Type-II Band Alignment Enhances Unassisted Photoelectrochemical Water-Splitting Performance of the BaTiO<sub>3</sub>/CdS Ferroelectric Heterostructure Photoanode under Solar Light Irradiation
Tianci Fang, Hong Hu, Jie Liu, Meng Jiang, Sibo Zhou, Junli Fu, Wenzhong Wang, Yuping Yang
Abstract
Here, we first use CdS nanoparticles to sensitize ferroelectric BaTiO3 nanostructures to construct the BaTiO3/CdS heterostructure photoanodes by a facile hydrothermal method and subsequent successive ionic layer adsorption and reaction. Combining the measurements of the valence band and core-level X-ray photoelectron spectroscopy spectra with energy band calculation, the type-II energy structure established at the BaTiO3 and CdS interface is confirmed. Benefiting from the type-II band alignment of the heterostructures, the spontaneous polarization electric field induced by BaTiO3, and the remarkable visible light absorption ability of CdS, the as-prepared BaTiO3/CdS heterostructure photoanode exhibits significantly improved and stable photoelectrochemical water-splitting activity. The highest photocurrent density of the constructed BaTiO3/CdS heterostructure photoanode with optimized CdS nanoparticle loading reaches up to 0.5 mA cm–2 at 0 V versus Ag/AgCl, which is about 12-fold that of the pure BaTiO3 photoanode. Additionally, the solar-to-hydrogen conversion efficiency of the BaTiO3/CdS heterostructure photoanode is 0.48% at 0.13 V versus reversible hydrogen electrode, 24-fold that of the bare BaTiO3 photoanode. In contrast with the photoelectrochemical performance of the other reported BaTiO3-based heterostructure photoanodes, the photocurrent density (0 V versus Ag/AgCl) and the solar-to-hydrogen conversion efficiency (0.13 V versus reversible hydrogen electrode) achieved by the present BaTiO3/CdS photoanode are the highest.