Establishing carrier transport channels based on TiS bonds and enhancing the photocatalytic performance of MXene quantum dots–ZnIn2S4 for ammonia synthesis

In the process of photocatalytic synthesis of ammonia, the kinetics of carrier separation and transport, adsorption of nitrogen, and activation of the NN triple bond are key factors that directly affect the efficiency of converting nitrogen to ammonia. Here, we report a new strategy for anchoring MXene quantum dots (MXene QDs) onto the surface of ZnIn₂S₄ by forming TiS bonds, which provide a channel for the rapid separation and transport of charge carriers and effectively extend the lifespan of photogenerated carriers. The unique charge distribution caused by the sulfurization of the MXene QDs further enhances the performance of the photocatalysts for the adsorption and activation of nitrogen. The photocatalytic ammonia synthesis efficiency of MXene QDs–ZnIn₂S₄ can reach up to 360.5 μmol g⁻¹ h⁻¹. Density functional theory calculations, various in situ techniques, and ultrafast spectroscopy are used to characterize the successful construction of TiS bonds and the dynamic nature of excited state charge carriers in MXene QDs–ZnIn₂S₄, as well as their impact on nitrogen adsorption activation and photocatalytic ammonia synthesis efficiency. This study provides a new example of how to improve nitrogen adsorption and activation in photocatalytic material systems and enhance charge carrier dynamics to achieve efficient photocatalytic nitrogen conversion.