Three-dimensional S-scheme heterojunction by integration of purple tungsten oxide nanowires and cadmium sulfide nanospheres for effective photocatalytic hydrogen generation.

The practical photocatalytic application of cadmium sulfide (CdS) has been significantly constrained by fast carrier recombination and significant photocorrosion. Therefore, we developed a three-dimensional (3D) step-by-step (S-scheme) heterojunction using the coupling interface between purple tungsten oxide (WO) nanowires and CdS nanospheres. The photocatalytic hydrogen evolution rate of optimized WO/CdS 3D S-scheme heterojunction can reach 9.7 mmol·h·g, 7.5 and 16.2 times greater than pure CdS (1.3 mmol·h·g) and 10 wt%-WO/CdS (mechanical mixing, 0.6 mmol·h·g), proving that the tight S-scheme heterojunction constructed by the hydrothermal method can efficiently enhance the carrier separation. Notably, the apparent quantum efficiency (AQE) of WO/CdS 3D S-scheme heterojunction approaches 7.5% and 3.5% at 370 nm and 456 nm, respectively, which is 7.5 and 8.8 times than pure CdS (1.0% and 0.4%). The produced WO/CdS catalyst also has relative stability of structure and hydrogen production. Additionally, the H evolution rate of WO/CdS 3D S-scheme heterojunction is 1.2 times greater than 1 wt%-platinum (Pt)/CdS (8.2 mmol·h·g), which indicates that the WO can effectively replace the precious metal for boosting the hydrogen production rate.