Surface mapping of photocatalytic activity in heterogeneous TiO₂ films

Recent developments in advanced spectroscopy and imaging techniques are shedding light on key charge transfer processes and kinetics in photocatalysis. Complementary photocatalytic reactions with local markers and surface structural mapping are essential to establish property–function correlations in photocatalytic materials. The current work describes a simple approach to probe heterogeneous photocatalytic surfaces using digital colorimetry and the well-established smart ink test, based on the photo-induced reduction of resazurin dye. Surface crystallographic phase mapping is carried out using valence band photoemission spectra (depth resolution of ca. 5 nm). The method has prospects for implementation in pixel-by-pixel analysis using high resolution cameras at the micron scale.