Mechanism of Energy Generation of Microbial Fuel Cells

20 7Π8 2008 8 PROGRESS IN CHEMISTRY Vol. 20 No. 7Π8 Aug., 2008 3 1,2 2 1 3 3 (11 100871 ; 21 510650) (MFC),, MFC MFC MFC 5,,, : TM911145 : A : 10052281X(2008) 07Π821233208 Mechanism of Energy Generation of Microbial Fuel Cells Lu Na 1,2 Zhou Shungui 2 Ni Jinren 1 3 3 (11Department of Environmental Engineering, Peking University, Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China ; 21Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco2Environment and Soil Sciences, Guangzhou 510650, China) Abstract Microbial fuel cells ( MFCs) are the emerging technology for producing electricity directly from biodegradable organic matter using bacteria as catalyst. One of the most promising applications for MFCs is to use them simultaneously treating organic wastes while accomplishing power generation. The main problems for MFC are low electron transfer and power density. The electron transfer from the microbial cell to the fuel cell anode, as a process that links microbiology and electrochemistry, represents a key factor that defines the MFC power and energy output. In the paper, five key steps including fuel bio2oxidation, electron transfer to anode, electron transfer through the external circuit, proton diffusion and cathode reaction for electricity generation by MFC systems are identified and discussed in detail. Finally, the potential study directions in the future are prospected. Key words microbial fuel cells ; mechanism of energy generation ; electron transfer ; output power 1,, (microbial fuel cell,mfc) [1,2 ],MFC, : (1), ; (2), ; (3), ; (4), Logan [3 6 ] : 2007 8, : 2007 9 3 (No. 40601043) (No. 7006759) 3 3 e2mail :nijinren @iee. pku. edu. cn

1234 20,,MFC 1911, Potter [7 ], MFC, MFC, 10 WΠm 2, MFC,, MFC, MFC 2 MFC MFC,, 1 MFC [3,8,9 ], MFC 5 : (1), ; (2), ; (3) ; (4), ; (5) ( ),, 211 21111 ( ), (electricigenic respiration),, [10 ] Fe ( ) ( ),,, Fe ( ) [10 ] Fe ( ), Fe ( ),, Fe ( ),, 1 :11 ;21 ;31 ;41 ;51 Fig. 1 Steps of electron2transfer in MFC system. 11fuel biooxidation, 21electron transfer to anode, 31resistance, 41proton diffusion, and 51cathode reaction MFC,,,,,, NADH Q [11 ] Kim [9 ] MFC, ;,,, ;,,,, 21112 MFC, 1, MFC MFC,,,, MFC,, [12 ] [13 ] [14 ] [15 ] MFC MFC( MFC)

7Π8 1235 1 Table 1 Anodic microorganisms and their electron transfer types microorganism bacterial example transfer type electron acceptor ref. mediator2driven microorganisms Butyribacterium methylotrophicum exogenous mediators neutral red 13 Desulfovibrio desulfurcans primary metabolites as mediators S 2-16 Pseudomonas aeruginosa secondary metabolites as mediators pyocyanin 40,41 electricigens Geobacteraceae membrane2driven cytochrome 25 27 Rhodoferax ferrireducens cytochrome 24 Clostridium butyricum cytochrome 23 Shewanella putrefaciens cytochrome 18 H 2 H 2 S ( ), ( Escherichia coli) Desulfobulbaceae Harbermann [16 ] Desulfovibrio desulfurcans, MFC, 212,, ( Pseudomonas aeruginosa [17 ] ) MFC, ( ), 2,,, 4 : MFC, 4,, [9,18 ] ( ), MFC, 2 Table 2 Development of anodic electron2transfer mechanisms in [9,19 ] MFC MFC MFC( MFC), [19 21 ], [22 ] ( Shewanella putrefaciens ) [18 ] ( Clostridium butyricum ) [23 ] ( Rhodoferax ferrireducens) [24 ] [25 ( Geobacteraceae) 27 ] ( Aeromonas hydrophila) MFC, MFC 16S rdna, MFC,,, 3615 % Gammaproteobacteria 2710 % Firmicutes [28 ] ;, Deltaproteobacteria, 70 %, 1713 % Gammaprote2 obacteria [29 ] ; 4019 % Betaproteobacteria 2712 % Alphaproteobacteria, Deltaproteobacteria Gammaproteobacteria [20 ] ; [30 ] year finder viewpoint ref. 1911 Potter demonstrating the production of electrical energy (the first reported MFC) 1931 Cohen proposing the introduction of electromotively active redox substances 1991 Harbermann & Pommer proposing the production of reduced primary metabolites as redox mediators 1999 Kim, et al demonstrating some microorganisms possessing membrane bound cytochromes to transfer electrons 2000 Newman & Kolter 2005 Reguera, Lovley,et al 21211 proposing the secondary metabolites being involved in extracellular electron transfer processes proposing the electron2transfer mechanism of electronically conducting nanowires 7 57 16 18 40, 41,,, 34

