Multi-Strategy Architecture of High-Efficiency Electrocatalysts for Underwater Zn-H2 O2 Batteries with Superior Power Density of 442 mW cm-2.

ABSTRACT

A facile multistage regulated strategy is reported to synthesize ZnCo-NC based carbon nanotubes including DMEA induced crystallization, Zn ion activation, and magnetic control growth of carbon nanotubes. Uniform Co distribution and the modulation of Zn, and their catalytic properties are carefully investigated by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. The surface contents of pyridinic N for the oxygen-reduction reaction (ORR) and the surface contents of CoNx and high valence Co for the oxygen-evolution reaction (OER) can be significantly modulated by Zn content in precursors and the sintering temperature. Furthermore, the catalyst also contains high specific surface areas, high porosity, and high electrochemical active surfaces. Therefore, the ZnCo-NC based catalyst exhibits outstanding bifunctional electrocatalytic activities for ORR with a high Eonset (1.02 V) and E1/2 (0.91 V) and OER with low Ej=10 (1.56 V), better than Pt/C and RuO2 . Importantly, the ZnCo-NC based Zn-H2 O2 batteries achieve the superior power density of 442 mW cm-2 , much higher than 238 and 198 mW cm-2 of Zn-air batteries with ZnCo-NC based catalyst and Pt/C respectively. More importantly, the high-power Zn-H2 O2 batteries can work well in underwater conditions while Zn-air batteries are out of work.