A Superior Bifunctional Electrocatalyst in Which Directional Electron Transfer Occurs Between a Co/Ni Alloy and Fe─N─C Support
Ziyi Xu, Shihao Wang, Wenmao Tu, Ling Shen, Wu Lu, Shilong Xu, Haining Zhang, Hongfei Pan, Xiaoyu Yang
Abstract
Abstract Stable, efficient, and economical bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are needed for rechargeable Zn–air batteries. In this study, a directional electron transfer pathway is exploited in a spatial heterojunction of Co y Ni x @Fe─N─C heterogeneous catalyst for effective bifunctional electrolysis (OER/ORR). Thereinto, the Co/Ni alloy is strongly coupled to the Fe─N─C support through Co/Ni─N bonds. DFT calculations and experimental findings confirm that Co/Ni─N bonds play a bridging role in the directional electron transfer from Co/Ni alloy to the Fe─N─C support, increasing the content of pyridinic nitrogen in the ORR‐active support. In addition, the discovered directional electron transfer mechanism enhances both the ORR/OER activity and the durability of the catalyst. The Co 0.66 Ni 0.34 @Fe─N─C with the optimal Ni/Co ratio exhibits satisfying bifunctional electrocatalytic performance, requiring an ORR half‐wave potential of 0.90 V and an OER overpotential of 317 mV at 10 mA cm −2 in alkaline electrolytes. The assembled rechargeable zinc–air batteries (ZABs) incorporating Co 0.66 Ni 0.34 @Fe─N─C cathode exhibits a charge–discharge voltage gap comparable to the Pt/C||IrO 2 assembly and high robustness for over 60 h at 20 mA cm −2 .