Type-II Band Alignment Enhances Unassisted Photoelectrochemical Water-Splitting Performance of the BaTiO₃/CdS Ferroelectric Heterostructure Photoanode under Solar Light Irradiation

Here, we first use CdS nanoparticles to sensitize ferroelectric BaTiO 3 nanostructures to construct the BaTiO 3 /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 BaTiO 3 and CdS interface is confirmed. Benefiting from the type-II band alignment of the heterostructures, the spontaneous polarization electric field induced by BaTiO 3, and the remarkable visible light absorption ability of CdS, the as-prepared BaTiO 3 /CdS heterostructure photoanode exhibits significantly improved and stable photoelectrochemical water-splitting activity. The highest photocurrent density of the constructed BaTiO 3 /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 BaTiO 3 photoanode. Additionally, the solar-to-hydrogen conversion efficiency of the BaTiO 3 /CdS heterostructure photoanode is 0.48% at 0.13 V versus reversible hydrogen electrode, 24-fold that of the bare BaTiO 3 photoanode. In contrast with the photoelectrochemical performance of the other reported BaTiO 3 -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 BaTiO 3 /CdS photoanode are the highest.