Band restructuring of ordered/disordered blue TiO2 for visible photocatalyst

TL;DR

This study develops a noble metal-free blue TiO2 heterostructure with type-II band alignment, significantly enhancing visible-light photocatalytic efficiency and reducing co-catalyst requirements compared to conventional TiO2 materials.

Contribution

It introduces a phase-selective reduction method to create a disordered rutile/anatase TiO2 heterostructure with restructured band alignment for improved photocatalysis.

Findings

55 times higher hydrogen evolution than P25 TiO2

Type-II heterostructure achieved with 3-day Li-reduction

Requires 10 times less Pt co-catalyst for similar performance

Abstract

Black TiO2 with/without noble metal has been proposed for visible photocatalyst, still leaving poor catalyst efficiency. Alternatively, phase-mixed TiO2 such as anatase and rutile has been commonly used for visible catalysts with the inevitable inclusion of noble metal. Here, we perform a noble metal-free visible photocatalyst blue TiO2 with type-II band-aligned ordered anatase/disordered rutile structure, via phase-selective reduction with alkali metals. The changed band alignment in this heterostructure was identified by absorption and ultraviolet photoemission spectroscopy, which was further confirmed by transient charge separation. The band alignment of type-I and type-II was clearly restructured by converting from ordered to disordered phase with a prolonged reduction period and as followed light absorbance enhancement also observed. Initiated type-I in a pristine sample, the type-II was organized from disordered rutile phase in 3-day Li-reduction. The type-II disordered rutile TiO2 heterostructure exhibits a remarkable photocatalytic performance by 55 times higher than conventional P25 TiO2 in solar-light driven hydrogen evolution reaction owing to an efficient electron and hole separation of type-II heterojunction. Furthermore, this restructured heterojunction type-II TiO2 demanded 10 times less Pt amount as a co-catalyst for the comparable photocatalytic performance, compared to Pt decorated type-I pristine anatase/rutile phase-mixed TiO2.