| As a large-scale energy storage device for solar and wind power generation,the vanadium redox flow battery plays an important role in ensuring clean energy output owing to the characteristics of large capacity and high security.Graphite felt electrode has been widely used in vanadium redox flow battery due to its superior corrosion resistance and good flexibility.However,the poor electrochemical activity of graphite felt electrode seriously hinders the charge-discharge performance and energy efficiency of vanadium redox flow battery with large current density.In order to improve the electrocatalytic activity of graphite felt,many researchers proposed to modify graphite felt electrode with graphene-based materials and micro/nano materials,respectively.However,the preparation process of graphene-based material is complex,and this material is non renewable;micro/nano materials are difficult to be evenly distributed on the surface of graphite felt fiber due to their nano effect.In order to solve the above electrode problems,this paper prepared high activity microbial-based carbon electrode materials based on the three-dimensional structure of Bacillus mycoides biofilm and the release characteristics of Aspergillus niger spores.It proves the feasibility of the application of microbial-based carbon materials in the field of new energy storage.In order to hunt for like graphene electrode materials and solve the renewable problem of energy storage carbon materials.The biofilm of Bacillus mycoides was anchored on the surface of graphite felt carbon fiber by microbial inoculation.Based on the fact that the biofilm was composed of cells and extracellular polymers,the structure formed a porous three-dimensional structure with graphitized carbon skeleton as the main structure and the distribution of heteroelements after high temperature carbonization.this material interlayer space is 0.348 nm.XRD shows that there are peaks at 27.4°,31.8°,45.5°and 53.9°,indicating that the material is highly graphitized.This material showed excellent electrochemical performance in both positive and negative electrolyte of vanadium redox flow battery,compared with the pristine electrode,the peak potential difference decreased 254 m V and 278 m V,respectively.In order to further elaborate the formation process of bacterial biofilm,optimize the formation conditions of bacterial biofilm and ensure the electrochemical performance of microbial-based carbon materials,based on IBM model,through the method of computational biology,designed and optimized the bacterial membrane growth model,established the relationship between the key factors such as carbon source concentration,nitrogen source concentration,dissolved oxygen content and membrane thickness,roughness,number of bacteria,extracellular polymer secretion.The results show that when the concentration of nitrogen source and dissolved oxygen are fixed,the time to reach 30000bacterias is shortened by 8.33 times when the concentration of carbon source is increased by5.33 times.Under the condition of a certain amount of the nitrogen source concentration and dissolved oxygen;the rate of bacterial reproduction and extracellular polymers production was controlled by regulating the concentration of the substrate;the culture system with different concentration of the substrate can achieve the same biofilm area by properly extending the culture time under the similar culture conditions.The growth rule and extracellular product distribution of bacterial biofilm model were verified by Mycobacterium fungoides.When the concentration of the medium was 0.5 g（100ml）-1,no membrane was formed,and the number of bacteria was less,and the secretion was less,showing a scattered state.With the increase of the concentration of the medium,the number of bacteria and secretion increased,and gradually formed a dispersed membrane.Aspergillus niger was inoculated on the graphite felt impregnated with bran juice,andAspergillus niger spores were obtained by adjusting the culture time of Aspergillus niger.The uniform distribution of spores on the surface of carbon fiber owing to their movement ability and instantaneous explosive force.Based on the cell structure of asexual spores,the spore after carbonization possessed wrinkle structure,which would increase the contact area between the material and the external materials.Therefore,the spore carbon composite electrode can greatly reduce the redox reaction overpotential in the vanadium redox flow battery,and the maximum current density of spore carbon composite electrodet and pristine electrode can reach 450 m A cm-2 and 250 m A cm-2,respectively.In terms of long sporulation period of Aspergillus niger under ordinary conditions,we proposed that the sporulation time and quantity was affected by the single factors,such as carbon source,nitrogen source,phosphate content,and blue light irradiation time.It is found that carbon source,nitrogen source and blue light irradiation time have significant influence on sporulation time and sporulation quantity.We found that flug gene is the key factor of blue light to promote the spore production of Aspergillus niger through real time q PCR technology.The flug gene can not only promote quantity and reduce time of Aspergillus niger spore production.On this basis,the sporulation time of Aspergillus niger was set as response,the optimum conditions for spore production of Aspergillus niger were obtained by response surface.The best culture condition of:the carbon source is 4%glucose,the concentration of ammonium sulfate is 0.1%,and the time of blue light irradiation is 48 hours.Based on this condition,the spores electrode decrease the positive and nagetive overpotential of 251 and 260 m V in the basic culture medium of bran juice,compared with pristine electrode.Based on the biological characteristics of Bacillus mycoides biofilm and Aspergillus niger Spore,we designed like graphene materials and micro nano fold materials with uniform distribution in the framework of graphite felt,which greatly improved the electrochemical performance of vanadium ions in the positive and negative electrolyte,not only solve the problem of poor chemical performance of the electrode,but also open up the micro growth as a renewable carbon material in the field of energy application research. |
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