Core–Shell Co‐CoxP Nanoparticle‐Embedded N‐Doped Carbon Nanowhiskers Hollow Sphere for Efficient Oxygen Evolution Electrocatalysis

Abstract The development of efficient oxygen evolution reaction (OER) electrocatalysts is critical to overcome the efficiency bottleneck in hydrogen generation via water electrolysis. Hollow nanostructured materials have emerged as a hot topic for electrocatalysis research because of their advantages, including abundant active sites, a large contact area between the catalyst and the electrolyte, and a short transmission path. As highly efficient and stable OER electrocatalysts, cobalt‐based nanostructured materials have attracted more and more attention. In this work, cobalt metal/cobalt phosphides/nitrogen‐doped carbon composites (Co‐Co x P/NC) with a hierarchical hollow structure are designed by using hollow ZIF‐67 microspheres as precursors. By coating ZIF‐8 on the surface of hollow ZIF‐67 microspheres and further carbonizing, carbon nanowhiskers are successfully formed on the surface of hollow carbon spheres under the catalytic effect of Co nanoparticles at a high temperature. In the subsequent phosphating process, solid Co nanocrystalline particles are transformed into core–shell CoP and Co 2 P nanoparticles on account of the Kirkendall effect. Through the optimization of the microstructure of the material and the synergistic effect of transition metal, transition metal phosphide, and nitrogen doping, the overpotential of the optimal material is only 287 mV at 10 mA cm −2 current density in 1 m KOH.