Search

It is significant to develop low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) via electrochemical water splitting. Herein, we constructed P-doped NiCo2S4 nanowire arrays on carbon fiber paper (NiCo2S4−xPx/CFP) as a HER electrocatalyst in both acidic and alkaline media. Benefitting from P doping into NiCo2S4, the as-prepared NiCo2S4−xPx/CFP exhibits low HER overpotentials of 80 and 132 mV in acidic and alkaline media at a cathodic current density of 10 mA cm−2, respectively, which are far superior to counterparts of NiCo2S4 nanowire arrays on the carbon fiber paper (NiCo2S4/CFP). Meanwhile, the NiCo2S4−xPx/CFP presents excellent HER stability of 20 hours in acidic and alkaline media. From the results of density functional theory calculations, P doping can not only optimize the hydrogen adsorption energetics on each kind of atomic site of catalysts, but also strengthen the H2O molecule binding ability on the catalyst surface for the alkaline HER and favor kinetics of hydrogen adsorption and H2 formation on the catalyst surface for the acidic HER, eventually improving overall HER performances. The investigation of the HER mechanism modulated by P doping in our work offers novel inspiration to develop highly efficient ternary metal sulfides for the HER. [ABSTRACT FROM AUTHOR]

The document is a contents list for the New Journal of Chemistry, a publication by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. It features a variety of articles and papers covering topics such as anti-counterfeiting printing, monitoring platinum(IV) complexes, and the removal of uranium from the kidneys. The journal also provides information on training courses and resources for professional development in chemistry. The papers offer valuable insights and advancements in the field, making it a valuable resource for researchers and professionals in chemistry. [Extracted from the article]

The document is a contents list for the New Journal of Chemistry, a publication by The Royal Society of Chemistry. It features papers on various topics such as boron nitride-carbon composites, organic/inorganic artificial bones, and metal-organic frameworks. The journal aims to connect the world with the chemical sciences. The document also includes corrections to previous publications. [Extracted from the article]

This document is a contents list for the New Journal of Chemistry, providing a summary of papers published in 2024. The journal covers a wide range of topics in the chemical sciences, including selenium compounds as antiviral agents, guanidinium-terminated gold nanoparticles for protein delivery, and the synthesis of macroporous nanocarbon for sodium ion batteries. The journal aims to connect the global chemistry community and reinvest profits into the field. Additionally, the document includes an expression of concern and a correction for previous articles. [Extracted from the article]

The document is a contents list for the New Journal of Chemistry, providing a range of research topics for library patrons interested in chemistry. It includes articles on the transformation of CO2, mechanochromic photoluminescence, nanocellulose-based electrocatalysts, bone formation rate prediction, and the synthesis of halogenated benzimidazolyl-C nucleosides. The journal also covers industrial chemistry, material innovations, and interdisciplinary features. Additionally, the document includes a retraction notice for a previous paper. [Extracted from the article]

The use of a methanesulfonic acid (MSA) electrolytic system is recommended as a green method for hydrometallurgical recovery of metallic Pb from waste lead-acid batteries (LABs), contributing to the sustainable protection of the ecosystem. Nevertheless, the system's high energy consumption is a current issue due to the substantial overpotential of the oxygen evolution reaction (OER) and competitive anodic oxidation of Pb2+. Herein, we propose an IrFe/nitrogen-doped pyrolytic carbon black (IrFe/NCBp) composite as a novel OER catalyst for the MSA electrolytic system, which demonstrates advanced OER catalytic efficiency and selectivity for H2O oxidation. This can be ascribed to the catalyst's thoughtful design, which enhances the number and uniformity of Ir and Fe species via increasing the specific surface area and employing NCBp as a sustainable substrate. The optimized IrFe/NCBp composite exhibits superior OER performance, with a low 252 mV@10 mA cm−2 overpotential and a 62 mV dec−1 Tafel slope, and excellent durability in a 1 M MSA electrolyte for 30 h operation compared to commercial Ir/C. In contrast to carbon paper (CP) and commercial Ir/C anodes, the anodic reaction of IrFe/NCBp is primarily OER-driven (97%) in 1 M MSA and 0.2 M Pb2+ electrolyte for Pb recovery. This effectively circumvents the high potential oxidation of Pb2+ into PbO2, reducing the electrolytic voltage to 488 kWh for the recovery of 1 ton Pb metal. This work provides a green, low-carbon footprint solution for the MSA electrolytic system, thereby promoting the commercialization of the hydrometallurgical Pb recovery. [ABSTRACT FROM AUTHOR]

Seawater, a plentiful natural resource, is promising for hydrogen production compared to traditional electrocatalytic methods based on high-purity freshwater. This strategy shift addresses the challenge of limited freshwater resources and holds significant potential for desalination applications. Hence, identifying effective electrocatalysts for seawater electrolysis is imperative to alleviate freshwater resource scarcity and achieve large-scale hydrogen production. Herein, we report a catalyst comprising zero-dimensional (0D) nitrogen-doped carbon-coated FeNi3 nano-particles (FeNi3-NC) grown on NiFeOx nano-sheets for the hydrogen evolution reaction in alkaline seawater. The combination of FeNi3-NC and NiFeOx significantly enhances interfacial interactions, resulting in an elevated rate of electron transfer. The FeNi3-NC/NiFeOx catalyst requires a low overpotential of 65 mV to achieve a current density of 10 mA cm−2 in alkaline seawater. In addition, the electrolytic cell constructed using it and its precursor also exhibits excellent water-splitting characteristics and it exhibits remarkable long-term stability and corrosion resistance. This discovery presents an innovative approach for designing zero-dimensional/two-dimensional catalysts to facilitate large-scale hydrogen production through seawater electrolysis. [ABSTRACT FROM AUTHOR]

Surface chemical etching for the in situ growth of metal–organic materials and electrochemical reconstruction are expected to efficiently improve the catalytic performance of oxygen evolution reactions (OERs). In this work, 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO4) was used to chemically etch the surface structure of nickel foams (NFs) and form metal–organic thin films in situ at the surface of the NF ([BMIM]–SO4–Ni@NF). Anion HSO4− in [BMIM]HSO4 chemically etched the NF surface to provide bivalent nickels (Ni2+). Ni2+ and [BMIM]HSO4 formed a [BMIM]–SO4–Ni coating in situ on the surface of the modified NF. During the OER process, nitrogen and sulfur leached out from the surface of [BMIM]–SO4–Ni@NF, along with the reconstruction of [BMIM]–SO4–Ni@NF to C–NiOOH@NF. C–NiOOH@NF possessed a hierarchical and defective nanoflower structure and enlarged the electrochemical active surface area and surface-active sites for OER activity. The effect of [BMIM]HSO4 on the performance of oxygen evolution reactions (OERs) was investigated. The results indicated that [BMIM]HSO4 modification promoted the formation of γ-NiOOH and significantly improved the OER performance of NFs. The OER performance was obtained at a [BMIM]HSO4 mass concentration ([BMIM]HSO4%) of 2.4%. However, high [BMIM]HSO4% results in the damage of the NF frame structure and a high content of carbon doping, leading to a reduction in OER activity. [ABSTRACT FROM AUTHOR]

