Bioresource Technology 189 (2015) 364–369

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Bioresource Technology

journal homepage: www.elsevier .com/locate /bior tech

Synergetic effect of conductive polymerpoly(3,4-ethylenedioxythiophene) with different structuralconfiguration of anode for microbial fuel cell application

http://dx.doi.org/10.1016/j.biortech.2015.04.0440960-8524/� 2015 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +60 3 7967 7678.E-mail address: saravananpichiah@um.edu.my (S. Pichiah).

Yee Li Kang, Shaliza Ibrahim, Saravanan Pichiah ⇑Environmental Engineering Laboratory, Department of Civil Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

h i g h l i g h t s

� Chemical polymerised PEDOT wassuccessfully applied for anodecoating.� MFC performances of PEDOT coated

are superior to control anodes.� Felt with open structure and loose

network of fibres is idealconfiguration.� Synergetic effect of PEDOT and felt

resulted in most improved MFCanode.

g r a p h i c a l a b s t r a c t

a r t i c l e i n f o

Article history:Received 2 March 2015Received in revised form 11 April 2015Accepted 15 April 2015Available online 20 April 2015

Keywords:Microbial fuel cellAnodeSynergeticPEDOTElectrode configuration

a b s t r a c t

PEDOT was synthesized by chemical polymerisation and characterised for its electrochemical insights.Three different anode configuration, namely graphite plate (GP), carbon cloth (CC) and graphite felt(GF) were then loaded with a fixed amount of PEDOT (2.5 mg/m2) denoted as GP-P, CC-P and GF-P respec-tively. The PEDOT coating improved the electrochemical characteristics and electron transfer capabilitiesof the anodes. They also contributed for enhanced MFC performances with maximum energy generationalong with coulombic efficiency than the unmodified anodes. The morphological characteristics likehigher surface area and open structure of felt material promoted both microbial formation and electro-chemical active area. A maximum current density of 3.5 A/m2 was achieved for GF-P with CE and COD of51% and 86% respectively. Thus, the GF-P anode excelled among the studied anodes with synergetic effectof PEDOT coating and structural configuration, making it as a potential optimum anode for MFCapplication.

� 2015 Elsevier Ltd. All rights reserved.

1. Introduction

Wastewater treatments are energy intensive processes. Forinstance, sewage requires �0.018 kWh/inhabitant (Svardal andKroiss, 2011). Conversely, around 1.5 � 1011 kWh of energy isstored in the domestic, animal and industrial wastewater (Logan

and Rabaey, 2012). Instead of expanding external source of energyto treat these wastewater, the ideal treatment process is one thatcan utilise these stored energy for wastewater treatment.

One possible technology that can convert the stored chemicalenergy in wastewater into electrical energy is through microbialfuel cell (MFC). Many bacterial species found in wastewaters facil-itates this conversion of energy through oxidation of carbonsources. These bacteria are classified as exoelectrogen as they areable to transfer electrons outside their cells and form the basisfor generation of electrical energy in a MFC system (Logan, 2009;

Y.L. Kang et al. / Bioresource Technology 189 (2015) 364–369 365

Logan and Rabaey, 2012). Additionally, the energy consumption ofwastewater treatment (aeration and recirculation pumping) can bereduced (Chang et al., 2014). These MFCs simultaneously generateclean energy, treat pollutants and recover resources from varioustypes of wastewater (Choi and Cui, 2012; Choi and Hu, 2013;Ichihashi and Hirooka, 2012; Lim et al., 2014). However; it is stillin preliminary development stage due its limitations such as lowpower production and high capital cost. Researchers have exploredways to improve all the possible components of MFC such as theseparator, electrodes and system configuration. This researchpaper will focus on the enhancement of anode as it holds the keyto improve the power production of MFC (Gnana kumar et al.,2014). Anode in MFC influences the biofilm formation as well asthe transport of electrons released from the microorganism tothe anode (Li et al., 2011). Hence, the characteristics of anode mustsupport microbial growth and attachment as well as efficient elec-tron collection and transfer.

Materials that have excellent biocompatibility, mechanical andchemical stability, large surface area, good conductivity and eco-nomical are suitable as anode. Materials like paper, cloths, foam,felt, fibres and granules of carbon or graphite materials were gen-erally employed as anode (Cai et al., 2013; Logan, 2008).Electrodes can be differentiated by their structure into two cate-gories; that is planar and three dimensional (Wei et al., 2011).Planar materials such as paper are brittle and smooth while clothmaterials are more flexible and has coarse surface. Three dimen-sional electrodes such as foam and felt materials have higher sur-face area and pores that promotes bacterial growth and adhesion.On the other hand, due to their thick structure, the mass transferof reactants and products on these materials could be hampered.The accumulations of biomass could subsequently clog the innersurfaces of the material and thereby reduces the durability ofthese electrodes. In short, every material has their own pro andcons that have to be deliberated based on their application andreactor design.

