Band-engineered LaFeO₃-LaNiO₃ thin film interfaces for electrocatalysis of water

Iron and nickel-based perovskite oxides have proven promising for the oxygen evolution reaction (OER) in alkaline environments, as their catalytic overpotentials rival precious metal catalysts when the band alignment is tuned through substitutional doping or alloying. Here, we report the engineering of band alignment in LaFeO3/LaNiO3 (LFO/LNO) heterostructures via interfacial doping that yields greatly enhanced catalytic performance. The 0.2 eV offset (VBO) between the Fermi level in metallic LNO and the valence band in semiconducting LFO that we predict using density functional theory makes LFO a p-type semiconductor, resulting in significantly lower barriers for hole transport through LFO compared to the intrinsic material. Experimental band alignment measured with in situ x-ray photoelectron spectroscopy of epitaxial LFO/LNO heterostructures confirms these predictions, producing a measured VBO of 0.3(1) eV. Furthermore, OER catalytic measurements on these samples in the alkaline solution show an increase in catalytic current density by a factor of similar to 275 compared to LFO grown on n-type Nb-doped SrTiO3. These results demonstrate the power of tuning band alignments through interfacial band engineering for improved catalytic performance of oxides.