Mn-doped Bi3O4Br has been synthesized using a solvothermal route. The undoped Bi3O4Br and Mn–Bi3O4Br materials possess orthorhombic unit cells with two distinct Bi sites forming a layered atomic arrangement. The shift in the (020) plane in the powder X-ray diffraction (PXRD) pattern confirms Mn-doping in the Bi3O4Br lattice. Elemental mapping indicated 7% Mn doping in the Bi3O4Br lattice structure. A core-level X-ray photoelectron study (XPS) indicates the presence of BiIII and MnII valence-states in Mn–Bi3O4Br. Doping with a cation (MnII) containing a different charge and ionic radius resulted in vacancy/defects in Mn–Bi3O4Br which further altered its electronic structure by reducing the indirect band gap, beneficial for electron conduction and electrocatalysis. The irreversible MnII to MnIII transformation at a potential of 1.48 V (vs. RHE) precedes the electrochemical oxygen evolution reaction (OER). The Mn-doped electrocatalyst achieved 10 mA cm−2 current density at 337 mV overpotential, while the pristine Bi3O4Br required 385 mV overpotential to reach the same activity. The pronounced OER activity of the Mn–Bi3O4Br sample over the pristine Bi3O4Br highlights the necessity of MnII doping. The superior activity of the Mn–Bi3O4Br catalyst over that of Bi3O4Br is due to a low Tafel slope, better double-layer capacitance (Cdl), and small charge-transfer resistance (Rct). The chronoamperometry (CA) study depicts long-term stability for 12 h at 20 mA cm−2. An electrolyzer fabricated as Pt(−)/(+)Mn–Bi3O4Br can deliver 10 mA cm−2 at a cell potential of 2.05 V. The post-CA-OER analyses of the anode confirmed the leaching of [Br−] followed by in situ formation of Mn-doped Bi2O3 as the electrocatalytically active species. Herein, an ultra-low Mn-doping into Bi3O4Br leads to an improvement in the electrocatalytic performance of the inactive Bi3O4Br material. [ABSTRACT FROM AUTHOR]

Electricity-driven water splitting is a promising approach for cost-effective and environment-friendly hydrogen production. However, the anodic oxygen evolution reaction (OER) remains a major bottleneck for its industrial application. An alternative strategy to bypass the OER is the electrocatalytic oxidation of benzyl alcohol for promoting hydrogen production, though achieving this efficiently remains challenging. In this study, we introduce a CoV-layered double hydroxide (LDH) designed specifically for the selective oxidation of benzyl alcohol. This is achieved by incorporating high valence vanadium into Co(OH)2, a conventional OER catalyst. Due to the synergistic enhancement in electron and proton transfer processes resulting from vanadium incorporation, the CoV-LDH grown on nickel foam (CoV-LDH/NF) displays outstanding activity and selectivity for the benzyl alcohol oxidation reaction (BOR). Notably, the CoV-LDH/NF achieves current densities of 10 and 100 mA cm−2 at just 1.28 and 1.31 V (vs. RHE), respectively. Moreover, the CoV-LDH/NF demonstrates remarkable durability, showing no decrease in the electrochemical performance over ten consecutive cycles. [ABSTRACT FROM AUTHOR]

Efficient and stable oxygen evolution reaction (OER) electrocatalysts are essential for improving the overall efficiency of water electrolyzers. Iron-doped cobalt phosphide (CoFeP) nanowires are prepared via a one-step solvothermal process using a cobalt metal--organic framework (Co MOF), P4 and dissolved Fe2+. The ion-exchange between Fe2+ and the Co MOF occurs first, and then phosphides are formed. CoFeP exhibits the Co2P phase, and there exists an electronic interaction between Co and Fe. When supported on nickel foam (NF) to catalyze the OER in alkaline solutions, CoFeP/NF exhibits an overpotential of 240 mV at a 10 mA cm-2 OER current density, which is much lower than that of Co2P/NF. Kinetic analyses indicate that the lattice oxygen oxidation mechanism occurs at the CoFeP/NF surface, whereas the adsorbate evolution mechanism dominates at the Co2P/NF surface. The change in the mechanistic pathway is due to the increased acidity of the Co4+ site in CoFeP, which favors the decoupled proton--electron transfer process. Lower apparent activation energy, charge transfer resistance and Tafel slope values, and higher electron rate constants are observed on the CoFeP/NF surface, and the charge redistribution induced by Fe during the OER process alters the adsorption energy of the hydroxyl groups at the Co sites, leading to more facile OER kinetics, as proved by density functional theory calculations. CoFeP/ NF shows good long-term durability in alkaline solutions, and the conversion of surface phosphides to oxides and (oxy)hydroxides is observed. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable non-precious metal electrocatalysts for the oxygen evolution reaction (OER) is an ongoing challenge due to the sluggish kinetics of the OER. In this study, the (Ni,Fe,V)3S4–NiS nanoheterostructure rich in Ni3+ was obtained by sulfidizing the NiFeV layered double hydroxide hydrogen precursor. The introduction of Fe and V effectively modified the electronic structure of NixSy and increased the content of Ni3+, which was conducive to enhancing the chemisorption of OH− and promoting the transfer of electrons to the surface during the OER process. At the same time, the self-supporting porous structure, the unique metallic characteristics of NixSy (continuous Ni–Ni bonds) and excellent electrical conductivity can facilitate electrolyte diffusion and bubble release. The designed (Ni,Fe,V)3S4–NiS/NF electrode shows excellent electrocatalytic OER performance with an overpotential of 236 mV at a current density of 10 mA cm−2, ultra-low Tafel slope (53.7 mV dec−1) and excellent long-term stability. Therefore, this work offers a simple strategy to design an efficient Ni based OER electrocatalyst enriched with Ni3+ sites by co-doping high-valence ions. [ABSTRACT FROM AUTHOR]

Water electrolysis is considered the most promising technology for hydrogen production. In the present study, RCoFe (regulated cobalt ferricyanide) is synthesized via the co-precipitation method, which is characterized by physical and electrochemical properties. XRD confirmed the crystalline phase of RCoFe and the diffraction peaks are consistent with JCPDS#82-2284. FE-SEM examines the nanoplatelet morphology, which could help with the mass transfer of electrons during the electrochemical process. Here, RCoFe promotes the extensive activity for the OER (oxygen evolution reaction) with 270 mV/GC; 252 mV/NF at 10 mA cm−2. The lower Tafel value for RCoFe (78 mV dec−1/GC; 107 mV dec−1/NF) was derived from LSV when compared to IrO2 (98 mV dec−1/GC; 123 mV dec−1/NF) and stable for a long time with minimal loss of potential (130 h/GC-1.5%; 250 h/NF-1.8%) owing to citrus sap, which stabilized the electrocatalyst. After electrochemical treatment, the post-SEM morphology reveals that the nanoplatelets are completely bound together to enhance the OER process. [ABSTRACT FROM AUTHOR]

Due to the slow kinetics and large overpotential of the oxygen evolution reaction (OER) in electrochemical water splitting, it is important to develop efficient and low-cost electrocatalysts for the OER. In this work, we used Co-PBA as the substrate, and induced the growth of NiFe-LDH on the surface of cubic Co-PBA by the hydrothermal method. The Co-PBA@NiFe-LDH electrocatalysts with a flower-like morphology and heterostructures were finally utilized to evaluate the OER performance. The results reveal that during the OER process, the flower-like structure allows Co-PBA@NiFe-LDH-30 to expose more active centers, and increases the contact area between the electrolyte and active sites. Meanwhile, benefiting from the synergistic effect of multi-metals and the heterostructure, Co-PBA@NiFe-LDH-30 demonstrated remarkable electrochemical performance with a lower overpotential of 253 mV at 10 mA cm−2 and a smaller Tafel slope of 54 mV dec−1. This design strategy provides a promising approach for the development of OER electrocatalysts in the future. [ABSTRACT FROM AUTHOR]

