Surface/Subsurface Interactions During Rh Oxidation Revealed by Atom Probe Tomography and Microscopy

Abstract

Metal catalysts may undergo a series of surface and subsurface structural and chemical transformations during a chemical reaction, which inevitably change the surface properties. Understanding such dynamics from a fundamental science standpoint is important to build rational links between chemical/structural surface properties and the desired catalytic performance. The research presented here addresses, the dynamics of early oxide formation on rhodium (Rh) single nanoparticle during O2 exposures revealing the important role that the subsurface plays. O2 dissociative adsorption, as well as its reaction with H2 mainly imply the Rh{012} regions and is directly observable on Rh nanoparticles with the use of Field Ion and Emission Microscopies (FIM/FEM). Adsorbed oxygen atoms (O(ads)) resulting of the O2 dissociative adsorption can migrate to the bulk through the surface. The combination of our observations by FEM and our observations using Atom Probe Tomography (APT) reveals an inter-facet cooperation between Rh{012} and Rh{113} during this process.