Application Of Polypyrrole Hydrogel Anode Doped With Bimetal ZIF Derivatives In Microbial Fuel Cells

Microbial Fuel Cell（MFC）was a power generation device that can convert biological energy into electrical energy,and was currently a hot research topic in the field of new energy and the environment.Among them,the choice of anodic material was crucial to power generation performance of MFC.In this paper,the polypyrrole（PPy）composite conductive hydrogel electrode modified with bimetal ZIF and graphene composite derivatives was selected as the MFC bioanode to improve the power generation performance of MFC.Introduced MOFs on the basis of PPy hydrogel,and used the method of combining physical doping with in-situ growth to prepare composite hydrogels（including Fe-NC/PPy,Zn-NC/PPy,Fe,Zn-NC/PPy）on the carbon felt.SEM test revealed that Fe,Zn-NC materials contained many conductive nanospheres,which were connected with the three-dimensional network of polypyrrole in the composite hydrogel.The results of electrochemical tests showed that the Fe,Zn-NC/PPy composite hydrogel has the best electrochemical performance,and the electrode had the best electrochemical performance when the molar ratio of Fe and Zn was 2:1.When the prepared electrode is used as the MFC anode,the MFC with Fe,Zn-2:1-NC/PPy as the anode exhibited the optimal electricity generation performance,with a maximum power density of 4.933 W/m³ and a lower charge transfer resistance（2.21Ω）.In order to further improved the EET efficiency of the composite hydrogel and the power generation performance of MFC,it was envisaged to increase the microbial membrane activity and the number of microorganisms colonized on the anode surface through the introduction of S element to achieve the improvement of MFC power density.The bimetallic ZIF was vulcanized with sulfur powder,thiourea and thioacetamide respectively to prepare S powder/PPy,thiourea/PPy and thioacetamide（TAA/PPy）hydrogels,which were used as MFC anode.The Fe,Zn-NS materials prepared by TAA vulcanization exhibited a polyhedral structure,while materials prepared by other vulcanization methods appeared varying degrees of collapse or aggregation.The stable output voltage of TAA/PPy anode MFC（603 m V）was higher than that of thiourea/PPy anode（577 m V）,and the sulfurized bioanode exhibited lower charge transfer resistance,achieving higher charge transfer kinetics between the microbial film and the electrode.Meanwhile,MFC with TAA/PPy anode exhibited a higher power density（6.546W/m³）.In order to improved the activity of composite hydrogel bioelectricity catalytic sites and charge transfer efficiency,it was envisaged to prepare rGO/Fe,Zn NS with intercalated structure to improve the overall performance of MFC.In this chapter,on the basis of using rGO to disperse the active site of MOFs,the sandwich structure of rGO/Fe,Zn-NS-X was prepared by intercalation of rGO with Fe,Zn-NS.Finally,the sandwich structure of rGO/Fe,Zn-NS-X was compounded with PPy hydrogel to prepare rGO/Fe,Zn-NS/PPy-X electrodes.Electrochemical performance tests confirmed that rGO/Fe,Zn-NS/PPy-3（65 mg GO）electrodes had a larger capacitance（1296.95 F/m²）,a lower charge transfer resistance（8.198Ω）,and a higher electrocatalytic activity（I₀=0.643 m A/cm²）.When rGO/Fe,Zn-NS/PPy-3 are used as MFC anodes,the maximum power density can reach 8.283 W/m³.Because the graphene active edge exposed on the hydrogel surface was more conducive to the colonization and contact of electrogenerating microorganisms,and was conducive to the direct extracellular electron transfer,while the evenly dispersed Fe-Zn-N and Fe-Zn-S catalytic active centers promoted the indirect extracellular electron transfer efficiency between the active microbial membrane and the bioanode to a greater extent.