Low temperature CO2 methanation on hydrothermal synthesis of Ni-Ba/Sm2O3 catalysts

A low temperature CO₂ methanation is a thermodynamically favorable route to produce highly selective methane while preventing catalyst deactivation. Ni-Ba/Sm₂O₃ catalysts synthesized using one-pot hydrothermal method exhibited enhanced reducibility with high CO₂ adsorption capacity to achieve CO₂ conversion at low temperatures. CO₂ conversion occurred at 200 °C with 5% conversion, progressively increasing to reach equilibrium at 400 °C with 100% selectivity to methane. BaO promotes surface oxygen vacancy in Sm₂O₃, which is responsible for forming bidentate formate species during CO₂ methanation. Comparative DRIFTS analysis with Ni-Ba/Sm₂O₃ synthesized using impregnation indicates the catalysts followed different mechanistic pathways depending on the amount of surface oxygen vacancy generated by BaO/Sm₂O₃ proximity.