Preparation and Electrocatalytic Activity of Nanophase WC-Co Composite Powder and WC Powder with Spherical Shell Structure

Abstract

Using ammonium metatungstate (AMT), soluble cobalt salt and organic carbon source as the raw materials, the W-Co precursor powder with spherical shell structure was first fabricated by spray conversion method. Then the nanophase WC-Co composite powder was fabricated via calcinations and low temperature reduction-carbonization methods. And the WC powder with the same spherical shell structure was prepared at last by dissolving the Co phase into H3PO4and H2O2. The phase composition, powder morphology, chemical components and its distribution of the samples at different stages were characterized by XRD, SEM and EDS. The results confirmed that the powders showing spherical shell structure after spray conversion, calcinations, reduction, carbonization and dissolution. While the amount of surface porosity changed after these treatments. The grain size of WC was about 50nm measured by FWHM of XRD. The electro catalytic activities of the powders towards methanol electro-oxidation were investigated by cyclic voltammetry with a three-electrode system in acidic solution. Compared with the granular WC powder, the electro-catalytic activity of WC-Co composite powder sample decreased, but the electro-catalytic activity of WC powder with spherical shell structure has been significantly improved. These results indicated that the electro catalytic activity of WC can be improved through the formation of spherical shell structure, while the existence and distribution of Co phase could hinder the electro-catalytic activity of WC.