Enhanced CdS quantum dots loading density and charge transport by Sn4+ doping improve the photoelectrochemical performance of TiO2 nanosheets with highly exposed {001} facets

Abstract

In this paper, the Sn4+ doping has been demonstrated to be an effective strategy to fundamentally enhance the photon absorption, improve the charge transport and increase the surface quantum-dots loading density of TiO2 nanosheets with highly exposed {001} facets, thereby improve their photoelectrochemical performance. The Sn4+ doped TiO2 (STO) nanosheet arrays with different doping concentrations are prepared by a facile one-pot hydrothermal method. And the STO nanosheet arrays (9 mM) enhance light absorption and decrease electron transport resistance, thus improving the photoelectrochemical properties due to the generation of doping energy level and mixed-cation composition of SnxTi1-xO2. Furthermore, after sensitizing CdS quantum-dots, the light absorption intensity of the CdS/STO films increases and the light absorption range extends to visible light region. Remarkably, compared to the pristine TiO2 NSs, the amount of surface active reaction sites of STO NSs increases arising from Sn4+ doping process, which is beneficial to sensitize more uniform and dense CdS quantum-dots on the surface of STO NSs, thereby increasing the heterojunction areas and enhancing the visible light absorption. Additionally, the CdS/STO photoelectrodes show the maximum photocurrent density of 5.71 mA cm−2 at 0 V versus Ag/AgCl, which is 11.4 and 1.7 times higher than those of TiO2 and CdS/TiO2 photoelectrodes respectively, due to the enhanced visible light absorption ability, increased heterojunction areas and superior photogenerated charge carrier separation and transport properties.