Ultrafast Dynamics in Gold-Palladium Antenna-Reactor Nanoparticles Revealed by Laser Pump and X-ray Probe*

Metal nanoparticles play a crucial role in photochemistry as efficient platforms for optical energy harvesting, primarily due to their strong plasmon resonances. However, the application of plasmonic nanoparticles in light-driven catalysis faces a significant challenge: their limited catalytic reactivity. By combining optically active noble metals (e.g. gold, silver) with catalytically reactive metals (e.g. palladium, platinum), these hybrid nanoparticles have emerged as promising candidates for enhanced photocatalytic applications, bridging the gap between efficient light absorption and catalytic activity. This study investigates the ultrafast dynamics of gold-palladium (Au-Pd) antenna-reactor nanoparticles in a visible laser pump X-ray probe experiment at SwissFEL. The results reveal an initial enhanced energy and charge localization on the catalytically active palladium satellites rather than the gold core. The study demonstrates direct electronic coupling between gold and palladium, with charge redistribution driving heat transfer through electron-phonon interactions. The ability to achieve precise localized heating and immediate cooling in palladium suggests a potential new paradigm for innovation in pulsed catalysis.