High-Performance Protonic Ceramic Fuel Cells with Thin-Film Yttrium-Doped Barium Cerate-Zirconate Electrolytes on Compositionally Gradient Anodes

In this study, we used a compositionally gradient anode functional layer (AFL) consisting of Ni-BaCe_0.5Zr_0.35Y_0.15O_3-δ (BCZY) with increasing BCZY contents toward the electrolyte-anode interface for high-performance protonic ceramic fuel cells. It is identified that conventional homogeneous AFLs fail to stably accommodate a thin film of BCZY electrolyte. In contrast, a dense 2 μm thick BCZY electrolyte was successfully deposited onto the proposed gradient AFL with improved adhesion. A fuel cell containing this thin electrolyte showed a promising maximum peak power density of 635 mW cm^-2 at 600°C, with an open-circuit voltage of over 1 V. Impedance analysis confirmed that minimizing the electrolyte thickness is essential for achieving a high power output, suggesting that the anode structure is important in stably accommodating thin electrolytes.