The Influence Of Modified Carbon Fiber Anode On The Performance Of Microbial Full Cell

Energy shortage and environmental pollution have brought forth global crises and seriously impacted human survival and development.Since utilising organic substrates as their feedstock,MFC can not only produce electricity but also have a great potential for simultaneous wastewater treatment,they offer the prospect of long-term eco-friendly energy generation.Due to facing the challenges of microorganism,technology and economy,most of MFC are limited to laboratory scale,and the performance of power generation is low.Anode materials,as one of the factors affecting the electrical properties of MFC,directly affect the adhesion of microorganisms,electron transfer,resistance and the reaction rate on the electrode surface.Therefore,the selection and development of suitable anode materials is of great significance to optimize and improve the electrical performance of MFC.In order to improve the surface roughness and conductivity of anode materials,in this paper,we first use Polyaniline(PANI)and reduced graphene oxide(rGO)composite modified mesophase pitch-based carbon fiber brush,and apply it as anode to single chamber air cathode MFC.The results show that the surface roughness of the carbon fibers is improved by the modification of PANI and the compound modification with rGO,while the surface of the untreated carbon fibers is smooth.In addition,a large amount of N+are introduced into the anode by PANI,which is beneficial to the improvement of surface zeta potential.After further modification of rGO,the surface zeta potential improve obviously because of the increase of the relative content of pyridine nitrogen,which is beneficial to the surface positive potential,alkalinity and microbial adhesion ability.When the external resistance is 1000?,the maximum power density of the unmodified carbon fiber brush anode is only 706mW/m2.The maximum power density of PANI-Pitch-CB and rGO-PANI-Pitch-CB increase to 788 mW/m2 and 862 mW/m2,which are 1.12 times and 1.22 times as much as that of unmodified anode.In addition,in order to further improve the specific surface area and conductivity of anode materials,carbon nanotubes(CNTs)with excellent conductivity modified carbon fibers are selected.The interaction between CNTs and microorganism and the effect on the electrical properties of MFC are investigated in this paper.CNTs stimulate the epidermis of the microorganism,cause the biological reaction,and make the microorganism consume energy or electrons to produce the exopolysaccharid(EPS).Thereby this process reduces the stimulation of the CNTs on the microorganism,and promotes the microorganism to produce a large number of nanowires in contact with the CNTs or carbon fibers.Therefore,when EPS is sufficient to counteract the stimulation or toxicity of CNTs,the carbon nanotubes modified with carbon fibers(CNTFs-Pitch-CF)anode with more microorganism can produce higher output voltage and power density than the unmodified carbon fiber brush anode.At the same time,CNTFs-Pitch-CF modified MFCs can maintain high voltage and power density for a long time at high extracellular electron transfer(EET)efficiency.As anode materials,CNTFs-Pitch-CF can withstand harsh hydraulic environment and ensure long-term operation,which is of great practical significance for its large-scale application.After understanding the advantages and disadvantages of CNTs from the action mechanism,we further use polypyrrole(PPy)and CNTs composite modified carbon fibers(VCNTs-PPy-Pitch-CF),and explore the effect of the modified anode on the electrical properties of MFC.The VCNTs-PPy-Pitch-CF anode can make full use of the high conductivity of CNTs and the good biocompatibility of PPy.The maximum power density of the MFC is 1876.62mW/m2 and the stable voltage is 600±10 mV.The excellent power generation performance of the MFC can be attributed to two factors.On the one hand,the CNTs with good electrical conductivity grow vertically on the carbon fibers,so that the electrons produced by the microorganism can be transferred to the surface of carbon fibers quickly,and the EET efficiency can be improved.On the other hand,PPy can improve the positive electricity and biocompatibility of anode,attract more microorganism,and promote the electricity production of the microorganism.Therefore,the composite modification of carbon fibers with CNTs/PPy can greatly improve the power production performance of the MFC,which has reference and guiding significance for the practical application and expansion of MFC.