Amorphization-crystallization synergism on MoSx homojunction for boosting photocatalytic H2 production of TiO2 in alkaline medium

Low-cost molybdenum sulfide (MoS2) has been widely regarded as a potential H2-production cocatalyst for various photocatalysts. However, compared with neutral or acidic medium, MoS2 cocatalyst generally exhibits a very limited H2-production activity in alkaline medium owing to the complex progress, including the H2O adsorption and activation, OH desorption and evolution of hydrogen. In this study, an amorphous-crystalline MoSx homojunction (ac-MoSx) is synthesized and anchored on TiO2 surface to greatly enhance its photocatalytic hydrogen production efficiency in alkaline medium. Herein, the ratio of amorphous to crystalline MoSx phase in the ac-MoSx homojunction can be regulated by controlling the calcination temperature (100–700 °C). Photocatalytic results show that the resultant ac-MoSx/TiO2(300 °C) has the highest hydrogen-production activity (3.43 mmol h−1 g−1, AQE = 16.3 %) in alkaline medium, which is higher compared to that of a-MoSx/TiO2 by 4 times. An amorphization-crystallization synergism of MoSx homojunction was proposed for the improved photocatalytic hydrogen-production activity of TiO2 in alkaline medium, where the Mo atom of crystalline MoS2 can act as the excellent water-activation site, while the unsaturated S atom of amorphous MoSx works as the outstanding H2-evolution active center. This work offers a new and innovative strategy to construct highly-active alkaline H2-production catalysts in photocatalysis and electrochemistry fields.