Ag supported on CeO2 with different morphologies for the catalytic oxidation of HCHO

Ag/CeO2 catalysts with various shapes of CeO2 (nanorods, nanoparticles, and nanocubes) were prepared by the hydrothermal and impregnation method and then used for the catalytic oxidation of HCHO at low temperature. TEM and XRD results showed that Ag nanoparticles were well dispersed on the surface of CeO2. According to the results from XPS, H-2-TPR and Raman spectra, Ag/r-CeO2, Ag/p-CeO2 and Ag/c-CeO2 exhibited different oxygen vacancy concentration, more oxygen vacancy and surface chemisorbed oxygen formed in Ag/r-CeO2. There might existed synergetic interaction between Ag and CeO2, and the presence of Ag nanoparticles could promoted the activation of surface chemisorbed oxygen, which is favorable for HCHO oxidation. The catalytic properties of the catalysts were significantly dependent on the shapes of CeO2, due to the highest surface oxygen vacancy concentration and best reducibility, Ag/r-CeO2 exhibited the best catalytic activity for HCHO oxidation. Ag/rCeO(2) showed higher specific reaction rate (7.43 nmol/(s.m(2)) at 100 degrees C) and TOFAg (0.0071 s(-1) at 100 degrees C) under 810 ppm of HCHO and 84,000 h(-1) of GHSV. Ag/r-CeO2 could reach complete HCHO oxidation at around 110 degrees C, which was lower than that of Ag/p-CeO2 and Ag/c-CeO2. Higher low-temperature reducibility, more surface oxygen vacancies, surface lattice oxygen species, and lattice defects produced by the interaction of Ag and CeO2 contributed to the excellent catalytic performance of Ag/r-CeO2 for HCHO oxidation. These results revealed that the HCHO catalytic oxidation activity was dependent on the shapes of CeO2 supports, this study suggested that the catalytic activity of the metal/CeO2 catalysts can be regulated by engineering the shapes of CeO2 supports.