Boosting the activity and stability via synergistic catalysis of Co nanoparticles and MoC to construct a bifunctional electrocatalyst for high-performance and long-life rechargeable zinc-air batteries.

ABSTRACT

The high overpotential of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) leading to slow air cathode kinetics is still a major challenge for zinc-air batteries (ZABs), hindering the commercialization of ZABs. With the advantages of cost-effectiveness and feasibility of synthesis at room temperature, zeolite imidazole frameworks (ZIFs) are regarded as advanced precursors. But a majority of ZIF-derived catalysts show only one catalytic activity, which limits their performance in ZABs as well as the cycling stability. In addition, molybdenum carbide (MoC) is recognized as an excellent candidate for renewable energy conversion due to its good chemical resistance and thermal stability. Herein, we report a ZIF-67-derived Co/MoC-NC multiphase doped carbon bifunctional ORR/OER catalyst with multiple active sites for the cathode of ZABs. The synergistic catalysis of Co nanoparticles and MoC nanoparticles in Co/MoC-NC which are embedded in a thin layer of N-doped graphitic carbon and immobilized on N-doped graphitic carbon, respectively, demonstrates superior ORR catalytic performance and durability both under alkaline and acidic conditions (E1/2 = 0.87 V in 1.0 M KOH and E1/2 = 0.76 V in 0.5 M H2SO4). Simultaneously, Co/MoC-NC also exhibits favorable OER performance (10 mA cm-2, η = 320 mV) in 1 M KOH. Furthermore, a remarkable peak-power density of 215.36 mW cm-2 and great cycling stability could be achieved while applying Co/MoC-NC in the cathode of ZABs (over 300 h). This work will provide a viable design concept for designing and synthesizing multifunctional catalysts to construct rechargeable ZABs.