Spray-flame-synthesized Sr- and Fe-substituted LaCoO3perovskite nanoparticles with enhanced OER activities

Abstract

La1–xSrxCoO3(x = 0, 0.1, 0.2) and LaCo0.8Fe0.2O3perovskite nanoparticles were synthesized by spray-flame synthesis, and their electrocatalytic water oxidation activity was evaluated in the prepared state. Highly crystalline, rhombohedrally distorted cubic structures of the cobaltite perovskites were confirmed by STEM and XRD analyses. The decreased JT distortions were observed in the cobaltite perovskite structure upon substitution with Sr, while orthorhombic distortions in Fe-substituted perovskites could explain the changes in their Raman spectra. Debye–Waller factors and coordination numbers from fitted EXAFS data indicate more disordered crystalline structures upon Sr substitution and a lower Co–O coordination number at 20 at% Sr. Thermal characterization of the catalysts by STA coupled with QMS shows higher mass losses in Sr-substituted catalysts, and these results were associated with a higher concentration of carbonate species in these catalysts, which was also confirmed by XPS measurements. Both Fe and Sr substitution lead to higher catalytic OER activity of the cobaltite perovskites with lower overpotentials of about 30–50 mV. The cobaltite perovskite catalyst substituted with 20 at% Sr exhibited the highest OER activity and stable electrocatalytic performance at moderate conditions.