CoNi alloys with slight oxidation@N,O Co-doped carbon: enhanced collective contributions of cores and shells to multifunctional electrocatalytic activity and Zn–air batteries

Abstract

This work develops CoNi alloys with slight oxidation@N,O co-doped carbon (NOC) as multifunctional catalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and Zn–air batteries. Their outer NOC shells have direct contributions to ORR, OER and HER activity that is dominated by N and O dopants that closely correlate with active adjacent C atoms. Meanwhile, the inner cores (CoNi alloys with slight oxidation) can provide indirect and important contributions. Relying on enhanced collective contributions of outer NOC shells and inner cores that are tuned by Co/Ni molar ratios, CoNi(1 : 1)-TB-800N₂ with a Co/Ni molar ratio of 1 : 1 affords optimized multifunctional activity. Furthermore, it also brings about optimal Zn–air battery performance: ∼98.6% and ∼74.8% of theoretical specific capacity and energy density, respectively, and more than 100 h of stable charge–discharge operation at high current densities.