Enhancing oxygen and hydrogen evolution activities of perovskite oxide LaCoO3via effective doping of platinum

In this study, a series of perovskite oxides LaCo_1−xPt_xO_3−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, LaCo_0.94Pt_0.06O_3−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 e_g orbital filling of Co approaching 1.2 in the B site might play a leading role.

Among the perovskite LaCo_1−xPt_xO_3−δ catalysts, LaCo_0.94Pt_0.06O_3−δ proved best for catalyzing OER/HER, with η = 454/294 mV, which might be attributed to LCP6 having the e_g orbital filling of Co closest to 1.2.