The Fabrication Of Chitosan/Carbon Composites And The Improvements Of Electricity Generation Performance On Electrochemically Active Biofilm

This study fabricated two types of hierarchical carbon-based composites including chitosan/carbon nanotubes(CS/CNTs)and chitosan/carbon black(CS/CB)by ice segregation induced self-assembly(ISISA)under different vacuum freeze-drying conditions including 0 h(natural dried),5 h and 10 h,further modified graphite electrode to improve the electrochemically active biofilms(EABs)performance of Geobacter sulfurreducens.Different characterization methods were utilized to analyze the CS/CNTs and CS/CB.X-ray diffraction(XRD)was employed to analyze the phase structure of CS,CNTs,CB,CS/CNTs and CS/CB.Fourier transform infrared spectroscopy(FTIR)was used to determine the functional groups of CS,CNTs,CB and chitosan/carbon composites via different vacuum freeze-drying time treatment(0 h,5 h and 10 h).The surface structures of various modified electrodes were observed by scanning electron microscopy(SEM)and the hierarchically crossing structures also were analyzed.Besides,the electrochemical activities of different electrodes were analyzed by cyclic voltammetry(CV).On the other hand,with regard to the performance of EABs on various electrodes,the growth and formation of EABs were recorded by chronoamperometry(CA).The classical electrochemical methods(CV and electrochemical impedance spectroscopy(EIS))were applied to assess the catalytic activity and electron transfer rate of EABs.Combining with SEM to observe the morphology of EABs on various electrodes,and the Coomassie brilliant blue method was utilized to measure the biomass of EABs on various electrodes.The main conclusions are as follows:(1)Porous CS/CNTs and lamellar CS/CB were prepared by the ISISA method.The pore diameter of 5 h and 10 h CS/CNTs was 28.0?m and 4.6?m,respectively.CS/CB exhibited the lamellar structure via vacuum freeze-drying;5 h CS/CB was more regular and orderly than that 10 h CS/CB,which was no report before.(2)As for electrochemical activity,5 h CS/CB was the highest(991.17?A)and the peak current(Ip)was 2.58 times higher than that of unmodified electrode(384.32?A).The electrochemcial activity of 5 h CS/CNTs was also 1.67 times higher than that of the unmodified electrode.For the peak potential difference(?Ep),5 h CS/CB(73 mV)and 5 h CS/CNTs(88 mV)were significantly lower than the unmodified electrode(142 mV).(3)Through the comparisons of EABs on different modified electrodes,the lamellar structure of 5 h CS/CB was the most conducive to the attachment of EABs.The protein content of 5 h CS/CB modified electrode on EABs was increased by 5.5 times compared with modified electrode and the electron transfer resistance(Rct)was the lowest(369±41?),which attributed to the maximum current density(1457±69?A/cm~2).The mesoporous structure of 5 h CS/CNTs also facilitated the adsorption of EABs,which may cause pore clogging during the formation of EABs,resulting in a higher charge transfer resistance(620±51?),and therefore in the production of electricity was lower by 16.7%than 5 h CS/CB.In this study,facile ISISA modified method was performed to fabricate hierarchical carbon-chitosan composites under 5 h and 10 h freeze-drying conditions,which would provide a suitable way to promote the performance of electrodes.5 h CS/CB modified electrode showed a series of performance in generating electricity,which would solid foundation for the cheap CB in the field of materials,bio-electrochemistry and practical applications of microbial fuel cells(MFCs).