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

The Cu NDs/Fe 2 O 3 Mott-Schottky heterojunction promoted the electron transfer from the Cu metal to Fe 2 O 3 semiconductive. The built-in electric field from Cu to Fe 2 O 3 may improve the adsorption of O 2 and OH − , thereby enhancing the electrocatalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). • The Cu NDs/Fe 2 O 3 -NPCs was developed by creating Cu NDs/Fe 2 O 3 Mott-Schottky heterojunction. • The Mott-Schottky built-in electric field from Cu to Fe 2 O 3 may improve the adsorption of O 2 /OH − . • The bifunctional oxygen electrocatalysis exhibits outstanding performance for ZABs. 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/Fe 2 O 3 -NPCs was developed by creating Cu nanodots (NDs)/Fe 2 O 3 heterojunction nanoislands rooted on N-rich porous carbon nanosheets (NPCs). The formed Mott-Schottky heterojunction Cu NDs/Fe 2 O 3 nanoislands promoted the electron transfer from the metallic Cu to the semiconductive Fe 2 O 3 phase, as a result, the adsorptions towards O 2 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/Fe 2 O 3 -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/Fe 2 O 3 -NPCs catalyst displayed a high power density of 138 mW cm −2 and an excellent long-term cyclability.