Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China.
Phys Chem Chem Phys. 2013 Jul 14;15(26):10841-8. doi: 10.1039/c3cp51944a. Epub 2013 May 22.
This work is concerned with the determination of two critical constitutive properties for mass transport of ions through porous electrodes saturated with a liquid electrolyte solution. One is the effective diffusivity that is required to model the mass transport at the representative element volume (REV) level of porous electrodes in the framework of Darcy's law, while the other is the pore-level mass-transfer coefficient for modeling the mass transport from the REV level to the solid surfaces of pores induced by redox reactions. Based on the theoretical framework of mass transport through the electrodes of vanadium redox flow batteries (VRFBs), unique experimental setups for electrochemically determining the two transport properties by measuring limiting current densities are devised. The effective diffusivity and the pore-level mass-transfer coefficient through the porous electrode made of graphite felt, a typical material for VRFB electrodes, are measured at different electrolyte flow rates. The correlation equations, respectively, for the effective diffusivity and the pore-level mass-transfer coefficient are finally proposed based on the experimental data.
本工作旨在确定通过多孔电极传输离子的两个关键本构特性，这些电极被饱和的液体电解质溶液所浸润。一个是有效扩散系数，这是在达西定律框架下模拟多孔电极代表性元体积（REV）水平上质量传输所必需的，另一个是在氧化还原反应引起的从 REV 水平到孔的固体表面的质量传输的孔级传质系数。基于通过钒氧化还原液流电池（VRFB）电极的质量传输的理论框架，设计了独特的电化学实验装置，通过测量极限电流密度来确定这两个传输特性。测量了由石墨毡制成的多孔电极的有效扩散系数和孔级传质系数，石墨毡是 VRFB 电极的典型材料，在不同的电解液流速下进行测量。最后，根据实验数据提出了有效扩散系数和孔级传质系数的相关方程。
