Electrospun nickel–tungsten oxide composite fibers as active electrocatalysts for hydrogen evolution reaction

Novel crystalline nickel–tungsten oxide composite fibers were synthesized for the first time, to the best of our knowledge, through the electrospinning method using nickel acetate and ammonium metatungstate as precursor solutions. Fibers with five different Ni:W molar ratios, 2:1, 1:1, 1:2, 3:1 and 1:3, were prepared. After calcination, the produced fibers were composed of tungsten oxide (WO 3 ), nickel oxide (NiO) and nickel tungstate (NiWO 4 ). Fiber morphology and structure were studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Selected fibers were investigated for electrocatalytic hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4 and 0.1 M KOH electrolytes. The electrospun composite fibers showed good electrocatalytic activity compared to pure NiO and WO 3 fibers with an overpotential of 80 mV and 60 mV in acidic and basic media, respectively. Low Tafel slopes were also registered as 50.27 mV/dec and 41.29 mV/dec in H 2 SO 4 and KOH, respectively. The presence of NiWO 4 compound, formed during the composite fabrication, was responsible for improving the electrocatalytic performance of the fibrous catalyst.