Structure, morphology and electrocatalytic properties of WOx thin films prepared by reactive pulsed laser deposition

Nanostructured WOx<3 films were prepared by pulsed laser deposition in air from W target. The pressure of air was varied in a range of 10 - 100 Pa and the temperature of a glassy carbon substrate during the film deposition was 22 or 500 degrees C. For the films deposited at 22 degrees C, thermal post-treatment in air of laboratory humidity at 500 degrees C was applied. The increase of air pressure during PLD at 22 degrees C caused both a decrease in packing density of ball-like amorphous nanoclusters of WOx and decline of their size. Post-treatment in air at 500 degrees C has initiated crystallization of the nanoclusters but characteristic morphology of the films was preserved in a whole. The PLD of WOx on a heated substrate resulted in the formation of nanoneedles and nanosheets. Fairly good catalytic properties in hydrogen evolution reaction (HER) and in electrolytic Pt deposition were revealed for the WOx films that consisted of loosely packed ball-like nanocrystals possessing a size of similar to 20 nm. The catalytic activity of the films consisted of nanoneedles and nanosheets was not good enough. Adjustable electrolytic deposition of Pt on the nanostructured WOx support film allowed to prepare effective hybrid HER catalyst containing only similar to 7 mu g/cm(2) of Pt.