Observation of NO molecules adsorbed on Rh cluster anions at different temperatures using photoelectron spectroscopy

Rh nanoparticles are often used as catalysts for reducing NO at high temperatures (∼500 K) <i>via</i> dissociation of the NO bond. In this study, utilizing a newly developed setup, we performed photoelectron spectroscopy on Rh_<i>n</i>NO^- (cluster size, <i>n</i> = 3-7) clusters at temperatures ranging from 300 to 800 K. The observed temperature-dependent spectral changes were concluded to arise from an increase in internal energy caused by heating, leading to dissociation of the NO bond on the cluster surface. This observation offers direct spectroscopic evidence of thermally activated surface chemistry in gas-phase clusters.