is because it has abundant defects, high specific surface area and sufficient Mn3+ active sites, which promote the transfer of electrons and oxygen-containing intermediates. Density functional theory (DFT) calculations show that MnO2 doped with N and Ni atoms reduces the reaction overpotential and improves the ORR kinetics. The peak power density and energy density of the Ni/N-MnO2 air electrode increased by 34.03 mW cm-2 and 316.41 mWh g-1, respectively. The results show that N and Ni co-doped MnO2 nanotubes are a promising air electrode, which can provide some ideas for the research of aluminum-air batteries.

Bi‐Doped In2O3 Nanofiber for Efficient Electrocatalytic CO2 Reduction

AbstractElectrocatalytic carbon dioxide reduction reaction (CO2RR) to formic acid (HCOOH) is attracted for superfluous CO2 removal and HCOOH production under ambient conditions. Indium‐based catalysts has considered as a good candidate material for CO2RR to HCOOH due to their environmentally friendly features. However, the catalytic efficiency is limited by the poor HCOOH Faradaic efficiency (FE) and high reaction overpotential of electrocatalyst, and the activity and stability of indium‐based catalysts are unsatisfactory, especially in industrial current density that is critical for commercialization. Herein, a fiber Bi‐doped In2O3 was synthesized through electrospinning method, and it demonstrate a FEHCOOH of 88.2% at −1.5 V versus RHE (reversible hydrogen electrode) with partial current density of −21.8 mA cm−2 in H type cell. Specially, the Bi‐In electrocatalyst also reach the industrial current density standard, which can work at −400 mA cm−2 current density with FEHCOOH of 92.7% (yield of HCOOH is 6.9 mmol h−1) in home‐made Flow cell. Importantly, Bi‐In shows 24 h long‐term stability test in −300 mA cm−2. The improvement catalytic activity of Bi‐In catalyst is ascribed to the optimized electronic structure of In site, and the reduced work function value of Bi‐In is beneficial for reducing the formation energy of the key *OCHO intermediates.

Highly selective photocatalytic oxidation of CH4 to CH3OH: A theoretical study

Photooxidation of methane (CH4) in aqueous solution to generate high-value organic compounds is an effective way to replace traditional industrial methods. It is crucial to select catalysts that can avoid competitive reactions and achieve high selectivity. Using first principles calculations, a novel one-dimensional (1D) Ti3C2O2 nanoribbon (NR)/two-dimensional (2D) monolayer MoS2 (MS) heterojunction photocatalyst was ingenious designed in this work, which can achieve the oxidation of CH4 molecules and suppress the execution of competitive reactions. The results indicate that the constructed 1D NR exhibits semiconductor properties and its energy level position meet the requirements of photocatalytic oxidation for CH4. The heterojunction structure composed of NR and MS forms an efficient S-Scheme electron transfer mechanism under illumination, which not only provides sufficient internal driving force for CH4 oxidation, but also effectively avoids the competitive reaction between water molecules and photo-generated holes. Specifically, the photocatalysts exhibits high selectivity and low reaction overpotential for the generation of methanol (CH3OH). This study provides a new perspective for photocatalytic CH4 oxidation and demonstrates the potential application value of 1D MXene in the future field of photocatalysis.

Complementary photoelectrochemical performances between dual heterojunctions and homojunction to achieve efficient solar water splitting of ZnIn2S4-based photoanode

The broken verge of carrier separation efficiency is invaluable factor to enhance photoelectrochemical performances of ZnIn2S4-based dual heterojunction. Hence, additional internal electric field is introduced when hexagonal/cubic ZnIn2S4 homojunction interface is used as medium to tandem Sb2S3/hexagonal-ZnIn2S4 and cubic-ZnIn2S4/Cu2S heterojunctions. The enhanced photoelectrochemical properties of Sb2S3/hexagonal/cubic ZnIn2S4/Cu2S are initiated through complementary properties of heterojunctions and homojunction components: (i) carrier separation efficiency verge of heterojunctions is broken to 56.29 % due to cooperation of homojunction, (ii) photoinduced carrier excitation energy homojunction is reduced to 2.06 eV with the modification of heterojunctions, (iii) built-in electric field is reinforced and electron delocalization of homojunction is enhanced by heterojunction, (iv) photoelectrochemical reaction sites of homojunction are increased through optimizing surface states effect of heterojunctions. As a result, the upgraded to 31.80 times higher water oxidization photocurrent density of 4.77 mA/cm2 is achieved by Sb2S3/hexagonal/cubic ZnIn2S4/Cu2S with decreased reaction overpotentials to 0.60 V. This work raises new thoughts on modified PEC performances of ZnIn2S4 via composite methods.

