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

Abstract

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‐C3N4/TiO2/C (SL‐EAC) consisting of few‐layer g‐C3N4 nanosheets on monolayer Ti3C2Tx MXene converted TiO2/C is prepared through an electrostatic self‐assembly and calcination method. The monolayer Ti3C2Tx can not only prevent g‐C3N4 from agglomerating through forming close contact with g‐C3N4, but its conversion to TiO2/C during calcination can build a bridge between the relatively inert TiO2 and multigroup‐terminated Ti3C2Tx, which indirectly enhances the interface contact between TiO2/C and g‐C3N4. SL‐EAC with a thickness of around 5 nm shows much better photocatalytic CO2 reduction performance than g‐C3N4, TiO2/C prepared by calcination of monolayer Ti3C2Tx and g‐C3N4/TiO2/C (EAC) prepared by the same method but monolayer Ti3C2Tx is altered by multilayer Ti3C2Tx. The excellent performance of SL‐EAC is attributed to the large contact area between g‐C3N4 and TiO2/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.