Catalytic performance of Ni catalysts supported on CeO2 with different morphologies for low-temperature CO2 methanation

In this study, a series of Ni catalysts supported on CeO2 with different morphologies including nanopolyhedrons (PH), nanorods (NR), nanoparticles (NP) and nanocubes (NC) was prepared via hydrothermal / wet impregnation method. The catalytic performance of as-prepared catalysts was evaluated for low-temperature CO2 methanation. The Ni/CeO2 catalysts exhibited a superior CO2 conversion and CH4 selectivity over METH (R) 134, a commercial methanation catalyst. The following order of activity was experimentally found : Ni/CeO2-PH > Ni/CeO2-NR > Ni/CeO2-NP > Ni/CeO2-NC > METH (R) 134. Among different CeO2 morphologies, the Ni/CeO2-NR catalyst exhibited the largest surface area and the highest reducibility, providing the high oxygen vacancies/oxygen storage capacity (OSC). Nevertheless, the strong metal-support interaction (SMSI) between Ni and Ce of the Ni/CeO2-NR catalyst determined by H-2-TPR posed a negative impact on the CO2 conversion at low temperature. Unexpectedly, the Ni/CeO2-PH catalyst possessed a single crystalline CeO2 nanostructure of ca. 7.4 nm with relatively high surface area and high reducibility especially at low reduction temperature. Therefore, the Ni/CeO2-PH catalyst was found to be the optimum catalyst for low-temperature CO2 methanation.