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The main prerequisite for designing electrocatalysts with favorable performance is to examine the links between electronic structural features and catalytic activity. In this work, Ni2P as a model electrocatalyst and one of the most potent catalysts for hydrogen evolution reaction (HER) was utilized to develop various Ni2P and carbon-based (graphene and N-doped graphene) heterostructures. The characteristics of such structures (Ni2P, graphene, N-doped graphene, Ni2P/graphene, and Ni2P/N-doped graphene), including binding energies, the projected density of states (PDOS), band structure, charge density difference, charge transfer, Hirshfeld charge analysis, and minimum-energy path (MEP) towards HER were calculated and analyzed by density functional theory (DFT) approach. The coupling energy values of hybrid systems were correlated with the magnitude of charge transfer. The main factors driving a promising water-splitting reaction were explained by the data of PDOS, band structures, and charge analysis, including the inherent electronegativity of the N species alongside shifting the Fermi level toward the conductive band. It was also shown that a significant drop occurs in the HER energy barrier on Ni2P/graphene compared to the pristine Ni2P due to N doping on the graphene layer in the Ni2P/N-doped graphene heterostructure.

The great promise of the combination of urea oxidation reaction (UOR) with hydrogen evolution reaction (HER) to simultaneously achieve wastewater treatment and hydrogen production calls for the rational design of high‐performance electrocatalysts. Herein, the reconstruction with the formation of Ni2P and Mo2O72− on the surface can largely enhance the alkaline HER activity of P‐NiMoO4 by on‐site electrochemical activation strategy. Systematic experimental results indicate that the reconstruction process enables the exposure of additional Ni sites and the adjustment of hydrogen adsorption to facilitate HER kinetics. Ultimately, a highly efficient alkaline HER electrode with low overpotential of −48.9 mV for 10 mA cm−2 is achieved. More importantly, a UOR electrolyzer assembled with A‐P‐NiMoO4 as the cathode and P‐NiMoO4 as the anode exhibits impressive performance with a small cell voltage of 1.363 V for 10 mA cm−2. The application of the fabricated electrodes in a practical cell driven by a commercial dry battery (1.5 V) demonstrates efficient and stable hydrogen production, making the developed strategy promising for the rational design of highly active electrocatalysts for green hydrogen production. [ABSTRACT FROM AUTHOR]

The great promise of the combination of urea oxidation reaction (UOR) with hydrogen evolution reaction (HER) to simultaneously achieve wastewater treatment and hydrogen production calls for the rational design of high‐performance electrocatalysts. Herein, the reconstruction with the formation of Ni2P and Mo2O72− on the surface can largely enhance the alkaline HER activity of P‐NiMoO4 by on‐site electrochemical activation strategy. Systematic experimental results indicate that the reconstruction process enables the exposure of additional Ni sites and the adjustment of hydrogen adsorption to facilitate HER kinetics. Ultimately, a highly efficient alkaline HER electrode with low overpotential of −48.9 mV for 10 mA cm−2 is achieved. More importantly, a UOR electrolyzer assembled with A‐P‐NiMoO4 as the cathode and P‐NiMoO4 as the anode exhibits impressive performance with a small cell voltage of 1.363 V for 10 mA cm−2. The application of the fabricated electrodes in a practical cell driven by a commercial dry battery (1.5 V) demonstrates efficient and stable hydrogen production, making the developed strategy promising for the rational design of highly active electrocatalysts for green hydrogen production.

