Modulate the electronic structure of Cu₇S₄ nanosheet on TiO₂ for enhanced photocatalytic hydrogen evolution

TiO₂ is a promising photocatalyst due to its high thermodynamic stability and non-toxicity. However, its applications have been still limited because of the high recombination rate of electron–hole pairs. Herein, we show that by combining heterojunction construction and electronic structure regulation, the electron–hole pairs in TiO₂ can be effectively separated for enhanced photocatalytic hydrogen evolution. The optimized Cu₇S₄ nanosheet decorated TiO₂ achieves much enhanced H₂ evolution rate (11.5 mmol·g⁻¹·h⁻¹), which is 13.8 and 4.2 times of that of TiO₂ and Cu₇S₄/TiO₂, respectively. The results of photoluminescence spectroscopy, transient photocurrent spectra, ultraviolet–visible diffuse reflectance spectra, and electrochemical impedance spectroscopy collectively demonstrate that the enhanced photocatalytic performance of Air-Cu₇S₄/TiO₂ is attributed to the effective separation of charge carriers and widened photoresponse range. The electron paramagnetic resonance and X-ray photoelectron spectroscopy results indicate that the increase of Cu²⁺ in the Cu₇S₄ nanosheet after calcination can promote the charge transfer. This work provides an effective method to improve the electron migration rate and charge separation of TiO₂, which holds great significance for being extended to other material systems and beyond.