Hollow structures with a hierarchical architecture and multi-composition have attracted extensive interest because of their fascinating physicochemical properties as well as wide applications. To improve the efficiency of overall water splitting, highly active and stable electrocatalysts are highly desirable. A novel high-efficiency oxygen defect based hierarchical hollow nanosheet-based-nanosphere Co–NiMoO4-HNS electrocatalyst for oxygen evolution was arranged by doping Co on a Ni-MoEG yolk/shell nanosphere. Co–NiMoO4-HNS has a greater hydrophilicity and smaller band gap than that of NiMoO4-CS. Post OER characterization indicates that the main active phase of the Co2–NiMoO4-HNS catalysts toward the OER are amorphous Ni3+, Co3+, and H–O and the high-valent Mo (+6) can make nickel and cobalt better maintain Ni3+ and Co3+ sites. Remarkably, this hierarchical hollow Co2–NiMoO4-HNS catalyst exhibits a favorable catalytic performance toward the oxygen evolution reaction (OER) with a receivable overpotential of 270 mV achieving a current density of 10 mA cm−2 and a Tafel slope of 65 mV dec−1. In expansion, as an electrocatalyst, Co2–NiMo4-HNS appeared to have a great long-term steadiness in the electrolyte. This work may give a broad hypothetical and specialized background for plans of cost-effective bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal sulfides possess high intrinsic catalytic activity for the oxygen evolution reaction (OER) during water splitting but are restricted by their low conductivity and unattractive stability in alkaline electrolytes. Herein, newly designed CoS2/MoS2 nanosheets with enriched heterointerfaces synthesized by the combination of hydrothermal and vulcanization methods showed great promise as a highly efficient OER electrocatalyst. Owing to the fast vulcanization process, some heterometallic sulfide nanoparticles get distributed on the nanosheets, thus forming a nanoparticle-nanosheet bridging structure. The rich heterogeneous interface between CoS2 and MoS2 regulates the electronic structure and provides sufficient electrochemical active sites, thus forming a fast channel conducive to electron transport and ensuring high OER activity. Besides, the rough heterostructured surface enhances hydrophilicity, which promotes the decomposition of H2O and decreases the energy barrier of intermediate reactions, leading to fast electrochemical kinetics. Benefiting from the structural merits, the optimized CoS2/MoS2-1 : 1 nanosheets exhibit a low overpotential of 283 mV at 10 mA cm−2, a small Tafel slope of 105.32 mV dec−1 and long-term durability for the OER. [ABSTRACT FROM AUTHOR]

This article presents the development of efficient catalysts for electrocatalytic water oxidation by synthesizing CoNi-LDH/HNT (cobalt–nickel layered double hydroxide/halloysite nanotube) binary composites. Four novel CoNi-LDH/HNT nanocomposites were fabricated on nickel foam substrates by electrodepositing CoNi-LDH nanostructures onto HNT-modified nickel foam. The electrocatalytic activities of these nanocomposites were evaluated in the alkaline oxygen evolution reaction (OER). Incorporating HNTs as a support material significantly enhanced the performance of pristine CoNi-LDH in the OER. Through the manipulation of the Co/Ni molar ratio in the LDH, a nanocomposite with optimal performance was achieved (denoted as CoNi/H-2). This nanocomposite demonstrated superior electrocatalytic activity in the alkaline OER. Specifically, it exhibited an overpotential of 183 mV (at 10 mA cm−2) and a Tafel slope of 68.2 mV decade−1. CoNi/H-2 also showed robust electrochemical stability over 24 hours under harsh OER conditions, maintaining a current density of 53 mA cm−2, while experiencing minimal activity loss. Significantly, the nanocomposite yielded an impressive current density of 475 mA cm−2 with an overpotential of only 308 mV. This study underscores the potential of HNTs as a cost-effective and abundant material for designing efficient catalysts for OER. [ABSTRACT FROM AUTHOR]

To find sustainable energy solutions, it is essential to explore electrocatalysts that are both efficient and robust in obtaining energy and making use of seawater. This study introduces a promising electrocatalyst, MnCoCr LDH@SCDs/NF, which is created by integrating sulphur-doped carbon dots (SCDs) into the layers of MnCoCr layered double hydroxides (LDHs) and drop casting them onto a nickel foam substrate. This novel approach aims to enhance the performance of the oxygen evolution reaction (OER) under alkaline seawater conditions. MnCoCr LDH@SCDs/NF showcases exceptional electrocatalytic capabilities in alkaline environments, effortlessly achieving a significant current density of 10 mA cm-2 with an impressively low overpotential of only 225 mV. These remarkable results were attributed to the strategic inclusion of SCDs within MnCoCr LDH layers, effectively functioning as efficient channels for transporting electrons. Because these sulphur-doped carbon dots contain many negatively charged functional groups, they effectively repel undesirable chlorine anions present in seawater during electrolysis. This innovative design not only enhances intrinsic catalytic activity but also provides a substantial specific surface area. This investigation underscores the potential of MnCoCr LDH@SCDs/NF as a strategic route for the development of high-performance electrocatalysts with exceptional stability. Such breakthroughs hold great promise in advancing the utilization of renewable energy harnessed from seawater sources. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOF) were used as templates to prepare transition metal sulfides and phosphides in order to expose the active site of the material to a greater extent. Utilizing the synergistic effect of bimetals, Ni2+ and Mo6+ were selected as metal ion centers and trimesic acid was selected as the ligand to prepare NiMo-MOFs by the hydrothermal method. Then, NiMo-P, NiMo-S and NiMo-P/S were prepared using NiMo-MOFs as the precursor, and the preparation conditions of the abovementioned hybrids were optimized through linear sweep voltammetry. The results show that when the molar ratio of NiMo-MOF to NaH2PO2 is 1: 5, and the as-prepared NiMo-P is further doped with S in a proportion of 1: 1, the overpotential of the final NiMo-P/S hybrid is 313 mV at a current density of 10 mA cm-2, and its electrochemical impedance (Rct), Tafel slope and electrochemical active surface areas are 22.38 Ω, 63.8 mV dec-1, and 707.5 cm-2, respectively. The optimized NiMo-P/S hybrid provides more active sites and reaction areas along with good stability, which is conducive to promoting the kinetics of the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

The electrocatalyst for methanol oxidation is the key to determining the performance and lifetime of direct methanol fuel cells (DMFCs). At present, the most effective and promising electrocatalysts for the methanol oxidation reaction (MOR) are Pt and platinum-based catalysts. Unfortunately, the toxicity of CO intermediates leads to rapid inactivation of the MOR catalyst, further lowering the durability of the MOR. In response to this issue, it has been found that effective screening of good oxygen evolution reaction (OER) active materials and synergistic application with Pt in the MOR can reduce the loss of activity and improve its durability. Based on this strategy, a series of Pt-based MOR catalysts (Pt/Ni, Pt/Co and Pt/NiCo) are synthesized by electrodeposition. The results indicate that the OER activity of Pt/Ni, Pt/Co, and Pt/NiCo is positively correlated with MOR activity and durability. Among the Pt-based MOR catalysts, the ultimate optimized Pt/NiCo exhibits excellent MOR performance, with a good mass activity of 495 A gPt-1, strong CV cycle durability (63.6% activity retained after 5000 cycles), and a long-term operating durability of 15 000 s in alkaline solution. [ABSTRACT FROM AUTHOR]

