Abstract:

An air-breathing membraneless microfluidic fuel cell (MMFC) with a three-dimensional graphite felt anode is proposed and simulated. The graphite felt,used as anode catalyst layer as well as diffusion layer of fuel cell,provides more possibility to improve the performance of MMFCs owing to its large porosity. A single-phase,three-dimensional and isothermal steady flow model under acidic electrolyte condition is established for the proposed MMFC with comsol multiphysics. The characteristics of mass transfer and fuel crossover as well as the influence of flow rate of reactants and thickness of the graphite felt on the cell performance are discussed. The results show that comparing with the carbon paper and the carbon cloth flow-through anode,the maximum current density and the maximum power density of the MMFC with a graphite felt anode increased 12% and 50% at the flow rate of 333 μl·min^-1,respectively. The ratio of parasitic current density caused by the fuel crossover to the output current density was 0.86% when the cell voltage is 0.8 V. The current density and power density increase with increasing thickness of graphite felt and reactant flow rate,and then trend to be steady.

Key words: microfluidics, fuel cells, graphite felt, flow-through anode, numerical simulation, mass transfer, flow

摘要：

针对采用三维石墨毡可渗透阳极的空气自呼吸无膜微流体燃料电池，建立了三维等温稳态数学模型，对电池中燃料及电解液的流动和传输、电极过程动力学及电荷传递过程进行了模拟，计算获得了具有石墨毡阳极的微流体燃料电池内的传质和燃料渗透特性，研究了石墨毡厚度及反应物（燃料和电解液）流量对电池性能的影响。结果表明：当入口流量为333 μl·min^-1时，采用石墨毡可渗透阳极相比碳纸和碳布可渗透阳极，极限电流密度和极限功率密度分别提升12%和50%；电池电压为0.8 V时燃料渗透引起的寄生电流密度仅占电流密度的0.86%。电池性能随着石墨毡电极厚度增加而升高，但增幅逐渐减小；反应物流量增大，电池的性能先增加后逐渐趋于稳定。

关键词: 微流体学, 燃料电池, 石墨毡, 可渗透阳极, 数值模拟, 传质, 流动