Effect of Sr doping on the electrochemical properties of bi-functional oxygen electrode PrBa1−xSrxCo2O5+δ
Résumé
Sr-doped double perovskite oxides PrBa1−xSrxCo2O5+δ (x = 0.0–1.0) are prepared and characterized by X-ray diffraction, X-ray photoelectron spectra, cyclic voltammetry and linear sweep voltammetry, respectively. Sr2+ doping is found to promote the electrocatalytic activity towards both oxygen evolution reduction and oxygen reduction reaction, due to the concentration enhancement of Co4+ (eg = 1) on the oxide surface. The PrBa0.25Sr0.75Co2O5.95 catalyst, with the highest concentration of Co4+, exhibits the superior electrocatalytic activity. The onset potential, Tafel slope and the overpotential at given current density of 10.0 mA·cmgeom−2 for the OER are 1.52 V, 75.8 mV·dec−1 and 0.42 V, respectively, comparable to the currently reported high performance OER catalysts. At the same time, the onset potential, Tafel slope, limiting current density and electron transfer number of PrBa0.25Sr0.75Co2O5.95 for ORR are 0.753 V, 58.3 mV·dec−1, 4.081 mA·cmgeom−2 and n = 3.92, respectively, implying much improved ORR activity.