Shihua Wu

Comparative study on catalytic properties for low-temperature CO oxidation of Cu/CeO2 and CuO/CeO2 prepared via solvated metal atom impregnation and conventional impregnation

Cu/CeO2 and CuO/CeO2 catalysts were prepared by solvated metal atom impregnation (SMAI) and conventional impregnation (CI) and used for carbon monoxide oxidation in CO and air. The catalysts were characterized by means of XRD, XPS, AES and H2-TPR techniques. The Cu/CeO2 catalyst prepared via SMAI exhibits higher catalytic activity in CO oxidation than that prepared via CI with the same Cu content due to the smaller Cu particles. The CuO/CeO2 catalyst prepared via SMAI also shows higher catalytic activity than that prepared via CI because the CuO particles of the former are smaller than the latter and can be reduced by CO more easily. The Cu/CeO2 catalysts display higher catalytic activities than CuO/CeO2 catalysts with the same Cu content and prepared by the same method. The TPR profile for CuO/CeO2 catalyst prepared via SMAI has a single peak, indicating a one-step reduction, whereas the TPR profile for CuO/CeO2 catalyst prepared via CI has two peaks, indicating a two-step reduction due to the existence of two kinds of CuO species.

Reed straw derived active carbon/graphene hybrids as sustainable high-performance electrodes for advanced supercapacitors

Reed straw-derived active carbon@graphene (AC@GR) hybrids were prepared by one-step carbonization/activation process using a mixture of reed straw and graphene oxide (GO) as raw materials and ZnCl2 as activation agent. The as-prepared hybrids exhibit high specific surface area in a range of 1971–2497xa0m2xa0g−1, abundant porosity, as well as excellent energy storage capability. The symmetric C//C supercapacitor using the hybrid obtained at 700xa0°C as electrodes demonstrates superior cycling durability, ca. 90xa0% retention after 6000xa0cycles at 2xa0Axa0g−1, and a high energy density of 6.12xa0Whxa0kg−1 at a power density of up to 4660xa0Wxa0kg−1 in 6xa0M KOH aqueous electrolyte. The excellent capacitive performance is attributed to the synergistic effect of AC and GR.

Comparative studies of gold catalysts prepared via solvated metal atom impregnation and conventional impregnation: characterization and low-temperature co oxidation

Supported Au catalysts for low-temperature CO oxidation were prepared by solvated metal atom impregnation (SMAI) and conventional impregnation (CI). X-ray photoelectron spectroscopy investigations indicated that gold in all the samples was in the metallic state. TEM and XRD measurements showed that the mean diameter of Au particles prepared by SMAI was smaller than that of those prepared by CI with the same gold content. Catalytic tests showed that SMAI catalysts had higher CO oxidation activity than CI catalysts with the same compositions. Both SMAI and CI Au/TiO2catalysts exhibited high activities in low temperature CO oxidation. Full CO conversion was obtained at 323 K for 3.1 wt.% Au/TiO2 (SMAI) catalyst, which displayed higher activity than the 3.1 wt.% Au/D-72(SMAI) and 3.1 wt.% Au/TiO2(CI). Although the sizes of gold particles prepared by the same method and supported on both TiO2 and resin were comparable, the Au/TiO2 catalysts showed significantly higher activities than the Au/resin catalysts with the same Au contents under the same reaction conditions. These results prove that not only the gold particle size, but also the support plays a key role in CO oxidation.