Anion-Exchange-Mediated Internal Electric Field: Boosting Photogenerated Carrier Separation and Utilization

Abstract

Constructing heterojunctions is a commonly used method for heterogeneous photocatalysts to modulate the internal electric field (IEF); however, this method suffers from narrow IEF distribution (primarily limited at the heterojunction interface) and long migration paths of photocarriers, and therefore results in suboptimal efficiencies in carrier separation and utilization. In this work, we report for the first time novel basic bismuth nitrate compound nanorods (denoted as BOH NRs) featuring surface-exposed open channels and a simple chemical composition; by simply modifying the bulk anion layers to overcome the limitations of heterojunctions, the bulk IEF could be readily modulated. A low exchange ratio (~10%) with halide anions (I–, Br–, Cl–) would give rise to a prominent elevation in carrier separation efficiency; for the reaction of photocatalytic oxidative coupling of benzylamine, the conversions over the modified catalysts are 1.6–2 times as high as that over pristine BOH. Benefiting from the unique crystal structure and the localization of valence electrons, the IEF intensity increases with the atomic number of introduced halide anions, leading to an enhanced efficiency of carrier separation and utilization. Our work here offers new insights into the design and optimization of semiconductor photocatalysts.