Reaction product-driven restructuring and assisted stabilization of a highly dispersed Rh-on-ceria catalyst

Understanding the structural dynamics of a catalyst under reaction conditions is challenging but crucial regarding catalyst design. Here, by a combination of in situ/operando characterization and first-principles modelling, we show that supported rhodium (Rh) catalysts undergo restructuring at the atomic scale in response to carbon monoxide (CO), a gaseous product formed during steam reforming of methane. Despite transformation of the initially prepared single-Rh-cation catalyst into Rh nanoparticles during hydrogen pretreatment, the formed Rh nanoparticles redispersed to low-nuclearity, CO-liganded Rh clusters (Rh m (CO) n ( m = 1–3, n = 2–4)) under catalytic conditions. Theoretical simulations under reaction conditions suggest that the pressure of the CO product stabilizes Rh m (CO) n sites, while in situ/operando spectroscopy revealed a reversible restructuring between Rh 3 (CO) 3 clusters and CO-ligand-free Rh clusters driven by CO pressure. Our findings demonstrate the importance of including product molecules in the atomic-scale understanding of catalytic active sites and mechanisms.