Hollow‐Structured and Polyhedron‐Shaped High Entropy Oxide toward Highly Active and Robust Oxygen Evolution Reaction in a Full pH Range

Abstract High entropy metal oxides (HEO) are superior to many reactions involving multi‐step elementary reactions. However, controlled synthesis of hollow‐structured HEO catalysts, which offers large surface area and fast mass transfer kinetics, remains challenging and unexplored due to the complicated metal precursors. Herein, a metal organic framework‐templated synthesis of hollow‐structured and polyhedron‐shaped HEO catalysts assembled with ultra‐small nanoparticles, with up to ten metal elements, can be achieved, by taking advantage of the ion‐exchange method. ZnFeNiCuCoRu‐O HEO catalyst displays excellent activity and ultra‐stability for oxygen evolution reaction in full pH range, with an overpotential of 170 mV at a current density of 10 mA cm −2 , a Tafel slope of 56 mV dec −1 , and a decay of activity by 7% in 30 h in alkaline medium, as well as a 12% and 8% decay in acidic and neutral medium, respectively. DFT calculation indicates that the energy barrier of the potential determining step on Ru‐Fe bridge site is significantly lower than any other Ru‐related bridge sites for the unique hollow structured HEO structures. This work highlights the importance of ion‐exchange method in preparing highly stable and active hollow‐structured HEOs catalysts toward highly efficient energy conversion and storage devices.