Abstract
The separator plays a key role on the performance of passive air-breathing flat-plate MFCs (FPMFC) as it isolates the anaerobic anode from the air-breathing cathode. The goal of the present work was to study the separator characteristics and its effect on the performance of passive air-breathing FPMFCs. This was performed partially through characterization of structure, properties, and performance correlations of eight separators presented in Part 1. Current work (Part 2) presents a numerical model developed based on the mixed potential theory to investigate the sensitivity of the electrode potentials and the power output to the separator characteristics. According to this numerical model, the decreased peak power results from an increase in the mass transfer coefficients of oxygen and ethanol, but mainly increasing mixed potentials at the anode by oxygen crossover. The model also indicates that the peak power is affected by the proton transport number of the separator, which affects the cathode pH. Anode pH, on the other hand, remains constant due to application of phosphate buffer solution as the electrolyte. Also according to this model, the peak power is not sensitive to the resistivity of the separator because of the overshadowing effect of the oxygen crossover.
Highlights
Microbial fuel cells (MFCs) can provide a unique opportunity for renewable energy production while removing organics from wastewater
The capital cost of the MFCs constructed in lab-scale is estimated to be in the order of ca. $15 kg1 chemical oxygen demand (COD) [3], which can hardly compete with the conventional biological wastewater treatment processes such as activated sludge and anaerobic digestion [4,5]
The model was used to estimate the kinetic parameters of the bio-electrochemical system, tested in the Part 1 of this work [24], along with the anodic and cathodic mixed potentials
Summary
Microbial fuel cells (MFCs) can provide a unique opportunity for renewable energy production while removing organics from wastewater. In a microbial fuel cell, electricity is generated through oxidation of organic matter in wastewater by the biofilm at the anode and reduction of an oxidant (e.g., oxygen) at the cathode. $15 kg chemical oxygen demand (COD) [3], which can hardly compete with the conventional biological wastewater treatment processes such as activated sludge To decrease the overall capital and operating costs of the MFCs, the passive air-breathing design has become of interest. The application of passive convection and diffusion in the fuel cell design and operation is well known for decreasing the parasitic load for running auxiliary pumps, fans, or compressors, and eliminating the utilization of expensive oxidants in direct methanol fuel cell
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