Induction heating boosts water splitting on iron-coated nickel foam

Abstract Alkaline water electrolysis at high temperatures can rival acidic proton-exchange membranes.
However, they suffer from increased energy consumption, reduced lifespan of materials and heightened safety risks. Magnetic hyperthermia is a method of localizing intense heating in the presence of an external high-frequency alternating magnetic field. In this study, we developed a custom electromagnetic induction device capable of generating a small magnetic field of about 2 µT. High-permeability nickel foam is used as electrodes. Results show that the iron coated nickel foam decreases the overpotential of the hydrogen evolution reaction and oxygen evolution reaction by ~150 mV and 60 mV, respectively, at 20 mAcm−2 when subjected to magnetic heating in a high-frequency alternating magnetic field. The overall water splitting current of Ni foam/Fe increases 540% under intermittent induction. The enhanced stability of Ni foam/Fe is attributed to the high binding energy of metal-O on the surface. The density function theory calculations further indicates that the lattice expansion of the metal electrode under induction heating optimizes the adsorption and desorption of H*, thereby enhancing the HER performance.

Monitoring Electrochemical Dynamics through Single-Molecule Imaging of hBN Surface Emitters in Organic Solvents.

Electrochemical techniques conventionally lack spatial resolution and average local information over an entire electrode. While advancements in spatial resolution have been made through scanning probe methods, monitoring dynamics over large areas is still challenging, and it would be beneficial to be able to decouple the probe from the electrode itself. In this work, we leverage single molecule microscopy to spatiotemporally monitor analyte surface concentrations over a wide area using unmodified hexagonal boron nitride (hBN) in organic solvents. Through a sensing scheme based on redox-active species interactions with fluorescent emitters at the surface of hBN, we observe a region of a linear decrease in the number of emitters against increasingly positive potentials applied to a nearby electrode. We find consistent trends in electrode reaction kinetics vs overpotentials between potentiostat-reported currents and optically read emitter dynamics, showing Tafel slopes greater than 290 mV·decade-1. Finally, we draw on the capabilities of spectral single-molecule localization microscopy (SMLM) to monitor the fluorescent species' identity, enabling multiplexed readout. Overall, we show dynamic measurements of analyte concentration gradients on a micrometer-length scale with nanometer-scale depth and precision. Considering the many scalable options for engineering fluorescent emitters with two-dimensional (2D) materials, our method holds promise for optically detecting a range of interacting species with exceptional localization precision.

Multifunctional Water Additive Enabling Stable Cycling of Chloride‐Free Magnesium Metal Batteries Based on Carbonate Electrolyte

AbstractRechargeable magnesium batteries (RMBs) face with the challenge of interphase passivation between electrolytes and Mg anodes. Compared with ether electrolytes, carbonate solvents possess the superior electrochemical stability at cathode side, but their incompatibility with Mg metal, high viscosity, and desolvation energy barrier restrict their practical utilization in RMBs. Herein, the “unwanted‐impurity” water with high concentration is revisited and employed as multifunctional additive in carbonate electrolyte to improve the reversibility of RMBs. Water additive enables the localized deep eutectic effect, reduces the viscosity of carbonate electrolyte, and improves the Mg ion conductivity. The water molecules also participate the solvation sheath of Mg ions, resulting in the reduction of Mg deposition overpotential and inhibition of parasitic reaction. Furthermore, the co‐intercalated water molecules in V2O5 cathode layers enable the stabilization of intercalation structure and supply of additional magnesiophilic sites. Cooperated with the binder‐decorated Mg powder anode, the propylene carbonate electrolyte with water additive endows Mg||Mg symmetric cells and Mg||V2O5 full cells with satisfactory cycling performance and high‐voltage stability. This work revisits the impact of impurity water and provides a practical strategy for the utilization of conventional low‐cost carbonate electrolyte family, broadening the design and formulation of electrolytes for chlorine‐free and high‐voltage RMBs.

