Core-Shell Co@v-CoO_x/C Electrocatalysts With Balanced Intermediate Adsorption for High-Performance Rechargeable Zinc-Air Batteries

Vacancy engineering offers an effective route to tailoring Co-based oxygen electrocatalysts, yet vacancy-rich sites can also intensify oxygen-intermediate binding and impede active-site regeneration if their polarized coordination environments are not properly regulated. Herein, a metal-core-buffered vacancy-shell strategy is proposed by coupling ultrasmall metallic Co nanodots with a Co-vacancy-rich CoO_x/C shell within a conductive mesoporous carbon framework. The metallic Co core serves as a nanoscale electron reservoir, while the vacancy-rich CoO_x/C shell provides adsorption-regulating Co─O─C motifs for oxygen intermediates. Structural and spectroscopic characterizations confirm the formation of a carbon-confined Co/CoO_x core-shell architecture with abundant vacancy-related defects. In situ Raman spectroscopy and density functional theory calculations reveal that interfacial electronic coupling buffers the vacancy-induced polarized Co─O─C motifs, downshifts the Co 3d-band center, and weakens excessive *OH binding, thereby balancing oxygen-species activation with active-site regeneration. As a result, Co@v-CoO_x/C delivers a high ORR half-wave potential of 0.871 V, an OER overpotential of 319 mV at 10 mA cm^-2, and a small bifunctional potential gap of 0.678 V. Rechargeable Zn-air batteries based on Co@v-CoO_x/C achieve a peak power density of 184 mW cm^-2 and stable cycling for approximately 3200 h, while flexible devices also show high power output and mechanical tolerance.