Research On The Improvement Of Power Generation Performance Of Soil Microbial Fuel Cells

Soil microbial fuel cells(soil MFCs)can transform the chemical energy generated by the decomposition of organic matter by electricity-producing bacteria into electric energy,which has great application potential in the fields of electricity production,environmental monitoring,bioremediation and seawater desalination.However,due to the low output power level of soil MFC,the electricity generation performance is poor,which seriously hinders the application progress of the above fields.Therefore,it is necessary to further improve the electrical performance of soil MFC.In this study,by series soil MFCs,inventing new anode materials and using rice straw powder organic matter coating instead of anode surface soil,the effect of soil MFC electricity generation and promotion was explored.Meanwhile,the problem of voltage reversal occurred in series process was explored and the solution was proposed.The main conclusions are as follows:(1)The application of series circuit can effectively improve the electrical performance of soil MFC.Paddy soil based MFC successfully improved the electrical performance of soil MFC in a series way.The open-circuit voltage was increased from 579.0 m V of single cell to 1.596V of series soil MFCs,which is more than the voltage of a single dry cell.The power density curves showed that the maximum power densities of single soil MFCs were 12.16m Wm^-2,4.80 m Wm^-2 and 16.02 m Wm^-2,and the maximum power densities of series soil MFCs were 14.73 m Wm^-2.The output power was increased from 78.4?W of single cell voltage to 144.3?W of series soil MFCS.The tandem soil MFCs continues to power the timer for 80 hours until the voltage of the tandem soil MFCs drops below 0.936V.The absolute abundance of the three exoelectrogenic bacteria related genera were 13.03%,27.78%and 16.17%,respectively.The exoelectrogenic bacteria were the active bacteria on the anode,among which Geobacter and Anaeromyxobacter were the dominant exoelectrogenic bacteria.Together,they account for more than 60%of the active exoelectrogenic bacteria related genera.(2)The application of new anodes can effectively improve the electrical performance of soil MFC.In this study,a new rigid and porous anode material--graphite-inorganic silica composite anode(patent number:CN110943230A)was invented.By connecting two new anode soil MFCs in series,the maximum power density reached 5.45 m Wm^-2,the maximum output power was 158.4?W,and the maximum output voltage was 1579.9 m V.The electronic timer was successfully driven,and the running time was extended from 80 h to more than 30 d.The relative abundance of the active genera of exoelectrogenic bacteria on the anode was 5.97%and 4.98%,respectively,14 of which were active in the soil on the anode surface.Among them,Geobacter,Bacillus,Clostridium,Desulfobulbus and Pseudomonas are the most active exoelectrogenic bacteria related genera.(3)The application of rice straw powder organic matter coating can effectively improve the electrical performance of soil MFC.The open-circuit voltages of soil MFC organic matter coated with rice straw powder reached more than 850 m V,which was much higher than that of soil MFC control group covered with soil anode(more than 600 m V).The cathodic charge transfer resistance of soil MFC organic matter group was 277.30?and242.40?,respectively,significantly lower than that of soil MFC control group(621.10?and 617.70?,).Polarization curves and power density curves showed that the maximum power densities of soil MFC organic matter group(6.19 m Wm^-2 and 7.74 m Wm^-2,respectively)were about three times that of soil MFC control group.By quantifying and sequencing the exoelectrogenic bacteria on the MFC anode surface of the two groups of soil,the abundance and activity of e exoelectrogenic bacteria on the MFC anode surface of soil coated with rice straw powder organic matter were higher.Sixteen genera associated with exoelectrogenic bacteria were detected in the DNA-derived community,accounting for 5.77%of the total bacterial sequences.Six genera associated with exoelectrogenic bacteria were detected in the RNA-derived community,accounting for 8.74%of the total bacterial sequences.Desulfitobacterium,Clostridium,Bacillus and Thermincola are the dominant exoelectrogenic bacteria on the anode.To sum up,all the three methods can improve the electrical performance of soil MFC,among which the series new anode soil MFC can not only effectively produce electricity performance,but also drive the electronic timer for a long time stably.