CO2 methanation with high-loading mesoporous Ni/SiO2 catalysts: Toward high specific activity and new mechanistic insights

Abstract

In the power-to-gas scenario, surplus renewable electricity is stored in the form of methane, by reacting green hydrogen with waste CO2 through the Sabatier reaction. Low-cost catalysts that feature a high activity at low temperature are needed. We disclose the sol–gel preparation of high-loading mesoporous Ni/SiO2 catalysts. (HR)-TEM, XRD, N2 physisorption, and H2 chemisorption show that small Ni particles (<5 nm) are obtained, even at loading up to 38 wt%. The best catalyst reached a specific activity of 10.2 µmolCH4.g−1.s−1 at 250 °C (TOF = 0.0155 s−1; almost 3 times higher than a reference catalyst prepared by impregnation). Being based on inert silica, these catalysts are ideal model materials to elucidate the reaction mechanism on nickel. Combining CO2-TPD, in-situ CO2-DRIFTS, and TPSR with DFT calculations, we show that CO2 methanation follows mostly the RWGS + CO-hydrogenation and the formate pathways, the former being dominant at low temperature.