1236 20 2 :A ;B ;C ;D Fig. 2 Identified anodic electron2transfer mechanisms in MFC. A) cell2membrane2bound cytochromes, B) electrically conductive nanowires, C) redox mediators, and D) oxidation of primary metabolites 0147 gπl),, (12 h 3 C),,,, Kim [18 ] 2121112, MFC,, (pili),, (nanowire) [34 ], 3 5 nm, MFC, 1 000 Reguera [34 ] (AFM) G. sulfurreducens :,,,, ( ),,,, NADH Q [11,31 ] :,, C,, [32 ],, 2 B, Kim [9 ],,,, NADH Q,, C 21212,,, Geobacter sulferreducens 100 ( ), C [33 ],,, ( Shewanella, putrefaciens ) [18 ] ( Rhodoferax ferrireducens) [24 ] [25 ( Geobacteraceae) 27 ] ( Aeromonas hydrophila), ( Clostridium butyricum) [23 ], : 2121111, C, 2 A Geobacter Desulfuromonas Shewanella,, Kim [9 ] MFC,, ( ( ), 3 2121211 20 80,

7Π8 1237,MFC,, MFC 2 C,,, ;,, : (1), ; (2),, ; (3), ; (4), ; (5), [14 ] [16 ] Fe ( ) EDTA [35 ] [12 ] [13 ], 3, Park [36 ],, 10,,,, [37 ] 3 MFC [38 ] Table 3 Exogenous redox mediators and their potentials used for MFC [38 ] substance class redox mediator redox potential phenazines neutral red - 0132 safranine - 0129 phenazine ethosulfate 0106 phenothiazines new methylene blue - 0102 toluidine blue o thionine 0103 0106 phenoxazines resorufin - 0105 gallocyanine 0102 quinones 22hydroxy21,42naphthoquinone - 0114 anthraquinone22,62disulfonate - 0118,, MFC, ;,, MFC 2121212, ( [39 ) 41 ],, (pyocyanine) 22 232 21,42 (ACNQ) [39 ] MFC,, 2 C,,, ;,,,,, [17,19 ], Rabaey [17 ] Pseudomonas aeruginosa MFC (pyocyanine) phenazine212carboxamide MFC,,16S rrna,mfc Lactobacillus Enterococcus [19 ] MFC, C [38 ],,, [10,42 ],,, MFC 2121213 H 2 H 2 S ( ),, 2 D,,,,, MFC, MFC,

1238 20 :, MFC, [43 ], MFC [44 ],, (1) SO 4 2- + 8H + + 8 e - S 2- + 4H 2 O (1) Harbermann [16 ] Desulfovibrio desulfuricans MFC,,,, [43 ],,,, Harbermann [16 ], S 2 -,, : MFC,,, Schrgder [45 ] E. coli K12,, 15 000 maπm 2, 213, MFC,,,,,, ;,,,,, Menicucci [46 ],,,,, MFC, MFC, ;,, MFC 214, MFC, MFC, MFC, [2 ], [47 ] MFC,, ph,, MFC :,Nafion,, (10-2 SΠcm) Logan [48 ],, MFC,, MFC, Min [49 ], Liu [47 ] MFC,, Nafion MFC 119 512,,,, ;,,,,,,, Liu [47 ], MFC Nafion MFC 3,, 28 %,MFC,, MFC,, 14 % [50 ] 215, ( ),, MFC

7Π8 1239,, ( ), MFC,, Oh [51 ], MFC 22 % Cheng [52 ], 2 mgπcm 2 011 mgπcm 2,, MFC, Morris [53 ] PbO 2, Pt 117,,, 319,,,, MFC,, [54 ],, MFC,, [55 ],,,, Oh [51 ] 50 % 80 %,,,,,,,, Rhoads [56 ],, ( + 38415 6410) mv 3 MFC MFC,, : ( ), ; ( ),,, MFC MFC 5,,, MFC,, MFC MFC, : (1),, MFC (2) MFC Fe ( ),Fe ( ) MFC (3),, MFC, MFC, MFC [ 1 ] Park D H, Zeikus J G. Biotechnol. Bioeng., 2003, 81 : 348 355 [ 2 ] Gil G C, Chang I S, Kim B H, et al. Biosen. Bioelectron., 2003, 18 : 327 334 [ 3 ] Liu H, Ramnarayanan R, Logan B E. Environ. Sci. Technol., 2004, 38 : 2281 2285 [ 4 ] Liu H, Logan B E. Environ. Sci. Technol., 2004, 38 (14) : 4040 4046 [ 5 ] Min B, Logan B E. Environ. Sci. Technol., 2004, 38 (21) : 5809 5814 [ 6 ] He Z, Minteer S D, Angenent L T. Environ. Sci. Technol., 2005, 39(14) : 5262 5267 [ 7 ] Potter M C. Proc. R. Soc. Lond. B, 1911, 84 : 2760 2761 [ 8 ] ( Guan Y), ( Zhang X). ( Progress in Chemistry), 2007, 19(1) : 74 79 [ 9 ] Kim H J, Park H S, Hyun M S, et al. Enzyme Microbiol. Technol., 2002, 30 : 145 152 [10] Lovley D R. Nat. Rev. Microbiol., 2006, 4 : 497 508

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