Heterostructured quantum dot architectures for efficient and stable photoelectrochemical hydrogen production

The long term stability of photoelectrochemical (PEC) devices based on colloidal quantum dots (QDs) for hydrogen production is a major challenge. The degradation is often caused by the self-oxidation of QDs induced by the excess accumulation of holes in the valance band. Here, we use heterostructured "giant" core/alloyed-shell CdSe/PbxCd1-xS/CdS QDs to sensitize TiO2 mesoporous films for PEC hydrogen production. Transient fluorescence analysis results show that the use of a PbxCd1-xS gradient layer leads to a three-fold increase in the hole transfer rate compared to a pure CdS shell with similar shell thickness. The as-prepared PEC cell using alloyed shell "giant" QDs exhibits an enhanced photocurrent density of 10.2 mA cm-2 (97 mL per cm2 per day) under one sun illumination (100 mW cm-2). The PEC cell based on alloyed shell "giant" QDs shows an enhanced PEC device stability, with retention of ∼94.9% of its initial photocurrent after 2 h under one sun illumination. This finding provides unique insights to improve the stability and functional performance of PEC devices in which the photoanode is sensitized using colloidal "giant" QDs.