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 (Rhm(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 Rhm(CO)n sites, while in situ/operando spectroscopy revealed a reversible restructuring between Rh3(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. The dynamic behaviour of low-nuclearity catalysts has major implications in their catalytic performance and is often overlooked. Here, it is shown how supported Rh catalysts undergo dynamic restructuring in response to gaseous products formed during steam reforming of methane.