A promising hydrogen evolution reaction performance is achieved in this work by Ni 2 P nanoparticles supported on Nitrogen, Sulphur co-doped reduced graphene oxide (N ,S-rGO) synthesized via hydrothermal method. The enhanced electrochemical activity of the electrocatalyst can be attributed to the presence of more defect sites in the graphitic carbon as well as the synergistic effect between both N and S co-doped reduced graphene oxide. Ni 2 P–N, S-rGO showed the comparative intensity ratio I D /I G value of 1.96, which is higher compared to other carbon materials. It shows that the defect was increased when nitrogen and sulphur co-doping occurs on reduced graphene oxide sheets which in turn leads to an increase in both active doping sites and improve conductivity. Ni 2 P incorporated with N, S-rGO was found to be the best for attaining a current density of 10 mA/cm2 at an overpotential of 179 mV in 0.5 M H 2 SO 4. As well, the Tafel slope of 71 mV/dec confirms that the Ni 2 P incorporated with N, S-rGO proceeds through the Volmer-Heyrovsky mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

Combination of catalytic active components with substrates is deemed to be a promising approach to pursue high active and stable catalysts. Wherein, carbon-based materials as a kind of frequently-used substrates are well developed, and thus the different effects of them on catalytic active components deserve investigating and contrasting. In this work, well dispersive and ultrafine Ni 2 P nanoparticles supported on N-doped reduced graphene oxide (N-RGO) were synthesized through a facial hydrothermal process and subsequent phosphorization. The prepared Ni 2 P/N-RGO demonstrates a superior electrocatalytic activity towards hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4 solution with a low onset overpotential (80 mV) and small Tafel slope (93.1 mV dec−1). Additionally, as compared with other representative carbon materials (carbon black (C) and carbon nanotubes (CNTs)) in the perspective of specific surface area (SSA), conductivity and electronic interaction in particular, N-RGO demonstrates a preeminent promotional effect as a substrate of Ni 2 P. Image 1 • Well dispersive and ultrafine Ni 2 P nanoparticles supported on N-RGO were synthesized. • Ni 2 P/N-RGO exhibits a superior electrocatalytic activity for HER in acid solution. • The promotional effect of N-RGO on Ni 2 P for HER was compared with C and CNTs. • The electronic interaction between the doped N in N-RGO and Ni 2 P was investigated. • The high SSA, conductivity and electron density change contribute to the performance. [ABSTRACT FROM AUTHOR]

Development of highly active, durable, and low-cost bifunctional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital to efficient and economical production of hydrogen. As a promising family of electrocatalysts, many perovskite oxides have demonstrated remarkable activities for both OER and HER under various conditions. Here we report an alternative strategy to dramatically enhance the catalytic activity of La 0.8 Sr 0.2 Cr 0.69 Ni 0.31 O 3−δ (LSCN) for overall water electrolysis by surface modification and interface engineering. Exsolution of discrete Ni 2 P nanoparticles from LSCN, induced by a partial reduction and subsequent phosphidization, creates a unique surface with LSCN/Ni 2 P interfaces, which enhanced the intrinsic OER activity by ∼6.2 times and mass activity by ∼10.2 times. The HER activity and durability are simultaneously enhanced as well. When used as the electrocatalyst in a symmetrical two-electrode water electrolyzer, a constant cell voltage of ∼1.70 V (vs. Reversible hydrogen electrode, RHE) is observed to sustain a water splitting current density of 10 mA cm−2 for a continuous operation of 14 h, achieving much better performance than a state-of-the-art Pt/C(−)//IrO 2 (+) electrolyzer. The bifunctional electrocatalyst has potential to be a cost-effective alternative to precious metal-based electrocatalysts in commercial water splitting systems. Further, the protocol developed in this work provides a new strategy to optimize bifunctional OER and HER activities of perovskite oxides, and broadens our horizons in rational design of heterogeneous electrocatalysts for other applications. Here we report a new strategy to dramatically enhance bifunctional electrocatalytic activity of La 0.8 Sr 0.2 Cr 0.69 Ni 0.31 O 3−δ (LSCN) perovskite oxide for water electrolysis by a partial reduction and a subsequent phosphatization process. The resulting LSCN surface, decorated with island-like Ni 2 P nanoparticles, enhanced the intrinsic activity by ∼6 times and mass activity by ∼10 times while maintaining excellent durability in an alkaline solution. Image 1 • Unique LSCN/Ni 2 P interfaces have been in-situ induced by a partial reduction and subsequent phosphatization. • Island-like Ni 2 P nanoparticles tend to be partially embedded in the surface of LSCN perovskite oxide. • Enhanced OER, HER and overall water splitting performances have been obtained after the formation of LSCN/Ni 2 P interfaces. • Unique LSCN/Ni 2 P interfaces contribute to high performance. [ABSTRACT FROM AUTHOR]

