Microscopic Insight into the Polarization-Dependent Oxygen Evolution Reaction on the Surface of Intrinsic Ferroelectric Semiconductor β-CuGaO2.

Ferroelectric semiconductors hold great promise in the field of photocatalysis due to their spontaneous polarization that can suppress the recombination of photogenerated charges, but the mechanism of the effect of ferroelectric polarization and the intensity of polarization on surface catalytic reactions have never been approached. Here, we have comparatively investigated the oxygen evolution reaction (OER) catalytic process on surfaces in polarized and unpolarized orientations of the intrinsic ferroelectric semiconductor β-CuGaO2 by first-principles calculations. Furthermore, semiquantitative effects of different polarization intensities on the OER on the surfaces are subsequently carried out. First, it is confirmed that the [011]-polarized surface with fully exposed Cu-O atoms is the easiest surface to form and the most attractive for water molecules, exhibiting the lowest OER free energy barrier of 1.71 eV. Second, the calculated results indicate that [011] surfaces with higher polarization intensity are capable of enhancing the photogenerated hole potential (U) due to the accumulation of microscopic polarization in the polar unit of the bulk phase within the [011] slab. The intrinsic mechanism behind the enhancement of the OER by ferroelectric polarization is attributed to the modulation effect of polarization intensity on the 3d orbit of Cu+. This work elucidates the effects of ferroelectric polarization orientations as well as polarization intensity for the water OER, and provides theoretical guidance for the intrinsic ferroelectric polarization to promote surface OER.