Potential-mediated growth of ultrathin hydrated tungsten oxide nanosheets with high electrochemical activity from amorphous precursor nanofibers

Morphology and size control is of great importance for enhancing the properties of nanomaterials. In this paper, a novel method to prepare hydrated WO₃ (HWO) nanosheets with controlled thickness is reported. The HWO nanosheets were grown from the precursor nanofibers with amorphous structure containing W and O, which were obtained by heating the electrospun ammonium metatungstate/polyvinyl pyrrolidone composite nanofibers at 400 °C. The growth of the HWO nanosheets was carried out by immersing the above precursor nanofibers in H₂SO₄ solution during which electrical potential was applied onto the precursor nanofibers to mediate the nanosheet growth. The morphology of the products and nanosheet thickness can be well controlled by changing the applied potential. Under appropriate potential, ultrathin HWO nanosheets with thickness well below 10 nm were radially grown from the precursor nanofibers. The ultrathin HWO nanosheets exhibit high electrochemical activity for hydrogen oxidation with the current density reaching 44.6 mA/cm², which is much higher than the values reported for WO₃ and commercial 20 wt% Pt/C catalysts.