Low-temperature CO oxidation over supported Pt, Pd catalysts: Particular role of FeOx support for oxygen supply during reactions

A Pt/FeOx catalyst exhibited high CO oxidation activity (TOF of 151 x 10-3 s-1, 1% CO balanced with air, atmospheric pressure, 27 degrees C) was reported. Clear evidence form characterizations show that FeOx acting as an oxygen supply is involved in the reaction. A series of FeOx- and Al2O3-supported Pt, Pd catalysts (0.23-2.1%) were prepared in this study. Pt/FeOx exhibited high CO oxidation activity with turnover frequency of 151 x 10-3 s-1 (1% CO balanced with air, atmospheric pressure, 27 degrees C). A systematical study of FeOx- and Al2O3-supported Pt, Pd catalysts by means of X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, temperature-programmed reduction, H2-O2 titration, and time-resolved CO titration is reported. From 7% to 39% of Fe3+ was reduced to Fe2+ over Fe(OH)x-supported Pd and Pt catalysts, accompanied by Pd, Pt hydrogenation and hydroxyl loss, and a large amount of oxygen vacancies were proposed to be produced. Results of H2-O2 titration and time-resolved CO titration showed that a large amount of oxygen adsorbed onto FeOx support in the presence of Pt, Pd. This made CO oxidations over Pt/FeOx, Pd/FeOx proceed over two adjacent but different active sites (Pt, Pd for CO and FeOx for oxygen) with low apparent activation energies (30-34 kJ/mol), which accounted for their high activity in low-temperature CO oxidation. [PUBLICATION ABSTRACT]