The Construction Of Graphene-based Anode Materials And Their Application In Microbial Fuel Cells

With the rapid development of the global economy,people are becoming more and more dependent on energy.Faced to the increasingly depleted fossil energy,exploring and developing a new type of sustainable energy structure is one of the most difficult research questions to be solved.Microbial fuel cell?MFC?is a kind of comprehensive technology combined green energy with environmental pollution,which utilize the metabolism of microbial to degrade organic pollutants to release electrons and protons stored in organic pollutants.One of the most critical factor to enhance the performance of MFC is to design a new kind of anode materials,which include the electron transfer capability,biocompatibility and specific surface area,etc.In this paper,various graphene-based materials were designed,including graphene aerogel,magnetic graphene gel balls and magnetic graphene sponge.Capacitance-enhanced graphene aerogel,magnetic graphene gel balls and magnetic graphene sponge were prapered by facile methods as MFC anode materials in this paper.Physical properties of electrode materials can be characterized by modern scientific methods,such as scanning electron microscopy?SEM?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,thermogravimetric analysis?TGA?and hysteresis loop?HL?,etc.In addition,the electrochemical properties of electrode materials can be characterized by electrochemical measurements,for example,cyclic voltammetry?CV?,Electrochemical impedance spectroscopy?EIS?and Tafel plots.The main conclusions are as follows:?1?In order to evaluate the power generation stability of MFC,long-time electricity generation stability?LEGS?which can be defined as the time span to stabilize in the 20%amplitude range of the maximum voltage in a stable operation period was given in this paper.Capacitance-enhanced graphene aerogel?GA?had a larger specific surface area,which enhanced the growth of electroless microorganisms.The maximum output voltage and power density were 488 mV and 2381.44 mW·m^-3,respectively.In addition,the larger double layer capacitance(3670 F·m^-2)enhanced the LEGS of MFC in some extent,which was up to 100 h,and 4 times higher than that of carbon paper.?2?To improve the biocompatibility of anode materials,graphene oxide was reduced by FeCl₂,generating Fe₃O₄ in situ in the chitosan gelation process with a chemical coprecipitation method.And the formation mechanism of urchin-like structure and the influence of different amount of FeCl₂ on the distribution of pore structure of gels were analysed.The average particle size of Fe₃O₄ particles in situ growth was 13 nm,which could be evenly distributed in gel beads,resulting the growth of nanowire between microorganisms.The enhanced biocompatibility of gel beads effectively improves the growth of microorganisms in unit volume so that the electricity generation performance of MFC can be enhanced.The maximum output voltage and power density of MFC filled with GFe100 were 759 mV and 17.823 W·m^-3,respectively,which was 23.21 times higher than that of GFe0(0.768 W·m^-3).?3?The graphene sponge was prepared by controlling the sequence of lyophilization.And the influence of compression ratio and respiration intensity on the electricity generation performance of respirable microbial fuel cell?RMFC?were researched.In the resoirable process,the respiratory frequency and static operating time can influence the MFC electricity generation ability.When the compression ratio and static operating time were 20%and 3 h,the open-circuit voltage can be up to 1 V,indicating a better microbial activity and faster metabolic rate of microorganism,and the maximum output voltage and LEGS were 902 mV and 224 h.