Design and optimization of functionally graded anode electrode with integrated functional layer for microtubular solid oxide fuel cells

This study investigates the influence of porosity-graded anode microstructures on the performance of microtubular solid oxide fuel cells (SOFCs). Fabricated using tape casting coupled with isostatic pressing, the anode microtubes consist of three layers with varying porosities. The porosity of each layer is regulated by the quantity of pore former added to the corresponding tape casting slurry. Homogeneous microtubular anode supports having different porosities are also fabricated similarly for comparison purposes. Microtubular cells are manufactured on both types of anodes by dip coating other cell layers, and test and characterization studies are carried out. Experimental results reveal that increasing the pore former content in the anode tape casting slurry leads to reduced triple phase boundary (TPB) density, primarily due to increased porosity and pore size, resulting in higher charge transfer resistance and decreased cell performance, despite an associated decrease in the gas transport resistance. However, optimization of the anode microstructure demonstrates that porosity gradients can enhance gas transport and overall cell performance. Additionally, the study explores the impact of anode thickness and the presence of transition layers on cell performance and structural integrity.