Preparation And Catalytic Ability Of Ag-ZSM-5 Modified Electrode

Most organic halides have chemical stability and strong toxic carcinogenic teratogenic effects, it can also pollute the environment. In order to protect the natural environment and reduce the threat to human health, reduction of organic halides has become an important research direction. Among numerous halogen reduction methods, electrocatalytic reduction of halides can not only shorten the process and reduce cost, but also reduce pollution to the environment. Recently, CO2 was used in people’s life and production more and more frequently. It provided people with convenience, but it was also the main reason of causing the serious problem "greenhouse effect". The concentration of greenhouse gases such as CO2 increasing aggravate the "greenhouse effect" in the atmosphere, which brings the serious consequences of global warming, endangering the human living environment and their own interests. However, electrochemistry fixing CO2 to react with organic halides, on the one hand can effectively use CO2, on the other hand can also conduct electricity reduction to organic halides. It saves energy and at the same time protects the environment, which is a research of multiple significance.Although good current efficiencies could be obtained by using Ni, Pd and other complexes, the separation processes are much more complicated. Nowadays, Ag is recognized as a powerful catalytic material for the electroreduction and electrocarboxylation of organic halides. Moreover, higher electrocatalytic activity was obtained on nano Ag electrodes for their higher active sites on the surface. Nowadays, metal nanoparticles were often scattered on the carrier, such as zeolite. This method can avoid the reunion between particles, and effectively improve the degree of dispersion. Thus, the preparation of silver zeolite modified electrodes to be used for electrocarboxylation of organic halides has become a promising research. As a sub branch of chemically modified electrodes, zeolite modified electrodes have great advantages because of their unique size, shape and charge selectivity and high ion exchange capacity. Nowadays, more and more attentions were paid to zeolite modified electrodes. In the field of electrochemistry, zeolite was gradually applied to electrocatalytic reaction. However, most researchers prepared the zeolite modified electrodes with the method of depositing. This method is relatively complicated, and the zeolite on the electrode is easy to fall off, not stable. Therefore, in this thesis, we adopted the in situ hydrothermal synthesis method to prepare zeolite membrane on surface of substrate electrode and effectively solved problem that the zeolite was easy to fall off. Moreover we combined Ag with zeolite membrane modified electrodes, adopting one-step method to prepare the silver zeolite modified electrodes. Then the modified electrodes were used in the electrochemical reduction of benzyl chloride. The silver zeolite modified electrodes have better catalytic properties than bulk silver electrode, tested by cyclic voltammetry, Tafel plot and potentiostatic electrolysis. The specific work of this thesis is mainly from the following aspects:(1) Preparation and characterization of silver zeolite modified electrodes. We prepared the silver zeolite modified electrodes on the substrate electrode, stainless steel 304, through in-situ hydrothermal synthesis method by one step. The silver zeolite modified electrode was characterization by XRD, SEM, TEM, EDX, H2-TPR, XPS, BET, IR, UV, and TGA. Then the silver zeolite modified electrode was applied as working electrode in the electrochemical reduction of benzyl chloride. The reduction peak potential of benzyl chloride in the cyclic voltammograms, exchange current density from Tafel plot and yield of methyl phenylacetate by potentiostatic electrolysis can all prove good catalytic ability of modified electrodes.(2) The research on preparation conditions of silver zeolite modified electrodes. The silver zeolite modified electrodes were still prepared by in situ hydrothermal synthesis method, and then the electrodes were made optimally in crystallization temperature, crystallization time, silver nitrate concentration, acid radical ion species, the proportion of alkali and proportion of A1 and Si in the seed solution. We research the influence of different preparation conditions on the morphology of silver zeolite modified electrodes. Then the modified electrodes were applied to electroreduction of benzyl chloride through cyclic voltammetric behavior, and the electrocatalytic activity of different electrodes could be test by the reduction peak potential of benzyl chloride.The experimental results show that, compared to bulk silver electrode, the silver zeolite modified electrodes prepared through the in-situ hydrothermal synthesis method have better catalytic ability. The modified electrodes have high stability and are easy to be prepared.