Charge Carrier Mapping for Z-scheme Photocatalytic Water Splitting Sheet by Categorization of Microscopic Time-resolved Image Sequence

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. The Z-scheme photocatalytic system is promising for producing renewable energy by sunlight, but the optimization of multiple materials is challenging. Here, authors directly map out the photocatalytic activity on a microscopic scale by the clustering analysis for the time-resolved image sequence.