Multicomponent gas transport is investigated with unprecedented precision by AC impedance analysis of porous YSZ anode-supported solid oxide fuel cells. A fuel gas mixture of H[subscript 2]-H[subscript 2]O-N[subscript 2] is fed to the anode, and impedance data are measured across the range of hydrogen partial pressure (10–100%) for open circuit conditions at three temperatures (800°C, 850°C and 900°C) and for 300 mA applied current at 800°C. For the first time, analytical formulae for the diffusion resistance (R[subscript b]) of three standard models of multicomponent gas transport (Fick, Stefan-Maxwell, and Dusty Gas) are derived and tested against the impedance data. The tortuosity is the only fitting parameter since all the diffusion coefficients are known. Only the Dusty Gas Model leads to a remarkable data collapse for over twenty experimental conditions, using a constant tortuosity consistent with permeability measurements and the Bruggeman relation. These results establish the accuracy of the Dusty Gas Model for multicomponent gas diffusion in porous media and confirm the efficacy of electrochemical impedance analysis to precisely determine transport mechanisms.
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机译:通过多孔YSZ阳极支撑的固体氧化物燃料电池的交流阻抗分析,以前所未有的精度研究了多组分气体的传输。将H [下标2] -H [下标2] ON [下标2]的混合气体送入阳极,并在开路条件下在氢分压范围(10-100%)范围内测量阻抗数据三种温度(800°C,850°C和900°C),并在800°C施加300 mA电流。首次导出了三种多组分气体传输标准模型(Fick,Stefan-Maxwell和Dusty Gas)的扩散阻力(R [下标b])分析公式,并针对阻抗数据进行了测试。由于所有扩散系数都是已知的,因此曲折度是唯一的拟合参数。使用与渗透率测量和Bruggeman关系一致的恒定曲折度,只有Dusty Gas Model才能在20多个实验条件下导致显着的数据崩溃。这些结果建立了多气体模型在多孔介质中多组分气体扩散的准确性,并证实了电化学阻抗分析有效地确定传输机理的功效。
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