On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.

Triggered Directed Electron Redistribution Endowed by Efficient Ohmic Contacts of NiMoN/Ni3S2 for Boosting Large Current‐Density Overall Seawater Splitting

AbstractThe rational construction of interfacial nanostructures of metal/semiconductor (MS) contacted electrocatalysts has a significant impact on improving their intrinsic activities. However, MS contacts are often plagued by a strong Fermi‐level pinning effect, resulting in the formation of the Schottky barrier that affects the adsorption of hydrogen/oxygen intermediates. Herein, an Ohmic contact between metallic Ni3S2 and semiconducting NiMoN is well‐designed, which effectively reduces the electron conduction barriers. The as‐obtained NiMoN/Ni3S2 has remarkable bifunctional water electrolysis performance. At 10 mA·cm−2, the overpotential of hydrogen evolution and oxygen evolution reaction is 70 and 154 mV, respectively. Impressively, the formation of hydroxide during surface reconstruction can avoid the chlorine evolution on the catalyst surface. At an industrial process temperature of 85 °C, it takes only 340 mV for the overall seawater splitting of 500 mA·cm−2. UPS and UV‐VIS diffuse spectra combined with theoretical calculation results confirm that the self‐driven directed electron transfer derived from the Ohmic contact can induce local electron enrichment at the interface region, thus promoting the formation of *O to *OOH. This study provides important insights into the coordinated modulation of built‐in electric fields and the preparation of efficient multifunctional catalysts with a high abundance of active sites.

Electronic regulation of Ce,F-Ni2P/CoP catalyst for efficient water splitting

Designing efficient non-precious-metal bifunctional electrocatalysts is still challenging at present. Herein, the efficient Ce,F-Ni2P/CoP electrocatalyst for water splitting was successfully fabricated. As shown from the present investigation, the codoping of Ce and F in Ni2P/CoP induced the f-p-d gradient orbital coupling in the Ce-F-metal structural unit of the catalyst, significantly reducing the work function of the catalyst, which accelerated the reaction kinetics and improved the intrinsic catalytic activity. The catalyst exhibited the outstanding hydrogen evolution reaction (HER) activity in the full pH range and, especially in alkaline electrolyte, an ultra-low oxygen evolution reaction (OER) overpotential of 243 mV at 50 mA·cm−2 and an excellent HER overpotential of 88 mV at 10 mA·cm−2 were achieved. Moreover, Ce,F-Ni2P/CoP displayed an excellent overall water splitting (OWS) performance with η10 = 1.52 V. DFT theoretical calculations also showed that the gradient orbital coupling resulted in the reduction of the work function of the catalyst. Our work provides a new understanding of designing and constructing high-performance catalysts.

Ruthenium highly dispersed in low crystallinity cobalt oxide as an efficient catalyst for Li-O2 battery

The performance of Li-O2 battery can be improved by adjusting the reaction active sites of cathode catalysts. In this study, noble metal ruthenium (Ru) was successfully added to the framework of Zeolitic Imidazolate Framework-67 (ZIF-67) through a dual solvent method, and prepared highly dispersed noble metal ruthenium cathode catalyst material for Li-O2 battery. At the same time, the phenomenon of aggregation of precious metal ruthenium on the catalyst surface is avoided, and the atomic utilization rate of precious metals is improved. The low crystallinity cobalt oxide (ZIF-67-280) and noble metal ruthenium act as the catalytic active center together, enriching the reaction active sites of the catalyst, further improving the performance of Li-O2 battery and reducing the reaction overpotential. Compared to commercial cobalt oxides (C-Co3O4), ruthenium doped low crystallinity cobalt oxides (Ru@ZIF-67-280) has better cycle stability (272 cycles) and higher energy efficiency.© 2023 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

