Band-Engineered LaFeO₃-LaNiO₃Thin Film Interfaces for Electrocatalysis of Water

Perovskite oxide thin films have been studied extensively for applications in electrocatalysis of water. Particularly, LaFeO₃ and LaNiO₃ have shown tremendous potential as catalysts in the oxygen evolution reaction. However, their catalytic performance needs to be improved significantly for commercial applications to compete with precious metal catalysts. Through band engineering we can fine tune the electronic properties of the material that might lead to the efficient energy conversion. By choosing suitable materials, charge can be driven across the heterostructure interface, which often leads to enhanced catalytic performance. The band alignment at the interface is crucial for charge transfer. In this work, we investigated the band offset at the LaFeO₃/LaNiO₃ interface combining experimental techniques as well as first principles calculations.

 

We synthesized LaFeO₃/LaNiO₃ heterostructures using molecular beam epitaxy. We performed band offset calculation from XPS data. Our result shows that charge transfer at the interface is minimal but that the valence band offset between the top LaFeO₃ layer, and the metallic LaNiO₃ Fermi level is only ~0.2 eV, pinning the LaFeO₃ in a p-type state. Models of the heterostructures using first-principles calculations within the density functional theory support this conclusion. Electrochemical measurements produced on these heterostructures revealed enhanced catalytic performance with respect to individual thin films. Comparison of these results with LaFeO₃ thin films indicate that thickness as well as doping between n-type, intrinsic, and p-type all play a role in the catalysis that may be exploited to further improve the efficiency of oxygen evolution reactions.