Research On Constructing Nanofiber-based Anodes And Their Performances In Microbial Fuel Cell

The weak biofilm colonization and sluggish extracellular electron transfer(EET)kinetics at the anode interface severely constrain the power output of the microbial fuel cell(MFC).Surface functionalizations toward the anode are considered to be a feasible strategy to solve these problems.Based on the characteristics of the cross-through transmission channel,high electrochemical surface area,multifunctional oriented structure construction,defect controllability of element doping,and flexible support of electrospinning nanofibers,four types of nanofiber-based wires with excellent electrocatalytic activity were constructed by optimizing their physicochemical properties through morphology regulation,heteroatomic doping,surface-interface coordination,and nanoconfined space regulation strategies,which realized high bacterial loadings,fast EET,and gradually enhanced the power density and sewage purification of MFC.The electrocatalytic mechanism of different nanofiber-based materials was also discussed.The main research contents and conclusions are as follows:(1)Carbon nanotubes doped oriented carbon nanofibers(CNTs/CNFs)were prepared as self-supporting electrodes by electrospinning and carbonization processes with morphology regulation strategy.Compared with oriented CNFs and non-oriented CNFs,the oriented CNTs/CNFs exhibited higher specific capacitance and lower charge transfer resistance.Co-filtering inoculum with oriented CNTs/CNFs favored dense and continuous biofilm formation,which promoted the direct EET rate and thus endowed the MFC with a maximum power density of 1016 mW/m2 and COD removal of 84.5%,significantly higher than those with the oriented CNFs(796 mW/m2,81.3%),non-oriented CNFs(511 mW/m2,70.3%)and pure carbon cloth(341 mW/m2,59.8%).This could be attributed to the orientation structure,high exposure of CNTs,dense biofilm structure,and rapid EET rate.(2)Different mass ratios of Fe/N doped CNFs(Fe/N-x@CNFs,x was the mass ratio of 0.5,1,3,5)were constructed by electrospinning and carbonization processes with the defect structural regulation strategy.Microstructure analysis implied that the Fe/N mass ratio could affect the surface morphology of CNFs.The small size of Fe nanoparticles was uniformly anchored on the CNFs at the Fe/N ratio of 3,which significantly improved the positive charge density,biocompatibility,and electrochemical surface area.MFC equipped with Fe/N3@CNFs modified carbon cloth(CC)achieved a maximum power density of 1873.8 mW/m2,which was 1.8 and 3.6 times higher than those with Fe@CNFs modified CC and pure CC anode,respectively.Additionally,the COD removal of Fe/N-3@CNFs modified CC was 1.1 and 1.36 times higher than those of Fe@CNFs modified CC and pure CC anode.The biofilm structure analysis implied that Fe/N3@CNFs embedded in the biofilms favored dense and continuous biofilm formation,activity,and selectively enriched large amounts of functional bacteria Geobacter,thus improving the EET process and MFC performance.(3)Based on the bimetallic synergies and pore structure regulation,hollow CoFe2O4 nanofibers supported CNTs nanowires were constructed by electrospinning and pyrolysis.The electrochemical analysis demonstrated that introducing CoFe2O4/CNTs greatly enhanced the electrochemical surface area and electron transfer efficiency of carbon cloth,which endowed the MFC with a maximum power density of 2290 mW/m2,361%higher than that with pure CC.CoFe2O4/CNTs modified CC presented high content of biofilm,excellent bacterial activity,and a high abundance of Geobacter,thus the associated COD removal was 1.43 times higher than that of CC.Such an enhancement was related to rapid interfacial mass transfer derived from the hollow structure of CoFe2O4/CNTs,the release of Co2+/Fe3+for promoting electronegative bacteria habitation,and electron mediation.(4)Based on the concept of "multi-phase collaborative catalysis",CNFs interpenetrated rGO-anchored MoS2 nanoflowers(rGO/CNFs@MoS2)were constructed through electrospinning,carbonization,freeze-drying and hydrothermal methods.Physicochemical properties and biofilm analysis suggested that the composite possessed a large electrochemical surface area,abundant electrocatalytic active sites,and good biocompatibility,which significantly enhanced the biofilm colonization,activity,and the number of electroactive bacteria(Rhodococcus and Pseudomonas)on CC,and thus promoted the interspecific electron transfer and information exchange process.MFC performance analysis implied that the rGO/CNFs@MoS2 modified CC achieved a maximum power density of 3584 mW/m2 and COD removal of 87.9%,which were about 4.5 and 1.33 times higher than that of pure CC,respectively.Superior electrochemical performance has been well applied in powering electrical devices.This study lays a foundation for designing high-performance anode electrocatalysts and promoting the practical application of MFC.