Polypropylene separator Figure S1: Schematic representation of single chamber microbial fuel cell (MFC) with SEA .
A D C B Voltage (V) Time (d) Fig S2: Voltage generations noticed in MFC with 1 K Ω as an external resistance, during long-term operation at different electrode distances; 0 mm(A), 3 mm(B), 6 mm(C), 9 mm(D).
Oxygen permeability analysis and Specific proton conductivity Explanation for Oxygen permeability analysis, specific proton conductivity, Columbic efficiency and internal resistance Oxygen permeability analysis and Specific proton conductivity The O2 mass transfer (Ko) and diffusion coefficients (Do) were estimated using DO (dissolved oxygen) probe (Orion A323; Thermo scientific co., USA) in abiotic MFC. The DO probe was fixed to the lid of the anode chamber and the anode solutions (PBS) was sparged with nitrogen gas to remove the dissolved oxygen (DO). Anolyte solution was continuously stirred (160 rpm) by placing on magnetic stirring plate (Anytech co., Korea). The mass transfer coefficient (KO) was determined by measuring the DO concentration and by using the following equation 𝐾 𝑂 = − 𝑉 𝐴𝑡 𝑙𝑛 𝐶 1,0 − 𝐶 2 𝐶 1,0 Where V is volume of liquid in anode chamber, A is membrane cross-sectional area (42 cm2), C1,0 is saturated dissolved oxygen (DO) concentration (7.2 mg/l) and C2 is DO in anode chamber at time t. Oxygen diffusion coefficient (DO) for each membrane was calculated using the equation Do = KO × Lt. Where, Lt is the membrane thickness as reported by the manufacturer. specific proton conductivity (SH, S/cm) was determined by substituting the ohmic resistance (Roh,Ω), thickness of membrane (T, μm) and the working surface area (A, cm2) in the following equation 𝑆 𝐻 = 𝑇 𝑅 𝑜ℎ ×𝐴
Columbic Efficiency Internal Resistance Columbic efficiency was obtained as CE = Cp/CT * 100%, where Cp is total coulombs calculated by integrating the current with time and CT is theoretical number of coulombs available, based on the COD removal during the operation of MFC Internal Resistance The internal resistance of the MFC was calculated on the basis of the linear portion of the voltage vs current graph (Fig. 2A). The currents in the graphs were calculated as of the voltage readings at each resistance divided by the external resistance. The slope of the linear regression is the internal resistance of the MFC