The active surface area is an important factor in improving the cell performance of a solid oxide fuel cell (SOFC). An electrochemical analysis incorporating an active surface area was performed to account for the effect of grading, which affects both the active surface area and the effective diffusivity within the electrodes. The analysis showed the good agreement with experimental data from the literature and used to predict the cell polarizations in porosity-graded and particle-size graded electrodes. The particle-size graded electrode demonstrated better cell performance than the porosity-graded electrode, due to a larger active surface area. Detailed studies were performed to investigate the effect of particle-size variation. As a result, the graded functional layers demonstrated improved performance than the base case with a fixed average porosity. Consequently, it can be concluded that the overall cell polarization was mainly affected by lowered activation overpotentials when the particle-size grading was conducted.

Keywords: SOFC, Functionally graded electrode, Model, Functional layer.