| In recent years,the global excessive consumption of fossil fuels(oil and gas)has caused increasingly serious problems such as energy shortages and environmental pollution.Microbial fuel cell(MFC)is a brand-new energy renewable technology.It uses electricity-producing microorganisms to convert the chemical energy stored in organic waste into directly usable electrical energy.While dealing with environmental pollution,it can also generate clean energy,which is of great significance to energy development and environmental protection.However,the insufficient output power density of MFC has become a bottleneck restricting the practical application of MFC.This research aims to improve the electricity-generating performance of microbial fuel cells(MFC),by modifying traditional carbon paper anodes as a means,and assisting light energy to realize the comprehensive utilization of multiple energy.First,?-Fe OOH nanowires are synthesized on carbon paper with iron oxyhydroxide(?-Fe OOH),which is widely present in nature,and used as the anode of MFC to improve the electricity generation performance of MFC.Then for the first time,?-Fe OOH-NWs was used as the photoanode of MFC to further enhance the electricity generation performance of MFC under light.Finally,we continue to load polyaniline(PANI)with good conductivity and strong photoelectric response on?-Fe OOH-NWs.For the first time,?-Fe OOH-NWs/PANI was synthesized,and its electrochemical performance,conductivity and photoelectric response ability were comprehensively studied.At the same time,?-Fe OOH-NWs/PANI was used as the photoanode of MFC,and the way and mechanism of enhancing the performance of MFC under light was proposed.The main research contents and results are as follows:(1)The?-Fe OOH nanowires were successfully synthesized on carbon paper by hydrothermal synthesis.The diameter of?-Fe OOH nanowires is between 30-50 nm,and the length is between several to tens of microns with goethite structure.Due to the loading of?-Fe OOH nanowires,the electrochemical activity of the carbon paper anode is improved,and the electron transfer resistance(Rct)of the anode is reduced.,thereby increasing the electron transfer rate on the anode surface.More microorganisms are attached to?-Fe OOH-NWs,indicating that?-Fe OOH-NWs is a good biofilm growth substrate with good biocompatibility.(2)During MFC operation,the maximum output voltage of the MFC assembled by?-Fe OOH-NWs is about 1.62 times that of CP,and the maximum power density is about3.2 times that of CP.The improvement of power generation performance is mainly attributed to the following factors:1)As a metal oxide,?-Fe OOH nanowires have good electrochemical activity,and can increase the electrochemical active sites on the carbon paper surface,and accelerate the interaction between bacteria and anode electron transfer speed.2)?-Fe OOH nanowires increase the specific surface area of carbon paper and provide more attachment sites for electricity-producing bacteria.At the same time,The network of nanowires helps the adhesion of bacteria and thus facilitates the formation of biofilms.and so,it can enhance the interaction between the bacteria and the anode surface,and can further promote the electron transfer between the bacteria and the electrode(3)Photoelectric test results prove that?-Fe OOH-NWs can generate photogenerated electrons and holes under light excitation,and can generate photogenerated current.It is a good MFC photoanode.When illuminated,the charge transfer resistance of the?-Fe OOH-NWs photoanode is reduced by 20.7%,and the electron transfer rate is increased.When?-Fe OOH-NWs is used as the photoanode of MFC,the maximum power density of MFC under light is about 1.48 times that of under darkness,indicating that light can greatly improve the electricity production performance of MFC.It shows that in MFC,?-Fe OOH-NWs photoanode will generate photo-excited electrons during illumination.These electrons travel through the anode to the external circuit of the MFC and through an external wire to the cathode chamber,where they accelerate the REDOX process at the cathode,which significantly improved the overall power generation performance of MFC.(4)The successful loading of polyaniline effectively increases the roughness and surface area of?-Fe OOH-NWs without changing the shape and crystal structure of?-Fe OOH nanowires.Because polyaniline introduced new surface electrochemically active groups on the surface of?-Fe OOH-NWs,the electrochemical activity of?-Fe OOH-NWs/PANI was significantly improved.At the same time,the good conductivity of polyaniline and the unique one-dimensional structure of nanowires reduce the charge transfer resistance(Rct)of the original electrode and increase the charge transfer rate.The photogenerated electrons generated by polyaniline can be transferred to the conduction band of?-Fe OOH and accept photogenerated holes in the valence band of?-Fe OOH,thereby inhibiting the recombination of?-Fe OOH-NWs electron-hole pairs and increasing the photogenerated electron-hole The separation efficiency and photo-generated current are enhanced.It shows that the photoelectric effect of?-Fe OOH-NWs/PANI electrode is significantly enhanced,and it is a better new type of photoanode for MFC.(5)When there is light,the charge transfer resistance of the?-Fe OOH-NWs/PANI photoanode(Rct=21.9?)is significantly lower than the charge transfer resistance in the absence of light(Rct=43.2?),with a decrease of 49.3%.At the same time,the voltage and power density of the MFC are also significantly improved unger light,from 1.38W/m~2 to 1.95 W/m~2 with increasement of 41%,indicating that?-Fe OOH-NWs/PANI photoanode It can enhance the power density and power generation performance of MFC under light.(6)Illumination can enhance the MFC electricity generation performance of?-Fe OOH-NWs/PANI anode mainly based on the following mechanisms:1)The electron-hole pairs are excited by polyaniline under light,and electrons can be transferred to the conduction band of?-Fe OOH,increasing the electron flow density;and polyaniline itself is also a good hole acceptor,which improves the separation efficiency of electron-hole pairs.So it can generate a larger photo-generated current.2)The excellent electrical conductivity of polyaniline and the unique one-dimensional photoelectron path of nanowires can promote the transfer of photogenerated electrons and further enhance the photoelectric response ability.3)The electrochemical activity,conductivity,roughness and surface area of?-Fe OOH-NWs/PANI have been greatly improved,these factors can also enhance the power density of MFC to varying degrees.The above mechanisms and synergistic effect make the MFC under light have more excellent power generation performance. |
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