The phase composition of the samples was analyzed by X-ray diffraction within the range from 30º to 70º (XRD, Bruker D8 P-XRD) using Cu Kα radiation (λ = 1.5418 Å). The morphology of as-prepared tungsten carbides was studied by scanning electron microscopy (SEM, Zeiss Supra 40). The chemical analysis of the samples was conducted by high-resolution X-ray photoelectron spectroscopy (XPS, Versa probe Ⅱ). The pass energy and energy step size for XPS were chosen to be 50 eV and 0.1 eV, respectively. Raman spectra were collected using Horiba Raman microscope with an excitation laser of 532 nm at a magnification of 50X.