Baize-like monolithic CeO and NiO/CeO nanorod catalysts were prepared by combined dealloying and calcination and the catalytic activities were evaluated using CO catalytic oxidation. The CeO catalysts were composed of nanorods and exhibited a three-dimensional supporting structure with pores. After introduction of NiO, dispersed NiO nanosheets and nanoparticles were supported on the surface of CeO nanorods and they were not well-crystallined due to CeO inhibiting the NiO crystallization. The Raman and x-ray photoelectron spectroscopy analyses revealed that the introduction of NiO species into CeO generated more coordinate unsaturated Ni atoms, oxygen vacancies, defects and active sites for CO catalytic reactions. The reaction activation energy of NiO/CeO nanorod catalyst prepared from the AlCeNi precursor alloy was just 31.2 kJ mol and the CO conversion can reach up to 97% at 240 °C, which was superior to that of pure CeO and nanoporous NiO. The enhanced catalytic activity of baize-like NiO/CeO nanorods can be attributed to the strong synergistic effects between finely dispersed NiO species and surface oxygen vacancies in CeO nanorods.
Nanoporous CuO/CeO2 ribbons are successfully prepared through dealloying melt-spun Al80−xCu20Cex (x = 0.5, 1, 2, 3, at%) alloy in a 5 wt% NaOH aqueous solution, followed by calcining in air. The samples are characterized by XRD, SEM, EDS, HRTEM, Raman and gas chromatograph. For the dealloyed melt-spun Al80−xCu20Cex (x = 0.5, 1, 2, 3, at%) alloy, the XRD results indicate that Cu and Cu2O are formed, while CuO and CeO2 are formed coupled with calcinations. The SEM shows that the CuO/CeO2 ribbons with a homogeneous pore/grain structure are thermally stable up to 600˚C because uniform CeO2 particles are dispersedly loaded on the fine CuO grains of the porous structure, which is validated by TEM again. Meanwhile, the Raman spectra show that the concentration of oxygen vacancies reach a maximum value when the calcining temperature at 600˚C. In addition, the gas chromatograph results show that the dealloyed Al78Cu20Ce2 ribbons with calcined at 600˚C have the best active catalysis for CO oxidation and the rates of CO conversation reaching at 50% and 100% are 150˚C and 320˚C, respectively, owing to the synergetic effects of the CuO and CeO2 species.
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