A Cost-Effective 3D Hydrogen Evolution Cathode with High Catalytic Activity: FeP Nanowire Array as the Active Phase

Enhancing electrochemical water-splitting efficiency with superaerophobic nickel-coated catalysts on Chinese rice paper

The quest for efficient hydrogen production highlights the need for cost-effective and high-performance catalysts to enhance the electrochemical water-splitting process. A significant challenge in developing self-supporting catalysts lies in the high cost and complex modification of traditional substrates. In this study, we developed catalysts featuring superaerophobic microstructures engineered on microspherical nickel-coated Chinese rice paper (Ni-RP), chosen for its affordability and exceptional ductility. These catalysts, due to their microspherical morphology and textured surface, exhibited significant superaerophobic properties, substantially reducing bubble adhesion. The nickel oxy-hydroxide (NiOxHy) and phosphorus-doped nickel (PNi) catalysts on Ni-RP demonstrated effective roles in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), achieving overpotentials of 250 mV at 20 mA cm-2 and 87 mV at -10 mA cm-2 in 1 M KOH, respectively. Moreover, a custom water-splitting cell using PNi/Ni-RP and NiOxHy/Ni-RP electrodes reached an impressive average voltage of 1.55 V at 10 mA cm-2, with stable performance over 100 h in 1 M KOH. Our findings present a cost-effective, sustainable, and easily modifiable substrate that utilizes superaerophobic structures to create efficient and durable catalysts for water splitting. This work serves as a compelling example of designing high-performance self-supporting catalysts for electrocatalytic applications.

Oxygen-doped FeP on Ti Foil with Ti3O Interlayer for Efficient and Durable Electrolysis

The development of electrocatalysts with low cost, high efficiency, and long-term durability is crucial for advancing green hydrogen production. Transition metal phosphides (TMPs) have been proved to be efficient electrocatalyst, while the improvement in the performance and durability of the TMPs remains a big challenge. Employing atmospheric pressure chemical vapor deposition (APCVD) and phosphorization, FeP/Ti electrodes are fabricated featuring controllable oxygen ingredients (O-FeP/Ti). This manipulation of oxygen content fine-tunes the electronic structure of the catalyst, resulting in improved surface reaction kinetics and catalytic activity. The optimized O-FeP-400/Ti exhibits outstanding HER activity with overpotentials of 142 and 159 mV at -10 mA cm-2 in 0.5 M H2SO4 and 1 M KOH, respectively. Notably, the obtained O-FeP/Ti cathode also displays remarkable durability of up to 200 h in acidic electrolyte with surface topography remaining intact. For the first time, the low-valence titanium oxide (Ti3O) interlayer is identified in the composite electrode and ascribed for the superior connection between Ti substrate and the surface O-FeP catalyst, as supported by experimental results and density functional theory (DFT) analysis. This work has expanded the potential applications of transition metal phosphides (TMPs) as a cost-effective, highly efficient and durable catalyst for water splitting.

Recent Development of Electrodes Construction for HER in Electrocatalytic Water Splitting

Production of hydrogen (H2) fuel using the hydrogen evolution reaction (HER) through electrocatalysis of water splitting is inexpensive, has optimal performance, and offers remarkable stability. Developing electrocatalysts with excellent stability and high efficiency has been a significant and challenging factor for practical applications of HER for decades. Hydrogen generation occurs on the HER electrode due to the emission of bubbles, proton diffusion, and the transfer of electrons. These considerations should be taken into account during the construction and development of the electrode. This review offers a synopsis of recent advancements in various electrodes used as a base for electrocatalysts, such as nickel foam, titanium foil, copper foam, carbon foam, and others, and discusses their HER catalytic activity, with a focus on the emission of bubbles, diffusion of ions, the structure of the electrode, and the formulation and preparation process. In conclusion, we provide an overview of ideas to further improve and address the significant issues in the manufacture of HER electrodes.

