Activating Cu/Fe₂O₃ nanoislands rooted on N-rich porous carbon nanosheets via the Mott-Schottky effect for rechargeable Zn-air battery

The fast electron transfer is a prerequisite to develop the high-performance bifunctional electrocatalysts for rechargeable Zn-air batteries (ZABs). In this work, the Mott-Schottky electrocatalyst Cu NDs/Fe₂O₃-NPCs was developed by creating Cu nanodots (NDs)/Fe₂O₃ heterojunction nanoislands rooted on N-rich porous carbon nanosheets (NPCs). The formed Mott-Schottky heterojunction Cu NDs/Fe₂O₃ nanoislands promoted the electron transfer from the metallic Cu to the semiconductive Fe₂O₃ phase, as a result, the adsorptions towards O₂ and OH⁻ species were improved, and sequentially the catalytic activities for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were both remarkably enhanced. In addition, the porous nature of the developed catalyst also contributed to the effectiveness of the required mass transfer. The optimal Mott-Schottky Cu NDs/Fe₂O₃-NPCs catalyst exhibited an onset potential of 0.98 V and a Tafel slop of 53.7 mV dec^-1 for ORR, and an overpotential of 328 mV at 10 mA cm⁻² for OER. Further, the ZAB assembled with Cu NDs/Fe₂O₃-NPCs catalyst displayed a high power density of 138 mW cm⁻² and an excellent long-term cyclability.