Mechanisms of carbon dioxide reduction on strontium titanate perovskites

Abstract

Strontium titanate (SrTiO₃) is a promising material for the light-driven conversion of carbon dioxide (CO₂) into renewable fuels. However, the mechanisms of the relevant reactions are not yet well understood. In this work, we have used density functional theory calculations to explore CO₂ reduction on the (001) surface of the SrTiO₃ photocatalyst. Our results indicate that, in contrast to COOH, the formation of a HCOO or CO₂⁻ intermediate is thermodynamically hindered, which is consistent with the fact that formic acid (HCOOH) is not a major product in the experiments reported in the literature. We show that a pathway to carbon monoxide (CO) is instead possible, and that the formation of COOH is the rate-limiting step. Finally, we suggest that substitutional doping of Sr ions represents a promising approach to lower the energy barrier of the COOH formation.