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

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 Ni2P and CoP nanocages. By controlling the molar ratio of Ni/Co atoms in Ni–Co bimetal hydroxides, the Ni0.6Co1.4P nanocages derived from Ni0.6Co1.4(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 Ni2P and CoP. This work also provides a general approach to optimize the catalysis performance of bimetal compounds. Ni–Co bimetal phosphide nanocages as highly efficient and robust electrocatalysts are synthesized by using Cu2O nanocubes templates. Through accurate regulation of Co doping concentration, the optimum oxygen evolution reaction performance can be achieved. Theoretical analysis suggests that the Co incorporation into Ni2P effectively optimizes the electronic structures of bimetal phosphide catalysts and enhances their interaction with reactants.