Design Of Microbial Fuel Cell Configurations And Carbon-based Electrode Materials For Improving The Electrochemical Performance And Large-Scale Application

Microbial fuel cell(MFC)is a new wastewater treatment device developed in the early 20 th century.It can synchronously degrade sewage and generate electricity,leading to a broad development prospect.However,low energy output,high cost,and amplification difficulties become the bottlenecks in the practical application of MFC.Among them,the anode materials,MFC configurations,and cathodic catalysts can affect the electrical performance of MFC.This work intends to explore the effect of MFC configuration and modification of carbon-based electrode materials on MFC performance.And the detailed research content is listed as follows:1.Study on carbon fiber-based anode materials and the corresponding configurations in MFCCarbon fiber brush is often used as MFC anode due to the high bioavailable area and conductivity.However,the part in the middle of the carbon brush tightly bound by titanium wire is not conducive to bacteria adhesion,which reduces the utilization rate of the carbon fibers.And in the part of the carbon brush far away from the cathode,the distance between the anode and cathode is larger,which increases the internal resistance of the cell.These two factors limit the electricity generation performance of the MFC using carbon fiber brush as the anode.Herein,carbon-based anode materials and their corresponding configurations were studied,and the following results were mainly obtained:(1)When the MFC configuration is changed from cubic to cylindric,the internal resistance is reduced from 127.2 ? to 49.7 ? and the performance of both anode and cathode is improved.With the increase of the cathode area,the dissolved O2 content in the cylindric MFC increased from 3.07 mg·L-1 to 6.13 mg·L-1,leading to power overshoot,which limits its actual power output.After the mixed bacteria were replaced by Pseudomonas aeruginosa with higher catalytic activity,the overshoot phenomenon was improved,and the maximum power density was increased from 1364 mW·m-2 to 3322 mW·m-2.In this work,the relationship between oxygen and power density overshoot is analyzed,and a new solution is provided,which is of great significance for the practical application of MFC.(2)Continuous carbon fiber bidirectional braided network(referred to as carbon fiber network,CFN)was used as MFC anode to study the power generation ability and massive applications.The experiments show that the CFN anode(6.48 mW·g-1)shows better MFC performance than the continuous carbon fiber(5.68 mW·g-1)due to the lower overall resistance.Meanwhile,the MFC with CFN anode(100 mg)has similar power generation with the MFC using carbon fiber brush(500 mg)as anode,which greatly reduces the carbon fiber consumption and thus reduces the cost.Since the CFN anode has the advantage of electricity generation,a 280 mL flat-plate reactor using CFN as anode was assembled for amplification study.This system is easy to construct and has good power generation performance,which shows great potential in massive applications.Under a 1000 ? external resistor,the working voltage of this system increased from 0.550 V to 0.695 V,which is of great significance to the design and amplification of MFC.(3)Carbon fiber veil(CFV)was used as MFC anode to study the power generation ability and massive applications.The results show that CFV anode(988 mW·m-2)shows better MFC performance than that of CFN(926 mW·m-2)due to the higher effective anode area and lower resistance.And CFV anode also has great potential in large-scale applications.2.Study on the oxygen reduction reaction(ORR)catalytic activity of carbon-based cathode materials in MFCIn addition,due to the high overpotential and slow oxygen reduction reaction dynamics,the influence of air-cathode catalysts on the performance of MFC can not be underestimated.Pt-based materials show excellent catalytic capacity.However,the high price limited their practical application.Fe-N/GNR@CNT material was prepared and used as cathode catalysts in MFC.As a result,the power production of MFC-Fe-N/C-1:4:4(801 mW·m-2)is similar to that of MFC-Pt/C(851 mW·m-2).Therefore,Fe-N/GNR@CNT has great potential to replace precious metal Pt-based catalysts and provide a new choice for reducing the cost of cathode catalysts.