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[Display omitted] Transition metal oxides have been acknowledged for their exceptional water splitting capabilities in alkaline electrolytes, however, their catalytic activity is limited by low conductivity. The introduction of sulfur (S) into nickel molybdate (NiMoO 4) at room temperature leads to the formation of sulfur-doped NiMoO 4 (S-NiMoO 4), thereby significantly enhancing the conductivity and facilitating electron transfer in NiMoO 4. Furthermore, the introduction of S effectively modulates the electron density state of NiMoO 4 and facilitates the formation of highly active catalytic sites characterized by a significantly reduced hydrogen absorption Gibbs free energy (ΔG H*) value of −0.09 eV. The electrocatalyst S-NiMoO 4 exhibits remarkable catalytic performance in promoting the hydrogen evolution reaction (HER), displaying a significantly reduced overpotential of 84 mV at a current density of 10 mA cm−2 and maintaining excellent durability at 68 mA cm−2 for 10 h (h). Furthermore, by utilizing the anodic sulfide oxidation reaction (SOR) instead of the sluggish oxygen evolution reaction (OER), the assembled electrolyzer employing S-NiMoO 4 as both the cathode and anode need merely 0.8 V to achieve 105 mA cm−2, while simultaneously producing hydrogen gas (H 2) and S monomer. This work paves the way for improving electron transfer and activating active sites of metal oxides, thereby enhancing their HER activity. [ABSTRACT FROM AUTHOR]

Mo-doping is introduced to synchronously improve the electro catalytic activity and anti-chlorine corrosion of Ni 3 s 2 toward the efficient overall seawater splitting, thanks to the enhanced binding with *OH but the weakened one with *CL. [Display omitted] Designing highly active electrocatalysts that can resist chloride ion (Cl-) corrosion during seawater electrolysis is still a challenge. Here, Mo-doping is introduced to synchronously improve the electrocatalytic activity and anti-chlorine corrosion of Ni 3 S 2 toward the efficient overall seawater splitting. With commercial nickel-molybdenum foam (NMF) as the reactive substrates, Mo-doped Ni 3 S 2 columnar arrays (Mo-Ni 3 S 2 /NMF) are fabricated via a one-step hydrothermal process, which expose abundant active sites with the ameliorated surface electronic configurations toward the enhanced binding with *OH (* denotes an active site) but the weakened one with *Cl. As expected, they afford the excellent bi-functionality for both oxygen and hydrogen evolution reactions (OER and HER), with the remarkably improved anti-corrosion to Cl- at anode as compared to pristine Ni 3 S 2. In alkaline mimic seawater (1.0 M NaOH + 0.5 M NaCl), Mo-Ni 3 S 2 /NMF requires 330 mV (for OER) and 209 mV (for HER) overpotentials at the current density of ±100 mA cm−2, and a low cell voltage of 1.52 V at 10 mA cm−2 for overall seawater splitting. This work highlights a feasible strategy to explore highly active and stable electrocatalysts for sustainable H 2 production. [ABSTRACT FROM AUTHOR]

• Electrocatalytic reduction of nitrogen-containing pollutants to ammonia are reviewed. • Strategy to improve NO solubility and product separation of NH 3 are proposed. • Strategies to achieve high performance of NO 3 − reduction to NH 3 are presented. • Strategies to enhance the performance of NO 2 − reduction to NH 3 are displayed. Nitrogenous pollutants have caused serious environmental pollution, which endangers human life and ecological environment. The electrochemical nitrogenous pollutants reduction to ammonia driven by clean electric energy has been considered as an ideal technology for the recovery and utilization of nitrogenous pollutants. Unfortunately, the electrochemical reduction of nitrogenous pollutants has long been limited by low solubility, slow mass transfer, low partial current density, and competitive hydrogen production. Recently, technologies such as gas diffusion electrodes, enrichment of reactant on catalysts surface and tandem catalytic sites have been applied to solve these problems and surprising progress has been made. In order to reduce the driving voltage of the actual two electrode electrolytic cell, some small molecules (hydrogen sulfide and glycerol) are used as backup oxidation reaction to replace slow kinetic oxygen evolution reaction, with nitrogenous pollutants reduction reactions as cathode reaction. In addition, efficient nitrogenous pollutants catalysts are also used to