C\(\mathrm {O_2}\) methanation: a review on optimizing catalysts and conditions

Abstract

The catalytic conversion of CO\(_2\) into methane via the Sabatier reaction offers a promising route for carbon utilization and renewable energy storage, producing grid-compatible CH\(_4\) from CO\(_2\) and H\(_2\). Yet performance depends strongly on catalyst design, synthesis, and operating conditions, which remain inconsistently reported. This review systematically compares formulations and process parameters to identify conditions enabling high CO\(_2\) conversion and CH\(_4\) selectivity. Ru catalysts deliver superior low-temperature activity (300–400 \(^{\circ }\)C), while Ni remains cost-effective and robust at higher temperatures. Metal loading shows an optimum, beyond which larger crystallites and weaker metal–support interactions reduce performance. Supports and promoters critically tune basicity, reducibility, and vacancy density: CeO\(_2\) and CeZrO\(_2\) outperform Al\(_2\)O\(_3\), and rare-earth (La, Ce) and transition-metal (Mn, Co) promoters enhance CO\(_2\) adsorption and H\(_2\) activation. Synthesis routes such as sol–gel, plasma-assisted, and ammonia-evaporation methods strengthen dispersion and metal–support synergy, while nanostructured morphologies improve defect chemistry and active-site accessibility. Operating conditions are equally important. Optimal performance arises from moderate GHSV to balance throughput and contact time, a H\(_2\)/CO\(_2\) ratio near 4:1, and elevated pressures. Photothermal and photo-assisted strategies further lower activation barriers, particularly for Ru catalysts. Overall, effective CO\(_2\) methanation integrates defect-rich supports, optimized promoters, nanostructured synthesis, and carefully tuned operating conditions, with light-assisted approaches offering added potential. Future progress requires standardized testing and scale-up under dynamic operation to translate laboratory findings into viable Power-to-Gas systems.