Enhanced performance of Ni catalysts supported on ZrO2 nanosheets for CO2 methanation: Effects of support morphology and chelating ligands

Abstract A series of Ni/ZrO2 catalysts was prepared by the impregnation method with modification of the morphology of ZrO2 support as well as the impregnation procedure and tested for CO2 methanation. The catalysts supported on the ZrO2 nanosheets displayed superior catalytic performance as compared with that on ZrO2 nanoparticles, which could be mainly attributed to the abundant oxygen vacancies promoting the adsorption and dissociation of CO2 molecules as well as the high dispersion of Ni species. With the introduction of ethylenediamine (En) in the impregnation procedure, the resulting Ni-15En/ZrO2-1.5 catalyst showed the optimal activity with CO2 conversion of 86% significantly higher than Ni/ZrO2-0 of 44% and Ni/ZrO2-1.5 of 79% at 0.5 MPa and 300 °C. The excellent performance was attributed to increased moderately basic sites for CO2 adsorption in ZrO2 nanosheets, as well as the enhanced dispersion of nickel caused by the complexation of Ni ions with En, which inhibited the aggregation of nickel particles in the subsequent thermal treatments. In conclusion, the synergistic effects of the morphology of ZrO2 nanosheets as well as the chelating behavior of En contributed to the enhanced performance of Ni-15En/ZrO2-1.5 in the CO2 methanation reaction. The strategy shows good prospects for controlling the size of active metals, especially those that were dispersed on the surface of the two-dimensional (2D) metal oxide materials.