Spontaneous reduction of copper on Ti3C2Tx as fast electron transport channels and active sites for enhanced photocatalytic CO2 reduction

• Cu cluster were successfully loaded on the surface of Ti 3 C 2 T x nanosheets by self-reduction. • The Cu cluster and Ti 3 C 2 T x acted as the fast transport channels for the photogenerated electrons. • The interface between Cu cluster and Ti 3 C 2 T x acted as the active sites for the adsorption and activation of CO 2 . • The photocatalytic CO 2 reduction performance of g-C 3 N 4 was greatly enhanced with Cu-Ti 3 C 2 T x as the cocatalyst. Graphitic carbon nitride (g-C 3 N 4 ) is regarded as a promising photocatalyst for photocatalytic CO 2 reduction into valuable solar fuels. In this work, Cu-Ti 3 C 2 T x was used as efficient cocatalysts to enhance the photocatalytic performance of g-C 3 N 4 . The tight interface between Cu-Ti 3 C 2 T x and g-C 3 N 4 significantly promote the separation of photogenerated electrons and holes. In addition, the Cu and the Ti 3 C 2 T x can act as the fast transport channels for the photogenerated electrons, and the interface between the Cu and Ti 3 C 2 T x can act as the active sites for the adsorption and activation of CO 2 . The optimized Cu-Ti 3 C 2 T x /g-C 3 N 4 exhibited the highest photocatalytic CO 2 reduction performance with the yield of CO and CH 4 reached 49.02 and 3.6 μmol·g −1 , respectively, which was 9.0 and 9.2 times than that of pristine g-C 3 N 4 . Moreover, the optimized Cu-Ti 3 C 2 T x /g-C 3 N 4 photocatalyst maintained satisfactory stability. This work will offer new insight into modulating g-C 3 N 4 with an MXene-metal-based cocatalyst for photocatalytic CO 2 reduction.