Boosting Charge Separation in a CdIn2S4/Mo2TiC2 MXene Schottky Heterojunction for Enhanced Photocatalytic Hydrogen Production

Abstract

Mo₂TiC₂ MXene was exfoliated in situ using hydrofluoric acid solution and subsequently integrated with CdIn₂S₄ through physical stirring and grinding. The composite material demonstrated exceptional photocatalytic hydrogen evolution (PHE) activity without the loading of any noble metal co-catalysts, achieving a hydrogen production rate as high as 3.35 mmol·h⁻¹ g⁻¹. This represents a 55.83-fold enhancement compared to pristine CdIn₂S₄ and surpasses the performance of most reported CdIn₂S₄-based photocatalytic materials. Furthermore, the composite material maintained consistent hydrogen evolution performance throughout four consecutive cycling tests, demonstrating excellent cycling durability. Through systematic experimental analysis and theoretical simulations, it was confirmed that a Schottky heterojunction forms between CdIn₂S₄ and Mo₂TiC₂ MXene. In this composite system, CdIn₂S₄ primarily serves as the light-absorbing component, whereas Mo₂TiC₂ MXene functions as an efficient co-catalyst. The formation of the Schottky junction drives the directional migration of photogenerated electrons from CdIn₂S₄ to Mo₂TiC₂ MXene. The resulting interfacial potential barrier significantly suppresses electron backflow, whereas the inherent high electrical conductivity of Mo₂TiC₂ MXene and its abundant exposed active sites further accelerate the hydrogen evolution process. This study demonstrates the significant potential of Mo₂TiC₂ MXene as a novel co-catalyst for photocatalysis oriented toward renewable energy.