Medium entropy alloys, consisting of four elements in close to isotropic proportions, have attracted a great deal of attention because of their unique properties (excellent strength, corrosion resistance, etc.). Here, we present a series of quaternary medium entropy alloy FeCoNiW electrocatalysts loaded onto nitrogen-doped carbon (NC) skeletons. The prepared medium entropy alloy catalysts have excellent OER catalytic activity and stability. In alkaline media, the FeCoNiW-NC electrocatalysts annealed at 350 °C were able to achieve an overpotential as low as 225 mV at a current density of 10 mA cm−2, which is 55 mV lower than that of the commercial RuO2, while it has a smaller Tafel slope of 54 mV dec−1. The introduction of W leads to a change in the electronic structure of the FeCoNi alloy and increases the specific surface area of the catalyst, exhibiting excellent performance. This work contributes to the exploration of OER catalysts by opening new avenues for the design of efficient and economical OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Cellulose nanofiber (CNF) is an environmentally friendly material with a high specific surface area, which is an ideal candidate for cathode catalysts in zinc–air batteries (ZABs). However, untreated CNF-based carbon materials suffer from low intrinsic activity and fewer micro-mesopores. Herein, we developed an N-doped porous carbon aerogel from CNF and graphite phase carbon nitride (g-C3N4) via hydrothermal pretreatment and the carbonization process. The CNF can serve as the skeleton of the aerogel that leads to an interconnected porous structure, while g-C3N4 guarantees the in situ N doping and the formation of more nanopores. Therefore, the as-prepared carbon aerogel exhibits excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances owing to the successful N doping with sufficient graphite-N and pyridine-N active sites (69.1%) and high specific surface areas (785.4 m2 g−1). The assembled ZABs with a carbon aerogel deliver a specific capacity of 790 mA h g−1 and an energy density of 945.6 W h kg−1 with a long-term stability over 100 h. This work opens a new avenue for the effective conversion of abundant biomass into bifunctional air cathodes for energy-related applications. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2)-based electrocatalysts have been considered as promising alternatives to platinum for use in the hydrogen evolution reaction (HER). Developing MoS2 electrocatalysts with more active sites has been recognized as an efficient way to enhance the HER activity. Moreover, phase transition and heteroatom doping show great influence on the HER performance. In this work, we develop a vapor-phase hydrothermal (VPH) approach to introduce phosphorus (P) atoms into a MoS2 nanosheet array on carbon fiber cloth, which presents enhanced HER activity compared with MoS2 without P-doping. The improved performance is due to the synergistic effects of the new active sites formed by the P dopants and the sulfur (S) vacancies in the MoS2 nanosheets generated by the doping of P atoms, which increases the number of active sites. In general, the obtained P-doped MoS2/CFC exhibits a lower onset potential of 80 mV and an overpotential of 162 mV at 10 mA cm−2 than MoS2 without P-doping in 0.5 M H2SO4, accompanied by extremely large cathodic current density and excellent stability. This strategy may open up opportunities for heteroatom doping of electrocatalysts for various applications and provide a new method for material synthesis. [ABSTRACT FROM AUTHOR]

Exploiting effective, stable, and cost-efficient electrocatalysts for the water oxidation reaction is highly desirable for renewable energy conversion techniques. Constructional design and compositional manipulation are widely used approaches to efficaciously boost the electrocatalytic performance. Herein, we designed a NiFe-bimetallic sulfide/N-doped carbon composite via a two-step thermal treatment of Prussian blue analogues/cellulose nanofibers (PBA/CNFs) film. The NiFe-bimetallic sulfide/N-doped carbon composite displayed enhanced OER performance in an alkaline environment, with an overpotential of 282 mV at 10 mA cm−2, a Tafel slope of 59.71 mV dec−1, and good stability, making the composite a candidate electrocatalyst for OER-related energy equipment. The introduction of CNFs in the precursor prevented the aggregation of PBA nanoparticles (NPs), exposed more active sites, and the resulting carbon substrate enhanced the electroconductivity of the composite. Moreover, the synergistic effect of Ni and Fe in the bimetallic sulfide could modulate the configuration of electrons, enrich the catalytically active sites, and augment the electric conductivity, thus ameliorating the OER performance. This study broadens the application of MOF-CNF composites to construct hierarchical structures of metal compounds and provides some thoughts for the development of cost-effective precious-metal-free catalysts for electrocatalysis. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting, which is a highly promising and environmentally friendly technology for H2 fuel production, faces significant hurdles due to the sluggish kinetics of the oxygen evolution reaction. Co -based oxides have garnered significant attention as alternative catalysts for the oxygen evolution reaction owing to the Co2+/Co3+ redox couple. Enhancing the challenging Co2+ → Co3+ oxidation process can further improve the catalytic oxygen evolution reaction. The aim of our work was to design a Co3O4-based catalyst to enhance reactivity by increasing the number of Co3+ active sites, serving as an excellent platform for facilitating the oxygen evolution reaction. To drive the effectiveness of the catalyst, in this study, we synthesized Co3O4 anchored on CeO2 (Co3O4/CeO2). The kinetics and efficacy of the oxygen evolution reaction catalysed by Co3O4/CeO2 was significantly improved by aliovalent doping of Sr into Ce sites and Cu into Co sites. The reducible nature of Ce stimulates the formation of Co3+ ions, resulting in an increased production of intermediate –OOH species, thus expediting the reaction. The transformation of Co2+ to Co3+ consequently leads to an increase in anion vacancies, which, in turn, promotes the adsorption of more intermediate species at the active site. The Sr- and Cu-doped Co3O4/CeO2 catalyst exhibited a high current density of 200 mA cm−2 at 580 mV and a low overpotential of 297 mV at 10 mA cm−2. The study functions as a key indicator to establish a connection between oxygen vacancies and metal oxidation states in order to investigate the mechanistic aspects of the oxygen evolution reaction on mixed metal oxides. Moreover, this study is expected to pave the way for the development of innovative oxygen evolution reaction catalysts with reducible supports, thus offering a new pathway for their design. [ABSTRACT FROM AUTHOR]

In the domain of photocatalysis, the oxygen evolution reaction (OER) serves as a crucial process in sustainable energy production. The development of efficient photocatalysts for the OER is therefore highly desirable. Two-dimensional (2D) materials, with their distinct structural and electronic properties, offer great opportunities for improving oxygen production. We propose H and H′ polymorphs of SnGe2N4 as appealing photocatalysts driving the OER using first-principles calculations together with non-adiabatic molecular dynamics (NAMD). The electronic properties and charge carrier dynamics of SnGe2N4 were evaluated, revealing insights into its potential for the OER under solar irradiation. Our findings indicate that SnGe2N4 has a favorable bandgap (∼2 eV) with appropriate band edges for the OER, promoting charge separation and transport. A significant difference in mobility facilitates electron and hole separation, leading to elevated reaction rates in the material. Moreover, the band edge alignment suggests the incorporation of water oxidation potential favoring the OER. The computed reaction pathways and free energy analysis show that SnGe2N4 can function as an effective photo-catalyst for the OER. Non-adiabatic coupling (NAC) matrix elements further ensure the ultrafast carrier dynamics, facilitating efficient charge transfer and slow recombination rates. Our findings highlight 2D SnGe2N4 as an appealing candidate for the OER. [ABSTRACT FROM AUTHOR]