Structural Design of Nickel Hydroxide for Efficient Urea Electrooxidation

Urea stands as a ubiquitous environmental contaminant. However, not only does urea oxidation reaction technology facilitate energy conversion, but it also significantly contributes to treating wastewater rich in urea. Furthermore, urea electrolysis has a significantly lower theoretical potential (0.37 V) compared to water electrolysis (1.23 V). As an electrochemical reaction, the catalytic efficacy of urea oxidation is largely contingent upon the catalyst employed. Among the plethora of urea oxidation electrocatalysts, nickel-based compounds emerge as the preeminent transition metal due to their cost-effectiveness and heightened activity in urea oxidation. Ni(OH)2 is endowed with manifold advantages, including structural versatility, facile synthesis, and stability in alkaline environments. This review delineates the recent advancements in Ni(OH)2 catalysts for electrocatalytic urea oxidation reaction, encapsulating pivotal research findings in morphology, dopant incorporation, defect engineering, and heterogeneous architectures. Additionally, we have proposed personal insights into the challenges encountered in the research on nickel hydroxide for urea oxidation, aiming to promote efficient urea conversion and facilitate its practical applications.

Transition Metal Phosphides: The Rising Star of Lithium-Sulfur Battery Cathode Host

Lithium-sulfur batteries (LSBs) with ultra-high energy density (2600 W h kg-1 ) and readily available raw materials are emerging as a potential alternative device with low cost for lithium-ion batteries. However, the insulation of sulfur and the unavoidable shuttle effect leads to slow reaction kinetics of LSBs, which in turn cause various roadblocks including poor rate capability, inferior cycling stability, and low coulombic efficiency. The most effective way to solve the issues mentioned above is to rationally design and control the synthesis of the cathode host for LSBs. Transition metal phosphides (TMPs) with good electrical conductivity and dual adsorption-conversion capabilities for polysulfide (PS) are regarded as promising cathode hosts for new-generation LSBs. In this review, the main obstacles to commercializing the LSBs and the development processes of their cathode host are first elaborated. Then, the sulfur fixation principles, and synthesis methods of the TMPs are briefly summarized and the recent progress of TMPs in LSBs is reviewed in detail. Finally, a perspective on the future research directions of LSBs is provided.

Electronic Structure Modulation of Nickel Sites by Cationic Heterostructures to Optimize Ethanol Electrooxidation Activity in Alkaline Solution

It is a good idea for efficient production of hydrogen to use ethanol oxidation reaction (EOR) in place of oxygen evolution reaction (OER) in water electrolysis process. Ni-based non-precious electrocatalysts are widely used in the conversion of ethanol to acetic acid. Here, different selenide heterostructures (NiCoSe, NiFeSe, and NiCuSe) are prepared in which Ni sites are regulated by transition metal. The valence state of Ni is NiCuSe < NiCoSe < NiFeSe in the three heterojunctions. NiCoSe shows the optimized charge distribution of Ni sites and outstanding catalytic activity. The effective modulations lead to optimized d-band center and facilitates both adsorption and desorption of reaction intermediates, which improves the kinetics of EOR. The results of this work prove that with appropriate designed catalyst it is possible to replace kinetically slow OER with faster EOR in water electrolysis to produce hydrogen.

Recent advances in understanding and design of efficient hydrogen evolution electrocatalysts for water splitting: A comprehensive review

An unsustainable reliance on fossil fuels is the primary cause of the vast majority of greenhouse gas emissions, which in turn lead to climate change. Green hydrogen (H₂), which may be generated by electrolyzing water with renewable power sources, is a possible substitute for fossil fuels. On the other hand, the increasing intricacy of hydrogen evolution electrocatalysts that are presently being explored makes it more challenging to integrate catalytic theories, catalytic fabrication procedures, and characterization techniques. This review will initially present the thermodynamics, kinetics, and associated electrical and structural characteristics for HER electrocatalysts before highlighting design approaches for the electrocatalysts. Secondly, an in-depth discussion regarding the rational design, synthesis, mechanistic insight, and performance improvement of electrocatalysts is centered on both the intrinsic and extrinsic influences. Thirdly, the most recent technological advances in electrocatalytic water-splitting approaches are described. Finally, the difficulties and possibilities associated with generating extremely effective HER electrocatalysts for water-splitting applications are discussed.

