Enhanced Photocatalytic Hydrogen Production of ZnIn2S4 by Using Surface-Engineered Ti3C2Tx 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, Ti3C2Tx (Tx = 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 Ti3C2(OH)x and Ti3C2Ox cocatalysts were synthesized through the alkalization treatment with NaOH and a mild oxidation treatment of Ti3C2Fx, respectively. ZnIn2S4/Ti3C2Tx composites, which were fabricated by the in-situ growth of ZnIn2S4 nanosheets on the Ti3C2Tx surface, exhibited the promoted photocatalytic performance, compared with the parent ZnIn2S4. The enhanced photocatalytic performance can be further optimized through the surface functionalization of Ti3C2Fx. As a result, the optimized ZnIn2S4/Ti3C2Ox composite with oxygen functionalized Ti3C2Ox cocatalyst demonstrated excellent photocatalytic hydrogen evolution activity. The characterizations and density functional theory calculation suggested that O-terminated Ti3C2Ox 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 ZnIn2S4 and Ti3C2Ox. This work paves the way for photocatalytic applications of MXene-based photocatalysts by tuning their surface termination groups.