Search

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-CuGaO2by 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.

Ferroelectric materials, leveraging an inherent built-in electric field, are excellent in suppressing electron–hole recombination. However, the reliance solely on bulk polarization remains insufficient in enhancing carriers’ separation and migration, limiting their practical application in photocatalytic overall water splitting (POWS). To address this, we incorporated cations with ns2lone pairs (P3+, As3+, Sb3+, and Bi3+) into ferroelectric semiconductors, successfully constructing 44 β-AIBIIIO2photocatalysts with dual polarization. Through rigorous first-principles calculations and screenings for stability, band characteristics, and polarization, we identified four promising candidates: β-LiSbO2, β-NaSbO2, β-LiBiO2, and β-TlBiO2. Within these materials, lone pairs induce local polarization in the xy-plane. Additionally, out of the plane, there is robust bulk polarization along the z-direction. This synergistic effect of the combined local and bulk polarization significantly improves the separation efficiency of electron–hole pairs. Explicitly, the electron mobility of the four candidates ranges from 105to 106cm2s–1V–1, while the hole mobility also increases significantly compared to single-phase polarized materials, up to 106cm2s–1V–1. Notably, β-TlBiO2is predicted to achieve a solar-to-hydrogen (STH) efficiency of 17.2%. This study not only offers insights for water-splitting catalyst screening but also pioneers a path for electron–hole separation through the dual polarization strategy.