Comprehensive determination of proton diffusion in protonated NdNiO3 thin film by a combination of electrochemical impedance spectroscopy and optical observation

Protonation of perovskite rare-earth nickelate, typically NdNiO3, can introduce a metal-to-insulator transition at room temperature, which will benefit practical ion electronics applications. In this work, the proton diffusion in NdNiO3 is analyzed by electrochemical impedance spectroscopy and the activation energy of the proton diffusion is obtained. For a comprehensive analysis, the method of optical observation is further evaluated and it is proved to be a quick route to obtain diffusion coefficient and activation energy in real time and real space. This work would guide future research on the evaluation of protonated perovskite rare-earth nickelate with microscale structure design.