Revealing the Essential Role of Iron Phosphide and its Surface-Evolved Species in the Photoelectrochemical Water Oxidation by Gd-Doped Hematite Photoanode

Phosphates are easily derived from transition metal phosphides under natural conditions, and the real roles of these two in catalytic reactions are not yet clear. Here, a multiphase FeP/Gd-Fe₂ O₃ shell-core structure photoanode was constructed and explored regarding the real role of FeP and its surface-reconstructed iron phosphate (Fe-Pi) in photoelectrochemical water oxidation. The FeP/Gd-Fe₂ O₃ photoanode exhibited an excellent photocurrent density of 2.56 mA cm^-2 at 1.23 V versus the reversible hydrogen electrode, up to 4 times greater than those of the pristine α-Fe₂ O₃ (0.64 mA cm^-2 ). Detailed studies showed that FeP could act as a photosensitizer to enhance light absorption and as a conductive layer to accelerate charge transfer. The FeP significantly enhanced the incident photon-to-current conversion efficiency of the photoanode and improved the electron transition within the photoanode. Naturally evolved Fe-Pi on the surface provided more active sites for water oxidation. They effectively passivated the surface capture state and synergistically inhibited the electron-hole recombination. Moreover, the in-situ constructed multiphase catalyst had a smaller interfacial contact resistance than the intentionally decorative cocatalyst. This work provides new insight into the understanding of the essential role of transition metal phosphides and their surface-reconstructed species in catalytic reactions.

Low-Pressure Plasma-Processed Ruthenium/Nickel Foam Electrocatalysts for Hydrogen Evolution Reaction

In this paper, low-pressure 95%Ar-5%H2, pure Ar, and 95%Ar-5%O2 plasmas were used for post-treatment of ruthenium (Ru) deposited on nickel foam (NF) (Ru/NF). Ru/NF was then tested as a catalyst for a hydrogen evolution reaction. Significant improvement in electrocatalytic activity with the lowest overpotential and Tafel slope was observed in an alkaline electrolyte (1 M KOH) with 95%Ar-5%O2 plasma processing on Ru/NF. Linear scanning electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) also indicate the lowest interfacial impedance and largest electrical double layer capacitance. Experimental results with 0.1 M phosphate buffered saline (PBS) and 0.5 M H2SO4 electrolytes were also demonstrated and compared.

Metal-Organic Frameworks-Derived Self-Supported Carbon-Based Composites for Electrocatalytic Water Splitting

Electrocatalytic water splitting has been considered as a promising strategy for the sustainable evolution of hydrogen energy and storage of intermittent electric energy. Efficient catalysts for electrocatalytic water splitting are urgently demanded to decrease the overpotentials and promote the sluggish reaction kinetics. Carbon-based composites, including heteroatom-doped carbon materials, metals/alloys@carbon composites, metal compounds@carbon composites, and atomically dispersed metal sites@carbon composites have been widely used as the catalysts due to their fascinating properties. However, these electrocatalysts are almost powdery form, and should be cast on the current collector by using the polymeric binder, which would result in the unsatisfied electrocatalytic performance. In comparison, a self-supported electrode architecture is highly attractive. Recently, self-supported metal-organic frameworks (MOFs) constructed by coordination of metal centers and organic ligands have been considered as suitable templates/precursors to construct free-standing carbon-based composites grown on conductive substrate. MOFs-derived carbon-based composites have various merits, such as the well-aligned array architecture and evenly distributed active sites, and easy functionalization with other species, which make them suitable alternatives to non-noble metal-included electrocatalysts. In this review, we intend to show the research progresses by employment of MOFs as precursors to prepare self-supported carbon-based composites. Focusing on these MOFs-derived carbon-based nanomaterials, the latest advances in their controllable synthesis, composition regulation, electrocatalytic performances in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting (OWS) are presented. Finally, the challenges and perspectives are showed for the further developments of MOFs-derived self-supported carbon-based nanomaterials in electrocatalytic reactions.

Multifunctional Metal Phosphides as Superior Host Materials for Advanced Lithium-Sulfur Batteries

For the past few years, a new generation of energy storage systems with large theoretical specific capacity has been urgently needed because of the rapid development of society. Lithium-sulfur (Li-S) batteries are regarded as one of the most promising candidates for novel battery systems, since their resurgence at the end of the 20th century Li-S batteries have attracted ever more attention, attributed to their notably high theoretical energy density of 2600 W h kg^-1 , which is almost five times larger than that of commercial lithium-ion batteries (LIBs). One of the determining factors in Li-S batteries is how to design/prepare the sulfur cathode. For the sulfur host, the major technical challenge is avoiding the shuttling effect that is caused by soluble polysulfides during the reaction. In past decades, though the sulfur cathode has developed greatly, there are still some enormous challenges to be conquered, such as low utilization of S, rapid decay of capacity, and poor cycle life. This article spotlights the recent progress and foremost findings in improving the performance of Li-S batteries by employing multifunctional metal phosphides as host materials. The current state of development of the sulfur electrode of Li-S batteries is summarized by emphasizing the relationship between the essential properties of metal phosphide-based hybrid nanomaterials, the chemical reaction with lithium polysulfides and the latter's influence on electrochemical performance. Finally, trends in the development and practical application of Li-S batteries are also pointed out.

