Influence of TiO₂ crystallinity on TiO₂ nanotube confined CdS nanoparticles for photocatalytic hydrogen production

Crystallinity is recognized as an important parameter that influences the photocatalytic performance, meanwhile the confinement effect of TiO₂ nanotube is efficient to improve the activity. But how TiO₂ crystallinity affects the property of TiO₂ nanotube-based catalysts remains unclear. Here, CdS nanoparticles inside of various temperature treated TiO₂ nanotube (CdS-in-TiO₂NT) was obtained. With the increase of calcination temperature from 300 to 500 °C, the crystallinity of TiO₂ nanotube is increased resulting in the enhanced hydrogen evolution property of CdS-in-TiO₂NT. When the calcination temperature is higher than 500 °C, TiO₂ nanotube is gradually collapsed, which leads to the decrease of photocatalytic performance of CdS-in-TiO₂NT. Further photoluminescence measurements confirm that CdS-in-TiO₂NT-500 has most quenched PL emission, which is in accordance with the H₂ production efficiency. The highest hydrogen production rate of CdS-in-TiO₂NT-500 is ascribed to the efficient confinement effect, good crystallinity of TiO₂ nanotube, and accelerated charge separation efficiency.