The utilisation of unmodified or untreated carbon electrodes isstill inadequate in terms of electrochemically-active surface areaand biocompatibility (Cai et al., 2013; Li et al., 2011). Specific mod-ifications are necessary to further enhance their overall perfor-mance as an anode. Coatings on carbon-based materials are oneof the possible methods to improve these electrodes. Attemptshave been made using mediators, metal, polymers and compositeof these materials (Godwin et al., 2014; Wei et al., 2011).Simultaneously, conductive polymers as potential coating sub-stance on carbon electrodes for MFC application has been gaininginterest owing to their conductivity and environmental durability(Li et al., 2011). Conductive polymer such as polypyrrole, polyani-lines and their composites have been successfully applied as MFCelectrodes. Chi et al. (2013) and Hou et al. (2013) had successfullyfabricated electropolymerised nano-polypyrrole and graphene/polyaniline nanocomplex anode for MFC application respectively.These reports substantiated the addition of conductive polymerfor improvement of MFC power production.

One of the upcoming conductive polymer is the poly(3,4-ethylenedioxythiophene) or commonly known as PEDOT. It is aversatile material possessing higher conductive in neutral condi-tion, stable and economical compared to the other conductivepolymers (Abdiryim et al., 2012; Wang et al., 2013). However theefficacy of this material is not much explored as a catalyst foranode. Wang et al. (2013) has successfully applied PEDOT/carbonpaper anode synthesized using electropolymerisation method forMFC application. Conversely, there is still inadequate research onchemically or oxidative polymerised PEDOT which is a more sus-tainable and facile synthesis method in MFC. Chemical polymerisa-tion of polyaniline and polypyrrole was successfully implementedby few research groups but to this point there is still a vacuum in

employing PEDOT obtained through this method in MFC research(Gnana kumar et al., 2014; Hou et al., 2015).

Hence, this investigation reports on the synthesis of PEDOTusing chemical polymerisation as potential anode catalyst inMFC. Three base anode materials of different morphology wereselected namely graphite plate, carbon cloth and graphite felt.The present study emphasised on the contribution of PEDOTand the impact of morphological and structural influence on theanode for improving the electrochemical and overall MFCperformance.

2. Methods

2.1. Chemicals and reagents

Graphite plate and felt was purchased from Hao Shi CarbonFibre Co. Ltd (China) while carbon cloth was obtained from FuelCell Earth (USA). Polytetrafluoroethylene or PTFE (60 wt.% disper-sion in H2O), Nafion� perfluorinated resin solution (5 wt.%), iso-propanol (95%), acetonitrile (99.8%, anhydrous), dioctyl sulfosucci-nate sodium salt (SDBS, 98%) and 3,4-ethylenedioxythiophenemonomer (EDOT) solution were purchased from Sigma–Aldrich.Iron (III) chloride hexahydrate (FeCl3�6H2O) (R&M Chemicals, UK)was used as oxidant. Deionized (DI) water was used throughoutthe experiment. All reagents were used without any furthermodifications.

2.2. Electrode synthesis

Poly(3,4-ethylenedioxythiophene), PEDOT was synthesizedusing oxidative polymerisation method. The oxidant, FeCl3�6H2O(10.0 mmol) and EDOT monomer (5.0 mmol) was dissolved in50 mL acetonitrile each (Madl et al., 2011). The two solutions weremixed together and stirred for 4 h. The solution changes colourfrom orange yellowish to dark blue indicating the formation ofPEDOT. The obtained product was filtered, washed with acetoni-trile and methanol until the filtrate becomes colourless. The pro-duct was further dried at 80 �C for 24 h in an oven.

Three different structural configuration of base anodes wereused; namely graphite plate, carbon cloth and graphite felt.Owing to the varied morphology of the base electrodes, modifiedtechniques were adopted to attach PEDOT onto the surface ofanodes. The graphite plate and carbon cloth, both categorised astwo dimensional electrodes adapt the same method while graphitefelt, a three-dimensional material employs a simple dip and drymethod. The loading rates of PEDOT onto all three electrodes werefixed at 2.5 mg/cm2 with electrode dimension of 4 � 4 cm.

