Improving photocatalytic activity of TiO$_2$ through reduction

TL;DR

This study uses density functional theory to show that reducing TiO₂ surfaces introduces defect states that enhance optical absorption and increase reducibility by shifting band edges, which could improve photocatalytic activity.

Contribution

It provides a detailed electronic structure analysis of various surface defects in TiO₂ and their effects on optical and electronic properties, advancing understanding of photocatalytic enhancement.

Findings

Defect states in the band gap enhance optical absorption.

Highly reduced surfaces have defect states near the valence band.

Defects cause an up-shift of the conduction band edge, increasing reducibility.

Abstract

The rutile TiO$_2$ (110) surface reduced by the bridging oxygen vacancy, bridging hydroxyl group or Ti interstitial atom has been investigated by calculating their electronic structures using the density functional theory plus U method. It is found that defect states located in the forbidden band gap can enhance optical absorption. When the surface is highly reduced, the defect states approach the valence band. More importantly, defects induce a substantial up-shift of the conduction band edge, rendering the reduced surface stronger reducibility. The shifts of both conduction and valence band edges are due to the dipole moments created by these defects.