Size controlled Pt over mesoporous NiO nanocomposite catalysts: thermal catalysis vs. photocatalysis

Abstract

Mesoporous nickel oxide and Pt@NiO nanocomposites were synthesized for the study of CO2 methanation in the fixed bed reactor, atmospheric pressure, and photocatalytic degradation of methyl orange. All synthesized catalysts were characterized by XRD, N2 isotherms, TEM, UV–Vis DRS, and ICP-MS analysis. NiO with 8 nm Pt nanoparticles was the most active catalyst in photocatalysis, however, the 2 nm Pt nanoparticles were most active in the thermal CO2 activation reaction. High CO2 consumption and CH4 formation rates were obtained for Pt@NiO nanocomposites below 673 K compared with bare NiO by the formation of Pt/PtOx/Ni/NiOx interface in reaction condition. Pt2@NiO nanocomposite has shown a high CO2 consumption rate because of high dispersion of 2 nm Pt nanoparticles within mesoporous NiO and high Pt to Ni surface area during the reaction. The photocatalytic degradation efficiency of Pt8@NiO nanocomposite was higher compared to that of bare NiO by a decrease in the recombination of electron–hole pair under UV–Vis irradiation.