Light-Induced Agglomeration of Single-Atom Platinum in Photocatalysis

With recent advances in the field of single-atoms (SAs) used in photocatalysis, an unprecedented performance of atomically dispersed co-catalysts has been achieved. However, the stability and agglomeration of SA co-catalysts on the semiconductor surface may represent a critical issue in potential applications. Here, the photoinduced destabilization of Pt SAs on the benchmark photocatalyst, TiO2, is described. In aqueous solutions within illumination timescales ranging from few minutes to several hours, light-induced agglomeration of Pt SAs to ensembles (dimers, multimers) and finally nanoparticles takes place. The kinetics critically depends on the presence of sacrificial hole scavengers and the used light intensity. Density-functional theory calculations attribute the light induced destabilization of the SA Pt species to binding of surface-coordinated Pt with solution-hydrogen (adsorbed H atoms), which consequently weakens the Pt SA bonding to the TiO2 surface. Despite the gradual aggregation of Pt SAs into surface clusters and their overall reduction to metallic state, which involves >90% of Pt SAs, the overall photocatalytic H-2 evolution remains virtually unaffected.

Automated summary

This paper describes the photoinduced destabilization of Pt single atoms (SAs) on the surface of titanium dioxide (TiO2), a benchmark photocatalyst. The SAs agglomerate into clusters and nanoparticles under illumination in aqueous solutions. The kinetics of this process depend on the presence of sacrificial hole scavengers and the intensity of light used. Despite the aggregation and reduction of the SAs, the overall photocatalytic hydrogen evolution remains largely unaffected.