Graphite plate and carbon cloth were coated with PEDOT byadapting the method commonly used to load catalyst on cathode(Cheng et al., 2006). Briefly, the desired amount of PEDOT wasweighed and mixed with Nafion solution and iso-propanol. Forevery 1 mg of PEDOT, 6.67 lL of Nafion and 3.37 lL of iso-propanolwere added. The mixture was vortexed in a sample vial and thepaste was coated uniformly onto the base electrodes. Theelectrodes were dried in an oven at 80 �C for 24 h.

A different approach was adapted for the three dimensionalgraphite felt electrodes. PEDOT powder (0.1%) was dispersed indeionized water with 1% SDBS as surfactant by sonicating for 2 h(Xie et al., 2012). Graphite felt was cut into desired size and dippedinto the PEDOT ink and dried at 80 �C. The dip-dry process wasrepeated until all the solution was consumed.

The unmodified or control anodes are herein after referred to asGP (graphite plate), CC (carbon cloth) and GF (graphite felt), andtheir corresponding PEDOT coated samples are labelled as GP-P,CC-P and GF-P respectively.

366 Y.L. Kang et al. / Bioresource Technology 189 (2015) 364–369

2.3. Characterisations of PEDOT and modified electrode

In order to confirm the successful synthesis of PEDOT, FourierTransform Infra-red spectroscopy (FT-IR) spectrum and X-rayDiffraction (XRD) were done using Perkin Elmer Spectrum 100and PANalytical Empyrean respectively. The elemental compositionand images of the synthesized PEDOT was analysed and capturedusing Energy Dispersive X-ray (EDX) and Field Emission ScanningElectron Microscope (FESEM) (Quanta 450 FEG, FEI) respectively.The attachment of PEDOT and surface morphology of the electrodesbefore and after modification was also confirmed with FESEM.

2.4. MFC setup and application

A dual chambered MFC was used in this study. Each chamberhad a working volume of 150 mL and were separated by a protonexchange membrane (Nafion 117, Sigma–Aldrich). Carbon clothwas used as the cathode for all the experiments. The dimensionsfor both the anodes and cathode were fixed at 4 cm � 4 cm. Thephotographic images of the base electrodes were shown inFig. S1. An anaerobic pond sludge obtained from palm oil mill efflu-ent treatment plant (Seri Ulu Langat Palm Oil Mill, Dengkil,Malaysia) was used as inoculum. The electrolyte for both chamberscontains 0.1 M of phosphate buffer solution (4.3 g/L NaH2PO4,9.2 g/L Na2HPO4, pH = 7), 0.6 g/L NH4Cl and 0.3 g/L KCl. Sodiumacetate trihydrate (1 g/L) and trace elements (12.5 mL/L) wasadded into anodic solution, while 100 mM of potassium ferricynidewas added into cathodic solution. The MFCs were operated underfed-batch condition and the anolyte was replaced once the operat-ing voltage dropped below 50 mV. The anode and cathode wereconnected with 1 kO resistor to complete the circuit.

2.5. Measurement and analysis

The CV were performed using AUTOLAB PGSTAT128 N(Metrohm Autolab B.V., Netherlands) under three-electrode modein an electrochemical cell. The anode electrode, Pt wire and Ag/AgCl were used as working, counter and reference electroderespectively. The scan rate was set at 10 mV/s. EIS measurementswere also conducted in similar mode with frequency ranging from100 kHz to 1 mHz with an amplitude of 10 mV as stimulus at opencircuit potential. Cell voltage was recorded for in a regular intervalusing a digital multimeter (UNIT 61D, Uni-Trend Group Ltd., China)with data acquisition module. Three cycles of voltage curve wererecorded to ensure the stability and reproducibility of the results.Polarisation curves and power density graph were attained by lin-ear scanning voltammetry (LSV) at a scan rate of 1 mV/s. The polar-isation for individual electrodes were obtained by using variousresistances (100 kO–100 O) and were recorded against Ag/AgCl ref-erence electrode. Chemical oxygen demand (COD) were examinedaccording to the Standard Methods (APHA, 1998) for each cycleand conducted in triplicates for all samples. The coulombic effi-ciency (CE) was calculated by the ratio of electrons converted toelectricity (CP) to the theoretical available electrons (CT) in thesolution as shown in Eq. (1). For a batch reactor, the CE can becalculated using Eq. (2)

