Exploration on structure-activity relationship over substituted Co-doped spinel AlFe2O4 for enhanced CO2 hydrogenation into C2-C4 hydrocarbons

As the main greenhouse gas, CO2 has caused some serious environmental problems. Hence the abatement of CO2 allows of no delay. Among all strategies for CO2 reduction, CO2 hydrogenation reveals the great potential for industrial application, and becomes the efficient path to achieve target of “Carbon Neutral”. In this work, the Co-doped AlFe2O4 catalysts were firstly reported for CO2 hydrogenation test, and the enhancement of Co doping on activity was explored systematically via a series of conventional characterization methods. The Fischer-Tropsch synthesis-based CO2 hydrogenation was conducted over Co-doped AlFe2O4, thus the dissociation of CO2 and the carbon chain growth were both important. The observation of CoFe2O4 in the composites indicated the strong electronic interaction between Co and Fe species. This could strengthen the electrons transfer to generate more metallic Co and Fe species during H2 reduction, and then increased the Fe3C percentage during CO2 hydrogenation process. Moreover, the generated Co0 species could provide the additional adsorption sites for reactant gas. Therefore, the strategy of Co doping could strengthen the CO2 hydrogenation performance, reflected in the increase of CO2 conversion, the selectivity and space time yield of C2-C4 products. However, the formed “too stable” structure in the condition of the excessive Co doping prohibited the electrons transfer and the generation of Fe3C active species, thus existing an optimum Co doping amount. [Display omitted] •Co-doped AlFe2O4 catalysts were firstly reported for CO2 hydrogenation.•CoFe2O4 and AlFe2O4 co-existed in the Co-doped AlFe2O4.•Co doping generated more metallic Fe, promoting the generation of iron carbide.•The C2-C4 products selectivity was enhanced by the Co doping.