Transient Absorption Microscopy Explores the Effect of Pt Deposition on Charge Carrier Dynamics in Individual Carbon Nitride Particles

This study aims to spatially understand the effect of Pt deposition on slow (μs-s) carrier dynamics in carbon nitride (CN_x) photocatalysts, using a homebuilt microsecond diffuse reflectance transient absorption microscopy setup. It is found that Pt deposition lengthens the overall charge half-lives about threefold, while having a spatial preference for binding with respect to defects that induce charge trapping in the μs-s timescale. The initial trapped charge population shows a slight decrease after Pt deposition, suggesting that the more reactive and mobile charges are extracted by Pt sites, leaving behind deeply trapped and long-lived charges. The results emphasize that spatial heterogeneity of surface cocatalysts likely plays a major role in controlling the charge carrier dynamics and activity of photocatalysts.