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Highlights • N doped carbon-wrapped Mo x C heterophase sheets are synthesized via in situ carbonation. • N-Mo x C@C HSs effectively combine the respective advantages of both γ-MoC and β-Mo 2 C. • Heterostructures possess a synergistically-enhanced activity on the interface and surface of γ-MoC/β-Mo 2 C. • N-Mo x C@C HSs exhibit excellent activity and stability in acid media. Abstract Advancement of non-precious-metal catalysts for hydrogen evolution reactions (HER) with both prominent activity and excellent stability has been becoming an ongoing challenge in the following decades. Herein, N-doped carbon-wrapped molybdenum carbide heterophase (γ-MoC and β-Mo 2 C) sheets (N-Mo x C@C HSs) were prepared by a facile chemical vapor reduction (CVR) procedure and following calcination at desired temperatures. The best HER electrocatalytic activity of N-Mo x C@C HSs was detailedly examined in 0.5 M H 2 SO 4 , which exhibited a small overpotential of 172 mV (10 mA cm−2) with a Tafel slope of only 60 mV dec−1 and durability. The improved HER activities and catalytic stability were due to heterocrystal Mo x C, nitrogen doping, and carbon coating. Particularly, this study effectively combined the respective advantages of both γ-MoC and β-Mo 2 C via the interface effect and matched polarity of hydrogen adsorption. [ABSTRACT FROM AUTHOR]

To achieve sustainable production of H 2 fuel through water splitting, noble-metal-free catalysts have been extensively studied for hydrogen evolution reaction (HER), especially molybdenum-based catalysts. Herein, we report the Ni, N-codoped MoC x (Ni–N–MoC x ) nanoparticles synthesized from NiMoO 4 precursor by oily-solvent-assisted strategy, following the calcination with dicyandiamide. As-obtained Ni–N–MoC x in different magnified SEM images shows grainy structure, MoC x nanoparticles uniformly disperse in carbon substrate. The obtained electrocatalysts can also efficiently electrocatalytic HER in a wide pH value. Ni–N–MoC x shows an onset potential of −74 mV, an overpotential of 163 mV to reach a current density of 10 mA/cm 2 in acid media, an onset potential of −37 mV and overpotential of 124 mV to reach 10 mA/cm 2 in alkaline media. The present study provides some guidelines for preparing the uniformly doped electrocatalysts from multiple compounds with devolatilization characteristics. [ABSTRACT FROM AUTHOR]

Ti 2 Cu, TiCu and TiCu 4 were synthesized and their electrocatalytic activities for hydrogen evolution reaction (HER) were investigated. The hydrogen overpotential observed at 10 mA/ cm2 (η 10) followed the order Ti 2 Cu (η 10 = −215 mV) > TiCu (η 10 = −182 mV) > TiCu 4 (η 10 = −170 mV). The hydrogen adsorption energy (∆G Had) on Cu site of TiCu 4 is exergonic and close to optimal position (i.e. ∆G Had = 0). A synergistic effect was proposed to account for the excellent HER performance of these Ti Cu binary intermetallics compounds that could replace PGM and achieve Midas touch in the future. [Display omitted] • High purity of Ti 2 Cu, TiCu and TiCu 4 were synthesized by using rapid arc-melting technique. • Hydrogen evolution reaction (HER) study on Ti 2 Cu, TiCu and TiCu 4 in alkaline media. • HER activity of Ti 2 Cu, TiCu and TiCu 4 were explored by using density functional theory. • Synergistic effect for these Ti Cu binary intermetallics toward HER activity was discussed. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is crucial for sustainable energy, enabling hydrogen fuel conversion, storage, and energy transfer. This review focuses on innovative approaches to replace costly precious metal catalysts with earth-abundant elements, known for their high catalytic activity and durability in alkaline hydrogen evolution reactions. Designing self-supporting electrodes, particularly using three-dimensional (3D) nickel foam (NF) substrates, has emerged as an effective strategy to enhance electrocatalyst performance and stability. The continuous porous structure of 3D NF ensures excellent electrical conductivity and a larger active surface area. This review extensively catalogs emerging nanostructured materials directly grown on 3D NF, including sulfides, phosphides, layered double hydroxides, nitrides, oxides, selenides, and alloys. Emphasis is placed on their cutting-edge achievements in structural design, controllable synthesis, performance optimization, and elucidation of catalytic mechanism. These insights facilitate the selection and fabrication of high-performance self-supporting electrodes, accelerating the commercialization and scalability of water electrolysis technology. [Display omitted] • Outlined the fundamental advancements in nickel foam-based electrocatalysts for hydrogen evolution in water splitting. • Elucidated the enhanced hydrogen evolution performance through the utilization of 3D nickel foam. • Provided future directions and insights into self-supporting 3D nickel foam-based electrocatalysts for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Transition metal phosphates have proved to be promising electrocatalysts for hydrogen evolution reactions (HER) of water splitting, however, further increasing their active sites and catalytic activity remains a major challenge. Herein, accordion-like Co-MOF with layered structure was synthesized. After subsequent carbonization and phosphidization, lamellar heterostructured Co/CoP nanocrystals encapsulated in a P, N co-doped C matrix (Co/CoP@PNC) was obtained. Heterojunction provides abundant active sites and improves electron transfer rate. Additionally, the effect of phosphating degree on the electrocatalytic activity was studied. In the alkaline electrolyte, the current density of the optimized Co/CoP@PNC-10 for HER reached 10 mA cm−2 at overpotential of 137 mV in 1.0 M KOH, which was superior to most of transition metal-based electrocatalysts. This work provides new guidance for the design and development of transition metal-based electrocatalysts. Co/CoP heterojunction embedded in P, N co-doped C matrix (Co/CoP@PNC) was prepared through further carbonization and phosphidization, the optimized Co/CoP@PNC exhibited excellent catalytic activity for alkaline HER. [Display omitted] • With accordion-like Co-MOF as the precursor, Co/CoP heterojunction embedded in P, N co-doped C matrix (Co/CoP@PNC) was prepared through further carbonization and phosphidization. • The phase and catalytic activity of the sample are related to the phosphating degree. • The optimized Co/CoP@PNC-10 exhibited the best performance among the series, with an overpotential of 137 mV at a current density of 10 mA cm−2 for alkaline HER. • P, N co-doped C substrate and Co/CoP heterojunction promote the overall HER performance through synergistic effect. [ABSTRACT FROM AUTHOR]