CdS Nanorods Anchored with Crystalline FeP Nanoparticles for Efficient Photocatalytic Formic Acid Dehydrogenation

Photocatalytic dehydrogenation of formic acid is a promising strategy for H₂ generation. In this work, we report the use of crystalline iron phosphide (FeP) nanoparticles as an efficient and robust cocatalyst on CdS nanorods (FeP@CdS) for highly efficient photocatalytic formic acid dehydrogenation. The optimal H₂ evolution rate can reach ∼556 μmol·h^-1 at pH 3.5, which is more than 37 times higher than that of bare CdS. Moreover, the photocatalyst demonstrates excellent stability; no significant decrease of the catalytic activity was observed during continuous testing for more than four days. The apparent quantum yield is ∼54% at 420 nm, which is among the highest values obtained using noble-metal-free photocatalysts for formic acid dehydrogenation. This work provides a novel strategy for designing highly efficient and economically viable photocatalysts for formic acid dehydrogenation.

Bifunctional and Self-Supported NiFeP-Layer-Coated NiP Rods for Electrochemical Water Splitting in Alkaline Solution

Designing efficient and robust nonprecious metal-based electrocatalysts for overall water electrolysis, which is mainly limited by the oxygen evolution reaction (OER), for hydrogen production remains a major challenge for the hydrogen economy. In this work, a bimetallic NiFeP catalyst is coated on nickel phosphide rods grown on nickel foam (NiFeP@NiP@NF). This self-supported and interfacially connected electrode structure is favorable for mass transfer and reducing electrical resistance during electrocatalysis. The preparation of NiFeP@NiP@NF is optimized in terms of (i) the coprecipitation time of the NiFe Prussian blue analogue layer that serves as phosphides precursor and (ii) the phosphidation temperature. The optimized sample exhibits excellent OER performance delivering current densities of 10 and 100 mA cm^-2 at low overpotentials of 227 and 252 mV in 1.0 M KOH, respectively, and maintaining 10 mA cm^-2 for more than 120 h without obvious degradation. Moreover, it can also be operated as a hydrogen evolution electrocatalyst, requiring an overpotential of 105 mV at 10 mA cm^-2 in the same medium. Thus, the as-prepared material was tentatively utilized as a bifunctional electrocatalyst in a symmetric electrolyzer, requiring a voltage bias of 1.57 V to afford 10 mA cm^-2 in 1.0 M KOH, while exhibiting outstanding stability.

Transition Metal Phosphide-Based Materials for Efficient Electrochemical Hydrogen Evolution: A Critical Review

As hydrogen has been increasingly considered as promising sustainable energy supply, electrochemical overall water splitting driven by highly efficient non-noble metal electrocatalysts has aroused extensive attention. Transition metal phosphides (TMPs) have demonstrated remarkable electrocatalytic performance, including high activity and robust durability towards hydrogen evolution reaction (HER) in acidic and alkaline as well as neutral electrolytes. In this Review, up-to-date progress of TMP-based HER electrocatalysts is summarized. Various synthesis strategies of TMPs based on selected phosphorus sources are presented, and the reaction mechanisms of HER as well as the contribution of phosphorus in the TMPs to HER activity are briefly discussed. The multiscale approaches for promoting the activity and stability of TMP-based catalysts are discussed with respect to intrinsic electronic structure, hybrids, microstructure, and working electrode interface. Some crucial issues and future perspectives of TMPs are pointed out. These modulated approaches and challenges are also instructive for constructing other high-activity energy-related electrocatalysts.

