Construction of Surface Ru oct ─O─Co oct Units With Optimized Co oct Spin States for Enhanced Oxygen Reduction and Evolution.

The introduction of noble metal into spinel structure is an effective strategy to develop efficient oxygen evolution/reduction reaction (OER/ORR) catalysts. Herein, surface Co oct is substituted by Ru oct in Ru x -Mn 0.5 Co 2.5-x O 4 /NCNTs by ion-exchange, where presence of Ru oct ─O─Co oct unit facilitates electron transfer. This strong electron coupling effect leads downward shift in d-band center and a narrowing of d-p bandgap. The increased charge density of Co oct bridged with Ru oct dioxygen optimizes adsorption of oxygen intermediates ( * OH) and occupation of electrons in e g -orbital octahedral. The measured ORR/OER voltage difference is only 0.71 V. The peak power density of assembled zinc-air battery reaches 148.8 mW h cm -2 , and energy density at 100 mA cm -2 reaches 813.6 mA h g Zn -1 , approaching a theoretical value of 820 mA h g Zn -1 . The catalyst demonstrates stable operation for over 500 h at 10 mA cm -2 and over 200 h at 50 mA cm -2 . This work provides new insights to guide fabrication of advanced oxygen electrocatalysts.