NiO Nano- and Microparticles Prepared by Solvothermal Method-Amazing Catalysts for CO₂ Methanation

Nickel oxide (NiO) is one of the most popular hydrogenation catalysts. In heterogeneous catalysis, nickel oxide is used, for example, as a suitable methanation catalyst in the Fischer-Tropsch reaction not only for CO hydrogenation but also in the modified Fischer-Tropsch reaction with CO₂. However, CH₄ selectivity and CO₂ conversion strongly depend on NiO micro- (MPs) and nanoparticles' (NPs) shape, size, and surface area. In this study, the synthesis of NiO micro- and nanoparticles was conducted using the simple solvothermal method. Different morphologies (microspheres, sheet clusters, hexagonal microparticles, and nanodiscs) were prepared using this method with different solvents and stabilizers. The prepared catalysts were tested in the hydrogenation of CO₂ in a gas phase with excellent conversion values and high selectivity to produce CH₄. The best results were obtained with the NiO with disc or sphere morphology, which produced methane with selectivity at a level near 100% and conversion close to 90%.