Preparation of Hierarchical Cube-on-plate Metal Phosphides as Bifunctional Electrocatalysts for Overall Water Splitting

To rationally design efficient and cost-effective electrocatalysts, a simple but efficient strategy has been developed to directly anchor prussian blue analogue (PBA) nanocubes on cobalt hydroxide nanoplates (PBA@Co(OH)₂ ) via the in-situ interfacial precipitation process. Subsequently, the thermal treatment in the presence of sodium hydrogen phosphite enabled the successful transition into metal phosphides with the hierarchical cube-on-plate structure. When used as electrocatalytsts, the obtained bimetal phosphides exhibited good bifunctional electrocatalytic activities for hydrogen and oxygen evolution reactions with good long-term stability. Thus, an enhanced performance for overall water splitting can be achieved, which could be ascribed to the hierarchical structure and favorable composition of as-prepared bimetal phosphide for rapid electron and mass transfer. The present study demonstrates a favorable approach to modulate the composition and structure of metal phosphide for enhancing the electrocatalytic ability toward water splitting.

Synthesis of Metal Phosphide Nanoparticles Supported on Porous N-Doped Carbon Derived from Spirulina for Universal-pH Hydrogen Evolution

Transition metal phosphides (TMPs) are regarded as highly active electrocatalysts for the hydrogen evolution reaction (HER). However, traditional synthetic routes usually use expensive and dangerous precursors as P donors. The development of a low-cost and ecofriendly method for the synthesis of TMPs is significant for sustainable energy development. Herein, cobalt phosphides anchored on or embedded in a spirulina-derived porous N-doped carbon matrix (Co₂ P/NC) was fabricated by two-step hydrothermal treatment and carbonization method, which utilized the intrinsic C, N, and P of biomass cleverly as the sources of C, N, and P, respectively. As a result of the high surface area and porosity that enhance the mass-transfer dynamics, Co₂ P/NC shows good electrocatalytic activity at all pH values in the HER. This work not only provides a facile and effective method for the fabrication of TMP nanoparticles loaded onto carbon materials but also opens a new strategy for the utilization of the intrinsic ingredients of biomass for the preparation of other functional electrocatalysts.

Unusual electrochemical N2 reduction activity in an earth-abundant iron catalyst via phosphorous modulation

FeP₂ nanoparticles-reduced graphene oxide hybrid acts as an efficient electrocatalyst for conversion of N₂ to NH₃ in 0.5 M LiClO₄, achieving a large NH₃ yield of 35.26 μg h⁻¹ mg_cat.⁻¹ and a high faradaic efficiency of 21.99%.

Tuning Electron Density Endows Fe1-xCoxP with Exceptional Capability of Electrooxidation of Organic Pollutants

The good performance of base metal catalysts for the electrooxidation of organic pollutants has attracted great attention. However, base metal phosphides for electrooxidation are seldom studied owing to the sluggish water adsorption and dissociation dynamics, which will hinder the production of the sorbed hydroxyl radicals (M(^•OH)) and thus inhibit the electrooxidation of organic pollutants. Herein, we proposed a universal strategy to improve the electrooxidation capability of metal phosphides by modulating the surface electron densities. The electron interactions between cobalt (Co) and phosphorus (P) are modulated after iron doping, resulting in more positively charged Co and more negatively charged P, which can promote the adsorption and activation of water molecules and produce large quantities of M(^•OH). Meanwhile, the experimental results show that the iron-modulated Fe_0.53Co_0.47P nanosheet arrays exhibit higher removal efficiency of tetracycline than the boron-doped diamond and Pt anode at low current intensity. Based on experimental results and density functional theory + U calculations (DFT + U), it is found that Fe_0.53Co_0.47P has lower barrier (0.45 eV) to form the sorbed hydroxyl radicals (M(^•OH)) and higher overpotential to produce O₂ than its counterparts, suggesting that Fe_0.53Co_0.47P can produce more M(^•OH) instead of O₂. The above results highlighted the feasibility of these base metal phosphides for electrooxidation for advanced water purification.

Nanobundles of Iron Phosphide Fabricated by Direct Phosphorization of Metal-Organic Frameworks as an Efficient Hydrogen-Evolving Electrocatalyst

Transition-metal-based phosphides (TMPs) have been considered as attractive electrocatalysts for water splitting due to their earth-abundance and remarkable catalytic activity. As a representative type of precursors, metal-organic frameworks (MOFs) provide ideal plateaus for the design of nanostructured TMPs. In this work, the hierarchically structured iron phosphide nanobundles (FeP-500) were fabricated by one-step phosphorization of an iron-based MOF (MET(Fe)) precursor. The derived FeP-500 nanobundles were constructed by quasi-paralleled one-dimensional nanorods with uneven surface, which provided channels for electrolyte penetration, mass transport, and effective exposure of active sites during the water-splitting process. With the addition of conductive Super P, the obtained FeP-500-S exhibited a good electrocatalytic performance towards the hydrogen evolution reaction in alkaline electrolyte (1 mol L^-1 KOH). Furthermore, to investigate the influence of secondary metal doping, a series of isoreticular MOF precursors and bimetallic TMPs were fabricated. The results indicated that the catalytic performance is structure dominated.

