In situ characterization of Cu–Fe–O x catalyst for water–gas shift reaction

Cu–Fe–O catalyst consisting of α-Fe2O3 with supported CuO nanoparticles was prepared through co-precipitation. Integrated analyses of surface and bulk of the catalyst particles showed that it consists of α-Fe2O3 with supported CuO nanoparticles. The supported CuO can be reduced to metallic Cu at a temperature of 100–150 °C with a following transformation of α-Fe2O3 to Fe3O4 at a temperature of 150–200 °C. The composition of Cu/Fe3O4 was identified by in situ X-ray diffraction, high-angle annular dark field scanning transmission electron microscope and ambient pressure X-ray photoelectron spectrometer. The formed Cu/Fe3O4 exhibits high activity for water–gas shift reaction in the temperature range of 180–250 °C. Activation barrier of WGS on Cu/Fe3O4 is lower than Cu/Al2O3 by 10–15 kJ/mol, suggesting that Fe3O4 participates into the WGS in the low-temperature range. Ambient pressure X-ray photoelectron spectroscopy studies show that the active surface phase during WGS consists of metallic Cu nanoparticles and Fe3O4 nanoparticles.