Enhanced carrier separation and increased electron density in 2D heavily N-doped ZnIn2S4 for photocatalytic hydrogen production

Abstract

Element doping is an effective approach to modify photocatalysts for boosting solar H₂ evolution, especially anion doping. However, there still exists controversy regarding the role of heavy doping in photocatalysis. Herein, 2D heavily N-doped ZnIn₂S₄ is reported based on an in-depth perspective on the role that N heteroatoms play in improving the photocatalytic properties. The electron dynamics was investigated via femtosecond transient absorption spectroscopy which revealed that the introduction of N doping in ZnIn₂S₄ provides a strong electron aggregation ability for improving the efficiency of charge separation. Meanwhile, the increased valence band width and the elevated conduction band, respectively, promote the mobility of holes and provide more reductive photogenerated electrons. As a result, 2D heavily N-doped ZnIn₂S₄ exhibited superior photocatalytic hydrogen production compared to the pristine ZnIn₂S₄. The optimal hydrogen evolution rate is 11 086 μmol g⁻¹ h⁻¹ under visible light irradiation. This work contributes to the improvement of photocatalytic performance in 2D ZnIn₂S₄ and provides an in-depth understanding of heteroatom doped photocatalysts.