The role of phosphate functionalization on the oxygen evolution reaction activity of cobalt-based oxides at different pH values

Cobalt-based oxides are active electrocatalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. However, their OER activity at near-neutral pHs is generally low and more active OER catalysts at neutral pHs are desired for practical applications. Herein, La0.2Sr0.8CoO3–δ, La0.2Sr0.8Co0.8Fe0.2O3–δ, La0.5Sr1.5CoO4–δ and CoOx catalysts were prepared by the flame spray synthesis method and their surface was functionalized by a dry phosphate incorporation process. Small amount of P was incorporated on the surface of the catalyst (in the range of ppm). All the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and soft and hard X-ray absorption spectroscopy (XAS) before and after the functionalization process. The electrocatalytic activity towards OER of the different nanoparticle catalysts was investigated in electrolytes with different pH values (pH = 7, 12.5, 13, and 13.5).