Investigation On The Electrochemical Characteristics Of The Interaction Between The Microbial Reduced Graphene Modified Electrode And Microbe

In the microbial electrochemical systems(MES),electrons are generated from organic matter oxidized by microorganisms driven by respiration and transferred to solid extracellular electrodes,thereby converting chemical energy into electrical energy.This process is known as bacterial extracellular electron transfer(EET).The extracellular electron transfer efficiency of exoelectrogen is still a bottleneck restricting the practical application of MES.The attachment of exoelectrogen on the surface of solid electrode and the formation of electrochemical active biofilm play crucial roles in the EET process.Therefore,the modification of electrode materials to improve biocompatibility and promote the growth of active biofilms are very important for electron transfer in the interaction process of "microorganism-electrode".In the current study,Shewanella putrefaciens ATCC 8071 was used as the exoelectrogen to prepare the biofilm electrode modified by microbial reduced graphene.Furthermore,the electrochemical activity characteristics of the growth of biofilm on the modified electrode surface and the interaction between microbe and electrode were investigated by applying electrode potential.In the three-electrode system,GO was added at different inoculation times(initial and 26 h later)to modified electrodes.Due to the respiration drive of microorganisms,GO was catalytic reduced.The results of XRD and FT-IR showed that GO was transformated to the reduced graphene.SEM examination showed that the reduced graphene formed on the electrode surface presented a three-dimensional folded layered structure,the carbon felt electrode surface modified by self-assembled 3D-br-GO in situ had a high bacterial loading capacity.The contact angle test showed that the hydrophilicity of the electrode surface was significantly enhanced,thereby the carbon felt electrode had better biocompatibility with microorganisms.Through electricity generation monitoring,cyclic voltammetry and electrochemical impedance spectroscopy testing,the results showed that the GO-modified carbon felt electrode was favorable for bacteria to attach to the electrode and form biofilms,the biogenic current response were significantly,the internal resistance of electrode electron transfer was effectively decreased,which promoted electron transfer between microbe and electrode.The addition of GO at the initial time was more conducive to the formation of self-assembled 3D-brGO structure on the electrode surface in situ in the system.Which showed more abundant multi-layer fold three-dimensional structure,more bacteria were absorbed and wrapped,and the electrochemical activity of the biofilm electrode was enhanced.The interaction of "microorganism-electrode" showed more active electron transfer,and MFC showed the best electrical performance.Furthermore,different electrode potentials(-0.4 V,-0.2 V,0 V,+0.1 V,+0.2 V vs.Ag/Ag Cl)were applied on the carbon felt electrode(working electrode)to investigate the exoelectrogen enrichment of the electrode surface,the formation of electrochemical active biofilm,and the catalytic activity characteristics of biofilm electrode.It was characterized by cyclic voltammetry,electrochemical impedance spectroscopy,and through analysis of morphology and structure of electrode,the results showed that the growth adaptability of bacteria was different under different electrode potentials,and the characteristics of electrochemical activity of biofilm electrodes were significantly different.Bacteria were propitious to the enrichment and growth of the directional electrode under the 0 V electrode potential,and the electrochemical active biofilm was formed on the electrode surface,the biofilm achieved strong activity and long activity cycle.The electron transfer resistance of the electrode surface was significantly reduced,the charge transfer quantity was 0.56 C,and the biogenic response current was 6 m A.At+0.1 V potential,the growth of bacteria and the biofilm formation on the electrode were inhibited,the charge transfer at the reaction interface of the electrode was small,however,such inhibition was limited,bacteria may express different active substances in the process of extracellular electron transfer,which could accumulate more growth drivers under this potential and achieve the highest electrical generation performance in MFC.At a potential of +0.2 V,bacterial growth was inhibited,this potential was not conducive to the process of 3D-br-GO modified electrode and adversely affected the electron transfer process between the microbe and electrode.At the potential of-0.2 V and-0.4 V,the bacteria loading capacity of electrode surface was relatively small,the biofilm showed low activity,and the interactions between microbe and electrode were weak.