Abstract
The Mn doping nanocrystalline Co–Ce–Zr–O
x
catalysts were prepared by the co-precipitation method and characterized by various physico-chemical characterization techniques such as X-ray diffraction (XRD), temperature- programmed reduction (TPR), O
2 temperature-programmed desorption (O
2-TPD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH). Their catalytic performances for methane reforming with CO
2 to hydrogen and carbon monoxide were investigated. Adding Mn remarkably enhanced the catalytic activity and stability of the Co–Ce–Zr–O
x
catalyst. The highest catalytic activity and long-term stability was obtained when the molar ratio of Mn/(Ce
+
Zr
+
Mn) was 10%. The improved catalytic behavior was closely related to the surface oxygen species and oxygen mobility. In comparison with that of Co–Ce–Zr–O
x
catalyst, the migration of bulk lattice oxygen species became easier, and the content of surface oxygen species was higher for the Mn-doped nanocrystalline Co–Ce–Zr–O
x
samples. TPH characterization showed that the surface coke species could be easily oxidized into CO
x
for the Mn-doped nano cobalt-composite catalyst due to the higher amount of mobile oxygen. The Mn incorporation promoted the dispersion of the nano-sized CoO
x
crystallites. In comparison with the impregnated samples, CoO
x
species dispersed better in the co-precipitated catalysts.