Preparation And Catalytic Performance Of Porous Ag/Co₃O₄Nanocomposites

Nanomaterials, with unique features such as small volume effect, surface and boundary effect, quantum size effect and so on has been widely used in fields of catalysis, lithium electricity and drug carrier. With the development of research, people have realized that simple-structured homogeneous catalyst, where the catalyst is in the same phase as the reactant can never meet the demand for fundamental research and industrial application for its low activity and difficult separation. Heterogeneous catalyst composed of more than two components is becoming a research hotspot in recent years. It can not only gather the outstanding performance of each component, but also bring interaction between different phases, which might have unexpectedly positive effect on the catalytic reaction. Herein, Ag3[Co3(CN)6] which has special structure as a kind of metal-organic frameworks (MOFs), was used as a precursor and annealed in air to obtain porous Ag/Co3O4nanocomposites. Catalytic performance of CO oxidation and production of2,5-dimethylfuran (DMF) from5-Hydroxymethylfurfural (HMF) as well as the influence of annealing temperature on the catalytic activity and the active component for the hydrogenation of HMF in Ag/Co3O4nanocomposites were studied. The concerns of the dissertation include following aspects:1. Homogeneous Ag3[Co3(CN)6] were faberacated using a template Co3[Co3(CN)6]2via a novel "in situ self-reduction" route. Porous Ag/Co3O4nanocomposites with various Ag particle sizes were prepared by calcining Ag3[Co3(CN)6] nanocubes at different temperatures in air. During calcinations, large amounts of Ag/Co3O4nanojunctions were generated and dispersed uniformly due to the rearrangement of Ag and Co atoms, which were propitious to catalyzed reaction by providing more active sites.2. The porous Ag/Co3O4nanocomposites were used as catalysts for CO oxidation. It proved that all the as-prepared samples show high catalytic activity, especially C200with a complete CO conversion temperature of100℃. Moreover, it could maintain high catalytic performances even after18h and being exposed to air for two months. The presence of abundant and highly dispersed Ag/Co3O4junctions in the nanocomposites was suggested to be responsible for the excellent catalytic performance. On the junctions, O2and CO are adsorbed on Ag and Co3O4, respectively and react with each other more easily. Furthermore, Ag particle aggregation and oxidation can be avoided during a catalytic reaction and storage due to the well-knit Ag/Co3O4junctions, which results in excellent catalytic activity and stability.3. Two samples with different Ag content were faberatcated in the same way to distinguish the active component which play a main role in the catalysis conversion of HMF. The result demonstrated the improvement of activity with increasing Ag content. But the problem is that Ag/Co3O4nanocomposites are tended to decompose after catalysis.