Indium oxide with oxygen vacancies boosts O 2 adsorption and activation for electrocatalytic H 2 O 2 production.

Oxygen reduction reaction via the two-electron pathway (2e - ORR) offers a sustainable opportunity for hydrogen peroxide (H 2 O 2 ) production, but suffers from low selectivity. In this work, indium oxide with oxygen vacancies (In 2 O 3- x ) exhibits a H 2 O 2 selectivity close to 98% at 0.6 V vs. RHE. Further, a Faradaic efficiency (FE) of around 95% at 0.4-0.6 V vs. RHE and a H 2 O 2 productivity of 3.7 mol g catalyst -1 h -1 are reached in a flow cell. In situ Raman spectra indicate that In 2 O 3- x promotes the adsorption and activation of O 2 and stabilizes oxygen intermediates. This work provides an insight into improving H 2 O 2 selectivity for 2e - ORR catalysts.