Catalytic Activity of LnCo0.5Ni0.5O3-Δ (Ln = La, Pr, Nd) "Positrodes" on Ceramic Protonic Electrolytes

Abstract

Proton-conducting solid-oxide electrolyzers and fuel cells represent viable, intermediate-temperature green energy conversion and storage technologies. Interest in this class of materials as electrolytes stems from their high ionic conductivity and inherent advantages in the gas flow configuration over traditional solid oxide cells in which the electrolyte is an oxygen ion conductor. However, their commercial viability has been hindered, in part, by the development of corresponding single-phase electrode components with mixed proton-electron conductivity and effective catalytic activity toward oxygen reduction and evolution reactions (ORR/OER). This paper investigates the origin of catalytic activity in LnCo0.5Ni0.5O3-δ (Ln=La, Pr and Nd) perovskites positrodes (positive electrode) by low energy-ion scattering (LEIS) and DFT studies. LEIS results reveal that La, Pr, and Pr cations dominate the outer atomic layer, with profound implications for catalytic activity. Whereas First principle calculations were performed using the plane-wave DFT method and hybrid HSE06 functional suggest, the catalytic activity and electronic properties depend on the valence shell structure of the Ln-site cation and their redox properties.AcknowledgmentsThe authors gratefully acknowledge financial support through JSPS KAKENHI Grant-in-Aid for Scientific Research (C), No. 19K05672, NEDO (International collaboration work in the field of clean energy) JPNP20005, the International Institute for Carbon-Neutral Energy Research (I2CNER) sponsored by the World Premier International Research Center Initiative (WPI),