Oxygen-vacancy-type Mars-van Krevelen mechanism drives ultrafast dioxygen electroreduction to hydrogen peroxide

The electrochemical oxygen reduction reaction (ORR) along a two-electron transfer pathway has been considered as an eco-friendly route for producing hydrogen peroxide (H2O2). However, large-scale industrial application of this ORR technology calls for ultrafast and effective generation of H2O2 under operating conditions (current densities >1 A/cm(2) and Faradaic efficiency approximate to 100%). This imposes strict criteria for exploring innovative strategies for enhancing the adsorption and activation of O-2 under vigorous reaction condition, which represents a significant challenge thus far. Here, we report an 'oxygen-vacancy-type' Mars-van Krevelen mechanism for promoting ORR. Our theoretical calculations show that the structural oxygen vacancies of zinc oxide catalysts effectively alter the electron densities of nearby metal active sites, producing a more electron-deficient Zn center, which, in turn, assists the adsorption and activation of O-2. A catalyst electrode designed as that exhibits superior ORR activities with a Faradaic efficiency of 98.1% at a current density of 1 A/cm(2) (H2O2 yield rate of 621.88 mg/h/cm(2)). Further mechanism study has been performed through in situ Raman spectroscopy to monitor the adsorption and activation of oxygen intermediate (& lowast;O-2) of ORR, providing additional experimental evidence for the Mars-van Krevelen mechanism.(c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

This study reports a novel oxygen-vacancy-type Mars-van Krevelen mechanism for promoting the electrochemical oxygen reduction reaction (ORR). The structural oxygen vacancies of zinc oxide catalysts effectively alter the electron densities of nearby metal active sites, facilitating the adsorption and activation of O-2. Experimental results demonstrate that the catalyst electrode designed based on this mechanism exhibits superior ORR activities with high Faradaic efficiency.