Enhanced photoelectrochemical water-splitting performance of TiO2 nanorods sensitized with CdS via hydrothermal approach

Abstract

In the photoelectrochemical (PEC) water splitting for the hydrogen production, the fabrication of a stable and efficient photocatalyst semiconductor remains a challenge. CdS, which is one of most used chalcogenide materials, coupled with metal oxide semiconductor exhibit a generally low durability. TiO2 nanorods arrays (TNR) sensitized with CdS were synthesized via hydrothermal method and denoted as TNR-CdS. CdS deposition on TNR surface was controlled by regulating the hydrothermal reaction time. The samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electronmicroscopy, X-ray photoelectron spectroscopy, and UV-visible absorption. A high PEC performance as well as a great CdS sensitized TNR photoanodes stability were exhibited. These results could be due to the intimate contact between CdS and TNR, favoring a fast separation of photogenerated charge carriers. The optimal PEC performance was achieved when CdS was deposited on TNR for 10 h. Under AM 1.5G illumination at applied potential of 0 V vs Ag/AgCl, TNR-CdS (10 h) is found to have a photocurrent density of 6.5 mA/cm2 against 2.25 mA/cm2 for TNR. Additionally, TNR-CdS (10 h) presented a photoconversion efficiency of 2.5% at −0.4 V vs Ag/AgCl, while that of TNR was 0.9% at-0.35 V vs Ag/AgCl. TNR-CdS showed great stability with and without sacrificial reagent. These results were confirmed by electrochemical impedance spectroscopy measurements, where the rapid transfer/transport and separation of photogenerated charge carriers were highlighted.