Rod-like and mushroom-like Co3O4–CeO2 catalysts derived from Ce-1,3,5-benzene tricarboxylic acid for CO preferential oxidation: effects of compositions and morphology

Abstract

Rod-like and mushroom-like Co3O4–CeO2 catalysts were synthesized using CeBTC MOFs as self-sacrifice templates. The two kinds of Co3O4–CeO2 catalysts with different shapes were characterized by SEM, TEM, N2 physical-sorption, XRD, TPR, Raman, XPS. The effects of compositions and morphology on the catalytic activity were investigated. The catalytic activities of Co3O4–CeO2 are correlated with the results of SEM, TEM, N2 physical-sorption, XRD, TPR, Raman, XPS to give insights into the catalytic sites. The results indicate the obtained Co3O4–CeO2 catalysts exhibit rod-like and mushroom-like, replicating the morphology of CeBTC templates. The catalytic activities of Co3O4–CeO2 were arranged in this sequence: Co1Ce > Co6Ce > Co2Ce > Co4Ce > Co8Ce, regardless their different catalyst morphology. The mushroom-like catalysts are superior to the rod-like ones due to their high surface areas and small Co3O4 crystal sizes. The sequence of catalytic activity versus Co/Ce ratio are coincidence with the order of Co–Ce synergistic interaction and Co3+/Co deduced from results of XRD, TPR, Raman, XPS. This evidence revealed that the Co–Ce synergistic interaction and Co3+ ions are responsible for the high activity of Co3O4–CeO2 catalysts. The highest CO conversion of 99% catalyst was achieved over M-Co1Ce catalyst with 12.5% CO2 and 15% H2O at 215 °C, 20,000 mL g−1 h−1. In addition, CO conversion of M-Co1Ce catalyst maintained more than 99% for 54 h in the atmosphere of simulated reformate at 20,000 mL g−1 h−1, suggesting the M-Co1Ce catalyst demonstrates potential in practice application.