Charge carrier mapping for Z-scheme photocatalytic water-splitting sheet via categorization of microscopic time-resolved image sequences

Makoto Ebihara,Kazunari Domen,Hiromasa Tokudome,Takeshi Ikeda,Sayuri Okunaka,Kenji Katayama

doi:10.1038/s41467-021-24061-4

Abstract

Photocatalytic water splitting system using particulate semiconductor materials is a promising strategy for converting solar energy into hydrogen and oxygen. In particular, visible-light-driven ‘Z-scheme’ printable photocatalyst sheets are cost-effective and scalable. However, little is known about the fundamental photophysical processes, which are key to explaining and promoting the photoactivity. Here, we applied the pattern-illumination time-resolved phase microscopy for a photocatalyst sheet composed of Mo-doped BiVO4 and Rh-doped SrTiO3 with indium tin oxide as the electron mediator to investigate photo-generated charge carrier dynamics. Using this method, we successfully observed the position- and structure-dependent charge carrier behavior and visualized the active/inactive sites in the sheets under the light irradiation via the time sequence images and the clustering analysis. This combination methodology could provide the material/synthesis optimization methods for the maximum performance of the photocatalyst sheets.

Highlights

Photocatalytic water splitting system using particulate semiconductor materials is a promising strategy for converting solar energy into hydrogen and oxygen
The timeresolved experiments were performed on a visible-light responsive photocatalyst sheet composed of SrTiO3:Rh, BiVO4:Mo, and ITO (STOR/ITO/BVOM) in two different solvents (acetonitrile (ACN) and water)
The refractive index change is proportional to the number of excited carriers if the probe wavelength matches an optical transition; otherwise, it is proportional to the number of free carriers[44]

Summary

Introduction

Photocatalytic water splitting system using particulate semiconductor materials is a promising strategy for converting solar energy into hydrogen and oxygen. It indicates that the second component (100 ns to 1 μs) in ACN was attributed to electrons in STOR or holes in BVOM on the surfaces because these surface-trapped charge carriers were consumed by water and utilized for water-splitting reactions.

Results

Conclusion