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

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. The introduction of Ag nanoparticles and CHNTs to MnO2can alter the pathway mechanism from a two-electron to a direct four-electron pathway for ORR, which is the nature of the remarkable enhancement of the electrocatalytic activity over Ag/MnO2-CHNTs. [Display omitted] •Ag nanoparticles and CHNTs can trigger construction of oxygen defects in the MnO2.•Triggering manganese dioxide defects boosts a direct four-electron direction for ORR.•Synergistic interaction between MnO2, Ag and CHNTs promote ORR activity.•Ag/MnO2-CHNTs displays superior stability and methanol tolerance compared with Pt/C.