Abstract
Catalytic methane decomposition (CMD) offers an eco-friendly method to produce COx-free hydrogen and solid carbon. An innovative approach for catalyst regeneration involves utilizing CO2 as a reactant to produce CO via the Reverse Boudouard Reaction, which serves as a valuable feedstock for various chemicals and fuels. This study aims to investigate the role and interaction of Ni nanoparticles on cerium oxide support by comparing two catalysts: one synthesized via the conventional impregnation method (Imp) and the other through solution combustion synthesis (SCS). Both catalysts containing the same Ni loading of 5 wt% and were tested under identical conditions. Comprehensive characterization techniques, including XRD, H2 and O2 TPR, TEM, SEM, XPS, and Raman spectroscopy, were employed to elucidate the observed performances. The SCS catalyst resulted in smaller Ni nanoparticles with stronger metal-support interaction. Observations revealed both tip and base carbon growth for the SCS catalyst, whereas the Imp catalyst predominantly characterized by tip growth. For the SCS catalyst, carbon nanofibers and nanotubes were observed, and both appeared active in carbon CO2 gasification. For the Imp catalyst, more crystalline carbon is observed. The amount of carbon produced was much more and managed to cover the entire catalyst. For SCS carbon coverage was partial. Two rates of CO2 gasification were observed depending on the extent of carbon coverage. Across all tested temperatures and space velocities, the catalyst prepared by impregnation exhibited higher reaction rates. The Imp catalyst demonstrated 15 % higher CMD and 29 % more generated carbon than SCS. This work demonstrated the critical role of key factors influencing the catalytic performance of this cyclic process. This includes the Ni nanoparticle size and distribution, the metal-support interaction's strength, and the graphitic carbon's nature.
