An efficient hierarchical nanostructured Pr6O11 electrode for solid oxide fuel cells

Abstract

A hierarchical nanostructured Pr₆O₁₁ phase, a potential electrocatalyst for the oxygen reduction reaction, is prepared for the first time by electrostatic spray deposition (ESD) on a GDC (Ce_0.9Gd_0.1O_{2 − δ}) electrolyte and evaluated as an Intermediate Temperature Solid Oxide Fuel Cell cathode. Different and innovative microstructures are found to be related to the solvent composition, deposition time, nozzle to substrate distance, substrate temperature and solution flow rate. Single phase Pr₆O₁₁ films crystallize in a Fmm fluorite cubic structure after calcination at 700 °C for 2 h in air. The electrochemical properties are found to be strongly dependent on the microstructure of the cathode films. A symmetrical cell based on the double layer architecture (a columnar-type active layer by ESD topped by a screen-printed current collector) cathode presents a low polarization resistance value of 0.02 Ω cm² at 600 °C. To the best of our knowledge, this Pr₆O₁₁ cathode shows the best performance reported to date for all SOFC cathode materials. A single cell made of a commercial (Ni-3YSZ/Ni-8YSZ/8YSZ/GDC) half cell and this double layer cathode delivers a maximum power density of 500 mW cm⁻² at 700 °C. Moreover, Pr₆O₁₁ does not show any reactivity with GDC over 10 days in air at 800 °C.