Research On Model Of Direct Methanol Redox Fuel Cell

The cathode flooding problem and the methanol crossover effect, together withthe cost and availability of precious-metal catalyst, are major obstacles to thecommercialization of direct methanol fuel cell (DMFC) technologies. The directmethanol redox fuel cell (DMRFC) technology is a highly promising alternative to theconventional DMFC. The DMRFC novel cathode employs a liquid-based Fe3+/Fe2+redox couple which avoids the effect of fuel crossover, eliminates cathode floodingand reduces the total platinum group metal content.The experiment method to obtain DMRFC internal physical and chemicalprocess is difficult, expensive and time-consuming. The simulation method is low costand time saving. The simulation of DMRFC can help deepen the understanding of thefuel cell internal working mechanism and determine the optimal working conditions.In this paper, two-dimensional single phase and two phase models for DMRFChave been developed to predict the performance of the cell by using Finite ElementAnalysis method and Comsol-Multiphysics software. The fluid flow, mass transport,charge transport and electrochemical reaction process are considered. The simulationareas include anode flow channel, anode diffusion layer, anode catalyst layer, protonexchange membrane and the cathode electrode.The two-dimensional single phase model of DMRFC which ignores theformation of CO2bubbles is established with considering the permeability ofmethanol and water through the proton exchange membrane. The different operatingconditions and structural parameters are studied to increase the performance of thefuel cell. The results show that the cathode electrode thickness, fuel cell operatingtemperature, methanol and Fe3+concentration have a significant influence on DMRFCperformance. The decrease of the cathode electrode thickness and the increase of theoperating temperature can significantly increase the performance of the fuel cell.When increasing the concentration of methanol from2M to16.7M, the performanceof DMRFC gets better, while the methanol concentration is higher than16.7M, theperformance of the fuel cell starts to decrease. The anode flow rate has little impact onfuel cell performance. Increasing the cathode flow rate and Fe3+concentration willhelp improve the fuel cell performance. On the basis of the DMRFC two-dimensional single phase model, a DMRFCtwo-dimensional two-phase model is established by considering the influence ofanode CO2bubbles. The concentration and pressure distribution of carbon dioxideinside the fuel cell are studied. Research results show that carbon dioxideconcentration increases along the direction of anode flow channel, carbon dioxidepressure decreases along the direction of anode catalyst layer to anode flow channel.Reducing anode diffusion layer thickness, increasing anode catalyst layer thickness,anode diffusion layer and catalyst layer porosity, increasing anode and cathode flowrate can improve the performance of the fuel cell. When Fe3+concentration is lowerthan1.41M, increasing Fe3+concentration can significantly improve the cellperformance. However, when Fe3+concentration is above1.41M, increasing Fe3+concentration can hardly improve the cell performance.