construct clean batteries for simultaneous nitrogenous pollutant recovery, ammonia synthesis, and electrical energy output. It is worth noting that nitrogenous pollutant reaction can also be combined with carbon dioxide reduction reaction to achieve the synthesis of carbon nitrogen compounds, which further expands the application scope of nitrogenous pollutant reaction. The research progress in the field of nitrogenous pollutants reduction is highlighted in this review. Finally, challenges facing and possible development direction in the future are presented. This review will hopefully provide suggestions for the industrial application of the electrochemical reduction of nitrogenous pollutants. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The uniform hierarchical microspheres MoNi synthesized from reducing NiMoO 4. • The MoNi HM exhibited a superior HER activity with a onset potential of −7 mV. • The MoNi HM was used as cocatalyst for photocatalytic HER with rate of 151.7 μmol mg−1 h−1. • This study revealed a process for building highly efficient electrocatalyst and cocatalyst. Abstract In industrial water electrolysis cell, the electrocatalyst has a sluggish water dissociation kinetics leading to low electrocatalytic activity for the generation of H 2 from water splitting. This work reports a hierarchical microsphere constructed by MoNi porous nanosheets derived from NiMoO 4 microsphere, as a rapid Tafel-step-decided electrocatalyst towards hydrogen evolution reaction (HER). Consequently, the synthesized MoNi hierarchical microsphere (MoNi HM) electrocatalyst exhibits an onset potential of as small as −7 mV vs. RHE, an operating potential of 72 mV for 10 mA cm−2, and a low Tafel slope of 36.6 mV per decade in 1.0 M KOH. Furthermore, MoNi HM as cocatalyst and CdS nanowires as photocatalyst are physically mixed (MoNi HM/CdS NWs) and presentes a champion photocatalytic performance for H 2 production with a prominent H 2 generation rate of as high as 151.7 μmol mg-1 h−1 at λ > 420 nm light illumination. The large contact area between MoNi nanosheets and CdS nanowires endows the fast separation of photogenerated charge carriers to significantly facilitate the photocatalytic H 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1. Spin-polarized Ni-Fe-Mo alloys were prepared by a magnetic field-assisted method. • 2. Ni-Fe-Mo alloys with enduring spin polarization can realize higher OER activity. • 3. Providing a promising strategy to prepare efficient ferromagnetic alloy catalysts. The oxygen evolution reaction (OER) constrains the efficiency of water splitting. The catalytic activity of electrocatalysts is mostly determined by the electronic structure, which is expressed as the electron transfer property and the reactant adsorption–desorption capacity. Ferromagnetic electrocatalysts exhibit promising applications in OER. However, an external magnetic field is indispensable for the electron spin polarization of ferromagnetic materials. Here, Ni-Fe-Mo ternary alloy nanowire electrocatalysts were prepared via a magnetic field-assisted self-assembly method in an aqueous-solution system at a mild temperature (65 °C). These Ni-Fe-Mo ternary alloy electrodes feature a spin polarization-dependent OER catalytic performance, which is attributed to ferromagnetic regulation. Ni 0.8 Fe 0.15 Mo 0.05 possesses the maximum ferromagnetism compared to other electrodes (Ni 0.8 Mo 0.2 and Ni 0.8 Fe 0.2) and improved substantially OER activity. The regulated OER activity is assigned to the favorable adsorption of oxygen-containing intermediates (OH*) due to Ni-Fe-Mo composition-dependent, and the accelerated kinetics of OER with enduring spin polarization. The Ni-Fe-Mo ternary alloy nanowires with higher magnetic properties contribute to in situ spin polarization at the surface. This magnetic field-assisted synthesis approach provides a new strategy to realize electrodes with enduring spin polarized. