Tuning the in-built potential at the LaCoO3/SrTiO3 hetero-interface with atomic precision to boost photoelectrochemical water splitting activity

Constructing semiconductor heterojunctions is an effective approach to enhance the efficiency of photoelectrochemical (PEC) water splitting. The augmentation is mainly attained by taking advantage of interfacial in-built electronic band potential to promoter the separation and transport of photo-generated charge carriers. In this work, p-n heterojunction LaCoO₃/SrTiO₃ (LCO/STO) photoelectrodes with atomically-grown LCO layer thicknesses by the pulsed laser deposition technique is developed and studied for visible light photoelectrochemical oxidation of water. The impact of the thickness of the deposited LCO layer on the interfacial in-built potential and the PEC property is thoroughly investigated by experimental analyses. It is demonstrated from the High-resolution X-ray photoelectron spectroscopy that the LCO/STO heterojunction displays a type-II “staggered” band alignment with a valence band offset between 2.05 and 2.73 eV and a conduction band offset in the range 0.05 to 0.73 eV. The photoanode with an LCO layer thickness of four unit-cells processes the maximum PEC water-splitting activity. It is ascribed to the optimal in-built potential at the LCO/STO and electrolyte interface. This finding provides significant perspectives on the design and enhancement of PEC water-splitting systems. It reveals the crucial role of meticulous control over the heterojunction thickness in the enhancement of photoelectrochemical performance.