University Park, Pennsylvania 16802, United States. Technology. No. 73 Huanghe Road, Nangang District, Harbin , China

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1 Supporting Information Single step fabrication using a phase inversion method of poly(vinylidene fluoride) (PVDF) activated carbon air cathodes for microbial fuel cells Wulin Yang* a, Weihua He b, Fang Zhang a, Michael A. Hickner c and Bruce E. Logan a a Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States b State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology. No. 73 Huanghe Road, Nangang District, Harbin , China c Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States *Corresponding Author. Telephone: Fax: wxy123@psu.edu. S1

2 Supporting information Figure S1. (A) Power density curve for cathodes with different PVDF loadings (8.8, 6.6 and 4.4 mg cm 2 ) (B) Electrode potentials (solid symbols for anode potentials and open symbols for cathode potentials). S2

3 Figure S2. SEM images for cathode surfaces with different PVDF loadings (A) 4.4 mg cm 2, (B) 6.6 mg cm 2 (C) 8.8 mg cm 2. Enhanced: brightness + 20% and contrast + 20% S3

4 Figure S3. (A) Scheme of a scale up MFC (B) Configuration of reactor with three anodes in the middle and two cathodes on air sides. Single chamber MFC (130 ml liquid volume) was constructed as previously reported, 1 with three brush anodes (0.25 cm in diameter and 0.35 cm in length) made from carbon fibers (PANEX K, ZOLTEK) wound into a titanium wire core. 2 The anodes were connected together externally by a single copper wire. Carbon cloth-based cathode with platinum catalyst (ETEK C % Pt on Vulcan XC-72) and a PTFE diffusion layer was prepared as previously described, 3 and used as a control to evaluate performance relative to the AC/PVDF cathode in the MFC. Both cathodes were fabricated with 7 cm in width and 10 cm in length (projected area 35 cm 2, 5 cm 7 cm) and operated without a separator. Domestic waste water, collected from the primary clarifier of the Pennsylvania State University Waste Water Treatment Plant, was used as the inoculum. The waste water was collected and then stored in 4 C room to minimize COD changes. The concentration of COD in the waste water was 500 ± 20 mg-cod L 1. S4

5 Figure S4. Power density curve for scaled up AC/PVDF cathode and carbon cloth based Pt/C cathode (5 cm 7 cm projected area). S5

6 Table S1 Unit prices of different materials in cathode fabrication Material Calculating price Supplier price Sources Stainless steel mesh, type 304 $12/m 2 $6-17/m 2 stainless-steel-wire-mesh_ html Nickel foam $20/m 2 $10-30/m 2 Metal-Nickel-Foam-for-NiMh_ html Activated carbon (AC) $1.4/Kg $ /Kg Carbon black (CB) $3.3/Kg $3.3/Kg PTFE powder $25/Kg $10-40/Kg PTFE-Powder_ html PVDF powder $24/Kg $ /Kg pvdf-powder-with-competitive_ html Polydimethylsiloxane-Dimethicone-Simethicone-Siliconsilicon_ html?s=p PDMS $2.6/Kg $2.2-3/Kg Nafion $3.6/g $3.6/g Platinum (Pt/C, 10%) $163/g $ /g Carbon cloth (30% wet proofed) $625/m 2 $625/m 2 (The prices were all reported based on specific suppliers and median price was adopted if a range was given in the supplier price) S6

7 References (1) Ahn, Y.; Logan, B., Domestic wastewater treatment using multi-electrode continuous flow MFCs with a separator electrode assembly design. Appl. Microbiol. Biotechnol., 1-8. (2) Logan, B. E.; Cheng, S.; Watson, V.; Estadt, G., Graphite fiber brush anodes for increased power production in air-cathode microbial fuel cells. Environ. Sci. Technol. 2007, 41, (9), (3) Cheng, S.; Liu, H.; Logan, B. E., Increased performance of single-chamber microbial fuel cells using an improved cathode structure. Electrochem. Commun. 2006, 8, S7