Plasma-catalytic CO₂ methanation over NiFe_n/(Mg, Al)O_x catalysts: Catalyst development and process optimisation

Plasma-assisted catalytic carbon dioxide (CO₂) methanation is a promising approach to valorise CO₂ under mild conditions, and the system requires rational design regarding both catalysts and processes to advance it towards practical applications. Herein, the bimetallic NiFe_n/(Mg, Al)O_x catalysts were developed for plasma-catalytic CO₂ methanation, and the effect of atomic ratio of Ni and Fe and reduction temperature on the catalysts was investigated systematically. The findings show that a higher reduction temperature was beneficial to the formation of Ni₃Fe alloy and abundant surface oxygen vacancies, and increased CO₂ adsorption ability. As a result, the NiFe_0.1/(Mg, Al)O_x-800 catalyst led to a good catalytic performance in the plasma-assisted catalysis with about 84.7% CO₂ conversion and 100% methane (CH₄) selectivity. In addition, this study also employed response surface methodology (RSM) to explore the optimisation of plasma-catalytic CO₂ methanation for the first time. Results from RSM show that in the plasma-catalytic system the selective CO₂ hydrogenation to CH₄ was favoured by higher applied voltage, lower gas flow rate and higher gas ratio (H₂: CO₂).