Preparation of Yolk-Shell-Structured Cox Fe1-x P with Enhanced OER Performance

The design and development of low-cost, highly efficient, and stable electrocatalysts to take the place of noble-metal catalysts for the oxygen evolution reaction (OER) remain a significant challenge. Herein, the synthesis of yolk-shell-structured binary transition metal phosphide Co_x Fe_1-x P with different Co/Fe ratios by phosphidation of a cobalt ferrite precursor is reported. The as-synthesized Co_x Fe_1-x P catalysts were used for the OER. All yolk-shell Co_x Fe_1-x P catalysts with different Co/Fe ratios showed much better performance than the corresponding solid catalyst. The formation of Co oxides on the catalyst surface during OER and the optimal Co/Fe ratio were found to be critical to their activity. Among the as-prepared Co_x Fe_1-x P catalysts, that with a Co/Fe ratio of 0.47/0.53 (Co_0.47 Fe_0.53 P) exhibited the best performance. Co_0.47 Fe_0.53 P has an overpotential of 277 mV at a current density of 10 mA cm^-2 , a Tafel slope of 37 mV dec^-1 , and superior stability in alkaline medium. The outstanding performance is partly ascribed to the transfer of valence electrons from Co to P and Fe. The Co_0.47 Fe_0.53 P matrix with excellent conductivity and Fe phosphate that is stable on the surface of the catalyst are also helpful for the OER performance. In addition, the yolk-shell structure of Co_0.47 Fe_0.53 P increases the contact area between electrolyte and catalyst. These characteristics of Co_0.47 Fe_0.53 P greatly improve its OER performance. This optimized binary transition metal phosphide provides a new approach for the design of nonprecious-metal electrocatalysts.

New Insight on Hydrogen Evolution Reaction Activity of MoP2 from Theoretical Perspective

We systematically investigated the hydrogen evolution reaction (HER) of six facets of MoP2 based on the periodic density functional theory (DFT). The calculated values of Gibbs free energy of hydrogen adsorption (ΔGH) indicated that the (111) facet has a good HER activity for a large range of hydrogen coverages. The zigzagged patterns before 75% hydrogen coverage suggest a facilitation among Mo1, P1 and Mo2 sites, which are attributed to repeat occupancy sites of H atoms. From ab initial atomistic thermodynamics analysis of hydrogen coverage, we gained that the most stable coverage of hydrogen is 18.75% at 1 atm H2 and 298 K. Finally, the doping effects on HER activity were investigated and found that catalytic performance can be improved by substituting P with an S or N atom, as well as substituting the Mo atom with an Fe atom, respectively. We hope this work can provide new insights on further understanding of HER for MoP2 and give instructions for the experimental design and synthesis of transition metal phosphides (TMPs)-based high-performance catalysts.

Porous Mn-Doped FeP/Co3 (PO4 )2 Nanosheets as Efficient Electrocatalysts for Overall Water Splitting in a Wide pH Range

Development of highly active and stable electrocatalysts for overall water splitting is important for future renewable energy systems. In this study, porous Mn-doped FeP/Co₃ (PO₄ )₂ (PMFCP) nanosheets on carbon cloth are utilized as a highly efficient 3 D self-supported binder-free integrated electrode for the oxygen evolution and hydrogen evolution reactions (OER and HER) over a wide pH range. Specifically, overpotentials of 27, 117, 85 mV are required for the PMFCP nanosheets to attain 10 mA cm^-2 for HER in 0.5 m H₂ SO₄ , 1.0 m phosphatebuffered saline (PBS), and 1.0 m KOH, respectively. In addition to the excellent performance for HER electrocatalysis, PMFCP nanosheets were also efficient electrocatalysts for the OER. Thus, the PMFCP nanosheets can serve as anodes and cathodes for overall water splitting (OWS). The OWS working voltages to attain 10 mA cm^-2 are found to be 1.75, 1.82, and 1.61 V in acid, neutral, and alkaline electrolytes, respectively. Chronopotentiometric tests show that the PMFCP electrode can maintain its excellent pH-universal OWS activity for more than 30 000 s. This work also provides new insights into developing high-performance electrocatalysts for water splitting over a wide pH range. The improvement in electrochemical performance by introduction of Mn dopant and nano-holes offers new opportunities in the development of effective electrodes for other energy-related applications.

