Core–shell C@SnO2 as bifunctional cathode electrocatalyst for high performance Zn-air batteries

The slow reaction kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the charging and discharging process result in inferior cycle life and low-energy conversion efficiency of commercial zinc-air batteries (ZABs). Stannic oxide (SnO2) has received increasing attention for its unique advantages such as low cost, good stability, and high catalytic activity. In present work, mesoporous nanosphere carbon@stannic oxide (C@SnO2) core–shell structures with C as the inner layer and SnO2 as the outer shell are successfully prepared. When C@SnO2 serves as the cathode for ZABs, its specific surface area (245 m2 g−1) provides amounts of chemically active sites for ORR and OER. Similarly, carbon can not only increase the electrical conductivity of electrocatalyst, but also act as a support body for the core–shell structure which gives the material a robust structure and distinctive morphology. When C@SnO2 are employed as cathode in ZABs, it exhibits excellent electrocatalytic activity with half-wave potential (0.88 V) for ORR and onset potential (1.45 V) for OER. In addition, it shows a superior charging-discharging cycle stability. This work offers an insight for the selection and preparation of high-performance electrocatalysts.