Facile Fabrication And Mechanistic Study Of New Carbon Based Electrodes For High-performance Microbial Fuel Cell

Microbial fuel cell(MFCs)is a new wastewater treatment technology,which combines organic pollutants degradation and direct bioelectricity generation.MFC exhibits vast potential application in the areas as wastewater treatment,biosensing and bioremediation.However,the high cost and low electricity generation capability,which is mainly ascribed to electrode preparation process and its performance,act as the one of the main bottlenecks that limits its industrial application.Therefore,it attracts tremendous research interests to explore new electrode preparation strategies with improved performance.Currently,carbon based composite electrodes are the prior choice for MFC studying.However,most of these carbon electrodes are fabricated with tedious and time-cost procedures.Furthermore,limited study has been conducted to unveil the underlying mechanism between the electrode characteristics and the improved bioelectrochemical system performance,which restricts the development of composite electrode for MFC application.In this thesis,in-situ fabrication strategies were developed to prepare a series of modified carbon electrode including graphene(GO)and polyaniline(PANI),graphene/polyaniline(GO/PANIOS).Comparison study on the electrode property and its performance as MFC anode were conducted.Furthermore,mechanism on how these composite carbon electrodes enhance the MFCs bioelectricity generation were investigated and clarified.The results are summarized as follows:1)Firstly,a two-electrode system was developed in 0.1 M sulfuric acid solution for graphene in-situ electrochemical fabrication.By applying a 10 V direct current for 4 minutes,graphene oxide(GO)layers were partially peeled off from the graphite paper surface and GP electrode modified with in-situ fabricated graphene structure was thus prepared(nominated as GO electrode).When applied as MFC anode,this GO electrode demonstrated a 4.1 times improvement in the maximum power density of MFCs compared with bare GP electrode.The improved MFC performance can be partially explained with the increased electrode surface area and wettability due to the formation of graphene structure on the GP electrode.More importantly,the in-situ fabricated graphene improves direct electron transfer(DET)between electroactive bacteria and electrode materials,which is evidenced by the electrochemical analysis.2)Secondly,PANI modified GP electrodes were developed both with chemical(PANIchem)and electrochemical(PANICV)in-situ fabrication strategies,which was fabricated either by a slow chemical polymerization in a solution containing aniline monomer,ammonium persulfate(APS)and GP electrode or electrochemical polymerization in three-electrode system with aniline monomer,sulfuric acid and GP electrode.These PANI modified GP electrode enhance the bioelectricity output when they were applied as MFC anode.The achieved maximum power density of PANICV and PANIchem were individually improved by 2.4 and 4.5 times compared with GP.Further analysis revealed that the the in-situ formed polyaniline improved the bacteria adhesion to the electrode surface and the synchronously enhanced the direct and mediated electron transfer between Shewanella and electrode,thus enhancing the electricity generation of MFCs.3)Further,as in-situ modification of graphene and PANI could promote the bioelectricity generation of MFCs and the graphene and PANI were electrochemically fabricated via an anode oxidation process,we developed a one-step in-situ fabrication strategy for graphene/polyaniline composite electrode(GO/PANIOS)preparation with could be finished in 4 minutes.The maximum power density of MFCs with this electrode was 22 times higher than that of GP.Further analysis indicated that in-situ formed graphene/polyaniline composite increased the surface area increases of electrode,improve the wettability,encouraged the bacteria attachment,and exhibited a synergistic enhancement of direct and mediated electron transfer of Shewanella and electrode,thereby enhancing production the electrical properties of MFCs.