Clarifying the Role of the Reducers-to-Oxidizers Ratio in the Solution Combustion Synthesis of Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> Oxygen Electrocatalysts
oleh: Francesca Deganello, Leonarda F. Liotta, Chiara Aliotta, Antonio Barbucci, Massimo Viviani, Davide Clematis, Maria Paola Carpanese, Sabrina Presto
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2020-12-01 |
Deskripsi
Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> perovskite-type compounds are well-known mixed ionic-electronic conductors for oxygen electrocatalytic applications, although their performance is strictly dependent on the selected preparation methodology and processing parameters. The reducers-to-oxidizers ratio (Φ) is a very important parameter in the solution combustion synthesis of mixed ionic-electronic conductors. Selection of Φ is not trivial and it strongly depends on the type of fuel used, the chemical composition and the specific application of the material. This work clarifies the role of Φ in the solution combustion synthesis of Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> for application as oxygen electrocatalysts. Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> powders were synthesized by solution combustion synthesis using sucrose-polyethylene glycol fuel mixtures with reducers-to-oxidizers ratio values between 1 (stoichiometric) and 3 (over-stoichiometric). Chemical-physical properties were studied by X-ray diffraction, scanning electron microscopy, N<sub>2</sub> adsorption at −196 °C, H<sub>2</sub>-temperature programmed reduction and thermogravimetric analysis. The results evidenced the direct role of Φ on the intensity and redox environment of the combustion process, and its indirect influence on the Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> electrode materials properties. Taking into account the general picture, the highly over-stoichiometric Φ was selected as the optimal one and the electrochemical activity of the corresponding powder was tested by electrochemical impedance spectroscopy on electrolyte-supported half-cells employing a Ce<sub>0.8</sub>Sm<sub>0.2</sub>O<sub>2-x</sub> electrolyte.