Preparation of bifunctional oxygen evolution reaction and oxygen reduction reaction catalyst CoO-TiO2@NG by high gravity-hydrothermal method for rechargeable Zn air battery

For rechargeable Zn air batteries (ZABs), the low cost and scalable preparation method for the catalyst with favorable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic properties is a critical influence factor for its large-scale application. In this paper, the composites (preTiO 2 @hG) consisting of the precursor of titanium dioxide and hydrophilic graphene were successfully prepared in a Rotating Packed Bed by high-gravity technology. Then, N and Co elements were doped by hydrothermal-reduction method to obtain composite catalyst CoO-TiO 2 @NG, which had excellent catalytic performances of both OER/ORR. The value of ΔE is 0.685 V for CoO-TiO 2 @NG. When used as the catalyst on the air cathode of rechargeable ZABs, the device exhibits a high power density of 146.8 mW/cm 2 and a large specific capacity of 815.8 mAh/g. It also has good cycle stability, the ZAB capacity using CoO-TiO 2 @NG as catalyst does not significantly decrease after more than 110 h of charging-discharging cycles. The improvement of OER and ORR catalytic performance of CoO-TiO 2 @NG is due to the synergistic effect of CoO, TiO 2 and N-doped graphene. This article provides a new method for low-cost and scalable preparation of bifunctional OER/ORR non-precious metal catalysts with novel component and high performances.