Constructing Co@WC1-x heterostructure on N-doped carbon nanotubes as an efficient bifunctional electrocatalyst for zinc-air batteries

Designing a bifunctional catalyst with efficient and consistent stability is important for development and application of zinc-air batteries. Herein, a Co@WC1-x/NCNTs composite that contains a heterostructure consisting of cobalt and tungsten carbide (WC1-x) and loaded on self-assembled N-doped carbon nanotubes (NCNTs), is synthesized from simple compounds using facile hydrothermal and calcination. Co@WC1-x/NCNTs composite demonstrates outstanding electrocatalytic performance for oxygen reduction reaction (ORR) with higher halfwave potential (0.81 V) and the current density of 5.75 mA cm(-2), as well as for oxygen evolution reaction (OER) having a lower overpotential (330 mV). Furthermore, it possess an ultra-high power density of 290 mW cm(-2), a specific capacity of 754.9 mAh g(-1) and charge-discharge stability in zinc-air batteries. The superior electrocatalytic performance of the composite may be ascribed to the synergistic effect between Co@WC1-x hetemstmcture, and N-doped carbon nanotubes. The formation of a heterojunction interface between Co and WCi_x may make possible the enrichment of electrons from carbon to Co (NCNTs -> WC1-x -> Highly active sites Co) during the catalytic process. This in turn facilitates the electrocatalytic process. This research offers a meaningful strategy for exploring efficient bifunctional catalyst used in zinc-air batteries.