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-MOF is used to uptake SeO 3 2−, and the capacity reaches to 280.0 mg g−1. • R-CoSeO 4 is recycled as an OER electrocatalyst in wastewater treatment process. • Co-Co 0.85 Se, an efficient HER electrocatalyst, is obtained by calcining of R-CoSeO 4. • R-CoSeO 4 /CC and Co-Co 0.85 Se/CC are constructed a cell for water electrolysis. A nanosheet-like cobalt-based metal-organic-framework (Co-MOF) is employed to uptake SeO 3 2− anions, and the remove capacity of Co-MOF reaches a record of 280.0 mg g−1. After uptake SeO 3 2− by Co-MOF, the recycling defect-rich CoSeO 4 (R-CoSeO 4) is used as an electrocatalyst for oxygen evolution reaction (OER), which displays an overpotential of 265 mV at 10 mA cm−2 in 1 M KOH. Furthermore, cobalt-cobalt selenide heterojunction nanoparticle (Co-Co 0.85 Se), a high-performance hydrogen evolution reaction (HER) electrocatalyst (overpotential of 97 mV at 10 mA cm−2 in 1 M KOH) is obtained by one-step calcining of R-CoSeO 4. Series experiments and density functional theory calculations confirm the anion vacancy in R-CoSeO 4 and heterojunction in Co-Co 0.85 Se can improve the OER and HER activity, respectively. Finally, two binder-free electrodes (R-CoSeO 4 /CC and Co-Co 0.85 Se/CC) are employed as anode and cathode, respectively, to construct a water electrolysis cell, which only needs 1.47 V to achieve 10 mA cm−2 in 1 M KOH. [ABSTRACT FROM AUTHOR]

• Phytic acid was used to controllably prepare heterostructural electrocatalyst. • HCHO-based water electrolysis saves 320 mV to reach 50 mA cm−2 than without HCHO. • The conversion of HCHO to CH 3 OH was realized with hydrogen sources from water. • This electrocatalytic system could be applied to detect HCHO widely in wastewater. Herein, we report the linearly distributed NiCo-NiCoP nanoparticles embedded into P-doped carbon nanotubes (NiCo-NiCoP@PCT) which are synthesized via the chelation of phytic acid (PA) on the surface of Ni-Co-precursor nanowires and the subsequent thermal reduction. The PA is used not only as chelating agent to form Ni-Co@PA coating but also as solid phosphorus source to safely synthesize heterostructured NiCo-NiCoP. The as-prepared NiCo-NiCoP@PCT used as bifunctional electrodes exhibit superiorly electrocatalytic performance toward both hydrogen evolution reaction (HER) with a low overpotential of 135 mV at 10 mA cm−2 and anodic oxidation reaction of formaldehyde (FOR) with an ultra-low overpotential of 1.18 V to acquire 10 mA cm−2. Besides, when a two-electrode cell is constructed by using NiCo-NiCoP@PCT as anode and cathode, the current density of formaldehyde-based water electrolysis (50 mA cm−2) is 6.25 times bigger than that of conventional water splitting (8 mA cm−2) at the same voltage of 1.76 V. In addition, methanol (CH 3 OH) is produced simultaneously by hydrogenation reduction reaction of formaldehyde at the cathode, which realized the upgraded conversion of HCHO to small molecular fuel by electrocatalytic reduction. Therefore, it is demonstrated that the two-electrode electrolyzer not only realize the oxidative degradation and upgraded conversion of formaldehyde-based wastewater, but also reduce the energy consumption of water splitting for hydrogen generation. This work presents a new idea of controllable preparation for multifunctional phosphide electrodes and a novel construction of electrochemical cell to realize efficient hydrogen energy preparation and environmental management. [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]

Although numerous ruthenium‐based phosphates possess high catalytic activities for hydrogen evolution reaction (HER), most of them rely on dangerous and toxic synthesis routes. Biological slices confirm that Ru ions can penetrate the cell walls of saccharomycete, which facilitates the adsorption of Ru ions. Herein, based on a green synthesis process by saccharomycete cells as the carbon template and nitrogen/phosphorus (N/P) sources, novel Janus‐like ruthenium–ruthenium phosphide nanoparticles embedded into a N/P dual‐doped carbon matrix (Ru–Ru2PΦNPC) electrocatalyst for HER are synthesized. Electrochemical tests reveal that Ru–Ru2PΦNPC displays remarkable performance with a low overpotential of 42 mV at 10 mA cm−2 and demonstrates superior stability at a high current density in 0.5 m H2SO4. Furthermore, ruthenium oxide nanoparticles coated N/P dual‐doped carbon (NPC@RuO2) are also synthesized with a yolk–shell structure using saccharomycete cells as the core template and RuO2 as a shell to isolate saccharomycete cells from the oxidation reaction during calcination in air. The NPC@RuO2 as oxygen evolution reaction electrocatalyst possesses a low overpotential of 220 mV at 10 mA cm−2. Finally, the Ru–Ru2PΦNPC is integrated as a cathode and NPC@RuO2 is integrated as an anode to construct a two‐electrode electrolyzer to enable an excellent performance for overall water splitting with a cell voltage of 1.50 V at 10 mA cm−2 in 0.5 m H2SO4. [ABSTRACT FROM AUTHOR]