Highly connected oxygen ion conduction pathways in anode functional layer for high performance solid oxide fuel cells

Maximizing triple phase boundary (TPB) sites in the anode functional layer (AFL) is critical in the development of high performance solid oxide fuel cells operating at an intermediate temperature. To activate the TPB sites, the continuous oxygen ion conduction pathways from the electrolyte to the TPB sites is essential to ensure the sufficient supply of reactants for hydrogen oxidation reactions (HORs). Here, we systematically investigate the connectivity of the oxygen ion conduction pathways in AFLs and its effect on the electrochemical performance with 10 types of AFLs by controlling the volume fraction of the electrolyte material to gradually decrease in thickness direction from the electrolyte to the anode support. Comparison of the electrochemical performances verifies that the electrochemical performances are improved mainly from the increased active TPB sites with connected ion conduction pathways, indicating a similar to 2.1-fold higher maximum power density of 1.64 Wcm(-2) at 600 degrees C for the modified AFL with the highest active reaction sites compared with conventional AFL. The calculated active reaction site using cross-sectional image processing exhibits a strong correlation with the electrochemical performance, substantiating the critical role of connected oxygen ion conduction pathways in the HOR in AFLs.