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 aggregate during the reaction and which species boost the activity remain unclear and even controversial. Herein, we designed a group of Ni/CeO2 catalysts from single atoms to nanoparticles (NPs) by increasing the Ni loading from 0.5 to 1.6 wt.% carefully, and the actual Ni states were verified by a series of advanced characterizations. Through the DRM studies, characterizations for reaction-spent Ni species and carbon deposits, kinetics, and time-resolved in situ infrared spectroscopy, we found that the atomically dispersed Ni species would aggregate into clusters or NPs upon contact with the DRM reactants, and it is necessary for the DRM activity. These in-situ aggregated Ni species boosted the overall reaction with less carbon, while the reaction-spent 0.5Ni/CeO2 still retaining some single atoms produced more graphitic carbon during the reaction.