Controlled synthesis of α-Fe2O3@Fe3O4 composite catalysts for exhaust gas purification

Single (alpha-Fe2O3 and Fe3O4) and composite iron oxides (alpha-Fe2O3@Fe3O4) have been prepared by chemical vapor deposition for clean combustion. The physio-chemical properties of the obtained thin films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and the redox properties via temperature programmed reduction analyses. The catalytic performance for the oxidation of C2H2 and CO and their mixtures as representatives of exhaust gases was performed at temperatures range of 100-400 degrees C. The best performance, with respect to total oxidation of individual gas, was achieved by alpha-Fe2O3@Fe3O4 composite that presented the highest amount of electrophilic oxygen on the surface (O-species) and the lowest reduction temperature. alpha-Fe2O3@Fe3O4 also exhibited good performance towards the total abatement of the mixed gases at different gas hourly space velocities. Moreover, the catalysts were reusable and stable upon several consecutive runs and no obvious deactivation was observed after 11 h prolonged time-on-stream at 300 degrees C. The higher quantity of surface oxygen species, the low-temperature reducibility and the porous-like morphology are suggested to play decisive roles in the catalytic oxidation processes. The deep oxidation of individuals and mixed gases by the coexisting alpha-Fe2O3@Fe3O4 is a promising strategy in energy utilization and environmental protection. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.