We studied the growth of epitaxial ferroelectric layers of BaTiO3/Pt­(001) in the framework of solar water splitting. The stoichiometry, that is, the Ti/Ba ratio, appears as a crucial parameter not only for the crystallographic structure but also for the photocurrent generation when the sample is used as a photoanode. We established an electrochemical poling method using a modulated potential, without altering the sample to control the electric polarization. Importantly, we show that the photoanode efficiency is improved when the polarization of the film is oriented toward the substrate. We demonstrate that this improvement is only due to the electrical field created by screening charges, which allows the separation of photogenerated charges.

Density functional theory calculations are performed to study the out-of-plane polarisation in BaTiO3 (BTO) thin films epitaxially grown on platinum.