Investigations On The Electrode Preparation And Bioelectrochemical Properties Based On Conductive Polymer And Ionic Liquid Modification Strategies

Microbial fuel cell（MFC）is a system that can decompose organic matter to generate electrons through microbial respiration,and transfers electrons to external electrodes through the interaction between microbial cytochromes and electrodes.In MFC,microorganisms are attached to the anode,so the efficiency of the microorganisms to transfer electrons to the anode through extracellular electron transfer is a key factor that limits the efficiency of microbial fuel cell power generation and practical applications.Therefore,it is an important step to break the bottleneck of practical application of microbial fuel cells by selecting high-biocompatibility and high-conductivity materials to modify microbial fuel cell anodes to promote microbial adhesion and growth and while improving anode electron transfer efficiency.The research work in this thesis mianly foused on the following mentions:The carbon felts modified by different conductive polymers and ionic liquid were applied as anodes in MFC,Shewanella putrefaciens ATCC 8071 was chosen the model electricity-producing microorganism and the extracellural electron transfer process between the microbe and the modified electrodes were also explored.Furthermore,the effect of anode modification on the attachment and reproduction of microorganisms were investigated.Finally,the influence of the electrode modification on the performance of microbial fuel cells was discussed in detail.First,by electrodeposition method,the carbon felt electrode（CF）was modified with polypyrrole（PPy）and sodium anthraquinone-2-sulfonate（AQS）as composite materials.Through the relevant experiments of microbial fuel cells,the electrochemical characteristics of the modified electrode（CF/AQS/PPy）and its interaction with microorganisms were studied.Scanning electron microscope（SEM）and Fourier infrared spectroscopy（FT-IR）characterizations showed that PPy and AQS have been successfully loaded on carbon felt electrode surface.Electrochemical characterization and water contact angle tests showed that the modified electrode could enhance electrode conductivity and improve biocompatibility.Cyclic voltammetry test calculations showed that in the three-electrode reaction system with CF/AQS/PPy as the working electrode,the maximum electron transfer amount between the electrode and the microorganism reached 5.24×10^-1Coulomb（C）,which is 127.8 times higher than that of the bare CF electrode(4.07×10^-3C).The water contact angle of the CF/AQS/PPy electrode is 41.89°,which is 49.11%of the corresponding value of the bare CF electrode.Cyclic voltammetry（CV）test using potassium ferricyanide as a probe to indicate the electron transport mode and electrochemical activity of the electrode.The electrochemical impedance spectroscopy（EIS）test was used to indicate the electronic difficulty of the electrode.Analysis of the data showed that the charge transfer resistance(R_ct)of the modified electrode（CF/AQS/PPy）was reduced to 12.7Ω,which was 13.2%of the corresponding value of the bare electrode（CF）.The CF/AQS/PPy electrode was further used as the anode of the dual-chamber system microbial fuel cell.The maximum power density obtained was 1233m W/m²,which was 3.1 times higher than that of the bare CF anode.SEM characterization confirmed that there were a large number of microbial colonies on the surface of the CF/AQS/PPy electrode,which effectively improved the biocompatibility of the anode electrode.By using data acquisition cards to monitor the voltage changes of single-and dual-chamber systems for microbial fuel cell,it was found that CF/AQS/PPy electrodes as anodes could accelerate the stage start-up of microbial fuel cells.The reflow method and constant voltage electrodeposition method were used to modify the CF electrode with ionic liquid（ILP）and sodium anthraquinone-2-sulfonate（AQS）as composite materials.Then explored the electrochemical characteristics of the interaction between the modified electrode（CF/AQS/ILP）and microorganisms.SEM and FT-IR characterizations showed that ILP and AQS had been successfully loaded on carbon felt electrodes.Electrochemical characterization and water contact angle tests show that the modified electrode could enhance electrode conductivity and improve biocompatibility.Cyclic voltammetry test calculations showed that in the three-electrode reaction system with CF/AQS/ILP as the working electrode,the maximum electron transfer amount between the electrode and the microorganism reached 1.71×10^-2C,which was 55.2 times higher than that of the bare CF electrode.The CF/AQS/ILP electrode had a water contact angle of 60.83°,which was 62.04%of the corresponding value of the bare CF electrode.CV test using potassium ferricyanide as a probe to show the electron transport mode and electrochemical activity of the electrode.The EIS test was used to indicate the electronic difficulty of the electrode.Analysis of the data showed that the charge transfer resistance(R_ct)of CF/AQS/ILP was reduced to 12.97Ωat least,this value was 3.6%of the corresponding value of the bare electrode（CF）.The minimum charge transfer resistance(R_ct)of the CF/ILP electrode was reduced to 9.23Ω,which was 2.6%of the charge transfer resistance R_ct（356.4Ω）of the bare carbon felt electrode.The CF/AQS/ILP electrode was furtherly used as the anode of the microbial fuel cell dual-chamber system.The maximum power density obtained was 336m W/m²,which was 16.8 times higher than that of the bare CF anode.The experimental results showed that the charge transfer resistance(R_ct)of the modified CF/ILP electrode and CF/AQS/ILP electrode was greatly reduced,which showed that the ILP material could effectively improve the conductivity of the electrode.Finally,cyclic voltammetry electrodeposition method was used to modify the CF electrode with polyaniline（PANI）and ionic liquid（ILP）as composite materials.Afterwards,the electrochemical characteristics of the interaction between modified electrodes（CF/PANI/ILP）and microorganisms were explored by applying them in microbial fuel cells.SEM and FT-IR characterizations indicated that PANI and ILP have been successfully loaded on carbon felt electrodes.Electrochemical characterization and water contact angle tests showed that the modification can enhance the conductivity and improve the biocompatibility of the modified electrode.Cyclic voltammetry test calculations showed that in the three-electrode reaction system with CF/PANI/ILP as the working electrode,the maximum electron transfer amount between the electrode and the microorganism reached 5.07×10^-2C,which was 129.9 times higher than that of the bare CF electrode.The charge transfer resistance(R_ct)of CF/PANI/ILP dropped to102.9Ω,this value is 28.9%of the corresponding value of the bare electrode（CF）.The CF/PANI/ILP electrode was furtherly used as an anode for a dual-chamber microbial fuel cell system.The maximum power density obtained was 228 m W/m²,which was 12times higher than that of a bare CF anode.