Core-shell hierarchical tungsten carbide composite microspheres towards methanol electrooxidation

Tungsten carbides microspheres are synthesized by in situ reduction of ammonium met tungstate microspheres (AMT) precursors as a function of reaction time under CO/CO2 mixture atmosphere. The morphology, size and composition of the as-prepared tungsten carbide microspheres are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Pt nanoparticles with a diameter of 4.6 nm are loaded onto the surface of WC microspheres using a conventional sodium borohydride reduction method. The electro-catalytic activity and stability toward methanol electrooxidation (MOR) are investigated using cyclic voltammetry (CV) and chronoamperometry (CA). The resultant Pt/WCO-6h catalyst exhibits low onset potential and excellent catalytic performances in comparison to the commercial JM Pt/C and Pt/WC-15h catalysts. Further investigation shows that besides the synergistic effect between WC and Pt, the existence of WO2 might also play an important role in improving the electro-catalytic activity, indicating the positive effect of the surface oxide on the activity and stability of Pt/WC catalysts towards MOR.