Novel design and synthesis of multi-anionic Co(OH)Se with ZIF-67 derived porous carbon matrix as a bifunctional electrocatalyst for rechargeable Zn-air batteries

Multi-anionic transition metal compounds with unique electron structures that are favorable for electron transfer are promising oxygen electrocatalysts. In this study, to synthesize a bifunctional oxygen electrocatalyst for Zn-air batteries (ZABs), unique structured composite of cobalt hydroxy selenide (Co(OH)Se) and nitrogen-doped carbon (C) was fabricated using a novel water vapor-assisted heat-treatment and an anion-exchange technique using a NaHSe solution. C@Co(OH)Se prepared under low-temperature and low-pressure condition successfully exhibited excellent electrocatalytic activities for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) via synergistic effects. Accordingly, C@Co(OH)Se-based ZAB displayed great cycle stability (discharge/charge potential gap of 1.01 V after 7,000 min cycling) and rate capability (1.25 V at 15 mA cm⁻²). By first demonstrating the potential use of multi-anionic Co(OH)Se as a bifunctional electrocatalyst for the ORR/OER and presenting a technique for complexing transition metal compounds and carbon matrices, our study expands the range of electrocatalyst design and synthesis.