Using electrochemical water splitting to generate hydrogen is considered a desirable approach, which is greatly impeded by the sluggish dissociation of H2O and adsorption and desorption of H*. Effective hydrogen production can be achieved by speeding up the chemical process with a suitable electrocatalyst. In this work, we designed and synthesized a rare earth element cerium (Ce) regulated iron–nickel bimetallic phosphide Ce-NiFeP@NF (here NiFeP represents Fe2P/NiP2) nanoarray with nanoflowers. For the hydrogen evolution reaction (HER), Ce-NiFeP@NF only needs an overpotential of 106 mV to provide a current density of 10 mA cm−2, compared to NiFeP@NF (175 mV@10 mA cm−2). This self-supported electrocatalyst Ce-NiFeP@NF with a composite morphology exhibits excellent performance in the HER. Specifically, the introduction of Ce promotes the electron transfer process at the Fe2P/NiP2 heterojunction interface and the Ce-NiFeP@NF nanocomposite structure with nanoflowers has a larger electrochemically active specific surface area, which is more conducive to improving the intrinsic catalytic activity. Also, a dual-electrode alkaline electrolytic cell (Ce-NiFeP@NF functions as both the anode and the cathode) operates with a cell voltage of only 1.56 V to achieve a current density of 10 mA cm−2. The synergistic effect of rare earth element doping and heterojunction engineering can improve the morphology of intrinsic catalysts to achieve more efficient electrochemical water splitting for hydrogen production. [ABSTRACT FROM AUTHOR]

A newly synthesized series of bimetallic CPM-37(Ni,Fe) metal–organic frameworks with different iron content (Ni/Fe ≈ 2, 1, 0.5, named CPM-37(Ni2Fe), CPM-37(NiFe) and CPM-37(NiFe2)) demonstrated high N2-based specific SBET surface areas of 2039, 1955, and 2378 m2 g−1 for CPM-37(Ni2Fe), CPM-37(NiFe), and CPM-37(NiFe2), having much higher values compared to the monometallic CPM-37(Ni) and CPM-37(Fe) with 87 and 368 m2 g−1 only. It is rationalized that the mixed-metal nature of the materials increases the structural robustness due to the better charge balance at the coordination bonded cluster, which opens interesting application-oriented possibilities for mixed-metal CPM-37 and other less-stable MOFs. In this work, the CPM-37-derived α,β-Ni(OH)2, γ-NiO(OH), and, plausibly, γ-FeO(OH) phases obtained via decomposition in the alkaline medium demonstrated a potent electrocatalytic activity in the oxygen evolution reaction (OER). The ratio Ni : Fe ≈ 2 from CPM-37(Ni2Fe) showed the best OER activity with a small overpotential of 290 mV at 50 mA cm−2, low Tafel slope of 39 mV dec−1, and more stable OER performance compared to RuO2 after 20 h chronopotentiometry at 50 mA cm−2. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) electrocatalysts are frequently made from noble metal-based oxides like ruthenium/iridium oxides. However, because of their scarcity and high price, researchers are now focusing on creating innovative OER catalysts based on affordable transition metals that have improved electrical conductivity and accessibility to active sites. Metal–organic frameworks (MOFs), a unique class of inorganic materials with excellent physical and chemical properties, have witnessed significant progress in promising green energy systems. In this work, a novel mixed-ligand metal–organic framework [Co(μ-1κN,2κN′-BDP)(μ3-1κoo′,2κo′′2κo′′′-BTC)]n·nH2O (BDP = boron-dipyrromethene or BODIPY; BTC = benzene tricarboxylate) denoted as CoBDPMOF has been synthesized, and its composites with different carbon materials have been designed. Compared to the pristine MOF, the composites showed enhanced electrocatalytic activity toward the oxygen evolution reaction (OER) in alkaline media. In addition, the CoBDPMOF with activated carbon showed the highest OER performance with a low Tafel slope (82 mV dec−1) and the highest j600 (59.8 mA cm−2), outperforming noble metal IrO2, the OER benchmark electrocatalyst. This study presents new insights into the design and application of CoBDPMOF-based materials for energy conversion and suggests promising avenues for further research and development in electrocatalysis. [ABSTRACT FROM AUTHOR]

Electronic modulation is of great importance in an attempt to enhance the catalytic activity of electrocatalysts towards the oxygen evolution reaction (OER), which dominates the energy efficiency of water splitting. Here, a facile and reliable strategy is reported based on the specific synergistic effects of the combination of early and late transition metals. The OER activity of a prototypical bimetallic NiFe-MOF was greatly promoted by introduction of a Cr ion dopant, and the as-prepared Cr-NiFe-MOF needed a low overpotential of only 242 mV to deliver a current density of 100 mA cm−2 with excellent stability. Detailed analyses revealed that Cr replaced the position of Ni in the NiFe-MOF and adjusted the electronic structure of nearby Fe sites, allowing the d-band center to shift down to efficiently regulate the adsorption behavior of key intermediates, which endowed the Cr-neighboring Fe sites with a lowered energy barrier for the OER. This work presents a strategy of early-and-late transition metal combination to provide new pathways for efficient water splitting catalyst development. [ABSTRACT FROM AUTHOR]

Currently, transition metal phosphides (Cu, Fe, Co, and others) have been identified as potential candidates for both the oxygen evolution reaction (OER, anode) and hydrogen evolution reaction (HER, cathode). One of the copper based phosphides has shown efficiency for the HER, however, it displays greater theoretical potential and instability compared to noble metal materials in the OER process. Herein, Cu–MOF–NH2 nanocubes were subjected to pyrolysis treatment in a low phosphorus atmosphere to produce highly dispersed Cu3P nanoparticles. Dispersed Cu3P nanoparticles coated with nitrogen–carbon matrix composite layers provide numerous active sites and high stability. In situ Raman spectra confirmed a significant reduction in Cu+ oxidation to Cu2+. Furthermore, according to XPS resolution results, the Cu–P bond provides electrons to the Cu–P–O bond, thus accelerating the OER process. We integrated experimental electrochemistry to verify the potential enhancement of the OER performance and stability of Cu3P using appropriate nanostructure coating techniques. [ABSTRACT FROM AUTHOR]

Exploring bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which combine the features of effective electrocatalytic activity, high electrical conductivity, and superior stability, remains a significant challenge for rechargeable Zn–air batteries (ZABs). Herein, we report a material, selenium (Se)-doped CoSe2 embedded in carbon nanofibers (CNFs) (denoted as Se–CoSe2/CNFs), which was synthesized as a bifunctional electrocatalyst for ZABs via electrospinning combined with in situ growth of Zeolitic Imidazolate Framework-67 strategy, followed by carbonization and a facile selenization process. The as-synthesized Se–CoSe2/CNF electrode exhibits satisfactory electrochemical performance in an alkaline environment with a low overpotential of 325 mV at 10 mA cm−2 toward OER and a half-wave potential of 0.80 V for ORR. Remarkably, the Se–CoSe2/CNF catalyst-based ZAB shows a peak power density of 149.4 mW cm−2 and the voltage window barely changes after 180 h of cycling at 5 mA cm−2, which proves its great potential application for advanced bifunctional electrocatalysis in ZABs. [ABSTRACT FROM AUTHOR]

