Nano-gold catalysts on Fe-modified ceria for pure hydrogen production via WGS and PROX: Effect of preparation method and Fe-doping on the structural and catalytic properties

• Gold on Fe-doped ceria prepared by mechanical mixing (MM) or by impregnation (IM).
• Significantly higher WGS activity of gold catalysts on MM compared to IM supports.
• Not very different PROX activity and selectivity for both methods of synthesis.
• Relationship between structural features and catalytic activity.
• Role of separate hematite phase for the catalytic behavior in WGSR and PROX.

Two series of Fe-doped (5, 10 and 20 wt% Fe2O3) ceria oxides were synthesized by mechanochemical mixing (MM) and impregnation (IM) methods. The Au catalysts (3 wt%) supported on these mixed oxides were tested in WGSR and PROX. Gold catalysts on supports prepared by IM exhibited WGS activity lower than that of gold on undoped ceria. Significantly better WGS performance was demonstrated over gold catalysts on supports synthesized by MM. The observed differences in the catalytic behavior were explained by the crucial role of the gold dispersion depending on the preparation method. The highest WGS activity of Au5FeCeMM catalyst was attributed to the cooperative catalytic work of Fe-modified ceria and magnetite with the highest extent of non-stoichiometricity. In contrast to WGSR, the catalytic behavior in PROX over gold catalysts on supports prepared by both methods did not differ significantly. Fe likely acted as a ceria modifier because no changes in Fe-phases and Fe valence state were observed upon reaction. The nanosized hematite particles covering the ceria grains in the case of the IM method could diminish the ceria basicity explaining the observed good and stable PROX performance over Au10FeCeIM catalyst in the presence of CO2 and water.

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