Hybrid Cobalt and Iron Based Metal Organic Framework Composites as Efficient Bifunctional Electrocatalysts towards Long‐Lasting Flexible Zinc‐Air Batteries

Abstract

AbstractHighly efficient and stable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts are urgently needed to realize the implementation of flexible rechargeable Zn‐air batteries (ZABs). Herein, a series of hybrid Co and Fe based metal‐organic frameworks (HCF‐MOFs) are rationally designed and synthesized. The HCF‐MOFs are directly used as electrocatalysts to enable oxygen catalysis. The unique hierarchical structure provides porous channels and ensures high exposure of metal sites, thus boosting the electrocatalytic activity. By composition regulation, the coordination environment of the active centers can be effectively modulated to achieve superior bifunctional oxygen electrocatalytic performance. Specifically, an OER overpotential of only 295 mV at 10 mA cm−2 and an ORR half‐wave potential of 0.82 V are obtained by the activated HCF‐MOF, outperforming those of commercial RuO2 and Pt/C. The results elucidate that HCF‐MOF/OOH is formed during oxygen evolution, and serves as the active center. When combined with polyacrylate hydrogel electrolyte, the quasi‐solid‐state flexible ZAB based on HCF‐MOF‐3 delivers the maximum power density of 113.5 mW cm−2, surpassing the Pt/C−RuO2 counterpart. Significantly, the battery exhibits excellent durability whilst being subjected to bending tests. This work demonstrates the prospect of these HCF‐MOFs as bifunctional electrocatalysts for high‐performance ZABs.