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

PEC devices are fabricated using 1D TiO 2 nanotubes and sensitized with QDs through a simple and low-cost solution-based process. Furthermore, an optimized nanoscale p-n heterojunction is employed using CuSe treatment to enhance the carrier dynamics. Finally, A detailed investigation is conducted on each parameter that affecting the PEC device performance. • Self-organized TiO 2 NTs/QDs photoanodes are fabricated for PEC water splitting. • Surface engineering through p-n heterojunction improves the device performance. • KPFM is used to investigate the surface potential enhancement of the photoanode. • PEC device performance is investigated by changing NTs length. Photoelectrochemical (PEC) water splitting is a promising approach to convert solar radiation into hydrogen (H 2 ) 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 TiO 2 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 TiO 2 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 TiO 2 NTs only (i.e., 0.08 mA.cm −2 ) and 7 times compared to TiO 2 /QDs nanoparticles (NPs) (i.e. 0.45 mA.cm −2 ) under one sun illumination. The p-type CuSe coating over the TiO 2 /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 TiO 2 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.