Abstract
Au–Mn co-precipitates were dried at different temperatures and in different atmospheres. The co-precipitates were tested for low-temperature CO oxidation without any additional thermal treatment. While samples dried at 120°C in air exhibited the highest activity for CO oxidation, samples dried at room temperature under vacuum were less active. The catalytic properties of most fresh samples improved after the first light-off test, during which a temperature of 400°C was reached. To investigate the physical and chemical state of gold and manganese support, dried samples were examined by 197Au Mössbauer spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The 197Au Mössbauer spectra showed that gold existed only in metallic form and was produced during the co-precipitation procedure. XRD and XPS analyses demonstrated that fresh samples contained manganese carbonate and oxides such as MnO2. The carbonate was converted to manganese oxides after the light-off test. TEM analysis indicated that the manganese support was present in plate-like shapes and the shape of gold particles was rectangular with rounded corners. Au particle sizes were in the range 4.5–6.5 nm before the light-off test. After heat treatment at 400°C, catalytic activity improved and a strong interaction between gold particles and the MnOx support was induced.
Published Version
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