CoP-Doped MOF-Based Electrocatalyst for pH-Universal Hydrogen Evolution Reaction

Although electrocatalysts based on transition metal phosphides (TMPs) with cationic/anionic doping have been widely studied for hydrogen evolution reaction (HER), the origin of performance enhancement still remains elusive mainly due to the random dispersion of dopants. Herein, we report a controllable partial phosphorization strategy to generate CoP species within the Co-based metal-organic framework (Co-MOF). Density functional theory calculations and experimental results reveal that the electron transfer from CoP to Co-MOF through N-P/N-Co bonds could lead to the optimized adsorption energy of H₂ O (ΔG H 2 O * ) and hydrogen (ΔG_H* ), which, together with the unique porous structure of Co-MOF, contributes to the remarkable HER performance with an overpotential of 49 mV at a current density of 10 mA cm^-2 in 1 m phosphate buffer solution (PBS, pH 7.0). The excellent catalytic performance exceeds almost all the documented TMP-based and non-noble-metal-based electrocatalysts. In addition, the CoP/Co-MOF hybrid also displays Pt-like performance in 0.5 m H₂ SO₄ and 1 m KOH, with the overpotentials of 27 and 34 mV, respectively, at a current density of 10 mA cm^-2 .

Boosting Alkaline Hydrogen Evolution Activity with Ni-Doped MoS2 /Reduced Graphene Oxide Hybrid Aerogel

Highly active, durable, and cost-effective non-precious-metal-based electrocatalysts are urgently needed to improve the sluggish hydrogen evolution reaction (HER) in an alkaline environment. Herein, a lyophilization/thermolysis method is successfully applied to prepare Ni-doped MoS₂ (Ni-MoS₂ )/reduced graphene oxide (RGO) hybrid aerogels. The MoS₂ aerogel possesses a higher density of exposed active sites than its corresponding bulk material. Inheriting from GO its abundant functional groups during pyrolysis, the RGO aerogel can uniformly disperse MoS₂ and simultaneously maintain excellent conductivity. The incorporation of Ni atoms can accelerate the cleavage of the HO-H bond and enhance the adsorption and desorption of intermediate OH^- . Owing to the synergistic effect of the compositional and structural advantages of aerogels, the Ni-MoS₂ /RGO hybrid aerogel delivers highly promoted HER kinetics in alkaline media. As a result, an optimal η₁₀ (overpotential at 10 mA cm^-2 ) of 168 mV in 1 m KOH is obtained, which is superior to the non-doped MoS₂ /RGO hybrid aerogel (225 mV) and MoS₂ aerogel (263 mV), letting alone bulk MoS₂ (448 mV). Moreover, the η₆₀ (overpotential at 60 mA cm^-2 ) is maintained at 262 mV after chronopotentiometry tests at a constant current density of 10 mA cm^-2 for 24 h, indicating an exceptionally stability of the HER catalyst.

Low-cost high-performance hydrogen evolution electrocatalysts based on Pt-CoP polyhedra with low Pt loading in both alkaline and neutral media

Low-cost Pt-CoP hollow polyhedra exhibited prominent performance for the HER in both basic and neutral solutions.

Boosting electrocatalytic N2 reduction to NH3 on β-FeOOH by fluorine doping

A β-FeO(OH,F) nanorod acts as an efficient electrocatalyst for the conversion of N₂ to NH₃ in 0.5 M LiClO₄, achieving a remarkably large NH₃ yield of 42.38 μg h⁻¹ mg_cat.⁻¹ and a high FE of 9.02%.

Metal-organic layer derived metal hydroxide nanosheets for highly efficient oxygen evolution

A series of metal hydroxide nanosheets have been fabricated from metal-organic layers (MOLs) through a conformal conversion process. Significantly, the MOL-derived Fe(OH)3 with an ultrathin layer structure exhibited enhanced alkaline oxygen evolution with a low overpotential of 271 mV at a current density of 10 mA cm-2.