Fabrication of Nickel–Cobalt Bimetal Phosphide Nanocages for Enhanced Oxygen Evolution Catalysis

Abstract Replacement of precious metals with earth‐abundant electrocatalysts for oxygen evolution reaction (OER) holds great promise for realizing practically viable water‐splitting systems. It still remains a great challenge to develop low‐cost, highly efficient, and durable OER catalysts. Here, the composition and morphology of Ni–Co bimetal phosphide nanocages are engineered for a highly efficient and durable OER electrocatalyst. The nanocage structure enlarges the effective specific area and facilitates the contact between catalyst and electrolyte. The as‐prepared Ni–Co bimetal phosphide nanocages show superior OER performance compared with Ni 2 P and CoP nanocages. By controlling the molar ratio of Ni/Co atoms in Ni–Co bimetal hydroxides, the Ni 0.6 Co 1.4 P nanocages derived from Ni 0.6 Co 1.4 (OH) 2 nanocages exhibit remarkable OER catalytic activity (η = 300 mV at 10 mA cm −2 ) and long‐term stability (10 h for continuous test). The density‐functional‐theory calculations suggest that the appropriate Co doping concentration increases density of states at the Fermi level and makes the d ‐states more close to Fermi level, giving rise to high charge carrier density and low intermedia adsorption energy than those of Ni 2 P and CoP. This work also provides a general approach to optimize the catalysis performance of bimetal compounds.