Three dimensionally ordered macroporous Au/CeO2 catalysts synthesized via different methods for enhanced CO preferential oxidation in H2-rich gases

Abstract

Three dimensionally ordered macroporous (3DOM) Au/CeO₂ catalysts were synthesized via a thermal decomposition-assisted colloidal crystal templating method following different synthetic procedures using citric acid and oxalic acid as chelating ligands and CeCl₃ and Ce(NO₃)₃ as cerium salt precursors. All 3DOM Au/CeO₂ catalysts possess well-defined 3DOM skeletons composed of well-crystallized CeO₂ nanoparticles, based on the different synthetic procedures, the 3DOM Au/CeO₂ catalysts show variations in surface elemental compositions, particle sizes of CeO₂, macroporous and mesoporous structures, and valence states of Au. The mesoporous walls with nanopores ∼3–4 nm on 3DOM Au/CeO₂ skeletons can be created when using Ce(NO₃)₃ as precursor. The catalytic performance of 3DOM Au/CeO₂ catalysts for CO preferential oxidation in H₂-rich gases was systematically investigated. The catalytic performance is closely correlated to surface elemental compositions, particle sizes of CeO₂, macroporous and mesoporous structures, and valence states of Au due to the different synthetic procedures. The 3DOM Au/CeO₂ catalysts prepared using oxalic acid as chelating ligand and Ce(NO₃)₃ as cerium salt precursor show the highest catalytic activity for CO preferential oxidation in H₂-rich gases with 90.1% CO conversion and 59.9% CO₂ selectivity at 50 °C, and 88.3% CO conversion and 59.3% CO₂ selectivity at 80 °C, respectively. The obtained 3DOM Au/CeO₂ catalysts may be of importance for guiding the design of efficient catalysts with desired porous structures that are potentially applicable in polymer electrolyte membrane fuel cells.