SCHEDULED MAINTENANCE
Low-temperature NOx (x = 1, 2) removal with ˙OH radicals from catalytic ozonation over a RGO–CeO2 nanocomposite: the highly promotional effect of oxygen vacancies†
Abstract
CeO2 grown on a reduced graphene oxide nanocomposite (RGO–CeO2) was successfully synthesized by a facile alkaline hydrothermal method with the addition of ethylene glycol. For the first time, it was utilized as an ozonation catalyst for denitrification at low temperatures. The RGO–CeO2 nanocomposite, in which the content of RGO was only 2.8 wt%, exhibited much higher catalytic activities (96.8% at 40 °C) than pure nano-CeO2 (78.2% at 40 °C), which was found to exhibit a positive relationship with the concentration of ˙OH radicals. There was no correlation between the surface hydroxyl densities and the catalytic activities of RGO–CeO2, RGO and CeO2, suggesting that not all surface hydroxyl groups exhibit the same high catalytic activity. The activity of surface hydroxyl groups becomes the dominant factor for determining catalytic performance. Compared with pure nano-CeO2, the surface hydroxyl activity was enhanced for RGO–CeO2 due to the generation of more oxygen vacancies from the reduction in crystallite size and better dispersion of CeO2. The surface –OH groups at the oxygen vacancy sites were more active than the intrinsic –OH of CeO2 at promoting the generation of ˙OH radicals and being conducive to denitrification.
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