Novel BDD-loaded bimetallic phosphide electrodes enable interesting bifunctional seawater electrolysis

The direct electrolysis of seawater for the production of green hydrogen energy is an economically attractive approach. However, this technique confronts technical problems because to the oxygen evolution reaction (OER) weak stability and inadequate selectivity due to competition with the chlorine evolution process. This work focuses on improving the stability of the electrode and electrolysis efficiency. The phosphating NiCoP active layer with 3D porous morphology was created by electrodeposition on the B-doped diamond (BDD) as an electrode inspired by the bifunctional catalysis strategy. The successfully constructed unique cube-on-nanosheets structure in the NiCoP active layer enables the electrode to exhibit excellent electrocatalytic performance. The porous NiCoP/BDD (Por-NiCoP/BDD) electrodes showed good catalytic activity in alkaline-simulated seawater with the OER and hydrogen evolution reaction (HER) overpotentials of 400 and 261 mV, respectively, at a current density of 100 mA cm−2. More importantly, the electrode exhibits interesting stability of the catalytic performance and structural in alkaline-simulated seawater electrolysis, with the current density decaying by only 1.52 % and 4.06 % after OER and HER processes for 50 h, respectively. This work expands the valuable application scenarios of BDD electrode and provides novel ideas for the development of seawater electrolysis.

Synergy of Interface Coupling and Sulfur Vacancies in Ni3S2/Fe2P for Water Splitting.

Integrated application of interface engineering and vacancy engineering is a promising and effective strategy for the design and fabrication of high-performance electrocatalysts. Herein, the heterointerface catalyst with rich sulfur vacancies, vs-Ni3S2/Fe2P, was successfully designed and constructed. The strong heterointerface coupling and rich sulfur vacancies in vs-Ni3S2/Fe2P significantly optimize the electronic structure of the catalyst and synergistically improve the inherent catalytic activity. Benefiting from the optimization of the electronic structure, vs-Ni3S2/Fe2P exhibits excellent bifunctional electrocatalytic performance in alkaline electrolytes. The overpotentials for hydrogen and oxygen evolution reactions (HER and OER) are 99 and 169 mV at a current density of 10 mA cm-2, respectively. Particularly, it achieves an ultrahigh OER performance with an overpotential of 251 mV at 300 mA cm-2. Moreover, the catalyst also displays outstanding long-term durability. Density functional theory (DFT) computations reveal that the synergy of interface coupling and sulfur vacancies is crucial to optimizing the electronic structure. This study offers a hopeful pathway for the design and construction of durable and efficient electrocatalysts.

Interfacial coupling of Ce-CoSe2 nanoneedle arrays with MXene for efficient overall water splitting

Designing highly effective, low-cost bifunctional electrocatalysts without noble metals for overall water splitting remains a significant challenge. In this work, interfacial coupling of Ce-doped CoSe2 nanoneedle arrays with MXene (Ce-CoSe2/MXene) is developed via the facile hydrothermal and selenization methods. The extensive specific surface area and favorable hydrophilicity of Ti3AlC2, combined with the optimized electronic structure and abundant active sites from Ce-doping and selenization, contribute to the exceptional bifunctional electrocatalytic performance of the Ce-CoSe2/MXene electrode. Specifically, this heterostructure achieves a low hydrogen evolution reaction (HER) overpotential of 34 mV at 10 mA cm−2, an oxygen evolution reaction (OER) overpotential of 279 mV at 100 mA cm−2, and an overall water splitting (OWS) potential as low as 1.45 V at 10 mA cm−2. In-situ Raman spectroscopy reveals that surface reconstruction would improve catalytic activity and stability. Theoretical calculations indicate that the Ce-CoSe2/MXene can improve the adsorption of intermediates and facilitate HER/OER process by lowering the kinetic barrier, thereby enhancing electrocatalytic activity. This research marks a substantial advancement in the development of low-cost, efficient electrocatalysts for overall water splitting.