Contribution of Different Species in Ni-Ceria Nanorods Catalysts Applied to Steam Reforming of Ethanol

Ni-CeO2 nanorods catalysts (1-10 wt% Ni loadings) were evaluated in steam reforming of ethanol (SRE). Ex situ and in situ characterization showed two populations of Ni species according to Ni loading: (i) one highly dispersed, strongly interacting with CeO2 (Ni-sup) and (ii) another one formed by Ni nanoparticles (Ni-bulk). While the metal loading impacted on the Ni-bulk fraction, the Ni-sup population remained similar, leading to similar activities of the catalysts toward SRE. The results highlight the role of the Ni-sup fraction in the catalyst performance. Nevertheless, we found that while Ni-bulk species favored carbon deposition, the Ni-sup species were easily oxidized at low temperatures, leading to catalyst deactivation. The results suggest that the co-existence of both Ni species may stabilize the reduced form of the Ni-sup species by hydrogen activation on the Ni-bulk species and represents a new strategy to be explored to optimize the activity and stability of SRE catalysts.