CE ð%Þ ¼ CP

CT� 100% ð1Þ

CE ð%Þ ¼MR t

0 I dtFbvAnDCOD

ð2Þ

where M is molecular weight of the substrate (g/mol), F is Faraday’sconstant, I is current obtained (A), b is number of electrons per molesubstrate, vAn is volume of liquid in the anode compartment (L),

DCOD is change in COD concentration over the duration of a cycle(g/L), t is duration of a cycle (s)

3. Results and discussion

3.1. Characterisation of synthesized PEDOT

The FT-IR spectrum for the synthesized PEDOT was carried outto confirm the polymerisation of EDOT and is illustrated inFig. S2(a). Peaks at 1575 and 1463 cm�1 are attributed to C@Cand CAC stretching vibrations of the heteroaromatic thiophenering respectively (Li et al., 2011; Wang et al., 2013). Peaks rangingfrom 1000 to 1300 cm�1 (1269, 1157, 1124 and 1070 cm�1) areindicative of CAOAC bond in the dioxane group (Abdiryim et al.,2012; Eren et al., 2012). The peaks around 995, 947 and865 cm�1 signifies the presence of CAS bonds present in the thio-phene ring (Abdiryim et al., 2012).

The crystallographic analysis of the synthesized PEDOT isdepicted in Fig. S2(b). The analysis reveals broad peaks that denotesthe amorphous nature of synthesized PEDOT (Selvaganesh et al.,2007). The spectrum exhibits three distinct peaks at 2h = 6.4�,12.8� and 26�. The peak seen at 6.4� represents the reflection ofthe (100) polymer backbone with d-spacing of 13.9 Å (Choi et al.,2004). As the d-spacing of 12.8� is 6.9 Å which is half of the (100)reflection, this peak corresponds to the (200) reflection of the poly-mer backbone. The peak �26� corresponds to (020) reflection.

Synthesized PEDOT particles were observed using FESEM under6000� and 25,000� magnification as shown in Fig. S3(a) and (b)respectively. Granules of PEDOT can be found agglomerating andform clumps. PEDOT particle also does not contain any pores asrevealed in Fig. S3(b). No specific shape can be deduced and theparticle sizes are not uniform. Elements of carbon (C), oxygen (O)and sulphur (S) were detected from EDX analysis as presented inFig. S4 which is consistent with the elemental composition ofPEDOT. Traces of iron (Fe) and chlorine (Cl) were found and arecontributed by the oxidising agent, FeCl3�6H2O.

3.2. Surface morphology of anodes

The surface morphology and coating condition of all the elec-trodes were observed using FESEM and depicted in Fig. S5. GPhas a smooth surface but consist of fine fracture lines which areattributed to the fragile and brittle nature of the GP. The imagefor GP-P in Fig. S5(d) disclosed that the surface of the electrodeis mostly covered uniformly with PEDOT particles. The GP-P anodenow has a rough and uneven surface due to the attachment ofPEDOT particles compared to the GP anode. The CC anode is madeup of carbon fibres which are arranged in a weaving pattern.PEDOT particles can be observed on the surface of the carbon fibresof the CC-P anode from Fig. S5(e). GF consists of loose network offibres and has an open structure. Owing to the web of fibres,PEDOT particles were trapped in the gaps and crevices of thesefibres as seen in the microscopy image of GF-P. It can be observedthat most particles are trapped in between the fibres while someparticles were directly attached to the fibres. It should be notedthat upon higher magnification, no pores were found on GP as wellas the fibres of CC and GF (Images not shown). The attachment ofPEDOT onto the anodes are on the surface of the plate (GP-P) andfibres (CC-P and GF-P).

3.3. Electrochemical analysis

The CV analysis of the electrodes was carried out to analyse thereactiveness of the electrode in terms of electrochemical activityand is shown in Fig. 1. The GF-P obtained the largest current peak

-0.015

-0.005

0.005

0.015

-0.8 -0.4 0.0 0.4 0.8

Cur

rent

(A)

Potential (V) vs. Ag/AgCl

GP CC GFGP-P CC-P GF-P

Fig. 1. Cyclic voltammograms of the prepared anodes at scan rate of 10 mV/s underthree-electrode setup.

Fig. 2. The Bode plot of the EIS analysis; (a) impedance, |Z| and (b) phase shiftversus frequency of the prepared anodes. The inset shows the equivalent circuitused to model the plot.

