Research on effect of anode microstructures on mass transfer and electrochemical reaction in SOFCs based on a fractional Brownian motion model

Abstract

The microstructure of the porous anode plays a crucial role in the mass transfer dynamics and electrochemical reaction of solid oxide fuel cells (SOFCs), significantly impacting their performance. This paper investigates the effect of microstructure of the porous anode on mass transfer and electrochemical reaction in SOFCs, which addresses the scarcity of research due to the complexity of microstructure modeling, offering supportive information for the structure optimization of SOFCs. Firstly, theoretical deductions of constructing microstructure and simulating mass transfer are conducted. Subsequently, a construction model is established based on the fractional Brownian motion (FBM) model to obtain different microstructures, encompassing various flow pore structures, triple phase boundary (TPB) structures, and inlet structures. Through a finite difference lattice Boltzmann method (LBM), the mass transfer is modeled to predict gas molar fraction distributions and calculate concentration overpotentials with different microstructures. Finally, thorough experiments are carried out to analyze the effect of structural parameters on mass transfer and electrochemical reaction. Taking the hydrogen-steam-nitrogen (H₂-H₂O-N₂) ternary mass transfer as an example, the comparison results indicate that complex flow pore structures increase both the distance and resistance of mass transfer. To improve the performance of SOFCs, reducing flow pore complexity and increasing TPB length both mitigate the effect of concentration polarization. Moreover, the change of inlet structure suggests minimal impact on mass transfer and electrochemical reaction.