The Research Of Anode Modification And Electricity Production Of Sediment Microbial Fuel Cell

Energy is essential to life.With the development of new energy,sediment microbial fuel(SMFC)as a new technology which produce electrical energy from the oxidation of organics in sediments by the microorganisms is booming.SMFC consists of an anode embedded in anaerobic sediment and cathode located in upper water.Anode was linked with cathode through external wires to form a circuit.In recent decades,SMFC is developing rapidly.However,the output power of SMFC is very low,which limits the development of this new energy technology.SMFC anaerobic sludges riched in organic matter and electrogenesis microorganism are key to enhancement of electricity production.In this paper,the anaerobic sludges were sampled from Dacheng River near the Qilu University of Technology.The SMFC is constructed by 600 mL of anaerobic sludges,activated carbon felt as the electrode,external 1000 ? resistance through the connection of wire to form a pathway.The cycles of electricity production and the maximum electricity production are recorded.The maximum voltage is about 0.19 V,which still has some difference in the production of electric voltage with reported by literature.According to the previous research,the production of electric power were influenced by volume ratio of anaerobic sludge with cathode buffer,electrode distance,exogenous additives and electrode type,therefore optimization tests of these factors are performed to promote the output power.Experimental results suggested that with electrode distance of 35 cm,anaerobic sludge and cathode buffer 600 mL,1400 mL,respectively,SMFC in 30 d electricity production cycle in 2 L glass cylinder system achieved optimum performance when the anaerobic sludge added with 20 mL of 1 g/L glucose solution.The anode of SMFC accept electrons from microbes,and thus the anode electrode materials become the key to the study of SMFC electricity.In our study,carbon nanotube anode material with the advantages of small internal resistance,good electrical conductivity,specific surface area and good biocompatibility was chosen as the research material.The activated carbon felt of anode was effectively modified through layer-by-layer self-assembly method.The maximum voltage of SMFC with modified by carbon nanotube is about 0.37 V,whereas the maximum voltage of SMFC without modifying anode is about 0.30 V.Comparison to that of the unmodified SMFC,the production electric voltage of SMFC with modified anode increased by 24.7%.The measurement of polarization curve showed that open circuit voltage of SMFC with modified anode is about 0.60 V,whereas the voltage of SMFC without modifying anode is about 0.40 V.The result showed that electricity production of modified SMFC is more stable than that of unmodified SMFC.In 22 d(electricity peak),anode biofilm was characterized by environmental scanning electron microscope(ESEM),and the result showed that biofilm of modified anode are much thicker than that of the control SMFC.The protein content of anode detection showed that the content of modified SMFC is about 11.24 ?g/mL,whereas the protein content of control SMFC is about 10.24 ?g/mL.The results of anode biofilm characterization and protein determination showed that electrogenesis microorganism could be riched in SMFC with carbon nanotubes modified anode.For lack of proton membrane in SMFC,anode organic matter easily lead to the breeding of heterotrophic bacteria resulting in the formation of biofilm in cathode,which limits the efficacy of SMFC electrogenesis.In this paper dual anode system located on the surface of sediment interface was successfully constructed to inhibit the formation of biofilm on cathode.The biofilm and protein content of cathode were measured in the 5 d,15 d and 30 d,respectively.The characterization of cathodic biofilm via ESEM was performed.The protein content results showed that the cathode protein content of interface dual anode SMFC were 0.03 mg/L,0.04 mg/L and 0.03 mg/L,respectively,whereas that of single anode SMFC were 0.10 mg/L,0.11 mg/L and 0.14 mg/L,respectively.The biofilm characterization of dual anode SMFC showed that compared with single anode SMFC,the thickness of cathode biofilm decreased significantly.The results of electrochemical alternating current impedance test indicated that the resistor of dual anode SMFC was about 2.13 ?,whereas that of single anode SMFC was about 3.10 ?.Compared with that of single anode SMFC,the output voltage of dual anode SMFC increased by 31% which demonstrated that dual anode SMFC could significantly improved electricity production.These experimental data including the determination of protein content,characterization of biofilm,impedance cathode and output electric voltage confirmed the dual anode SMFC could effectively prevent the migration of organic matter to the cathode and inhibit the formation of heterotrophic bacteria biofilm on cathode.Dual anode SMFC could guarantee the running of reduction reaction on cathode and improves the output electricity power.