Materials based on Pr2NiO4+δ have attracted widespread research attention as air electrodes for proton conducting electrochemical devices due to a wide range of promising properties, such as low values of polarization resistance and high conductivities. However, problems of their chemical interaction with electrolyte materials are insufficiently investigated. In the present work, we optimize the thermomechanical and chemical properties of Pr2NiO4+δ-based electrode materials via a Ba-doping strategy (Pr2–xBaxNiO4+δ) to reduce their chemical interaction with the-state-of-the-art Ba(Ce,Zr)O3-based electrolytes. A decrease in the chemical interaction degree between the Ba-doped nickelites and Ba(Ce,Zr)O3-based oxide was confirmed experimentally. The average values of the thermal expansion coefficients were found to decrease from 13.9·10−6 К−1 for the undoped material to 13.5·10−6 К−1 for the material with x = 0.2. The barium-doped materials were found to have good thermal stability and acceptable stability in a CO2 environment. This work, being the first part of a comprehensive analysis, reports advantages in chemical stability and mechanical properties of the developed Pr2–xBaxNiO4+δ materials. © 2022 Hydrogen Energy Publications LLC.