MOF-derived hierarchical hollow spheres composed of carbon-confined Ni nanoparticles for efficient CO2 methanation

The hydrogenation of CO2 to CH4 is attracting growing attention due to the universal energy and climate challenges. In this work, we present the facile synthesis of hierarchical Ni@C spheres composed of dispersed Ni nanoparticles confined in carbon shells as an efficient catalyst for low-temperature CO2 methanation at ambient pressure. With Ni-based metal-organic frameworks (MOFs) as a precursor, the Ni@C composite was produced by thermal annealing in a N-2 atmosphere. The MOF-derived Ni@C hybrid with unique hollow and porous structures could afford high surface area and rich isolated active sites for CO2 adsorption/activation and redox processes. Therefore, the Ni@C catalyst exhibited high activity, excellent selectivity and superior stability for CO2 methanation reaction. The possible intermediates and reaction pathway of the CO2 conversion catalysis were carefully investigated by CO2-TPD measurements and in situ FTIR characterization. Furthermore, a possible CO2 methanation mechanism over the Ni@C catalyst was proposed.