Unraveling the Effect of Rh Isolation on Shallow d States of Gallium–Rhodium Alloys

In this study, we report the electronic and chemical structure of supported GaRh alloys as model systems for the active phase in supported catalytically active liquid metal solutions (SCALMS). We prepared a series of gallium–rhodium samples with different Rh contents and tracked the evolution of the sample topography and surface electronic structure via photoemission spectroscopy in combination with ab initio calculations and electron microscopy. Our results reveal a characteristic shift of the Rh 3d core levels and narrowing and shifting of the Rh 4d derived band with decreasing Rh content. Calculations show that these spectroscopic observations can be explained by the coexistence of isolated Rh atoms in random GaRh alloys and GaRh intermetallic compounds (IMCs). These results contribute to an enhancement of the fundamental understanding of the electronic surface structure of GaRh alloys, which is crucially required for apprehending and thus further exploiting the improved catalytic activity of GaRh SCALMS.