Engineering charge redistribution on high-density RuCo nanoclusters loaded on N-doped graphite carbon as robust bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

A major challenge for the development of rechargeable Zn-air batteries (ZABs) is represented by the lack of effective bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this work, a high-density alloy nanocluster catalyst evenly loaded on N-doped porous sheet-like graphite carbon layer arrays (RuCo/NC) was fabricated by one-step electrochemical exfoliation, accelerating the active site exposure and mass transfer. RuCo/NC exhibited a lower reversible oxygen overpotential of 0.713 V for the OER / ORR compared to the benchmark Pt/C//RuO2 (0.755 V). Moreover, density functional theory (DFT) calculations revealed an optimized adsorption / desorption behavior of *OOH, *OH, and *O species caused by the charge redistribution between Ru and Co in RuCo/NC, which dramatically lowered the reaction energy barrier for the rate-limiting steps in ORR / OER. A home-assembled ZAB with a RuCo/NC air electrode catalyst exhibited a higher open-circuit voltage (OCV) of 1.422 V and a power density of 130 mW cm−2, exceeding those of Pt/C//RuO2 (OCV = 1.348 V, power density = 108 mW cm−2). This work introduces a promising method for fabricating hierarchical sheet-like carbon-based functional materials with potential application in fuel cells and water electrolysis.