In situ grown two-dimensional TiO2/Ti3CN MXene heterojunction rich in Ti3+ species for highly efficient photoelectrocatalytic CO2 reduction

Converting CO2 into chemicals is a promising avenue to mitigate the energy crisis and global warming. Herein, two-dimensional (2D) heterojunctions of TiO2/Ti3CN MXene were fabricated through a facile hydrothermal oxidation method and used as the photocathode in photoelectrocatalytic (PEC) CO2 reduction. The in situ grown TiO2/Ti3CN heterojunctions demonstrate excellent light absorption abilities, possess large specific surface areas and Ti3+ species, which are beneficial to the generation and transportation of photoelectron-hole pairs. In a new PEC system of Pd@TiO2/Ti3CN||SCE||BiVO4, formate, methanol and C2 of ethanol were obtained as the major reduction products, with the maximum and total formation rate of 45.6 μM cm−2h−1. Furthermore, density functional theory (DFT) calculations indicate that TiO2/Ti3CN heterojunction can spontaneously activate CO2 and stabilize the key reaction intermediates for facilitating HCOOH production. This research highlights the great prospect of titanium carbonitrides MXene in the green energy conversion field.