Unravelling the High‐Temperature Diffusion Behavior in the Hydrogen Electrode of BaCeO ₃ ‐Based Proton‐Conducting Ceramic Cells

Abstract Proton‐conducting ceramic cells (PCCs) with BaCeO ₃ ‐based electrolytes have emerged as promising energy conversion devices for low/intermediate‐temperature applications, and their performance critically depends on the microstructure of the composite hydrogen electrodes. However, the atomic‐level characterization and understanding of the interfacial interactions within the hydrogen electrode are still lacking. Herein, the atomic‐scale investigation of the high‐temperature element diffusion behavior and interface evolution between NiO and BaZr _0.1 Ce _0.7 Y _0.2 O _3‐δ （BZCY）is presented. The interdiffusion of Ni and Ba elements at the NiO/BZCY interface leads to the formation of a BaNiO _x phase, and the interdiffusion extent is intensified with increasing the sintering temperature and time. The formation of BaNiO _x , along with Ba loss‐induced stoichiometric deviation and Y ₂ O ₃ precipitation, impairs proton conduction in the hydrogen electrode and across the electrode/electrolyte interface. The results highlight the significance of atomic‐level interface modulation of the cermet hydrogen electrode, and a low‐temperature fabrication process is vital to improving the cell performance.