燃料灵活性是固体氧化物燃料电池(Solid Oxide Fuel Cell,SOFC)的显著优势之一，但在使用碳氢化合物为燃料时，阳极碳沉积导致的电池性能衰减是影响SOFC长期稳定运行的最主要原因之一。为探明阳极碳沉积对电池性能的影响机制，构建了以合成气(H2、CO、H2O、CO2、CH4)为燃料的固体氧化物燃料电池一维瞬态基元反应动力学模型，模型考虑了阳极非均相反应、电化学反应、电极微观结构演变、电荷和质量传输过程以及碳相变过程的耦合效应。参考试验中不同时刻的电化学阻抗谱验证了模型的准确性，基于该模型提出了SOFC阳极碳沉积机制：在高温(>1 000 K)条件下，碳以薄膜碳的形式覆盖在阳极Ni表面和Ni/YSZ/气体三相界面，阻断了非均相反应和电荷转移反应的进行；在较低温度(<1 000 K)条件下，薄膜碳演化为固体碳，固体碳生长在多孔阳极内部，堵塞阳极孔隙，阻碍燃料气体扩散。所构建模型可以反映出这一机制。最后，利用模型研究不同燃料组分下阳极碳沉积导致的SOFC性能衰减。研究表明，降低燃料中CH4含量，可有效降低SOFC的性能衰减速度，提升SOFC运行性能。

Fuel flexibility is one of the most significant advantages of Solid Oxide Fuel Cell (SOFC). However, when using hydrocarbons as fuel, the degradation of cell performance caused by anode carbon deposition is one of the most important reasons affecting the long-term stable operation of SOFC. To investigate the mechanism of the influence of anode carbon deposition on cell performance, a one-dimensional transient elementary reaction kinetic model of an SOFC fueled with syngas(H2，CO，H2O，CO2，CH4) was developed. This model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure evolution, the charge and mass transport processes and the detailed evolution reaction of surface adsorbed carbon. The accuracy of the model was verified using the electrochemical impedance spectra at different moments in the reference experiment, and the mechanism of carbon deposition at SOFC anode was proposed based on the model. Under high temperature (>1 000 K) conditions, carbon is coverd on the Ni surface and Ni/YSZ/gas three-phase interface in the form of thin-film carbon, blocking the nonhomogeneous phase reaction and charge transfer reaction. At lower temperatures (<1 000 K), film carbon evolves into solid carbon, which grows inside the porous anode, blocking the anode pores and impeding gas diffusion. The constructed model can reflect this mechanism. Finally, the SOFC performance degradation due to carbon accumulation in different fuel components was investigated using the model. Study show that reducing the CH4 content in the fuel can effectively reduce the performance degradation rate of SOFCs and improve its operational performance.

0 引言

1 模型构建

   1.1 几何结构与模型假设

   1.2 控制方程

   1.3 模型参数

2 碳相变反应

3 电化学阻抗谱加速计算模型

4 结果和讨论

   4.1 模型验证

   4.2 结果讨论

5 结论