Pd catalysts supported on Co3O4 with the specified morphologies in CO and CH4 oxidation

Firstly, the spinel cobalt oxide (Co3O4) was controllably synthesized with different morphologies (cubical, flower-like, plate-like and rectangular-like) via a hydrothermal method. Then Pd was loaded on them by incipient wetness impregnation. The properties of the samples prepared were characterized by XRD, H-2-TPR, CO-TPR, SEM, TEM, HRTEM and XPS. The impacts of Pd addition on CH4 and CO oxidation were investigated under lean methane and CO atmosphere, respectively. The effectiveness of Pd was different for CH4 and CO oxidation. For methane oxidation, the activities of Co3O4 were enhanced due to Pd loading. And the orders of activity primarily kept consistent before and after impregnation, while the extent of improvement on activity from Co3O4 to Pd/Co3O4 was consistent with the order of surface O-ads/O-lat of Pd/Co3O4, indicating that different interaction occurred between Pd species unit cell and the Co3O4 unit cell with different crystal planes. In the case of CO oxidation, a significant decline on activity was observed over the Pd/Co3O4-R (rectangular-like Co3O4), Pd/Co3O4-F (flower-like Co3O4), Pd/Co3O4-P (plate-like Co304), while a distinct promotion on activity was observed over the Pd/Co3O4-C (cubical Co3O4). Similarly the variations in the activity of Pd/Co3O4 were ascribed to the shifts on surface O-ads/O-lat molar ratio and the specific area reaction rate. (C) 2016 Elsevier B.V. All rights reserved.