The utilization of cost-effective and excellent precious metal-free catalysts for the hydrogen evolution reaction (HER) working in alkaline media is of paramount importance to meet the growing demand for hydrogen energy, yet it remains a major challenge because of the slow water dissociation kinetics. Herein, a series of cation metal-doped MoSe2-based catalysts with enriched edge active sites using a straightforward one-pot hydrothermal treatment are designed, which concurrently consider the modulation of the electronic environment and effective exposure of active sites via nanostructure engineering. It was found that the NiFe atoms incorporated into MoSe2 (denoted as NiFe@MoSe2 hereafter) could remarkably alter the electronic configuration of the reactive species, enhance the conductivity, and facilitate the electron and mass transfer to accelerate the alkaline HER. Moreover, the highly nanopetal architecture assembled by plenty of NiFe@MoSe2 nanosheets could effectively inhibit undesirable active site masking and evaluate the overall mechanical robustness of the electrode. Consequently, the as-designed NiFe@MoSe2 electrode only required 146 mV to achieve 10 mA cm−2 with a Tafel slope of 79 mV dec−1 in a basic environment, which is superior to the majority of the reported MoSe2-based nanomaterials. The integration of cation metal incorporation and architecture engineering in this work highlights a general and instructive pathway to design diversified energy nanomaterials. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

The wide application of lithium-ion batteries (LIBs) for electric vehicles forebodes a future decommissioning tide of spent LIBs. Therefore, the recycling of spent LIBs has garnered significant attention, primarily due to the scarcity of resources and the detrimental effects of environmental pollution. However, traditional recycling technologies such as pyrometallurgy and hydrometallurgy methods are limited by their high energy consumption, high pollution, and complicated separation processes. Herein, we propose a novel and general approach to convert a series of spent LiNi1−x−yCoxMnyO2 (NCM) cathodes into Ni–Co–Mn hydroxide (NCM-OH) catalysts for the oxygen evolution reaction (OER) using deep eutectic solvents to extract valuable metals, followed by an in situ precipitation process using oxalic acid and a final self-templating process in an alkaline solution. The NCM-OH catalyst obtained from the spent LiNi0.33Co0.33Mn0.33O2 cathode is found to possess a nanoflake-assembled microrod structure with a large surface area (385.8 m2 g−1) and high porosity, which is endowed with abundant active sites and gas channels for the electrocatalytic reaction and mass transfer process. As a result, the NCM-OH catalyst for the oxygen evolution reaction exhibits a low overpotential of 273 mV at a current density of 10 mA cm−2 with a Tafel slope of 50.46 mV dec−1 as well as satisfactory stability. The effect of the composition on the catalytic performance is also evaluated by comparing different Ni1−x−yCoxMny hydroxide catalysts derived from commercially prevailing spent cathodes. This work provides a promising strategy for recycling spent LIBs into electrocatalyst materials for the OER. [ABSTRACT FROM AUTHOR]

A new heteroleptic Ni(II) dithiolate [Nidppe(dtsq)] (Nidtsq) (dppe = 1,2-bis-(diphenylphosphino)ethane, dtsq2− = 3,4-dioxocyclobut-1-ene-1,2-dithiolate) has been synthesised and characterized spectroscopically and by single crystal X-ray diffraction. The single crystal X-ray diffraction study reveals a square planar geometry around the Ni(II) center wherein dtsq2− and dppe ligands exhibit bidentate chelating coordination modes by their respective sulfur and phosphorus centers. The solid-state framework of Nidtsq is stabilized by C–H⋯O, C⋯H, C⋯O and π⋯π intermolecular interactions and the complex displays an interesting pair of intramolecular C–H⋯Ni anagostic interactions. The nature of these interactions has been addressed with Hirshfeld surface analysis, density functional theory, quantum theory of atoms and molecules (QTAIM) and non-covalent interaction-reduced density gradient (NCI-RDG) analyses. Furthermore, the electrocatalytic properties of Nidtsq have been assessed for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The electrocatalytic properties of Nidtsq have been found to be better than those of the previously reported Ni-mtsq complex.17 In the OER, the complex displayed an overpotential of 0.37 V with η10 of 414 mV and a Tafel slope of 237 mV dec−1 and in the HER it exhibited an overpotential of −0.35 V with η10 of −670 mV and a Tafel slope of 368 mV dec−1. Chronoamperometry and chronopotentiometry experiments for four hours in 0.1 M KOH and 0.5 M H2SO4 indicate the robustness of the complex in alkaline and acidic environments and the post-electrocatalytic stability of Nidtsq has been assessed with the aid of FESEM and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

The metal–organic framework (MOF) materials with large active sites and excellent catalytic properties have attracted widespread attention and are expected to be promising for oxygen evolution reaction (OER) for water splitting. Herein, we report a new and efficient heterogeneous nanostructure OER system constructed by a bimetallic 2D-layered porous metal–organic framework (Cu/Ni-MOF) and semiconductor nano-TiO2 particles. The bimetallic MOF can control its porous layered morphology by adjusting the ratio of surfactants. The OER performance of the hybrid system can be enhanced by introducing nano-TiO2 particles, and the performance of reducing the overpotential value is about 2.4 times higher than the pure Cu/Ni-MOF. Under illumination, the overpotential (η=10) is only 79 mV, which is much lower than the pure Cu/Ni-MOF (189 mV). At the same time, it can still maintain a low overpotential value of 168 mV after a 24 h stability test. This study also briefly tested the catalytic performance of the material in hydrogen evolution reaction (HER), and under the illumination conditions, the overpotential (η = 10) is 209 mV. Furthermore, it revealed the key role of bimetallic synergy and P–N heterojunction (via electrical and simulated photo-excited electrons) in boosting the OER performance of the system. The finding and proposed concept provide a new approach for synthesizing multi-metal MOFs and combining them with semiconductors to enhance the photoelectrochemical water splitting and open a new avenue to design high-performance MOF heterojunctions for photo-electrocatalysis. [ABSTRACT FROM AUTHOR]

Infiltration of the mesoporous structure of SBA-15 silica as a hard template with phenanthroline complexes of Fe3+ and Co2+ allowed the simultaneous dispersion of nitrogen, iron and cobalt species on the surface of the obtained carbonaceous CMK-3 silica replica, with potential as bifunctional heterogeneous catalysts for the cathodic oxygen reduction and evolution reactions (ORR and OER). The textural properties and mesopore structure depended on the composition of the material. The carbonaceous FeCoNCMK-3 (1/1), obtained with an Fe/Co molar ratio of 1/1, exhibited an ordered cylindrical mesoporous structure with a high mesopore volume, a rather homogeneous composition in terms of total and surface concentrations of iron and cobalt, and a balanced presence of pyridinic-, pyrrolic- and graphitic-N species. FeCoNCMK-3 (1/1) could improve the ORR kinetics by adsorption and reduction of O2 through the 4-electron mechanism with a current density of −17.37 mA cm−2, Eonset of 1.13 V vs. RHE and E1/2 of 0.75 V when compared to metal-free, monometallic or bimetallic electrocatalysts with a higher amount of cobalt than that of iron. In addition, FeCoNCMK-3 (1/1) exhibited activity for the OER, presenting lower values of Eonset (1.52 V), Ej10 (1.78 V) and the Tafel slope (76.3 mV dec−1) with respect to other catalysts. When evaluated as a cathode in a prototype of a Zn–air battery, FeCoNCMK-3 (1/1) exhibited a high open circuit voltage of 1.41 V, a peak power density of 66.84 mW cm−2, a large specific capacity of 818.88 mA h gZn−1, and cycling for 20 h but with deactivation upon cycling. [ABSTRACT FROM AUTHOR]

