Hydrogen plasma favored modification of anatase TiO$_2$ (001) surface with desirable water splitting performance

TL;DR

This study demonstrates that hydrogen plasma treatment modifies the anatase TiO$_2$ (001) surface, enhancing its water splitting ability by altering surface structure and electronic properties, leading to improved solar energy conversion efficiency.

Contribution

The paper introduces a novel surface modification of anatase TiO$_2$ via hydrogen plasma that improves water splitting performance by changing surface structure and band alignment.

Findings

Modified surface has higher water splitting activity.

Energy barrier for water splitting is eliminated on the modified surface.

Valence band maximum is raised, better matching solar spectrum.

Abstract

We show that when TiO$_2$ anatase (001) is exposed to hydrogen plasma that the pristine surface termination becomes unfavorable to another, slightly modified, surface. On this modified surface the topmost TiO$_2$ layer is intact but out of registry with the bottom layers. Nevertheless, the modified surface has significantly improved ability to split water under exposure to sunlight. We show by explicit calculation of the water splitting reaction that the energy barrier that exists on a pristine surface is not present on the modified surface. The valence band maximum of the surface is raised relative to the pristine surface, which is a favorable way of adjusting the band gap in TiO$_2$ to the solar spectrum.