Lattice Strain Engineering of Ni 2 P Enables Efficient Catalytic Hydrazine Oxidation-Assisted Hydrogen Production.

Hydrazine-assisted water electrolysis provides new opportunities to enable energy-saving hydrogen production while solving the issue of hydrazine pollution. Here, the synthesis of compressively strained Ni ₂ P as a bifunctional electrocatalyst for boosting both the anodic hydrazine oxidation reaction (HzOR) and cathodic hydrogen evolution reaction (HER) is reported. Different from a multistep synthetic method that induces lattice strain by creating core-shell structures, a facile strategy is developed to tune the strain of Ni ₂ P via dual-cation co-doping. The obtained Ni ₂ P with a compressive strain of -3.62% exhibits significantly enhanced activity for both the HzOR and HER than counterparts with tensile strain and without strain. Consequently, the optimized Ni ₂ P delivers current densities of 10 and 100 mA cm ^-2 at small cell voltages of 0.16 and 0.39 V for hydrazine-assisted water electrolysis, respectively. Density functional theory (DFT) calculations reveal that the compressive strain promotes water dissociation and concurrently tunes the adsorption strength of hydrogen intermediates, thereby facilitating the HER process on Ni ₂ P. As for the HzOR, the compressive strain reduces the energy barrier of the potential-determining step for the dehydrogenation of *N ₂ H ₄ to *N ₂ H ₃ . Clearly, this work paves a facile pathway to the synthesis of lattice-strained electrocatalysts via the dual-cation co-doping.
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