Microstructure optimization of fuel electrodes for high‐efficiency reversible proton ceramic cells

Reversible protonic ceramic cells (R‐PCCs) are efficient energy storage and conversion devices that can operate in two modes, namely, in the fuel cell mode for the conversion of fuel to electricity, and in the electrolysis (EC) mode for the EC of water into hydrogen and oxygen. Fuel electrode is a critical component of fuel‐electrode‐supported R‐PCCs, and its pore structure directly affects the electrochemical performance of the R‐PCCs, but it has not been fully studied yet. Herein, the pore structure of Ni–BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3− δ (Ni–BZCYYb) fuel electrodes was systematically modulated by varying the weight ratio (0, 5, 10, and 15 wt.%) of the pore‐former added to Ni–BZCYYb, and the electrochemical performance characteristics in the fuel cell and EC modes were investigated. The cell with 10 wt.% pore‐former in the Ni–BZCYYb electrode achieved a remarkable peak power density of 540.7 mW cm −2 and a high current density of –2.28 A cm −2 at 1.3 V at 700°C in the fuel cell and EC modes, respectively, and showing excellent durability for over 100 h. These results further highlight the critical role of the microstructure of fuel electrodes, which can be modified to achieve exceptional performance, particularly in EC operations.