Ceria–zirconia encapsulated Ni nanoparticles for CO2 methanation

We prepared uniformly-sized Ni nanoparticles on ceria–zirconia (CZ) as model catalysts for CO2 methanation in the context of renewable energy storage. CZ was synthesized via a sol–gel method with Ni being introduced either via incipient-wetness impregnation on calcined CZ or as a colloidal Ni nanoparticle (NiNP) dispersion during sol–gel synthesis. Catalysts were characterized with XRD, N2 physisorption, H2-TPR, H2 chemisorption, XPS and HAADF-STEM with EDX mapping. The Ni/CZ (IWI) catalyst contained large Ni particles after reduction, whereas co-gelation led to NiNP encapsulated in CZ, the particles retaining their initial size of 4.5 nm obtained by the earlier colloidal synthesis. Encapsulated Ni@CZ exhibited superior catalytic activity and stability for CO2 methanation over Ni/CZ. A comparison of Ni@CZ with (encapsulated) Ni@SiO2 prepared from the same colloidal NiNP dispersion showed that CZ shows a strong synergy with Ni in CO2 methanation and results in an order of magnitude higher activity compared to SiO2.