Abstract: Development of electrocatalysts for hydrogen evolution reaction (HER) with low overpotential and robust stability remains as one of the most serious challenges for energy conversion. Herein, a serviceable and highly active HER electrocatalyst with multilevel porous structure (Co‐Co2P nanoparticles@N, P doped carbon/reduced graphene oxides (Co‐Co2P@NPC/rGO)) is synthesized by Saccharomycete cells as template to adsorb metal ions and graphene nanosheets as separating agent to prevent aggregation, which is composed of Co‐Co2P nanoparticles with size of ≈104.7 nm embedded into carbonized Saccharomycete cells. The Saccharomycete cells provide not only carbon source to produce carbon shells, but also phosphorus source to prepare metal phosphides. In order to realize the practicability and permanent stability, the binderless and 3D electrodes composed of obtained Co‐Co2P@NPC/rGO powder are constructed, which possess a low overpotential of 61.5 mV (achieve 10 mA cm−2) and the high current density with extraordinary catalytic stability (1000 mA cm−2 for 20 h) in 0.5 m H2SO4. The preparation process is appropriate for synthesizing various metal or metal phosphide@carbon electrocatalysts. This work may provide a biological template method for rational design and fabrication of various metals or metal compounds@carbon 3D electrodes with promising applications in energy conversion and storage. [ABSTRACT FROM AUTHOR]

