Band bending and band alignment at reconstructed perovskite-electrolyte interfaces under applied voltage

Perovskite photoelectrodes have been extensively studied at the first-principles level in search for photocatalytic materials for hydrogen production through water splitting. The solar-to-fuel efficiency for these materials is critically dependent on the voltage-dependent restructuring of the electrode-electrolyte interface. Here, we develop an embedded quantum-mechanical method using the self-consistent continuum solvation (SCCS) model to predict the relation between band alignment and band bending at photoelectrochemical interfaces under electrical bias taking into account the polarization of the depletion region of the semiconductor electrode over length scales of thousands of nanometers. Using this comprehensive model, we calculated the voltage-dependent Schottky barriers and the full electrical response of various reconstructions of SrTiO₃ photoelectrodes. The results reveal that interfacial charge trapping exerts primary control on the Schottky barriers at the redox potentials of hydrogen and oxygen, thereby affecting the driving force for charge separation and charge transfer at SrTiO₃-water interfaces. Our results highlight the necessity to account for voltage-dependent interface reconstruction in assessing the photocatalytic activity of candidate perovskite materials.