Pr1.9A0.1NiO4 (A = Ca, Sr, Ba) are synthesized and characterized by X-ray powder diffraction (XRD), infrared spectrum (IR), and X-ray photoelectron spectroscopy (XPS). The effects of alkaline earth doping on the covalence of Pr–O and Ni–O bond, the mean valence of Ni, and the hydroxide absorption ability of material surface are studied. It is found that the covalence of Pr–O and Ni–O bond increases with the decrease of alkaline earth element radius. Meanwhile, the mean valence of Ni and the surface hydroxide absorption ability are enhanced. The electrochemical measurement results indicate that the O2−2 /OH− replacement reaction is facilitated by the increase of mean valence of Ni in the material. The best oxygen reduction reaction (ORR) activity is found in Pr1.9Ca0.1NiO4. The current density of 2.16 mA cm−2 is obtained at a potential of −0.6 V (versus Hg/HgO). The tafel slope is 66.48 mV decade−1, close to Pt/C material.
Fabricating high-loading Fe-N4 single-atom catalysts for oxygen reduction reaction by carbon-assisted pyrolysis of metal complexes
