Enhanced Oxygen Reduction Reaction Activity of Manganese Oxide via p−d Hybridization with Aluminum Group Element Dopants

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 the p-block metal doping of catalysts prepared with other transition metals with excellent electrocatalytic activity and durability for energy storage and conversion.