From Single Atoms to Nanoparticles: Pathways Toward Efficient and Durable Pt/TiO ₂ Photocatalysts

ABSTRACT We develop a simple and scalable strategy to control the size of Pt species on anatase TiO 2 nanosheets (TNS), ranging from atomically dispersed single atoms (SAs) to nanoparticles (NPs). The method relies on photodeposition, where the temperature regulates the adsorption of the Pt precursor and determines whether Pt is stabilized as isolated atoms or agglomerated particles. Ethanol photoreforming under simulated sunlight is used to evaluate catalytic performance and stability. At low light intensity, SA‐rich samples exhibit the highest apparent activity and stable performance. However, post‐reaction characterization reveals that Pt atoms migrate and agglomerate into clusters, indicating that activity alone cannot be taken as evidence of atomic stability. At higher light intensities, SA‐rich samples deactivate rapidly due to accelerated Pt coalescence, while larger particles show comparatively greater stability. The results indicate distinct sintering pathways: dissolution–redeposition dominates in liquid‐phase reactions, whereas surface migration is prevalent in gas‐phase conditions. Thermochemical treatments further modulate Pt speciation: oxidation preserves SAs, whereas reduction induces agglomeration and preferential migration to the {101} facets, where Pt efficiently traps electrons and sustains hydrogen evolution. This study highlights how precursor adsorption, reaction environment, and post‐treatments govern the structural evolution of Pt, providing design guidelines for durable single‐atom photocatalysts.