In-Situ FTIR Study of CO2 Adsorption and Methanation Mechanism Over Bimetallic Catalyst at Low Temperature

Ni-based catalysts are the most promising catalysts for CO2 methanation. The development of catalysts with low-temperature activity could bring significant energy and environmental benefits. In this work, the hydrogenation of CO2 to methane was studied on Ni-M/γ-Al2O3 (M = Fe, Co, or Mn) bimetallic catalysts. The optimum reaction was obtained using Ni-Mn/γ-Al2O3 (CO2 conversion: 85%, CH4 selectivity: 99%, 280 °C). In situ FTIR studies revealed the excellent performance of Ni-Mn/γ-Al2O3, which lowers the required reaction temperature. Based on in situ FTIR studies, CO2 methanation proceeded over three intermediates on the catalysts: bicarbonate → carbonate → formate → methane. The second metal (Co or Mn) promoted the dispersion of both Ni and itself and improved the ability of Ni to crack H2. And introduced more oxygen vacancies to strengthen the basicity of surrounding O2− on the surface of the catalysts. In effect, the number of carbonate active sites could be increased accordingly, thereby improving the adsorption capacity for CO2.