Construction of an Ultrathin S‐Scheme Heterojunction Based on Few‐Layer g‐C3N4 and Monolayer Ti3C2Tx MXene for Photocatalytic CO2 Reduction

As charge carriers transfer is critical for the photocatalytic activity enhancement of step‐scheme (S‐scheme) photocatalysts, facile construction of a S‐scheme heterojunction with great contact area and strong interaction between the compositions is highly desirable. Herein, an ultrathin S‐scheme heterojunction g‐C 3 N 4 /TiO 2 /C (SL‐EAC) consisting of few‐layer g‐C 3 N 4 nanosheets on monolayer Ti 3 C 2 T x MXene converted TiO 2 /C is prepared through an electrostatic self‐assembly and calcination method. The monolayer Ti 3 C 2 T x can not only prevent g‐C 3 N 4 from agglomerating through forming close contact with g‐C 3 N 4 , but its conversion to TiO 2 /C during calcination can build a bridge between the relatively inert TiO 2 and multigroup‐terminated Ti 3 C 2 T x , which indirectly enhances the interface contact between TiO 2 /C and g‐C 3 N 4 . SL‐EAC with a thickness of around 5 nm shows much better photocatalytic CO 2 reduction performance than g‐C 3 N 4 , TiO 2 /C prepared by calcination of monolayer Ti 3 C 2 T x and g‐C 3 N 4 /TiO 2 /C (EAC) prepared by the same method but monolayer Ti 3 C 2 T x is altered by multilayer Ti 3 C 2 T x . The excellent performance of SL‐EAC is attributed to the large contact area between g‐C 3 N 4 and TiO 2 /C, which is conducive to the S‐scheme transfer of photogenerated charge carriers. Moreover, the samples prepared using different methods are also investigated, which further confirms the great contact area and strong interaction between the composites in ultrathin SL‐EAC.