Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO$_{3}$ Thin Films

TL;DR

This study investigates how the thickness of epitaxial LaFeO$_{3}$ thin films influences their efficiency as electrocatalysts for oxygen evolution, highlighting the importance of band alignment and engineering in optimizing renewable energy catalysts.

Contribution

It provides new insights into the thickness-dependent electrocatalytic performance of LaFeO$_{3}$ thin films and links this behavior to interfacial band alignment and engineering.

Findings

Electrocatalytic efficiency varies strongly with film thickness.

Interfacial band alignment influences OER activity.

Band engineering is crucial for designing effective thin film catalysts.

Abstract

Transition metal oxides have long been an area of interest for water electrocatalysis through the oxygen evolution and oxygen reduction reactions. Iron oxides, such as LaFeO$_{3}$, are particularly promising due to the favorable energy alignment of the valence and conduction bands comprised of Fe$^{3+}$ cations and the visible light band gap of such materials. In this work, we examine the role of band alignment on the electrocatalytic oxygen evolution reaction (OER) in the intrinsic semiconductor LaFeO$_{3}$ by growing epitaxial films of varying thicknesses on Nb-doped SrTiO$_{3}$. Using cyclic voltammetry and electrochemical impedance spectroscopy, we find that there is a strong thickness dependence on the efficiency of electrocatalysis for OER. These measurements are understood based on interfacial band alignment in the system as confirmed by layer-resolved electron energy loss spectroscopy and electrochemical Mott-Schottky measurements. Our results demonstrate the importance of band engineering for the rational design of thin film electrocatalysts for renewable energy sources.