LaPr3Ni3O9.76 as a candidate solid oxide fuel cell cathode: Role of microstructure and interface structure on electrochemical performance

A new higher-order Ruddlesden-Popper phase composition LaPr3Ni3O9.76 was synthesised by a sol-gel route and studied for potential intermediate-temperature solid oxide fuel cell cathode properties by electrochemical impedance spectroscopy. The focus of the work was optimisation of the microstructure and interface structure to realise the best performance, and therefore symmetrical cells after impedance testing were subsequently studied by scanning electron microscopy for post-microstructural analysis. It was observed that the cathode ink prepared after ball milling the material and then triple roll milling the prepared ink gave the lowest area specific resistance (ASR) of 0.17 Ω cm2 at 700 °C when a La0.8Sr0.2Ga0.8Mn0.2O3-δ (LSGM) electrolyte that had been previously polished was used. The post-microstructural studies, as expected, showed an improved interface structure and relatively good particle interconnectivity and much less sintering when compared to the symmetrical half-cells constructed using the ink prepared from the as-synthesised material. The interface structure was further improved significantly by adding a ∼10 µm thick LSGM ink interlayer, which was reflected in the electrochemical performance, reducing the ASR of the material from 0.17 Ω cm2 to 0.08 Ω cm2 at 700 °C. This is to date the best performance reported for an n = 3 Ruddlesden-Popper phase material with LSGM as the electrolyte