Nano-film coated cathode functional layers towards high performance solid oxide fuel cells

Nano-structured composite electrodes, from a carefully conducted infiltration process, are one of the most promising electrode structures for intermediate temperature solid oxide fuel cells (IT-SOFCs), due to their ability to promote the oxygen reduction reaction (ORR) and enlarge triple phase boundaries (TPBs). Here, we demonstrate rational design of infiltrated nano-structures for IT-SOFCs with enhanced ORR kinetics and excellent stability. We systematically designed a nano-structured cathode functional layer (CFL) from the infiltration of Sm_0.5Sr_0.5CoO_3-δ (SSC) into porous Gd_0.2Ce_0.8O_2-δ (GDC). By controlling the drying process during the infiltration process, two distinct nano-structures of SSC, discrete coating and film-like coating, were fabricated on the GDC scaffolds. The CFL with the film-like coating showed ∼30% reduction in polarization resistance (R_p) and ∼15% increase in peak power density at 650 °C compared to the CFL with the discrete coating in spite of ∼12-fold lower loading of infiltration materials. Furthermore, the CFL with the film-like coating showed an excellent stability, maintaining an R_p of 0.029 Ω cm² for 100 h at 650 °C. Our results demonstrated that the high performance and stability of composite electrodes for IT-SOFCs can be achieved through a thin-film coated CFL.