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In this study, a series of free-standing as well as controlled size Pt nanoparticles-loaded mesoporous metal oxides (NiO, Co3O4, CeO2 and MnO2) with high surface area and designed pore structure were prepared by hard template method and used as catalysts for CO2 hydrogenation together with dry reforming of CO2 with methane. The physicochemical properties of catalysts were analysed by N2 adsorption-desorption isotherm, XRD, TEM, and H2-TPR. Pt-free and Pt-loaded mesoporous NiO and Co3O4 performed with high catalytic activity and selectivity for both CO2 activation reactions. Pt-free NiO exhibited the highest catalytic activity and also showing 100% CH4 selectivity between 473–673 K and ˜1:1 H2/CO2 ratio between 673–973 K in CO2 hydrogenation and dry reforming with methane, respectively. The enhanced catalytic properties can be due to the existence of metallic Ni as well as the optimal dynamics of Ni/NiOx structure under reaction conditions.

A series of 5 wt% NiO-xP-Al2O3 with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. A significant promotional effect of phosphorus on NiO-Al2O3 in CO2 hydrogenation is observed. All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al2O3, 5 wt% NiO-5P-Al2O3, 5 wt% NiO-15P-Al2O3 and 5 wt% NiO-20P-Al2O3 catalysts. Ni/NiO/Ni2P/Ni5P12/AlPO4 interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni2P/Ni5P12 form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity.