One-pot synthesis of iron-doped ceria catalysts for tandem carbon dioxide hydrogenation

We report on the one-pot synthesis of inexpensive and abundant CeO2 and 1.5, 4.5, and 9 mol% Fe-doped ceria (Ce1-xFexO2-delta) systems and their catalytic activity for tandem CO2 hydrogenation. XAFS and XRD demonstrate that oxygen vacancies are generated via two mechanisms: firstly, by the substitution of Ce4+ by Fe3+ in the lattice and the subsequent loss of oxygen anions. Secondly, by the partial reduction of Ce4+ to Ce3+, which is enhanced by the presence of Fe. All the samples tested show high activity for CO2 hydrogenation and the production of CO, CH4, and light (C2-C4) alkanes and alkenes, with the 9 mol% Fe-doped CeO2 showing the best performance in terms of CO2 reaction rate and product selectivity. During reaction, Fe exsolves/seggregates from the ceria, resulting in particles decorating the surface of the catalyst and increasing the reaction rates of CO2. This system is composed of two functionalities, the oxygen vacancy and the Fe, whose close vicinity results in a high selectivity toward CO and CH4 detrimental to the more valuable hydrocarbons. A rather complex interplay between the two functionalities, their interface, and the particle size of the catalysts exists for this tandem reaction network on this catalytic system and deserves further studies. Solid solutions of Fe-doped ceria have been synthesized, characterized and applied as catalysts for tandem carbon dioxide hydrogenation.