Synergistic effect of oxygen species and vacancy for enhanced electrochemical CO2 conversion to formate on indium oxide

Abstract

Indium-based oxides are promising electrocatalysts for producing formate via CO2 reduction reaction, in which ∗OCHO is considered the key intermediate. Here, we identified that the ∗COOH pathway could be preferential to produce formate on In2O3 of In/In2O3 heterojunction due to the synergistic effect of oxygen species and vacancy. Specifically, ∗CO2 and ∗COOH were observed on In2O3 and related to formate production by in situ Raman spectroscopy. The theoretical calculations further demonstrated that the energy barrier of the ∗COOH formation on In2O3 was decreased in the presence of oxygen vacancy, similar to or lower than that of the ∗OCHO formation on the In surface. As a result, a formate selectivity of over 90% was obtained on prepared In/In2O3 heterojunction with 343 ​± ​7 ​mA ​cm−2 partial current density. Furthermore, when using a Si-based photovoltaic as an energy supplier, 10.11% solar–to–fuel energy efficiency was achieved.

Keywords

• Electrocatalytic CO2 reduction
• Formate
• In2O3
• Oxygen species
• Oxygen vacancy