Yolk‐Shell Structured Zinc‐Cobalt‐Ruthenium Alloy Oxide Assembled with Ultra‐Small Nanoparticles: A Superior Cascade Catalyst toward Oxygen Evolution Reaction

Abstract Structure engineering has proven to be an effective strategy for improving the catalytic performance and reducing the cost of ruthenium oxide‐based catalysts toward oxygen evolution reactions (OER). Herein, a polyhedron‐shaped yolk‐shell structure composed of zinc‐cobalt‐ruthenium ternary metal alloy oxide (ZnCo‐RuO 2 /C) is prepared, by taking advantage of the Kirkendall effect. The yolk‐shell frame and the ensembled metal oxide nanoparticles are 116.9 ± 25.9 nm and 3.1 ± 0.7 nm in diameter, respectively. The porous yolk‐shell structure of ZnCo‐RuO 2 /C exposes abundant active sites and facilitates mass transfer for OER. Theoretical calculations indicate that ZnCo‐RuO 2 may break the linear scaling relationship for the OER intermediates and dramatically reduces the energy barrier of the potential determining step, which may be one of the factors that are responsible for the enhanced OER performance of ZnCo‐RuO 2 /C. In 1 m KOH aqueous electrolyte, ZnCo‐RuO 2 /C delivers an overpotential of only 180 mV at 10 mA cm −2 and a Tafel slope of 63 mV dec −1 , superior to that of single metal‐doped, pristine and commercial RuO 2 . As an anode catalyst of zinc‐air batteries, ZnCo‐RuO 2 /C exhibits improved power density and durability relative to commercial RuO 2 , very promising for practical application.