Dual role of iron in alumina supported bimetallic nickel catalysts for CO2 methanation

The methanation reaction plays a critical role in CO 2 utilization and renewable energy storage, supporting global decarbonization efforts. The effect of iron on the structural, surface, and catalytic properties of alumina-supported NiFe catalysts for CO 2 methanation was investigated. Catalysts containing up to 10 wt% Fe and 20 wt% Ni were prepared via a modified citric acid assisted impregnation method and characterized using TPR, XRD, TEM, H 2 -TPD, CO 2 -TPD, TPO, Mössbauer spectroscopy, XPS, in situ DRIFTS. An increase in Fe content enhanced catalysts reducibility at low temperatures, decreased hydrogen chemisorption, and strengthened H 2 and CO adsorption sites, without significantly altering the NiFe crystallite size. Iron simultaneously facilitated surface oxides formation, promoting CO 2 activation, C-O bond cleavage, and hydrogenation of intermediates, particularly at low temperatures. However, at high temperatures, above 300 °C catalytic activity declined, likely due to excessive surface oxidation and structural changes of the bimetallic NiFe particles. The catalyst containing 10 wt% Fe showed the highest activity at low temperatures (220 °C), while catalyst with 2 wt%. Fe was superior to the others at high temperatures of 320 °C. These findings suggest that adjusting the Fe content enables catalyst optimisation for different thermal zones in methanation reactors.