Altering B-site surroundings with low-valence Cu to regulate La1.2Sr0.8NiO4+δ electrocatalysis for protonic ceramic fuel cells

Modulating B-site atomic environment in K2NiF4-type material has the potential to regulate material properties and electrocatalysis, thereby altering the electrode electrochemical behaviors. Herein, to realize the regulation of B-site surroundings, a low-valence Cu-doping in La1.2Sr0.8NiO4+δ (LSNO) was attempted to introduce more oxygen vacancies and more effective transition path Cu2+-O-Cu+ and Ni3+-O-Ni2+ for electron-hopping, thus enhancing the electrical conductivity dramatically with an increase from 197.1–216.3 S cm−1 to 409.4–422.4 S cm−1 at 400–700 °C. Hence, the highly-active La1.2Sr0.8Ni0.5Cu0.5O4+δ (LSNC) is developed. Next, the single cell NiO-BaZr0.1Ce0.7Y0.2O3-δ|BaZr0.1Ce0.7Y0.2O3-δ|LSNC exhibits a predominant cell power performance of 1570 and 858 mW cm−2 at 700 and 600 °C, outperforming the cells with LSNO cathode and other Ln2NiO4-based R-P phase cathodes in the literature significantly. This is associated with the greatly enhanced proton/oxygen migration in the resultant LSNC that is evidenced by the electrical conductivity relaxation results, contributing to the increased catalytic activity for faster electrode reactions. On balance, the superior power and polarization properties coupled with good durability suggests that the LSNC cathode candidate is a preferential alternative for protonic ceramic fuel cell (PCFC) in terms of its promising potential for working at low temperatures. This work provides a new idea to open up new path towards material designs to get highly-active electrode materials via regulating B-site surroundings at atomic level in K2NiF4-related structure, which is beneficial to the related electrocatalytic fields.