Enhancing oxygen and hydrogen evolution activities of perovskite oxide LaCoO₃ via effective doping of platinum

In this study, a series of perovskite oxides LaCo_1- Pt O_3- (x = 0, 0.02, 0.04, 0.06, and 0.08) were prepared by the citric acid-ethylenediaminetetraacetic acid (CA-EDTA) complexing sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then, the samples were investigated as OER and HER bifunctional electrocatalysts in alkaline media. Compared with other catalysts, LaCo_0.94Pt_0.06O_3- had good stability and presented more activity at a lower overpotential of 454 mV (at 10 mA cm^-2), a lower Tafel slope value of 86 mV dec^-1 and a higher mass activity of 44.4 A g^-1 for OER; it displayed a lower overpotential of 294 mV (at -10 mA cm^-2), a lower Tafel slope value of 148 mV dec^-1 and a higher mass activity of -34.5 A g^-1 for HER. The improved performance might depend on a larger ECSA, faster charge transfer rate and higher ratio of the highly oxidative oxygen species (O₂ ^2-/O^-). Furthermore, the e_g orbital filling of Co approaching 1.2 in the B site might play a leading role.