Ow-cost And High-performance Air Cathode Reparation For Microbal Fuel Cells And Exploration Of Cathode State

This paper focuses on the exploitation and optimization of two kinds of air cathodes, and an exploration based on the operation states of the cathode. The air cathode made with polytetrafluoroethylene as binder, foamed nickel as current collector and super capacitor activated carbon as catalyst not only has high performance but also has low cost, our results show that the catalytic activity of the catalytic layer is improved by using high catalyst loading and less binder in the catalyst layer. The type of conductive carbon in carbon based diffusion layer has not significant effect on cathode performance. The maximum power density of microbial fuel cell with the nickel foam air cathode was32W/m3, which is only around10%lower than that of platinum-carbon cathode (36W/m3), but the cost of this new kind of air cathode is1/30of that of the cathode using carbon cloth as current collector and Pt/C as catalysts Therefore, the nickel foam cathode holds broader prospects for building large scale microbial fuel cell.The systematic research on preparation of nickel foam air-cathode shows that the air-cathode performance is influenced by type and loading of activated carbon, type of conductive carbon in the catalytic layer, by carbon loading in the carbon based diffusion layer, and by the structure of PTFE diffusion layer, while different conductive carbons in the carbon based diffusion layer have not significant effect on the cathode performance. The optimal conditions for preparing the nickel foam air-cathode are as follows:carbon based layer made with5.83mg/cm2F900carbon black,23.3uL/cm260%PTFE and33.3uL/cm2isopropanol; catalytic layer with15mg/cm2Supercapacitor activated carbon,0.6mg/cm2F900carbon black,37.5uL/cm210%PTFE,16.7uL/cm2isopropanol, and16.7uL/cm2distilled water.The structure of current collector has great influence on cathode performance. Single-layer stainless steel cathode has a maximum power density of24.4W/m3, which is6%less than cathode made with carbon cloth and activated carbon. By using double stainless steel, the structure of current collector transfers from two-dimension porous structure to three-dimension porous structure, which can not only attribute to the uneven distribution of catalysts, but also increase the conductivity of catalyst layer. Using two-layer stainless steel current collector consist of120mesh and30meshresults in a maximum power output of29.5W/m3,which is as great as that using nickel foam cathode, indicatingthat the structure of the current collector is a key factor affecting the cathode performance.Exploration cathode working state manifests the importance of preventing the external short circuit and the need to minimize the internal resistance. When two external circuits exist, potential of cathode is initially controlled by the circuit with higher current. While there are two internal circuits, potential of cathode is initially under the control of the circuit with lower internal resistance.For the first time this article put forward the definition of multi-circuit, which is very instructive for MFC scale-up.