Electronic Origin of Enhanced Photocatalytic Activity at the Anatase/Rutile Boundary: A Case of Acetic Acid on the TiO2 Surface

The photocatalytic activity of titanium dioxide (TiO2) was investigated with a particular focus on the band-bending profile at the anatase/rutile (A/R) boundary. Various microfocused X-ray spectroscopic techniques were employed, including X-ray photoemission and absorption spectroscopies, as well as X-ray photoemission electron microscopy. The photocatalytic degradation of acetic acid adsorbed on a biphasic TiO2 surface was monitored both with and without ultraviolet irradiation. The study found that the photocatalytic activity at the A/R boundary was higher compared to that of either the anatase or the rutile monophase. Additionally, the bending profiles of both the valence and conduction bands across the A/R boundary were experimentally determined. Notably, a steep potential gradient of more than 1 eV/μm at the boundary was revealed for the first time, which is likely responsible for the observed enhancement in photocatalytic activity.

本研究针对二氧化钛（TiO₂）的光催化活性展开探究，重点关注锐钛矿（anatase）与金红石（rutile，A/R）界面对应的能带弯曲分布特征。研究采用了多种微聚焦X射线光谱技术，涵盖X射线光电子能谱、X射线吸收光谱以及X射线光电子发射电子显微镜（X-ray photoemission electron microscopy）。本研究对双相二氧化钛表面吸附的乙酸，在有、无紫外辐照的两种条件下的光催化降解过程进行了实时监测。结果显示，锐钛矿/金红石界面处的光催化活性高于单一锐钛矿相或单一金红石相的对应活性。此外，研究通过实验手段明确了锐钛矿/金红石界面两侧价带与导带的弯曲分布。尤为关键的是，本研究首次在该界面处观测到了超过1 eV/μm的陡峭电势梯度，该梯度极有可能是导致观测到的光催化活性提升的关键诱因。