| Microbial fuel cell, using the conductive bacteria as catalyst to convert biodegradable organic into carbon dioxide and water, is a new type of energy technologies. It can deal with the sewage without pollution and recycle energy simultaneously. Anaerobic fluidized bed microbial fuel cell, coupling the fluidized bed with MFC, improves the electrical characteristics of MFC by strengthening mass transfer. Low activity and expensive price of cathode catalyst is one of the important factors which limit the MFC application. Based on the preparation of hyperbranched molecules templates, the preparation of the high active, high stability, cheap Pt-DENs cathode catalyst and its performance were investigated, the main research contents and results are as follows:(1) The experiment results showed that, the best condition to prepare PAMAM using 0.5G PAMAM were as follows. The reaction time is 24 h, reaction temperature is 25 ℃, and reaction substance ratio is more than 4:1, high yield ratio of PAMAM can be obtained. Under the condition, the high generation of PAMAM is prepared. Its structure is characterized by FT-IR and its purity is characterized by thermogravimetric analysis.(2) The Pt-DENs composite material is prepared by complexation-reduction method. In the solvent, Pt-DENs is prepared by complexation reaction of K2 Pt Cl4 and prepared 5.0G PAMAM, using sodium borohydride as reduction reaction. The effections of reaction time, reaction temperature and reaction substance ratio for the prepared Pt-DENs were characterized by FT-IR, XRD and TEM. The experiment results revealed that, when water was used as solvent, the optimal reaction conditions were as follows. Reaction time is 48 h, reaction temperature is 75 ℃, and reaction substance ratio is 37.5:1. When methanol was used as solvent, the optimal reaction conditions were the following.The reaction time is 12 h, reaction temperature is 75 ℃,and reaction substance ratio is 37.5:1.(3) The prepared Pt-DENs were used as cathode catalysts for AFBMFC to investigate those waste water treatment and electrical production performance. Usingwater as solvent, the prepared Pt-DENs using by 5.0G PAMAM was marked sample a,and that of sample prepared by 4.5G PAMAM was marked b. For sample a and sample b, the reaction time is 48 h, reaction temperature is 75 ℃, and reaction substance ratio is 37.5:1. Using methanol as solvent, the prepared Pt-DENs using by 5.0G PAMAM was marked sample c, and that of sample prepared by 4.5G PAMAM was marked d.For sample c and sample d, the reaction time is 12 h, reaction temperature is 75 ℃, and reaction substance ratio is 37.5:1. The Pt-DENs prepared under different conditions is applied in MFC. After a cycle of stable operation, the maximum voltage are 836.2 m V,805.2 m V, 819.4 m V and 666.2 m V; the open circuit voltage is 850 m V, 825 m V, 830 m V and 810 m V; the maximum output power density is 74 m W·m-2, 70 m W·m-2, 67 m W·m-2 and 55 m W·m-2; COD removal rate is 89.63%, 87.65%, 87.1% and 84.5% for sample a, b, c and d respectively. The experimental results showed that, sample a, the Pt-DENs prepared by 5.0G PAMAM in water solvent has the best performance.(4) Compared with the cathode catalyst, the Pt-DENs cathode catalyst has better performance than that of Pt/C cathode catalyst. After a cycle of stable operation, the performances of the MFCs using Pt-DENs, Pt/C and free cathode catalyst are listed as follows respectively. The maximum voltage were 902.4 m V, 836.2 m V and 535.5 m V,the open circuit voltage were 902 m V, 850 m V and 550 m V, the maximum output power density were 74 m W·m-2, 68 m W·m-2 and 18 m W·m-2;COD removal rate were89.63%, 89.75% and 83.62%, respectively. The conclusion is that the Pt-DENs cathode catalyst has best catalytic activity, and has promising application in MFC in the future. |
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