Simultaneous reactant accessibility and charge transfer engineering in Co-doped RuO2-supported OCNT for robust rechargeable zinc-air batteries

The sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics greatly limits the application of zinc-air batteries (ZAB). Regarding this, searching for high-efficient electrocatalysts should be emphatically considered, while reactant accessibility and charge transfer on catalysts are the decisive factors for ORR/OER activities. Here we propose the incorporation of excess Co into (101) plane of RuO2 to form a single-phase material with abundant Ru/Co dual-atom sites on the active (110) surface to simultaneously optimize the charge transfer and reactant accessibility in the electrode reactions, while oxidized carbon nanotube applied as supports for electron transfer. Ru and Co atoms serve as the main ORR and OER catalytic sites respectively, while Ru/Co dual atoms tend to co-adsorbs the intermediate *OOH to produce the synergistic effects. As a result, the optimal electrocatalysts achieve an ultralow overpotential gap of 0.67 V in 0.1 M KOH and superior stability over 800 cycles at 10 mA cm-2 for ZAB.