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Analysis of effects of meso-scale reactions on multiphysics transport processes in rSOFC fueled with syngas

Yang, Chao, Jing, Xiuhui, Miao, He, Wu, Yu, Shu, Chen, Wang, Jiatang, Zhang, Houcheng, Yu, Guojun, Yuan, Jinliang
Energy 2020 v.190 pp. 116379
active sites, adsorption, catalysts, desorption, electrochemistry, electrodes, electrolysis, electrolytes, fuel cells, mathematical models, microstructure, particle size, porosity, synthesis gas
A two-dimensional mathematical model is developed for a single-cell based on the planar configuration and validated by relevant experimental data, with an aim to describe the coupling phenomena of the multiphysics transport processes and the meso-scale elementary reactions. It is revealed that desorption and adsorption reactions in the electrode mostly take place near the electrolyte and the channel, respectively; the distribution of the surface species depends on the gas diffusion in the porous electrode affected by the thickness and microstructure of the electrode. The electrochemical reactions are centralized in about 100 μm thick electrode from the electrolyte. Nis and COs are the major surface species in both fuel cell (FC) and electrolysis cell (EC) modes. Os is higher in the FC mode, particularly near the electrolyte due to the desorption and charge transfer reactions; The microscopic structure properties, including average porosity, tortuosity and particle size, are also influential on the elementary reactions due to the gas diffusion through the tortuous pathways and the active sites on the catalyst surfaces. It is also found that the performance predicted in the global models is often overestimated, because the limitations of the local elementary reactions are not considered in the global model.