Exceptional power density and stability at intermediate temperatures in protonic ceramic fuel cells

Over the past several years, important strides have been made in demonstrating protonic ceramic fuel cells (PCFCs). Such fuel cells offer the potential of environmentally sustainable and cost-effective electric power generation. However, their power outputs have lagged behind predictions based on their high electrolyte conductivities. Here we overcome PCFC performance and stability challenges by employing a high-activity cathode, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), in combination with a chemically stable electrolyte, BaZr0.4Ce0.4Y0.1Yb0.1O3 (BZCYYb4411). We deposit a thin dense interlayer film of the cathode material onto the electrolyte surface to mitigate contact resistance, an approach which is made possible by the proton permeability of PBSCF. The peak power densities of the resulting fuel cells exceed 500 mW cm−2 at 500 °C, while also offering exceptional, long-term stability under CO2. Protonic ceramic fuel cells use oxide electrolytes with high protonic conductivity but suffer from low power densities due to sluggish oxygen reduction kinetics and high contact resistances. Here the authors integrate a PrBa0.5Sr0.5Co1.5Fe0.5O5+δ cathode and a BaZr0.4Ce0.4Y0.1Yb0.1O3 electrolyte, achieving exceptional power density and stability.