Modulate the electronic structure of Cu 7 S 4 nanosheet on TiO 2 for enhanced photocatalytic hydrogen evolution

TiO 2 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 TiO 2 can be effectively separated for enhanced photocatalytic hydrogen evolution. The optimized Cu 7 S 4 nanosheet decorated TiO 2 achieves much enhanced H 2 evolution rate (11.5 mmol·g −1 ·h −1 ), which is 13.8 and 4.2 times of that of TiO 2 and Cu 7 S 4 /TiO 2 , 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-Cu 7 S 4 /TiO 2 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 Cu 2+ in the Cu 7 S 4 nanosheet after calcination can promote the charge transfer. This work provides an effective method to improve the electron migration rate and charge separation of TiO 2 , which holds great significance for being extended to other material systems and beyond.