Constructing quantum dots sensitized TiO2 nanotube p-n heterojunction for photoelectrochemical hydrogen generation

Photoelectrochemical (PEC) water splitting is a promising approach to convert solar radiation into hydrogen (H2) as a clean fuel. The PEC device performance depends on the light harvesting efficiency of the photoanode and the carrier dynamics (i.e. separation/transport rate) at the photoanode/electrolyte interface. Herein, we report a photoanode architecture consisting of self-organized TiO2 nanotubes (NTs) sensitized by CdS/CdSe quantum dots (QDs) and treated with a Cu-based solution to create a p-n heterojunction. Our results demonstrate that the TiO2 NTs/QDs PEC device yields a photocurrent density of 4.18 mA.cm−2 at 0.5 V vs RHE, which is 51 times higher than the device based on TiO2 NTs only (i.e., 0.08 mA.cm−2) and 7 times compared to TiO2/QDs nanoparticles (NPs) (i.e. 0.45 mA.cm−2) under one sun illumination. The p-type CuSe coating over the TiO2/QDs NTs photoanodes forms a p-n heterojunction that improves the carrier dynamics. The resulting PEC device shows a 13% improvement in the photocurrent density. In addition, employing longer TiO2 NTs improves the device's stability. Our results offer a simple and scalable method for the design and optimization of the photoanodes to enhance the performance of PEC and other optoelectronic devices.