Abstract
Doping engineering is an effective strategy to improve the electrocatalytic activity of manganese oxides by enhancing their poor electrical conductivity and oxygen adsorption capacity. Herein, p-block aluminum group metal ions (Al3+, Ga3+, and In3+) are introduced into cryptomelane-type manganese oxide octahedral molecular sieves (OMS-2), leading to p−d orbital hybridization between the p-orbitals of the aluminum group metals and d-orbitals of Mn, facilitating the oxygen reduction reaction. The aluminum group metal-doped OMS-2 exhibits excellent catalytic activity, rapid reaction kinetics, and favorable stability compared to commercial Pt/C. Among the three prepared catalysts, Ga-doped OMS-2 (Ga-OMS-2) has stronger oxygen reduction activity. Experimental and theoretical calculations show that the superiority of Ga-OMS-2 is attributed to p−d hybridization, which enriches the reaction sites and enhances the binding strength of the catalyst to the O2 reaction intermediates. As a proof of concept, Zinc−air batteries assembled with Ga-OMS-2 as a catalyst exhibit superior power density and cycle life to commercial Pt/C. This p−d hybridization strategy gives insight into 2 the p-block metal doping of catalysts prepared with other transition metals with excellent electrocatalytic activity and durability for energy storage and conversion.