Developing efficient non-noble metal and earth-abundant electrocatalysts with tunable microstructures for overall water splitting is critical to promote clean energy technologies for a hydrogen economy. Herein, novel three-dimensional (3D) flower-like Ni2P composed of mesoporous nanoplates with controllable morphology and high surface area was prepared by a hydrothermal method and low-temperature phosphidation as efficient electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Compared with the urchin-like Ni xP y, the 3D flower-like Ni2P with a diameter of 5 μm presented an efficient and stable catalytic performance in 0.5 m H2SO4, with a small Tafel slope of 79 mV dec−1 and an overpotential of about 240 mV at a current density of 10 mA cm−2 with a mass loading density of 0.283 mg cm−2. In addition, the catalyst also exhibited a remarkable performance for the OER in 1.0 m KOH electrolyte, with an overpotential of 320 mV to reach a current density of 10 mA cm−2 and a small Tafel slope of 72 mV dec−1. The excellent catalytic performance of the as-prepared Ni2P may be ascribed to its novel 3D morphology with unique mesoporous structure. [ABSTRACT FROM AUTHOR]

The development of non-noble metal hydrogen evolution catalysts that can replace Pt is crucial for efficient hydrogen production. Herein, we develop a type of well-dispersed Ni2P on N-doped nanomesh carbon (NC) electrocatalyst by a facile pyrolysis method, which shows excellent hydrogen evolution reaction (HER) catalytic performance. It is rather remarkable that the overpotential of Ni2P/NC prepared under optimal proportion is 108 mV at 10 mA·cm−2 current density in 1 M KOH solution with the tafel slope of 67.3 mV·dec−1, the catalytic activity has no significant attenuation after 1000 cycles of cyclic voltammetry (CV)method. The hydrogen evolution performance of the electrocatalytic is better than most similar catalysts in alkaline media. The unique mesh structure of the carbon component in the catalyst facilitates the exposure of the active site and reduces the impedance, which improves the efficiency of electron transport as well as ensuring the stability of the hydrogen evolution reaction. In addition, we prove that nitrogen doping and pore structure are also important factors affecting catalytic activity by control experiments. Our results show that N-doped nanomesh carbon, as an efficient support, combined with Ni2P nanoparticles is of great significance for the development of efficient hydrogen evolution electrodes.

A reliable strategy has been developed to prepare Ni2P nanofilms on carbon nanosheets (CNS) nanohybrids (Ni2P/CNS), which involves the preparation of three-dimensional (3D) CNS followed by in situ growth of Ni2P nanofilms on the surface of CNS. The Ni2P/CNS nanohybrids possess a robust 3D hierarchical structure, in which the Ni2P films are solidly overlaid on the surface of the CNS. The Ni2P/CNS nanohybrid was characterized by a variety of techniques, including X-ray diffraction (XRD), electron microscopy, X-ray photoelectron spectroscopy (XPS), etc. A series of electrochemical tests demonstrate the Ni2P/CNS nanohybrid shows high catalytic activity and excellent stability towards the hydrogen evolution reaction (HER) in pH-universal electrolyte, that is, in acidic, neutral, and basic media. The outstanding performance for Ni2P/CNS is correlated with the synergic effects between Ni2P and CNS associated with its unique and robust structure. [ABSTRACT FROM AUTHOR]

