Quantum dots (QDs) sensitized metal oxides are considered as promising photoelectrodes for efficient and low-cost photoelectrochemical (PEC) hydrogen generation. However, harsh environments with extreme temperature can largely affect the PEC performance under an unclear mechanism. In this work, the temperature effect on PEC performance as well as dynamic behavior of the charge carriers were systematically investigated by using a CdSe/CdSexS1–x/CdS alloyed QDs/TiO2 as photoelectrode. The results show that the PEC performance is impacted drastically by the temperature with the variation on the saturated current density ranging from 2.6 to 14.2 mA/cm2 under 1 sun illumination (AM 1.5 G, 100 mW/cm2). In a similar fashion, the carrier dynamics of alloyed QDs based anodes under different temperatures is also strongly affected. At low temperatures (from −20 to 0 °C), the electrons transfer was slowed down, leading to the lower PEC performance, while at higher temperatures (from 30 to 60 °C), the electron transfer rate increased, leading to more efficient carrier separation and transfer. As a result, the saturated current density increased. However, when the temperature reached 60 °C, the surface of the QDs was damaged, causing an irreversible deterioration of PEC performance.
