Study On Preparation And Electricity Generation Characteristics Of Microbial Fuel Cell Hydrogel Electrode

As a green energy conversion device,the low power density of microbial fuel cell（MFC）restricts its further application.As a place where electricity producing microorganisms adhere and breed,anode electrodes are a key factor affecting the output power of MFC.At the same time,the output power is also affected by many factors such as the concentration of organic matter in the anode chamber,sewage flow rate,load resistance,temperature,and pH value.In this paper,the preparation of polyaniline（PANI）and polypyrrole（PPy）hydrogel electrodes was studied and applied in MFC to improve the output power of MFC.At the same time,a mathematical model of dielectric free continuous flow MFC was established,and the model equations were solved by MATLAB software to explore the influence of different factors on the output power of MFC.The main research content and results of this paper are as follows:（1）PANI/PPy/CC hydrogel electrodes with different molar ratios of aniline to pyrrole（undoped,1:2,1:4,1:6）were prepared by chemical oxidation method using carbon cloth（CC）as the substrate material.The results of characterization and electrochemical tests showed that the 1:4 PANI/PPy/CC hydrogel electrode had a water droplet contact angle of 23.311°and an electron transfer impedance of 3.24Ω,which is significantly lower than other ratios of hydrogel electrodes.The composite hydrogel prepared under different ratios was applied to MFC as an anode electrode,and it was found that the maximum stable output voltage of 1:4 PANI/PPy/CC hydrogel electrode was 648.52 m V and the highest power density was 2187.5 m W/m²,which was significantly higher than that of the hydrogel electrode under other ratios,and the electrode could maintain stable operation under all four cycles.Therefore,1:4 is the optimal doping ratio for the preparation of composite hydrogel electrode.（2）In order to further improve the electrical generation performance of MFC,a PANI/PPy/MnO₂/CC hydrogel electrode with porous structure was prepared by in-situ polymerization method based on the composite hydrogel electrode with the optimal ratio of 1:4 and doped with MnO₂,It was tested using a variety of characterisation techniques including SEM,FTIR and contact angle,and the test results showed that PANI,PPy and MnO₂ were successfully compounded on the hydrogel electrode.Three sets of hydrogel electrodes,PANI/MnO₂/CC,PPy/MnO₂/CC and PANI/PPy/MnO₂/CC,were used as MFC anodes to construct and start the MFC with stable output voltages of 652 m V,645m V and 671 m V,respectively.The maximum output power densities were 1600.28m W/m²,2106.64 m W/m² and 2406.22 m W/m²,respectively.All these data indicate that the PANI/PPy/MnO₂/CC hydrogel electrode has better power production performance than the other two groups of electrodes.（3）A dielectric-free continuous flow MFC mathematical model was established to investigate the influence of different factors on the output power of the MFC.Through simulation analysis,it was found that when the initial concentration of glucose increased from 1.5 kg COD/m³ to 3.5 kg COD/m³,the output voltage of the battery increased and the stable discharge time became longer,but the influence of glucose concentration on the performance of the battery was small.When the external resistance of the battery is less than 1000Ω,increasing the external resistance value can improve the power density of the MFC,while when the resistance value is greater than 1000Ω,increasing the external resistance value will significantly reduce the output power of the battery.The internal resistance has a large impact on the performance of the battery,and reducing the internal resistance can improve the power density of the battery.An increase in effluent flow rate is beneficial to improving the battery’s power production performance,but increasing the flow rate above 2.1 mm/s will lead to a decrease in the battery’s power production performance.The power density of the battery is highest when the temperature is 28°C,and decreases when the temperature is higher or lower than 28°C.The output voltage of the battery is best when the pH value is 7,and is not conducive to increasing the output voltage of the MFC when the pH value is too high or too low.The simulated data was verified experimentally and it was found that the difference between the two sets of data was small and the trends matched well,indicating that the model was accurate and reliable.