Investigation On The Performance Of Microbial Fuel Cells With Polyaniline-Polypyrole Composite Hydrogel Anodes

Microbial fuel cell（Microbial fuel cell,MFC）has atracted much attention as one of the most promising new energy technologies,which could directly convert the energy in organic matter into electrical energy.Among the structure,the anode in a MFC is not only the current collection but also acts as bio-carrier of microbes.Thus the anodic material would play a significant role for high-performance MFC.In this paper,the preparation and property of polyaniline-polypyrrole hydrogel（PANI-PPy）were studied and the performance of MFC with these derived composite hydrogel was also invstigated.During the experiment,cultured bacteria extracted from sea mud were used as the strain,and sodium acetate was used as the carbon source.Firstly,the composite hydrogel electrode,polyaniline-polypyrrole/carbon felt（PANI-PPy/CF）,was prepared through chemical oxidation method,and the properties of the composite hydrogel obtained under different ratio conditions of aniline and pyrrole were also investigated.Through characterization and electrochemical tests,the optimal molar ratio of aniline to pyrrole was 1:5.Moreover,the composite hydrogel electrode prepared under different ratio conditions（1:2,1:3:1:5,1:7,and 1:10）were used as bioanodes in MFC,in which the MFC with1:5 PANI-PPy/CF exhibited a best power output of 4413.81 m W/m³.In the long-term experiment,each MFC could maintain stable operation.Secondly,in order to improve the performance of the electrode,the PANI-PPy-CNTs/CF,hydrogel electrode was prepared by doping CNTs on the basis of a 1:5 composite hydrogel electrode by in-situ growth method.This modified hydrogel electrode was characterized by SEM and FTIR,which indicated that the PANI,PPy and CNTs were successfully recombined and this ternary composite hydrogel electrode had a rough and porous 3D structure.At the mean time,the electrochemical tests were also carried out on four hydtrogel electrodes of PANI/CF,PPy/CF,PANI-PPy/CF and PANI-PPy-CNTs/CF,and the PANI-PPy-CNTs/CF electrode showed excellent electrochemical performance among them.Then,these four hydtrogel electrodes were applied as anodes to MFCs.The MFC with PANI-PPy-CNTs/CF anode deliver a best power generation of 5315.44 m W/m³,which was much higher than that of other three anodes.And the PANI-PPy-CNTs/CF anode had the highest protein content.Finally,to further improve the biocompatibility,the PANI-PPy-CNTs-Fe₃O₄/CF composite hydrogel electrode was prepared bythe in-situ growth method through introducing Fe₃O₄ nanoparticles on the basis of the PANI-PPy-CNTs/CF electrode.The electrochemical test results showed the PANI-PPy-CNTs-Fe₃O₄/CF electrode had a higher area specific capacitance and smaller electrochemical impedance.Then,the CF,PANI-PPy-CNTs/CF and PANI-PPy-CNTs-Fe₃O₄/CF composite hydrogel electrodes were used as anodes to construct MFCs.Among them,the maxmuim power density of MFC with PANI-PPy-CNTs-Fe₃O₄/CF anode could reach 5901.50 m W/m³,which was 3.18 and 1.11 times higher than that of CF and PANI-PPy-CNTs/CF anodes,respectively.Meanwhile,the PANI-PPy-CNTs-Fe₃O₄/CF anode also exhibited the largest protein content of 70.28 mg/cm³.