Laser flash photolysis study of Nb₂O₅/g-C₃N₄ heterostructures as efficient photocatalyst for molecular H₂ evolution

Improvements of visible light activity, slow recombination rate, stability, and efficiency are major challenges facing photocatalyst technologies today. Utilizing heterostructures of g-C₃N₄ (bandgap ∼2.7eV) with Nb₂O₅ (bandgap ∼3.4eV) as an alternative materials for the first time, we tried to overcome such challenges in this work. Heterostructures of Nb₂O₅/g-C₃N₄ have been synthesized via hydrothermal technique. And then a time-resolved laser flash photolysis of those heterostructures has been analyzed, focusing on seeking how to improve photocatalytic efficiency for molecular hydrogen (H₂) evolution. The transient absorption spectra and the lifetime of charge carriers at different wavelengths have been observed for Nb₂O₅/g-C₃N₄, where g-C₃N₄ was used for a control. The role of hole scavenger (methanol) has also been investigated for the purpose of boosting charge trapping and H₂ evolution. The long lifetime of Nb₂O₅/g-C₃N₄ heterostructures (6.54165 μs) compared to g-C₃N₄ (3.1651897 μs) has successfully supported the increased H₂ evolution of 75 mmol/h.g. An enhancement in the rate of H₂ evolution (160 mmol/h.g) in the presence of methanol has been confirmed. This study not only deepens our understanding of the role of scavenger, but also enables a rigorous quantification of the recombination rate crucial for photocatalytic applications in relation with efficient H₂ production.