The electronic state of metallic centers plays a crucial role in electrocatalytic reactions such as oxygen evolution reaction (OER), which usually require high-valence transition metallic centers. Herein, we propose an organic ligand coordination strategy to modulate the electronic state of metallic centers in NiFe LDH, by introducing three different organic linkers including 2,6-naphthaleneducarboxylic acid, 4,4′-bipyridine, and 1H-1,2,3-triazole on the surface of NiFe LDH to derive atomic-layered metal–organic framework (NiFe LDH@MOF). Experimental results indicate that the electronic structure of metal centers in the composite was modified after the coordination of organic linker, among which the most amount of high-valence state was for Fe species in the 1H-1,2,3-triazole involved catalysts (NiFe LDH@MOF-3). Density functional theory (DFT) calculations further demonstrate that the 1H-1,2,3-triazole linkers around Fe centers optimized the d-band center together with the beneficial Gibbs free energy of the intermediate. Therefore, NiFe LDH@MOF-3 exhibited a superior electrocatalytic OER performance with a low overpotential of 242 mV to achieve a current density of 100 mA cm−2, a small Tafel slope of 32.3 mV dec−1. This work provides a general strategy for the modulation of the electronic structure of metallic centers using organic linker coordination to achieve a high-performance electrocatalyst. [ABSTRACT FROM AUTHOR]

The electrolysis of water is currently the most promising method for hydrogen production. Developing low-cost, highly active, and stable electrocatalysts is crucial for advancing large-scale industrial electrolysis of water for hydrogen production. Fe-CoMoP/NF electrocatalysts were fabricated on nickel foam (NF) by a simple cation exchange method. Benefiting from the synergistic effect of multiple metals and the ordered distribution of multi-level nanosheets, Fe-CoMoP/NF demonstrates outstanding bifunctional electrocatalytic performance for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1 M KOH solution, with overpotentials of 205 mV and 94 mV at 10 mA cm−2, respectively. Moreover, the electrolytic cell assembled with this catalyst as the cathode and anode can achieve a current density of 10 mA cm−2 with a cell voltage of only 1.55 V and can operate stably for more than 115 h. The excellent performance of Fe-CoMoP/NF is attributed to the inherent HER activity and high conductivity of phosphide, as well as the slow introduction of Fe ions, which can regulate the charge density around Co and Mo, thus maintaining the integrity of the nanostructured Fe-CoMoP/NF and exposing a larger active surface area. This work offers an effective strategy for preparing high-efficiency, low-cost integrated water splitting reaction electrodes. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) can be coupled with renewable energy power generation technology and is considered to be a highly promising hydrogen production technology. However, the acidic electrolyte environment, as well as the numerous sulfonic acid groups on the proton exchange membrane surface, can seriously corrode the oxygen evolution reaction (OER) catalyst and even cause deactivation. To develop an efficient acidic OER catalyst, the IrOx/WO3 heterostructure OER catalyst was prepared by a hydrothermal-calcination method. The coordination environment of IrOx was regulated through the electronic rearrangement effect, improving the OER activity and stability of the catalyst in acidic media. The prepared IrOx/WO3 exhibits excellent OER activity in 0.5 M H2SO4, with an overpotential of only 260 mV to achieve a current density of 10 mA cm−2 and a mass activity of 176.8 A gIr−1. It can stably operate for over 12 hours at a current density of j = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

The development of urea oxidation reaction (UOR) and oxygen evolution reaction (OER) bifunctional electrocatalysts has dual significance in promoting hydrogen energy production and urea-rich wastewater treatment. Herein, a carboxylated multi-walled carbon nanotube (MWCNT–COOH)–ferrocene carboxylic acid (Fc–COOH) modulated NiMOF hybrid material (MWCNT–NiMOF(Fc)) has been synthesized for dual electrocatalysis of the UOR and OER. The material characterization results indicated that MWCNT–COOH and Fc–COOH were integrated into the framework structure of the NiMOF. The direct interaction between the NiMOF and MWCNT/Fc facilitated electron transfer in the hybrid material and led to lattice strain, which improved the charge transfer kinetics, promoted the exposure of more unsaturated Ni sites, and increased the electrochemically active surface area. These factors together enhanced the electrocatalytic activity of MWCNT–NiMOF(Fc) towards the UOR and OER. Using a glassy carbon electrode as the substrate, MWCNT–NiMOF(Fc) exhibited low potential requirements, low Tafel slopes, and high stability. In overall urea and water splitting electrolysis cells, the excellent UOR and OER dual functional catalytic ability and enormous practical application potential of the MWCNT–NiMOF(Fc) modified foam nickel electrode were further demonstrated. On the basis of the above research, the influence of a KOH environment on urea electrolysis was further studied, and the urea electrolysis products were analyzed, promoting a more comprehensive understanding of the catalytic performance of MWCNT–NiMOF(Fc) for urea oxidation. This study provides a new approach for developing high-performance NiMOF-based electrocatalysts for challenging bifunctional UOR/OER applications, and has potential application value in hydrogen production from urea-containing wastewater electrolysis. [ABSTRACT FROM AUTHOR]

Cobalt hydroxide Co(OH)2 is considered to be a potential material for electrocatalyst, especially for oxygen evolution reaction (OER), owing to the earth's abundance, environmentally benign nature, and redox-active properties of cobalt. Herein, we report the fabrication of pristine Co(OH)2 and AgNP-integrated Co(OH)2 (Ag–Co(OH)2) by simple wet chemical methods and explore the electrocatalytic OER activity in the alkaline medium. High-resolution transmission electro-microscopic (HR-TEM) analysis revealed featureless nanostructures for Co(OH)2 with coexisting amorphous and crystalline phases, as well as the inclusion of crystalline AgNPs in Ag–Co(OH)2. X-ray photoelectron spectroscopic (XPS) analysis confirmed the inclusion of metallic AgNPs and the presence of Co at a mixed oxidation state. Electrocatalytic OER studies indicated that pristine Co(OH)2 required the overpotential of 299 mV to achieve a geometric current density of 10 mA cm−2. The integration of AgNPs in Co(OH)2 (Ag–Co(OH)2) showed a gradual improvement in the OER activity. The optimized sample, Ag–Co(OH)2-5, required the overpotential of 253 mV to produce 10 mA cm−2 current density. Tafel slope analysis revealed a lower value upon AgNP integration and electrochemical impedance showed lower charge transfer resistance. The lower Tafel value and charge transfer resistance of Ag–Co(OH)2-5 indicated good chemical coupling and faster reaction kinetics at the electrode surface. AgNPs incorporation with Co(OH)2 also showed enhanced turn-over frequency, electrochemical active surface area, and double-layer capacitance. The fabricated hybrid Ag–Co(OH)2-5 catalyst also exhibited good stability over 60 h. Thus, the electrocatalytic activity of low-cost Co(OH)2 was improved by fabricating coexisting amorphous and crystalline phases and integrating noble silver nanoparticles. [ABSTRACT FROM AUTHOR]

