Multivalent CoSx coupled with N-doped CNTs/Ni as an advanced oxygen electrocatalyst for zinc-air batteries.

• The formation of Co-N bond in hybrid catalyst can effectively enhance interfacial charge transfer. • Enhanced oxygen catalytic activity using NCNTs/Ni offers excellent electrical conductivity. • The CoS x /NCNTs/Ni exhibits outstanding ORR/OER performance and realizes the potential for application on zinc-air batteries. The slow kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remain the primary problem impeding the commercialization of zinc-air batteries (ZABs). Herein, we demonstrate a hybrid composite consisting of multivalent CoS x nanoparticles and nitrogen-doped carbon nanotubes catalytically active-nickel (NCNTs/Ni) as an advanced ORR/OER electrocatalyst with excellent electrocatalytic activity. The Co-N bonds in the hybrid catalyst effectively enhance interfacial charge transfer, resulting in synergetic effects for enhanced oxygen electrochemistry. The optimized hybrid, CoS x /NCNTs/Ni-2, affords excellent performance in an alkaline ZAB, achieving a high-power density of 131 mW cm−2, and the voltage gap remained at only 0.87 V after 200 h of continuous charge–discharge at 5 mA cm−2. This study provides a facile strategy for the construction of bifunctional hybrids with non-precious metals for potential application in ZABs and other sustainable energy conversion devices. [ABSTRACT FROM AUTHOR]