The electrochemical hydrogen evolution reaction (HER) was studied over silica/tungsten oxide nanofacets (SiO2/WO3-x) that was prepared by calcinations of electrospun polyacrylonitrile nanofibers containing silicotungstic acid under air atmosphere. It was found that the Keggin structure of precursor (H4SiW12O40.29H(2)O) was decomposed and transferred to crystalline monoclinic WO3 after calcinations at 500 degrees C. The morphology of prepared catalyst after pyrolysis, observed by FE-SEM, was nanocrystals deposited on joined nanoparticles fiber. The size of nanocrystal increases with increasing annealing time. In addition, increasing annealing time also enhances interaction between SiO2 and WO3-x. The synthesized catalyst was employed as an electrocatalyst for HER. It was found that the catalyst annealed at 500 degrees C for 5 h showed 6.6 times higher HER activity than the bulk WO3 and exhibits excellent electrochemical stability over 100 cycles. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.