Preparation Of Polyaniline Anode Materials And Their Applications In Benthonic Sediment Microbial Fuel Cell

Microbial fuel cell (MFC) is a renewable energy device that converts organic and inorganic matter to electrical energy via the catalyzation of bacteria. It is clean, non-polluting, producing electricity while degrading organic waste. Benthonic sediment microbial fuel cell (BMFC) is a special kind of MFC. BMFC's anode is embedded in anaerobic marine sediments, and connected with the cathode in upper seawater through the external circuit. BMFC has a promising potential application in supplying the instruments of remote marine areas.However, the BMFC's commercial application is limited due to the low output power density. The electron transfer rate between the current-producing microbes and the anode is an important factor in determining the battery performance. The nature and structure of the anode material is closely related on the adhesion of current-producing microbes, electron transport, and substrate oxidation. Since polyaniline has a high conductivity, environmental stability and good reduce activity, it has a wide range of applications in the rechargeable battery and electric catalysis.In this study, we prepared four kinds of polyaniline anode materials, which are made into composite anodes, and applied in the BMFC. Four kinds of polyaniline anode materials can significantly improve the performance of the battery. Thus they are highly expected to be used in BMFC and give higher output power density. Main results are as follows:(1) A novel polyaniline-camphorsulfonic acid (PANI-(D-CSA)) composite anode was prepared. We studied the best ratio and tested the electrochemical properties when PANI-(D-CSA) applied in the BMFC. The composite anode was characterized by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Structural analysis shows that PANI-(D-CSA) is partially crystallined and has good thermal stability. Performance tests show that the composite anode with 50% (mass fraction) PANI-(D-CSA) gives the lowest resistance and the lowest slope of anodic polarization curve, while the battery output power density is significantly increased. The maximum output power density is 233.9mW/m², which is 3.7 times the pure graphite anode.(2) Sulfonated polyaniline, sulfonated polyaniline/manganate composite, sulfonated polyaniline/vanadate composite were synthesized and utilized as composite anodes in the BMFCs, respectively. XRD and TGA were used to characterize the chemical composition and morphology of these anode materials. Because polytetrafluoroethylene (PTFE) leads to the fall of hydrophilic property, we adopted the linear sweep voltammetry and Tafel curves to study the electrochemical properties of the composite anode. Compared with the pure graphite anode (34.1mW/m²), sulfonated polyaniline, sulfonated polyaniline/manganate composite, and sulfonated polyaniline/vanadate composite give the maximum output power density with 129.1, 140.6, and 187.1 mW/m², respectively. The apparent internal resistance was decreased from 10644Ω(for graphite anode) is reduced to 3253, 2402, and 1716Ω. Exchange current density was increased from 2.2189×10^-7A/cm² (graphite anode) to 2.3015×10^-6, 3.6308×10^-6, and 5.9863×10^-6A/cm², respectively. In this part, we proposed a synergistic mechanism occurred between sulfonated polyaniline and vanadium salts. It gives a reasonable explanation for the reason why the composite anodes enhance the electrochemical performance of BMFC.