0.0

0.4

0.8

1.2

1.6

2.0

0.0

0.2

0.4

0.6

0.8

0.0 1.0 2.0 3.0 4.0

Pow

er D

ensi

ty (W

/m2 )

Vol

tage

(V)

Current Density (A/m2)

GP CC GFGP-P CC-P GF-P

Fig. 3. Polarisation and power density curves of the MFC system equipped with theprepared anodes.

Y.L. Kang et al. / Bioresource Technology 189 (2015) 364–369 367

followed by CC-P and GP-P while the three unmodified anodesrecorded almost similar voltammogram. It is evident that the addi-tion of PEDOT resulted in considerable increase in current peak aswell as area under the curves for the modified anodes for all threeconfigurations. This improvement of electrochemical characteristicwas ascribed to enhanced electrical conductivity and electrontransfer contributed by PEDOT. Redox peaks of graphite were

observed on the voltammogram of GF and GF-P electrodes.However, the redox peaks were shifted for the GF-P anode. Theseshifts are characteristic of decreasing rate constant owing to thedelay in current response to the applied voltage (Bard andFaulkner, 2001). This phenomenon suggests that the presence ofPEDOT particles on the open structure of GF-P obstructs the diffu-sion of the electrolyte to the inner section of the electrode.

EIS analysis was performed to evaluate the internal resistanceof the anodes and the Bode plot was presented in Fig. 2. The anal-ysis were then fitted into an equivalent circuit as shown in theinset of Fig. 2(a) where Rs, Rp, CPE and W represent solution resis-tance, polarisation resistance, constant phase element andWarburg impedance respectively. The addition of PEDOT reducedthe polarisation resistance of carbon cloth and graphite felt anode.The Rp for CC (�150 O) dropped down to �10 O (CC-P) while GFanode which has low Rp of �17 O was further reduced to �10 Owith the addition of PEDOT (GF-P). However, the opposed trendwas observed for the plate anodes. The coating of PEDOT on GP-Pincreased the Rp to �33 O. The GP naturally has a low resistancedue to its conductive nature. However, PEDOT coatings usingNafion solution as binder reduced the conductivity and hamperedthe electron transfer on the surface of the GP-P causing a signifi-cant surge in Rp. The presence of Warburg impedance in the equiv-alent circuit for all the tested anodes established that the reactionswere also governed by mass transfer resistance. Based on theseelectrochemical analysis, GF-P recorded the optimum featuresamong the tested anodes due to the synergetic effect of bothPEDOT and the felt configuration.

3.4. MFC Performances

The electrochemical analysis revealed the preliminary electro-chemical properties of the anodes. However, the actual perfor-mance and durability of the electrodes can only be determinedby applying these electrodes in a MFC system. Polarisation andpower density curves were computed to obtain a more compre-hensive analysis of these anodes performance and are presentedin Fig. 3. The short circuit current density (V = 0) for GF-P was3.50 A/m2 which is 7.3 times higher than GF, 0.48 A/m2. The addi-tion of PEDOT enable the anode to sustain greater current densitydue to the high capacitive nature of PEDOT (Lei et al., 2011). Thecurrent density obtained by GF-P is comparable to preceding studyby Wang et al. (2013) using graphene/PEDOT on carbon paperwhich was reported at 3.59 A/m2. The current density for CC-P

Table 1Coulombic efficiency and COD removal of prepared anodes.

Anode CE (%) COD (%)

GP 38.2 85.3GP-P 40.1 86.8CC 31.0 79.1CC-P 33.1 81.7GF 45.4 81.9GF-P 51.0 86.3

368 Y.L. Kang et al. / Bioresource Technology 189 (2015) 364–369

and GP-P were 3.48 A/m2 and 2.74 A/m2 respectively. The currentdensity of all the three unmodified electrodes falls in the rangeof 0.43–0.55 A/m2. Similar trend was observed from the maximumpower density of the sample anodes. The highest power densitywas achieved by GF-P at 1.62 W/m2 and is 10 times higher thanGP (0.16 W/m2) which is the least performing anode. It is palpablethat the coating of PEDOT onto all three configuration improves themaximum power density compared to the control anodes. Forinstance, GP-P anode exceed the GP by 4 times to reach a maxi-mum power density of 0.64 W/m2 while CC-P (0.79 W/m2) was atwofold improvement from the CC (0.35 W/m2). GF recorded amaximum power density of 0.52 W/m2.

