The in situ growth of atomically dispersed Ni species on CeO2 during low-temperature CH4/CO2 reforming

Abstract

The ceria-supported nickel catalyst is a widely used benchmark for low-temperature dry reforming of methane (DRM). Nonetheless, whether the atomically dispersed Ni species aggregates during the reaction and which species boost the activity remains elusive. Herein, we designed a group of Ni/CeO₂ catalysts ranging from single atoms to nanoparticles (NPs) by carefully increasing the Ni loading from 0.5 to 1.6 wt%. The actual Ni states were verified by a series of advanced characterizations. Through DRM studies, characterizations of reaction-spent Ni species and carbon deposits, kinetics, and time-resolved in situ infrared spectroscopy, we found that the atomically dispersed Ni species aggregate into clusters or NPs upon contact with the DRM reactants, which is necessary for the DRM activity. These in situ aggregated Ni species boosted the overall reaction with less carbon formation, while the reaction-spent 0.5Ni/CeO₂ still retaining some single atoms produced more graphitic carbon during the reaction.