Abstract
Au/Fe2O3 catalysts prepared using co-precipitation are described and discussed for the preferential oxidation of CO in the presence of H-2, H2O and CO2. A catalyst prepared using a two-stage calcination procedure (400 degrees C followed by 550 degrees C) achieves target conversion and selectivity (> 99.5% CO conversion and > 50% selectivity, based on O-2, for the competing conversion of H-2 with O-2 at 80-100 degrees C) for the competitive oxidation of dilute CO in the presence of moist excess H2 and CO2. The effect of the preparation method of the uncalcined precursor is described and the effects of calcination on the catalyst activity in the absence of H2, CO2 and H2O is initially explored. The catalysts are characterised in detail using electron microscopy (TEM), X-ray photoelectron spectroscopy and Mossbauer spectroscopy. For the target conversion to be achieved, it is necessary that the activity for the reverse water gas shift activity (CO2 + H-2 -> CO + H2O) of the catalyst is suppressed, since under the fuel cell conditions this reaction reforms CO at high CO conversions due to the presence of excess CO2 and H-2. It is proposed that the two stage calcination procedure removes active sites for the water gas shift reaction whilst retaining active sites for preferential CO oxidation.