Layered materials with a robust structure and reversible intercalation behavior are highly sought-after in applications involving energy conversion and storage systems, energy converting devices, supercapacitors, batteries, superconductors, photonic materials, and catalysis involving hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), solar cells and sensors. In the current study, quasi-2D rhombohedral Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples, synthesized by a solution combustion route, have been demonstrated to intercalate iodine reversibly. A solid–vapor reaction was employed to intercalate iodine at moderate temperatures, and deintercalation occurred on heating at higher temperatures. Expansion of the rhombohedral c-axis by ∼10 Å occurred, and the iodine between the interlayers existed as triiodide ions (I3−) in an unsymmetrical fashion. The amount of intercalated iodide has been determined from thermogravimetric analysis. Electron microscopic analysis confirmed these systems' intercalation and subsequent lattice expansion. In the diffuse reflectance spectra, charge transfer from the triiodide ions to the host oxide was noticed, and it caused the absorption edge to fall beyond the visible region for the intercalated samples. XPS analysis of iodine intercalated Bi0.775Pr0.225O1.5 has shown the mixed valence states for Pr and the existence of I3− along with some IO3− species. The quasi-2D structure was stable during the thermal deintercalation process. The evaluation of iodine intercalated Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples as anode material in the lithium-ion battery system has given quite promising results, exhibiting fast Li+-ion diffusion, low charge transfer resistance, good reversible capacity, capacity retention (after cycling back to 10 mA g−1), and structural stability (after long cycles). [ABSTRACT FROM AUTHOR]

Developing efficient and economical catalysts is essential for water splitting. The application of MOF catalysts in water splitting is limited by poor conductivity; however, the introduction of conductive TMS could enhance their activity. Herein, novel composite Fe9S10/Fe-MOF/NF-2 was constructed by introducing dendritic Fe9S10 onto the surface of a 2D ultrathin Fe-MOF. Composite catalysts elaborately utilize the structural and chemical advantages of MOF and TMS while improving the deficiencies of monomers through the combination. Owing to the optimal structure, the hybrid catalyst Fe9S10/Fe-MOF/NF-2 displayed better catalytic performance than bare Fe-MOFs and Fe9S10, with low overpotentials of 202 and 216 mV at 10 mA cm−2 in alkaline solution and simulated seawater, respectively. This work provides an innovative approach to modify MOFs as electrocatalysts for OER. [ABSTRACT FROM AUTHOR]

The rational design of earth-abundant and efficient electrocatalysts to replace precious metal-based materials is highly anticipated for overall water splitting. Herein, NiCo2O4 electrocatalysts with different Fe doping amounts (Fex-NCO, x = 1, 2, 3) were synthesized by a low-temperature chemical method. It was interesting to find that the doping of Fe induced the formation of NiCo2O4 nanotube arrays by modulating the Fe content. The Fe3-NCO electrode with a nanotube structure and rich oxygen vacancies exhibited exceptional electrocatalytic activities for the hydrogen evolution reaction (97 mV, 10 mA cm−2) and oxygen evolution reaction (188.4 mV, 10 mA cm−2). DFT calculations revealed that Fe promoted the modulation of the electronic structure, which played a crucial role in optimizing the reaction intermediates and altered the energy level of the d band center, and as a result, enhanced the water dissociation ability. Additionally, a low cell voltage of 1.56 V (10 mA cm−2) was realized for water splitting based on an as-fabricated Fe-doped NiCo2O4 nanotube array bifunctional electrode. [ABSTRACT FROM AUTHOR]

Manganese dioxide (MnO2)-modified lead-based anodes (LBAs) are promising candidates to boost the oxygen evolution reaction (OER), but they usually suffer from structural instability and catalytic deactivation upon their irreversible digestion and the insertion of lead (Pb) in the MnO2 arrays, which consequently restrict their industrial application. Herein, we propose a novel structure tuning strategy to fully exploit the potential of MnO2 by employing a TiB2 interlayer that effectively suppresses the in situ electromigration of Pb2+ ions across the LBA interface. In situ tests with theoretical calculations indicate that the atomic substitution of Pb in [MnO6] units alters the electronic states of the host and compresses the length of the adjacent Mn–O space. This is caused by the electronic interaction between Pb and adjacent O atoms in the MnO2 lattice, finally resulting in a sluggish OER activity. By leveraging the unique pinning effect of TiB2 on LBA, we synthesized an asymmetric structure of MnO2 (ASM), which was characterized by axial elongation along the dz2 orbital of [MnO6], on the LBA/TiB2 surface. The presence of a high-spin Mn3+ cation in octahedral coordination promotes oxygen vacancy formation within ASM lattices, leading to enhanced robustness and low energy barriers for OER. Scaling up the experiments further confirmed the superior advantages of ASM in an Mn electrowinning system. This work provides valuable insights into the industrial applications of structure-controllable MnO2 materials in electrometallurgy to significantly reduce energy consumption and hazardous by-products. [ABSTRACT FROM AUTHOR]

Exploring non-noble metal dual-functional electrocatalysts with high activity and stability for water splitting is highly desirable. In this study, using zeolitic imidazolate framework-L (ZIF-L) nanoarrays as the precursor, manganese oxide-decorated porous nickel–cobalt phosphide nanosheet arrays have been prepared on nickel foam (denoted as MnOx/NiCoP/NF) through cation etching, phosphorization and electrodeposition, which are utilized as an efficient dual-functional electrocatalyst for overall water splitting. The hierarchical porous nanosheet arrays provide abundant active sites for the electrochemical process, while the MnOx modification induces strong interfacial interaction, benefiting charge transfer. Thus, the MnOx/NiCoP/NF exhibits excellent electrocatalytic activity toward the hydrogen evolution reaction (HER, overpotential of 93 mV at 10 mA cm−2), oxygen evolution reaction (OER, overpotential of 240 mV at 10 mA cm−2) and overall water splitting (cell voltage of 1.59 V at 10 mA cm−2). Furthermore, it shows superior stability during continuous overall water splitting for 200 h. This work provides a simple and effective approach for developing efficient non-noble metal dual-functional catalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

Developing advanced electrocatalysts toward the oxygen evolution reaction (OER) has always been recognized as the key challenge for green hydrogen production via water electrolysis due to the commonly required high OER overpotential. In this work, we report a branched FeCo-based hydroxide nanotube array (Fe–CoCH NT) synthesized by an ambient Fe-modification strategy, which could be used as a monolithic electrode for efficient OER catalysis. Its OER performance was even comparable to that of RuO2 with a low overpotential of 290 mV to attain a current density of 10 mA cm−2 due to its unique branched nanotube array structure and intrinsic high catalytic activity. Moreover, an acid–base hybrid electrolysis system was built based on this catalyst and an FeCo-based phosphide nanotube array electrode. By collecting electrochemical neutralization energy, this system just needs an ultralow cell voltage of 0.97 V to attain a current density of 10 mA cm−2 with a large decrease in energy consumption of 41.9% compared to traditional alkaline water splitting systems. [ABSTRACT FROM AUTHOR]