Enhanced Photocatalytic Hydrogen Production of ZnIn 2 S 4 by Using Surface-Engineered Ti 3 C 2 T x MXene as a Cocatalyst.

Developing efficient and stable photocatalysts is crucial for photocatalytic hydrogen production. Cocatalyst loading is one of the effective strategies for improving photocatalytic efficiency. Here, Ti 3 C 2 T x (T x = F, OH, O) nanosheets have been adopted as promising cocatalysts for photocatalytic hydrogen production due to their metallic conductivity and unique 2D characterization. In particular, surface functionalized Ti 3 C 2 (OH) x and Ti 3 C 2 O x cocatalysts were synthesized through the alkalization treatment with NaOH and a mild oxidation treatment of Ti 3 C 2 F x , respectively. ZnIn 2 S 4 /Ti 3 C 2 T x composites, which were fabricated by the in-situ growth of ZnIn 2 S 4 nanosheets on the Ti 3 C 2 T x surface, exhibited the promoted photocatalytic performance, compared with the parent ZnIn 2 S 4 . The enhanced photocatalytic performance can be further optimized through the surface functionalization of Ti 3 C 2 F x . As a result, the optimized ZnIn 2 S 4 /Ti 3 C 2 O x composite with oxygen functionalized Ti 3 C 2 O x cocatalyst demonstrated excellent photocatalytic hydrogen evolution activity. The characterizations and density functional theory calculation suggested that O-terminated Ti 3 C 2 O x could effectively facilitate the transfer and separation of photogenerated electrons and holes due to the formation of a Schottky junction, with the largest difference in work function between ZnIn 2 S 4 and Ti 3 C 2 O x . This work paves the way for photocatalytic applications of MXene-based photocatalysts by tuning their surface termination groups.