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

Proton-conducting ceramic cells (PCCs) with BaCeO₃-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_0.1Ce_0.7Y_0.2O_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 Y₂O₃ 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.