Oxygen vacancy-rich N-doped carbon encapsulated BiOCl-CNTs heterostructures as robust electrocatalyst synergistically promote oxygen reduction and Zn-air batteries.

Abstract The development of non-precious metal catalysts for oxygen reduction reactions (ORR) is vital for promising clean energy technologies such as fuel cells, and zinc-air batteries. Herein, we present a stepwise synthesis of N-doped and carbon encapsulated BiOCl-CNTs heterostructures. Electrocatalytic ORR studies show that the optimized catalyst has a high half-wave potential (E1/2) of 0.85 V (vs. RHE), large limiting current density (-5.34 mA cm−2@0.6 V) in alkaline medium, and nearly perfect 4e− reduction characteristics, even surpassing commercial Pt/C. Meanwhile, the catalyst has exceptional durability (above 97.5 % after 40000 s) and strong resistance towards methanol poisoning. The good ORR activity also results in high-performance zinc-air batteries with a specific capacity (724 mAh g−1@10 mA cm−2), a high open-circuit potential of 1.51 V and a peak power density of 170.7 mW cm−2, as well as an ultra-long charge–discharge cycle stability (155 h), comparable with the Pt/C catalyst. The catalytic mechanism reveals that the excellent electrocatalytic performance originates from the synergistic effect of N doping, oxygen vacancies, and BiOCl sites.