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.

Automated summary

Understanding the structural dynamics of catalysts under reaction conditions is essential for catalyst design. In this study, supported rhodium catalysts were found to undergo atomic-scale restructuring in response to carbon monoxide. The pressure of CO product stabilized CO-liganded rhodium clusters, and reversible restructuring between CO-ligand-free rhodium clusters and CO-liganded clusters was observed. These findings highlight the importance of considering product molecules in the atomic-scale understanding of catalytic active sites and mechanisms.