The surge of current and power density after electrode modifi-cation demonstrates the influence of PEDOT in increasing the con-ductivity, electron transfer, electrochemical activity and overallcharacteristic of the anodes. In the perspective of biofilm forma-tion, the electrostatic force between the positively chargedPEDOT polymer backbone and the negatively charged microbialcell wall increased the quantity and stability of the microbesattached to the electrode (Park et al., 2013; Wang et al., 2013).Organic conductive compounds or conductive polymer are capableto mediate electron transfer from bacteria to electrode (Park et al.,1997). The presence of mediator allows more types of bacteria totransfer their electron externally and enhance the performance ofMFC. The coarse and increased surface area due to the coating ofPEDOT encourages the biofilm formation, enables space for thebacteria to grow and leads to a direct contact with the electrode.This factor increases the electron transfer efficiency and improvesthe contact between the microbes and electrode. Structurally, it isevident that felt anodes have the best construction followed bycloth and plate configuration. This is also in good agreement withthe early research by Chaudhuri and Lovley (2003) that the highprojected geometrical surface area of graphite felt increased itscurrent generation compared to graphite rod. The disorganisednetwork of graphite fibres provides ample space for bacterialgrowth and the open structure encourages the mass transfer ofthe reactants into the felt anodes. In contrast, the smooth surfaceof plate electrodes discourage the biofilm formation while clothhave fairly rough surface that encourage the biofilm formation,but have lower surface area compared to felt anodes.

Fig. 4. Voltage generation for the prepared anodes across a

Individual polarisation curves for both anode and cathode wereperformed to establish the limiting electrode for MFC performance(Fig. S6). The potential of anodes plunged drastically when reach-ing high current density while cathode potential remained almostconstant; revealing that anode is the limiting factor in this system.This observed phenomenon is attributed to electron transfer limi-tations by the microbes in the system (Logan and Regan, 2006;Thorne et al., 2011).

The anode and cathode were connected with a 1 kO resistor andthe obtained voltage output for three stable cycles is reported inFig. 4. The voltage generation for GF-P electrode recorded the high-est at 710 ± 3 mV followed by CC-P (662 ± 2 mV), GP-P(660 ± 7 mV), GF (637 ± 26 mV), CC (553 ± 1 mV) and GP(445 ± 12 mV). All the modified anodes (GF-P, CC-P and GP-P)recorded higher voltage production compared to their respectivecontrol anodes (GF, CC and GP) signifying the role of PEDOT inincreasing the voltage generation regardless of the configurationof the anodes. In contrast, the intensity of improvement differsfrom each base material under similar loading rate of PEDOT(2.5 mg/cm2). For example, the GP-P and CC-P recorded a notableincrease of 48% and 20% in voltage generation compared to GPand CC respectively while GF-P only documented 11% improve-ment against GF. This demonstrates that not all types of anode con-figuration benefit equally from the same amount of PEDOT coating.

The COD removal and CE data were tabulated in Table 1. TheCOD removal falls in the range of 79–86%, demonstrating that allthe tested anodes are able to remove acetate effectively in theMFC system. The range of CE% achieved by the anodes are around31–51%. The most efficient anode was the GF-P with CE of 51%

1000 X external resistor for three consecutive cycles.

Y.L. Kang et al. / Bioresource Technology 189 (2015) 364–369 369

which is concurrent with its high voltage generation. GF recordedthe second highest CE at 45% while the planar electrodes recordedlower CE in the range between 31% and 40%. It is clear that thestructural configuration plays a vital role in determining the sys-tem efficiency. The presence of PEDOT also marginally contributedfor the increase of CE of all three anode configuration. The low CEof MFC system can be contributed from several factors such as thepresence of methanogen, bacteria growth and metabolism andsubstrate diffusion (Feng et al., 2010; Rismani-Yazdi et al., 2013).

4. Conclusions

The present work proved that chemical polymerised PEDOT hasbeen successfully synthesized and that the coating of PEDOT ontoMFC anodes enhanced the performance of electrodes significantly.Additionally, electrode structure and configuration plays anequally important role in determining the capability of the anodeas well. Felt anodes emerged as a prospective anode over planarelectrodes of cloth and plate construction. The biofilm formationand electron transfer capabilities was well acknowledged by themorphology of the felt structure. Over all the combined effect ofPEDOT and felt structural configuration anchored the GF-P as apromising anode for MFC applications.

Acknowledgements

This work was supported by High Impact Research Grant(UM.C/625/1/HIR/053/2) and Postgraduate Research Grant(PG022-2013A), University of Malaya.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.biortech.2015.04.044.

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