N, S-codoped CNTs supported Co4S3 nanoparticles prepared by using CdS nanorods as sulfur sources and hard templates: An efficient catalyst for reversible oxygen electrocatalysis

Abstract Non-precious efficient bifunctional catalysts towards oxygen reduction/evolution reactions (ORR/OER) are highly desired to enable the widespread application of rechargeable Zn-air batteries (r-ZABs). Herein, Prussian blue analogues (PBA) anchored on CdS nanorods (CdS NRs) pre-coated with polydopamine (PDA) are utilized as precursors to prepare ultrafine Co4S3 nanoparticles supported on N, S-codoped CNTs (Co4S3@N,S-CNT), where CdS NRs are served as sulfur sources and hard templates. After pyrolysis, the resulting Co4S3@N,S-CNT-800 shows a high specific surface area of 142.4 m2 g−1, together with merely 0.780 V difference between the OER potential at 10 mA cm−2 and the ORR potential at 3 mA cm−2. The Co4S3@N,S-CNT-800 based air cathode displays a higher discharge capacity of 787 mAh gZn−1 at 10 mA cm−2, a higher output power density of 154 mW cm−2, better working stability, as well as a lower charge–discharge voltage gap than the Pt/C + RuO2 based air electrode at various working current density. The remarkable oxygen reversible catalytic activities are mainly attributed to the presence of a thin layer of mesoporous carbon on partial sections of the open-end N,S-CNTs, which not only shortens the mass diffusion length but also prevents N,S-CNTs from excessively bundling to maximize the exposure of Co4S3 nanocrystallites and graphitized carbon skeletons with N or S heteroatoms.