Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles

Abstract

The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidation and reduction reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 kelvin. A Wulff analysis of high-resolution in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen–rhodium–oxygen surface oxide at the rhodium nanofacets. This experimental access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.