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

Abstract

In this study, a series of perovskite oxides LaCo1-xPtxO3-δ (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, LaCo0.94Pt0.06O3-δ 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 (O22-/O-). Furthermore, the eg orbital filling of Co approaching 1.2 in the B site might play a leading role.