Vacancy-engineered CeO2/Co heterostructure anchored on the nitrogen-doped porous carbon nanosheet arrays vertically grown on carbon cloth as an integrated cathode for the oxygen reduction reaction of rechargeable Zn–air battery

Abstract

A rechargeable zinc–air battery (ZAB) is regarded as a promising energy storage device owing to its high energy density, good safety, and environmental friendliness. However, the development of non-precious metal catalysts for improving the sluggish oxygen reaction kinetics of the air cathode of ZAB still presents a challenge. Herein, nitrogen-doped porous carbon nanosheet arrays vertically grown on carbon cloth decorated with CeO₂/Co heterostructure (Co/CeO₂–NCNA@CC) as an integrated cathode have been successfully constructed using a facile carbonization–hydrolysis procedure using a metal–organic framework (MOF) as a precursor. The size of CeO₂ nanoparticles can be controlled with an average diameter of about 6.0 nm through unique hydrolysis to form the heterostructure with Co species, which are uniformly dispersed on the surface of nitrogen-doped porous carbon nanosheet arrays (NCNA). NCNA vertically grown on carbon cloth (CC) has improved wettability and allows for the CeO₂/Co heterostructure to be easily accessible. The abundant intrinsic oxygen vacancies in CeO₂ bring the catalyst an excellent ability to tune the oxygen concentration during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes. The integrity of the electrode accelerates the transfer of electrons from the active sites to the CC current collector. Therefore, ZAB using Co/CeO₂–NCNA@CC as the integrated cathode exhibits an impressive electrocatalytic performance toward both ORR and OER. The ZAB with Co/CeO₂–NCNA@CC cathode has an open-circuit voltage of 1.47 V and supply capacity of 784.4 mA h g_Zn⁻¹ even after 380 h operation at 5.0 mA cm⁻², which surpasses the catalysts of commercial Pt/C + RuO₂ and the most reported catalysts.