Mechanochemical synthesis of Ni/MgO dual functional materials at room temperature for CO2 capture and methanation

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Storing and in-situ hydrogenating CO2 to CH4 by dual functional materials (DFMs) is an efficient solution to alleviate the greenhouse effect and energy shortage. However, in the multi-step preparation process of DFMs, high-temperature calcination is usually required, solvent is used, and NO2/CO2 is inevitably emitted. In this work, we first reported that the Ni/MgO DFMs could be mechanochemically synthesized in one step at room temperature by magnesium-induced hydrogenation of Ni-mixed magnesium carbonate without using any solvent and NO2/CO2 emission. Integrated CO2 capture and methanation performance of the Ni/MgO DFMs are investigated isothermally in a TG-MS apparatus and a fixed bed reactor. The CO2 uptake and CH4 yield over the 80Ni/MgO DFM at 300 ℃ are 0.37 mmol/g and 0.27 mmol/g, respectively, with a CO2 conversion of 73.0 % and CH4 selectivity of 100 %. After 5 consecutive CO2 capture and methanation cycles at 300 ℃, the CO2 uptake and CH4 yield over the 50Ni/MgO DFM still are 0.26 mmol/g and 0.18 mmol/g, respectively, with a CO2 conversion of 69.2 % and CH4 selectivity of 100 %. Furthermore, the mechanism of CO2 adsorption, activation, and hydrogenation to methane over the Ni/MgO DFM is systematically investigated by using density functional theory (DFT) calculations. This study offers an alternative, green, and sustainable strategy to acquire DFMs for CO2 capture and methanation.