PNNL

Abstract

The polarity of oxide surfaces can dramatically impact their surface reactivity, in particular with polar molecules such as water. The surface species that result from this interaction change the oxide electronic structure and chemical reactivity in applications such as photoelectrochemistry, but are challenging to probe experimentally with atomic-scale understanding. Here we report a detailed study of the surface chemistry and electronic structure of the perovskite LaFeO3 in humid conditions using ambient pressure X-ray photoelectron spectroscopy. Comparing the two possible terminations of the polar (001)-oriented surface, we find that the LaO surface is more reactive toward water, forming hydroxyl species and adsorbing molecular water at lower relative humidity than its FeO2-terminated counterpart. Our results demonstrate how the termination of a complex oxide can dramatically impact its reactivity, providing insight into the design of catalyst materials.