Visualizing light-induced anisotropic growth of Rh nanoparticles on the SrTiO3 surface

STEM and EELS identify the atomic SrTiO 3 surface and Rh precursor layer. • Rh precursor evolution and nanoparticle formation were in situ tracked. • UV light triggers anisotropic Rh growth onSrTiO 3 . Elucidating the complex light-matter interplay and the resulting atomic and electronic structural changes is fundamental to mastering light-driven surface processes. However, direct in situ observations capturing these dynamic pathways at the atomic scale remain limited, particularly for facet-engineered materials with intrinsic anisotropy. Here, using in situ transmission electron microscopy (TEM) with integrated illumination, we provide direct evidence of the transition from isotropic Rh precursor to anisotropic growth of Rh nanoparticles on faceted SrTiO 3 nanocrystals. While thermal decomposition in the dark leads to a homogeneous distribution of Rh across both {100} and {111} facets, UV irradiation induces a significant shift toward facet-selective growth, with Rh nanoparticles preferentially nucleating and expanding on the {100} facets. The anisotropic work functions of the SrTiO 3 facets, coupled with the interfacial electronic modulation of Rh-SrTiO 3 Schottky junctions, facilitate site-selective Rh precursor reduction and enhanced growth on the {100} surfaces. Moreover, the synergistic photo-thermal effect drives the subsequent evolution of Rh nanoparticles, which predominantly coarsen through an Ostwald ripening mechanism. These findings provide direct experimental evidence of light-driven, facet-dependent nanostructure evolution and offer insights into the role of carrier regulation in the rational design of photocatalytic systems.