Ti2CO2 MXene: a highly active and selective photocatalyst for CO2 reduction

Abstract

Photocatalytic reduction of carbon dioxide (CO₂) into hydrocarbons could promote the CO₂ utilization and retard the greenhouse effect, which has gained much attention. Due to high surface–bulk ratio, two-dimensional materials can be promising candidates for catalysis. In this study, by means of first-principles computations, we have investigated the reduction of CO₂ at the oxygen vacancy on MXene monolayers. Among Ti₂CO₂, V₂CO₂ and Ti₃C₂O₂, Ti₂CO₂ has exhibited the best catalytic performance for the reduction of CO₂. The reaction pathway CO₂ → HCOO → HCOOH was found to be favorable with an energy barrier of 0.53 eV. The energy barriers of the reaction pathways for other single-carbon organic products were much higher, indicating high selectivity for HCOOH. Moreover, we have proposed that CO and H₂ can introduce sufficient oxygen vacancies on O-terminated MXene. This study provides new insights into the design of catalysts for the reduction of CO₂ and further widens the applications of MXene-based materials.