Synthesis, characterization of a CoSe2 catalyst for the oxygen reduction reaction Original Research Article

Crystalline CoSe2, with the pyrite structure, supported on carbon powder has been synthesized by a wet chemical method. Samples were characterized by a range of techniques, including X-ray diffraction and transmission electron microscopy for structure, and X-ray photoelectron spectroscopy and scanning Auger microscopy (SAM) for surface composition. Electrochemical dynamic polarization measurements were carried out using the CoSe2-decorated carbon powder as part of a rotating disk electrode to assess its catalytic activity for the oxygen reduction reaction (ORR), and the surface analysis methods were used to identify changes in surface composition. Comparisons of ORR activities were made with CoSe and Pt powder catalysts prepared by comparable methods. Stationary cyclic voltammetry was used to assess the stability of the as-prepared CoSe2 powder catalyst in an acidic electrochemical environment. A preliminary investigation was also made of an electrochemical modification treatment for CoSe2. The surface formed was characterized by the rotating ring-disk electrode technique and by micro-Raman spectroscopy, backscattered-electron imaging and SAM. The latter combination of characterization techniques helped to relate an observed passivation to a thin layer of Se formed by the modification treatment.