Wrinkle-free atomically thin CdS nanosheets for photocatalytic hydrogen evolution

Two-dimensional (2D) nanosheets of atomic thickness have attracted extensive research interest recently. In this work, atomically thin (0.7 nm) flat CdS (F-CdS) nanosheets of several tens of micrometers in lateral size were synthesized by a solvent-thermal method. The as-synthesized F-CdS could maintain flat morphology well in solution, while irreversible wrinkles could be generated after drying, forming wrinkled CdS (W-CdS) samples. It was revealed that the formation of wrinkles could reduce light absorbance, narrow the band gap, move down the conduction band position and accelerate electron-hole recombination. As photocatalysts, the F-CdS achieved a photocatalytic H-2 evolution rate of 138.7 mmol g(-1) h(-1) without any co-catalyst under visible light, which was much higher than that of the W-CdS sample (with an H-2 evolution rate of only 52.8 mmol g(-1) h(-1)). This work demonstrates that great attention should be paid to the wrinkles in 2D materials as photocatalysts.