Unravelling the High-Temperature Diffusion Behavior in the Hydrogen Electrode of BaCeO3-Based Proton-Conducting Ceramic Cells

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.