Self-assembled La_0.7Sr_0.3Fe_0.9Ni_0.1O_3-δ-Ce_0.8Sm_0.2O_2-δ composite cathode with a three-dimensional ordered macroporous structure for protonic ceramic fuel cells

Self-assembled La_0.7Sr_0.3Fe_0.9Ni_0.1O_3-δ-Ce_0.8Sm_0.2O_1.9-δ (LSFN-SDC) composite cathode with a three-dimensionally ordered macroporous (3DOM) structure is synthesized using poly(methyl methacrylate) as the template for protonic ceramic fuel cells. The LSFN and SDC phases both distribute uniformly in the cathode. The SDC phase reduces the thickness of the walls of the 3DOM structure and thus hinders the bulk conduction of electrons. SDC also decreases the specific surface area and the surface oxygen reactivity of the cathode, leading to the suppression of the adsorption and dissociation of O₂. However, the SDC phase provides the conduction pathway for oxygen ions and enlarges three phase boundary consequently, which facilitates the charge transfer steps. The thickness of the walls and the specific surface area of the composite cathode are both increased with the rise of the concentration of the nitrate precursor solution, resulting in the acceleration of the cathode process. Nevertheless, an excessive precursor concentration leads to the destroy of the 3DOM structure. The 3DOM composite cathode exhibits the lowest R_p of 0.039 Ω cm², and a single cell with that cathode shows maximum power density of 1484 mW cm⁻² at 700 °C. The cell exhibits a short-term stability of 120 h at 700 °C without noticeable degradation.