Effects of praseodymium oxide infiltration on the surface segregation behavior and electrocatalytic properties of La0.3Ca0.7Fe0.7Cr0.3O3-δ cathode

Abstract

Aiming at improving the electrocatalytic properties of La_0.3Ca_0.7Fe_0.7Cr_0.3O_3-δ cathode towards oxygen reduction reaction, precursor solutions nominally containing 3–15 vol% Pr₆O₁₁ were infiltrated into the electrodes and then pyrolyzed. The structure and electrocatalytic activity of the infiltrated electrodes were investigated in relation to infiltrate loading and cathodic polarization history. The infiltrated electrodes presented a bi-phase structure at 800 °C, comprised of La_0.3Ca_0.7Fe_0.7Cr_0.3O_3-δ grains and Pr₇O₁₂ infiltrate deposited on the surface of the perovskite grains. It was shown that the two phases interacted with each other at the elevated temperature, exemplified by a repression of the thermally-induced formation of oxygen vacancies in the La_0.3Ca_0.7Fe_0.7Cr_0.3O_3-δ phase relative to a pure La_0.3Ca_0.7Fe_0.7Cr_0.3O_3-δ and a spillover of electrocatalytic activity beyond the perovskite phase. The electrocatalytic properties of the electrodes were found to be dependent to a great extent on the interaction between the two phases. The optimal infiltrate loading was determined to be 12 vol% in terms of the electrocatalytic activity of the electrodes at 800 °C. The 12 vol% Pr₆O₁₁-infiltrated electrode achieved a polarization resistance of 0.051 cm² at 800 °C, which was lowered by ca. 40 % relative to the pristine electrode. Moreover, the surface calcium segregation behavior of the infiltrated electrode after experiencing cathodic polarization was appreciably alleviated and the stability of the electrode activity against cathodic polarization was substantially improved.