Evaluation Of Anode Performance Of Microbial Electrochemical System Using Three-dimensional Graphene-based Materials

Microbial electrochemical system is a device that has capable of degrading contaminants while generating electrical energy.Its application has been hampered by its lower output power density and longer start-up time of the system.The anode acts as a carrier for enriching electroactive microorganisms,receiving and transmitting extracellular electrons,so the effect of the anode on system performance is self-evident.Conventional anode materials such as graphite rods,carbon cloth,carbon felt,etc.,microorganisms cannot enter the structure of the material to grow inside,reducing the amount of microbial enrichment.In this paper,the anode of microbial electrochemical system wss taken as the research object.The purpose of improving the performance of the system was improved by preparing the three-dimensional structure anode material,and the surface of the material was improved by introducing oxygen-containing and nitrogen-containing functional groups.The effect of functional group introduction on the system performance and the biofilm structure during the stable period of the system was investigated..Firstly,a kind of three-dimensional graphene material with a relatively hydrophilic surface was prepared.When used as an MES anode material,it was found that the system performance increased with the enhanced hydrophilicity of the surface of the material.Since the hydrophilicity of the surface of the electrode material increases the bioaffinity of the surface of the material and the three-dimensional sheet structure provides more attachment sites for microbial enrichment which lead to the more hydrophilic anode surface is enriched with more complex community structure and a larger number of microorganisms?3.68mg/cm³?,and the maximum output power density of the system can reach 9.43W/m³,the maximum output voltage can reach 490mV,and coulombic efficiency of the system can reach 38.3%.At the same time,it is found that the hydrophilicity of the material is related to the content of carbon and oxygen in the material.The greater the ratio of oxygen to carbon in the material,the better the hydrophilicity of the material.The carbon nanotube/graphene composite aerogel was prepared by adding carbon nanotubes to the precursor liquid of oxide graphene dispersion,and the carbon nanotubes are intercalated between the graphene sheets to improve the problem of sheet stacking.The introduction of carbon nanotubes increased the transmission of electrons inside the material and promoted the production of“nanowires”.The maximum output voltage of the system was 70 mV higher than that of a single graphene aerogel electrode system,and the maximum output power density was increased by 5.9 W/m³;At the same time,the introduction of two kinds of functional groups?oxygen-containing functional groups:hydroxyl group and carboxyl group;nitrogen-containing functional group:amino group?increased the hydrophilicity of the surface of the material.When used as MES anode material,the startup time of the unmodified carbon nanotube composite aerogel system was shortened by 92 h,93 h and 25 h,respectively;In addition,The COOH and-NH₂functional groups can promote the enrichment of the electroactive microorganism Geobacter on the electrode surface,and the enrichment ratio increased by 3.2%and10.4%.