2.4 Characterization of Catalysts
X-ray diffraction (XRD) was collected on a Rigaku diffractometer (D/MAX,
3 kW) equipped with Cu Kα radiation (40 kV, 30 mA, λ=0.1543 nm) (Bruker,
Germany) and the patterns were recorded in the 10-90º. X-ray
photoelectron spectroscopy (XPS) was carried out on a Kratos Axis Ultra
DLD system. Transmission electron microscopy (TEM) was performed using a
JEOL Model 2100F electron microscopy at 200 kV. Aberration-corrected
scanning STEM images were taken using a Cs-corrected FEI Titan G2 60-300
Microscope operated at 300 KV using an HAADF detector. Field emission
scanning electron microscopy (FFSEM, Merlin, Germany) was performed to
measure the morphology of the samples. The X-ray absorption spectra were
collected on the beamline BL01C1 in NSRRC. The radiation was
monochromatized by a Si (111) double-crystal monochromator. X-ray
absorption near-edge structure (XANES) and extended X-ray absorption
fine structure (EXAFS) data reduction and analysis were processed by
Athena software. N2 adsorption isotherms of catalysts at
77K were measured on a Tristar II 3020, USA. The samples were pretreated
at 200 °C for 12 h under vacuum. The metal content of the catalysts was
confirmed by Perkin-Elmer TJA RADIAL IRIS 1000.