3D Cross-Linked Structure of Manganese Nickel Phosphide Ultrathin Nanosheets: Electronic Structure Optimization for Efficient Bifunctional Electrocatalysts

As the important anodic reactions in electrochemical hydrogen production, both the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) are proved to be the bottleneck needed to be resolved because of their sluggish 4e– or 6e– transfer process. High-efficiency and low-cost electrocatalysts are urgently in need to overcome these blocks. In this work, the manganese nickel phosphide nanosheets (MnxNi2–xP) with a three-dimensional (3D) cross-linked structure in situ grown on Ni foam are developed and serve as a bifunctional electrocatalyst toward OER and UOR. The experimental and theoretical methods are employed to get a comprehensive understanding of the catalytic behaviors of the obtained samples. Compared with the monometallic phosphide, Ni2P, and commercial RuO2, MnxNi2–xP exhibits superior performance with the lowest overpotential and impressive longevity. MnxNi2–xP requires a small overpotential of 196 mV and an ultralow potential of 1.24 V to obtain a current density of 10 mA cm–2 during the OER and UOR process, respectively. The theoretical consequences also confirm the benign electronic conductivity and efficient active sites for the OH– adsorption of MnxNi2–xP, reconfirming that MnxNi2–xP can serve as an effective bifunctional electrocatalyst for both OER and UOR.