Growth of Gd_0.3Ca_2.7Co_3.82Cu_0.18O_9-δ-BaCe_0.6Zr_0.2Y_0.2O_3-δ bulk heterojunction cathode interlayer by pulsed laser deposition for enhancing protonic solid oxide fuel cell performance

The triple-conducting (e⁻/H⁺/O²⁻) oxides have been extensively studied as the most promising cathode materials for protonic solid oxide fuel cells (P-SOFCs) because of their excellent catalytic activity at lower operating temperatures of <600 °C. However, direct application of these cathode materials by brush-painting or screen-printing provides limited contact area with the underlying electrolyte layer, resulting in high cathode ohmic and polarization resistances. In this study, it is demonstrated that a bulk heterojunction Gd_0.3Ca_2.7Co_3.82Cu_0.18O_9-δ (GCCCO)-BaCe_0.6Zr_0.2Y_0.2O_3-δ (BCZY) layer with a domain width of ∼5 nm can be grown by pulsed laser deposition (PLD) via spontaneous phase separation. Such a nanocomposite interlayer between spin-coated BCZY electrolyte and brush-painted GCCCO cathode can effectively increases the interfacial area between the two distinct phases and facilitates proton transport across the interface. This electrode design reduces the ohmic resistance by 0.35 Ω cm² and the polarization resistance by a factor of three, thus significantly boosting the cell performance.