• This review provides an introduction to the characteristics and advantages of MOF electrocatalysts, as well as an overview of the primary mechanism involved in water electrolysis. • The application of MOF-based electrocatalysts in water splitting is reviewed. • The preparation, modification, and catalytic activity of electrocatalysts for MOF derivatives are summarized. Green hydrogen is generated by water electrolysis using renewable energy sources. For green hydrogen to become cost-effective in front of hydrogen production from fossil fuels, highly active, efficient, and durable electrocatalysts based on abundant and low-cost elements need to be developed. Great efforts have been invested in designing and engineering water-splitting electrocatalysts with optimized compositions and architecture. In this last direction, metal–organic framework (MOF) compounds have received particular attention on account of their high specific surface area (SSA) and excellent chemical stability. This work affords an overview of the latest progress in the design, engineering, and application of MOFs and their derivatives as electrocatalysts in water splitting. It further discusses the challenges encountered and the new research directions and application prospects. First, the characteristics and advantages of MOF electrocatalysts and the main mechanism of water electrolysis are introduced. Next, the research progress on the application of MOFs and their derivatives in water electrolysis is reviewed, with special emphasis on the preparation, modification, and catalytic activity of the catalysts. Finally, the present challenges and future development prospects of MOFs as water-splitting electrocatalysts are discussed. Overall, this review aims to provide new insights into the design and synthesis principles of MOF materials, promoting their practical application in water splitting, and further broadening their future uses. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting for the production of hydrogen proves to be effective and available. In general, the thermal radiation synthesis usually involves a slow heating and cooling process. Here, a high‐frequency induction heating (IH) is employed to rapidly prepare various self‐supported electrocatalysts grown on Ni foam (NF) in liquid‐ and gas‐phase within 1–3 min. The NF not only serves as an in situ heating medium, but also as a growth substrate. The as‐synthesized Ni nanoparticles anchored on MoO2 nanowires supported on NF (Ni‐MoO2/NF‐IH) enable catalysis of hydrogen evolution reaction (HER), showing a low overpotential of −39 mV (10 mA cm−2) and maintaining the stability of 12 h in alkaline condition. Moreover, the NiFe layered double hydroxide (NiFe LDH/NF‐IH) is also synthesized via IH and affords outstanding oxygen evolution reaction (OER) activity with an overpotential of 246 mV (10 mA cm−2). The Ni‐MoO2/NF‐IH and NiFe LDH/NF‐IH are assembled to construct a two‐electrode system, where a small cell voltage of ≈1.50 V enables a current density of 10 mA cm−2. More importantly, this IH method is also available to rapidly synthesize other freestanding electrocatalysts on NF, such as transition metal hydroxides and metal nitrides. [ABSTRACT FROM AUTHOR]

• Saccharomycetes are used as green phosphorus source to produce metal phosphides. • Interface phosphating for solid-solid contact can efficiently utilize phosphorus. • Graphitizing & migration of metal-catalyzed carbon matrix to form hollow structure. • The Ni/Ni 3 P heterostructure can weaken strong Ni–H bonding to obtain small Δ G H*. • Achieve hydrogen production from wastewater treatment at low input voltages. The development of new, clean and efficient catalytic materials for hydrogen evolution reaction (HER) has become extremely unstoppable. Herein, the heterostructural Ni-Ni 3 P nanoparticles embedded into N\P co-doped carbon shells on 3D graphene frameworks (Ni-Ni 3 P@NPC/rGO) was synthesized via an in situ phosphatization of nickel well-integrated with the structure engineering of carbon matrix derived from saccharomycetes. The in-situ phosphating process of nickel using P source provided by saccharomycetes is particularly simple, economical and environmentally friendly. In addition, the as-prepared Ni-Ni 3 P@NPC/rGO exhibits superior bifunctional electrocatalytic performance toward both HER (extremely low overpotential of 113 mV at 20 mA cm–2) and urea degradation reaction (UDR, only 1.38 V to attain 50 mA cm–2). Furthermore, a two-electrode electrolyzer employing the 3D block electrode (Ni-Ni 3 P@NPC/rGO/GFB) couple on both cathode and anode, can produce higher current density with lower voltage in urea-based wastewater splitting less than pure water splitting (saved 448 mV to deliver 500 mA g–1). [ABSTRACT FROM AUTHOR]

Hydrogen (H2) production is a key step in solving the energy crisis in the future. Electrocatalytic water splitting suffers from sluggish anodic oxygen evolution reaction (OER) kinetics leading to low energy conversion efficiency. Herein, a strategy is presented that integrates anodic electrochemical flocculation with cathodic hydrogen production from water splitting in 0.5 m Na2SO4. Iron encapsulated in a nitrogen‐doped carbon nanotubes array on iron foam (Fe@N‐CNT/IF) is employed as an electrode for the hydrogen evolution reaction (HER), and the Fe@N‐CNT/IF possesses superior HER activity requiring an overpotential of 525 mV to achieve 10 mA cm−2, which is close to that of 20 wt% Pt/C. Benefiting from the lower oxidation potential of iron (E°Fe/Fe2+, 0.44 V) than that of OER (E0OH‐/O2, 1.23 V), the cell voltage for integrated electrochemical flocculation and H2 production is significantly reduced by 1.31 V relative to overall water splitting to achieve 20 mA cm−2. More important, the production of electrochemical flocculation can be applied to water purification, because of the excellent adsorption capacity. Finally, metal–carbon electrocatalysts are prepared again by pyrolysis of flocculation adsorbents containing toxic heavy metals and organics. This result provides a new direction for designing a heterogeneous electrolysis system for energy conversion and environmental treatment applications. [ABSTRACT FROM AUTHOR]