Enhancing O2 electroreduction to H2O on Ag/MnO2-CHNTs by boosting a four-electron catalytic pathway

Abstract

A fundamental question in the oxygen reduction reaction (ORR) is how to rationally control the electrocatalytic selectivity for opening a four-electron reaction pathway. However, it still lacks direct experimental evidence to understand the reaction mechanism. This work unravels that Ag nanoparticles and carbonizing halloysite nanotubes (CHNTs) can trigger the construction of oxygen defects in the MnO₂, which contribute to the generation of active sites. The Ag/MnO₂-CHNTs delivers a superior activity toward ORR with high onset potential, half-wave potential, diffusion-limited current density, long-term durability and methanol tolerance. More importantly, combined with density functional theory calculations, triggering manganese dioxide defects upon the introduction of Ag nanoparticles and CHNTs can alter the electrocatalytic pathway from a two-electron to a direct four-electron direction for ORR, which is the nature of enhanced ORR activity. Based on the analysis of the results, this finding points out a very effective approach for exploring catalysts with the improved performance and durability for ORR reaction.