• Heterostructure of Ru 2 P particles decorated Ni 2 P nanosheets is prepared. • Synergism induces accelerated kinetics and intrinsic activity. • Improved active sites density and enhanced charge transfer are obtained. • Showing robust activity and stability for HER in wide pH range. Lacking efficient and pH-universal catalysts is currently the main obstacle for the large-scale production of hydrogen through electrochemical water splitting. The hetero material of Ru 2 P nanoparticles and Ni 2 P nanosheets is constructed on carbon fiber cloth as pH-tolerant catalyst for hydrogen generation. The designed heterointerface provides synergism and structure advantages for improved intrinsic catalysis activity, more accessible active sites, and enhanced charge transfer for hydrogen evolution. The electrochemical measurements demonstrate the active hydrogen production properties, such as low overpotentials (46 mV, 47 mV, and 51 mV in 0.5 M H 2 SO 4 , 1 M KOH, and 1 M phosphate-buffered saline, respectively) at a current density of 10 mA cm−2, as well as rapid catalysis kinetics with small Tafel slopes and good stability. [ABSTRACT FROM AUTHOR]

• Ultrathin Ni 2 P nanomeshes on nickel foam (Ni 2 P-UNMs/NF) is successfully synthesized. • Ni 2 P-UNMs/NF has high specific surface area and sufficient active sites. • Ni 2 P-UNMs/NF shows high electroactivity for hydrogen evolution reaction. • Ni 2 P-UNMs/NF also shows high electroactivity for benzylamine oxidation reaction (BOR). • BOR boosted water-splitting gives a cost/energy-competitive method for H 2 production. In this work, ultra-thin Ni 2 P nanomeshes (1.9 nm thickness) on nickel foam (NF) substrate (denoted as Ni 2 P-UNMs/NF) are successfully achieved through phosphidation treatment using ultra-thin Ni(OH) 2 nanomeshes on NF substrate (denoted as Ni(OH) 2 -UNMs/NF) as reaction precursor. Because of the sufficient active sites in edge of the holes, high specific surface area, porous framework and high conductivity of NF substrate, Ni 2 P-UNMs/NF nanocomposites show the outstanding activity for both hydrogen evolution reaction (HER) and benzylamine oxidation reaction (BOR) in alkaline electrolyte. Importantly, Ni 2 P-UNMs/NF nanocomposites can directly act as a bifunctional electrocatalyst for the electrochemical water-splitting in two electrode system in the presence of benzylamine, which only requires an electrolysis voltage of 1.41 V to achieve the 10 mA cm-2 current density in alkaline electrolyte, accompanying with H 2 production at cathode and value-added benzonitrile production at anode. Obviously, the BOR boosted electrochemical water-splitting provides an energy-saving and cost-competitive H 2 production method. [ABSTRACT FROM AUTHOR]

The development of non-noble metal hydrogen evolution catalysts that can replace Pt is crucial for efficient hydrogen production. Herein, we develop a type of well-dispersed Ni2P on N-doped nanomesh carbon (NC) electrocatalyst by a facile pyrolysis method, which shows excellent hydrogen evolution reaction (HER) catalytic performance. It is rather remarkable that the overpotential of Ni2P/NC prepared under optimal proportion is 108 mV at 10 mA·cm−2 current density in 1 M KOH solution with the tafel slope of 67.3 mV·dec−1, the catalytic activity has no significant attenuation after 1000 cycles of cyclic voltammetry (CV)method. The hydrogen evolution performance of the electrocatalytic is better than most similar catalysts in alkaline media. The unique mesh structure of the carbon component in the catalyst facilitates the exposure of the active site and reduces the impedance, which improves the efficiency of electron transport as well as ensuring the stability of the hydrogen evolution reaction. In addition, we prove that nitrogen doping and pore structure are also important factors affecting catalytic activity by control experiments. Our results show that N-doped nanomesh carbon, as an efficient support, combined with Ni2P nanoparticles is of great significance for the development of efficient hydrogen evolution electrodes. [ABSTRACT FROM AUTHOR]