1. Study on the multi-metal oxygen reduction catalysts for high performance air cathode microbial fuel cells for wastewater treatment Young-Chae Song *, Tae-Sun Choi *, Jung-Hui Woo *, Kyuseon Yoo **, Jae-Woo Chung ***, Chae-Young Lee **** * Department of Environmental Engineering, Korea Maritime University, Busan 606-791, Korea ** Department of Civil and Environmental Engineering, Jeonju University, Chonbuk 560-759, Korea *** Department of Environmental Engineering, Gyeongnam National Univ. of Sci. and Technol., Gyeongnam 660-758, Korea **** Department of Civil Engineering, The University of Suwon, Gyeonggi 445-743, Korea Introduce  A bioelectrochemical device converting the chemical energy contained in organic matter into electricity directly by a microbial catalytic role Microorganism Organics (Chemical energy) Electric power - ORR(oxygen reduction rate) on the spot of cathode : a three phase reaction Challenges for the efficient ORR on cathode - how to supply enough reactants (e -, H +, O 2 ), and remove the product (H 2 O) - how to reduce the activation energy for ORR - How to provide a wide surface area for ORR Challenges for the efficient ORR on cathode - how to supply enough reactants (e -, H +, O 2 ), and remove the product (H 2 O) - how to reduce the activation energy for ORR - How to provide a wide surface area for ORR 2e - + 2H + + O 2  H 2 O Electron : conducted from cathode (solid) Oxygen : diffused from air (gas) Proton : transported from electrolyte (liquid)  Eileen Hao Yu, et al., Journal of Power Sources 171 (2007) 275–281  Metal pthalocyanine(FePc, CuPc, FeCoPc, etc.) or porphyrin (CoTMPP) would be good alternatives Metal compounds for ORR catalyst : Pt, FePc, CoTMPP, MnO x, CuPc, etc. Metal compounds for ORR catalyst : Pt, FePc, CoTMPP, MnO x, CuPc, etc. Materials and Methods  Anode  Graphite fiber fabric(GFF) w/ SUS mesh as current collector  Artificial wastewater  synthesized using Sodium Acetate, phosphate buffer, minerals and vitamins  COD 1,000mg/L; pH 7 ; Conductivity 28mS/cm  Separater  Non-woven polypropylene  Preparation of primitive electrode Hydrophobic layered CNT structure cathode SUS mesh PTFE GDL Hot pressing MWCNT ( 질산처리 NO) + PTFE dispersion US mixing CNT on SUS mesh Hot pressing Screen printing Brushing Hydrothermal method : autoclaving to expose under high vapor pressure  ORR catalyst fixing on MWCNT by HTMW (Hydrothermal+Microwave) method Microwave method : microwave radiation Combination of multi-metal catalysts 1. MnOx-FePc-CuPc 2. FePc-CuPc 3. MnOx-FePc 4. MnOx-CuPc Results & Discussion Slope = IR 4 catalystOCV(mV) Internal resistance ( Ω ) Maximum power dencity (mW/m 2 ) Mn-Cu-Fe482201036 Cu-Fe505101620 Mn-Fe382101220 Mn-Cu438201164 Conclusion MARITIME UNIVERSITY Table: OCV, internal resistance, and maximum power density of the MFCs with cathodes prepared using different catalyst loading methods  Raw materials for cathode MWCNT (Carbon Nano-material Technology, Co., LTD, Korea) SUS mesh as the current distributor PTFE as a binder (Sigma-Aldrich Co.) FePc, CuPc, KMnO 2 : by screening printing of the ORR catalyst fixed on primitive cathode  Formation of catalyst layer on electrode - Common ORR catalysts 40ml SDS CNT MnSO 4 5H 2 0 KMnO 4 FePc CuPc 0.5g 0.075g 1.205g 0.79g 0.01 mM The best ORR efficiency was obtained from a cathode with FePc and CuPc combination as the multi-metal catalyst. The activation resistance for ORR could be reduced by both FePc and MnOx, and the ohmic resistance could be reduced by the CuPc in the metal catalyst. The concentration resistance for ORR was smaller than the activation resistance or the ohmic resistance, but slightly reduced by the CuPc content in the multi-metal catalyst.