Study On Modification Of Microbial Fuel Cell Anodes By Carbon Materials With Different Biocompatibilit

Microbial fuel cells（MFCs）are an emerging technology that has been developed since the early 1990s and is capable of converting chemical energy into electrical energy.However,the output power of MFCs is usually low,so further development and large-scale applications are limited.As a carrier for microbial growth in MFCs,the stability,biocompatibility,electrical conductivity and active surface area of the anode directly affect the ability of microbial extracellular electron transfer and the performance of MFCs.Carbon material anodes are biocompatible,inexpensive,and have great advantages in terms of enrichment of electromicroorganisms and output voltage.In this study,the influence of the material and binder of the anode on the biocompatibility and MFCs performance was analyzed.Three different types of carbon materials were used to modify the anodes of MFCs,and the electrochemical methods were used to examine and analyze the electrical production performance and provide a theoretical basis for the subsequent anode modification of carbon materials.（1）Compared with inorganic materials,organic materials are usually considered to be toxic to microorganisms,so in this study we tried to construct air cathode MFCs by choosing anodes modified with the energy storage organic material POP_M-TFP-rGO to examine their effects on microorganisms and the performance of MFCs.The POP_M-TFP-rGO powder was modified on carbon paper（2 cm²）by using Polyvinylidene fluoride（PVDF）as a binder.A maximum current density of about162.5 m A m^-2was obtained,which is 301%higher compared to the unmodified anode(40.5 m A m^-2).The maximum power densities were 48.84 m W m^-2and 4.16 m W m^-2,respectively,with an increase of nearly 107%over the unmodified anode.Further extracellular electron transfer kinetic analysis showed that the electron number n and charge transfer coefficientαincreased by 74%and 65%,respectively,after modification by POP_M-TFP-rGO.For the degradation of methyl orange（MO）,the degradation efficiency of MO in the anode MFCs modified with POP_M-TFP-rGO material reached 69.5%,and the degradation efficiency of MO was increased by26.4%compared with the unmodified electrode MFCs.The results of the kinetic analysis indicated that when POP_M-TFP-rGO material modified anode,the primary kinetic constant reached 0.309 h^-1,which was 219%higher compared to the unmodified CP anode(0.0043 h^-1).The final biomass concentrations in the control anode MFCs and POP_M-TFP-rGO modified anode MFCs were 0.114±0.001 mg/ml and 0.116±0.001 mg/ml,respectively,with no significant difference in anode fluid biomass,indicating that POP_M-TFP-rGO modification did not affect the pH value of the anode fluid or the growth of microorganisms.Therefore,POP_M-TFP-rGO can be an effective choice for MFCs treatment of azo dye wastewater.（2）In order to better adapt microorganisms to the growth conditions of MFCs,we tried the feasibility of sodium alginate（SA）of biological origin as a binder by bonding super activated carbon（SAC）to the carbon cloth anode（2 cm²）of MFCs.The results show that the maximum output voltage of the SAC/SA/carbon cloth anode MFCs is 0.028 V,which is 180%higher than that of the blank carbon cloth anode（control）.the internal resistance of the MFCs is 9429.3Ω,which is 18%lower than that of the control（11560Ω）.The maximum power density was 6.24 m W/m²,which was 365%higher than that of the control.After modification by SAC/SA hydrogel,the chemical oxygen demand（COD）removal efficiency reached 56.36%,which was12.72%higher compared to the control group.The Coulombic efficiency（CE）of the modified anode MFCs reached 17.65%,which was 9%higher than that of the control group.The results indicate that the anode modification with biocompatible SA as binder enhanced the electrical production performance of MFCs.Our work provides a new option for binders of biological origin in anodic modification.（3）In terms of modified materials,we also tried biochar of biological origin as anode.Biochar was prepared by high-temperature pyrolysis using three algae,kelp,copper algae and green algae,and the properties of biochar were physicochemically analyzed.XRD and FTIR results showed that the surface of the prepared biochar had aromatic functional groups and excellent graphitic carbon properties,which promoted extracellular electron transfer and increased the electrical conductivity of the material.The electrical conductivity of the carbon material is also a function of the degree of graphitization.At higher temperatures,as the carbon approaches sp²hybridization,due to higher electron mobility.After modifying three types of biochar to MFCs anodes,the electrochemical activity of anaerobic microorganisms in the anode chamber was measured and used for the degradation of the antibiotic chloramphenicol.The maximum output voltages of green algae,copper algae,and kelp biochar-modified anodes were 0.386 V,0.368 V,and 0.29 V,respectively,all of which were much higher than the control anode MFCs（0.196 V）.The maximum power densities were 362.9 m W m^-2,278.9 m W m^-2,and 262.4 m W m^-2,respectively,all of which were larger than the maximum power density of carbon cloth anode of 82m W/m²,which improved the dual-chamber MFCs power density by 342%,240%,and220%,respectively.The internal resistance of kelp,copper algae and green algae biochar anode cells are 1623Ω,1410Ωand 586Ωrespectively,which are 76.6%,79.6%and 91.5%lower than the internal resistance of carbon cloth anode cells respectively,significantly reducing the internal loss of the cells,increasing the unit output power of MFCs and improving the power production capacity of MFCs.