The effect of small molecular linkers on the solar driven photoelectrochemical hydrogen production performance of CdS quantum dot-sensitized TiO2 photoanodes

In the pursuit of highly efficient hydrogen production through photoelectrochemical water splitting, expanding the utilization of the visible spectrum and extending the lifetime of photogenerated electrons are crucial challenges for improving the efficiency. To address these challenges, we prepared CdS sensitized TiO 2 photoanodes using a one-step hydrothermal method, employing thioglycolic acid (TGA) and mercaptopropionic acid (MPA) as linkers. The successful synthesis of CdS QDs and the CdS/TiO 2 photoanode was confirmed through various characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction, and scanning electron microscopy. Performance evaluations revealed that the TGA-decorated CdS/TiO 2 photoanode exhibited superior photocurrent density and stability compared to the MPA-modified counterpart. Notably, its applied bias photo-to-current conversion efficiency was 1.7 times greater than that of the MPA-modified CdS/TiO 2 photoanode. Furthermore, UV–visible absorption spectrum analysis demonstrated that the incorporation of CdS QDs significantly broadened the spectral response of the TiO 2 photoanode, extending it from the ultraviolet to the visible range. This enhancement is crucial for improving light harvesting capabilities. Additionally, our analysis of electron lifetime indicated that the shorter molecular chains of TGA effectively minimize the transfer distance for photogenerated electrons from the CdS QDs to the TiO 2 , resulting in improved electron lifetimes and, consequently, enhanced photocurrent density.