  Hybrid supports composed of chemically-reduced graphene-oxide-aligned with
tungsten oxide nanowires are considered here as active carriers for dispersed
platinum with an ultimate goal of producing improved catalysts for
electroreduction of oxygen in acid medium. Here WO3 nanostructures are expected
to be attached mainly to the edges of graphene thus making the hybrid structure
not only highly porous but also capable of preventing graphene stacking and
creating numerous sites for the deposition of Pt nanoparticles. Comparison has
been made to the analogous systems utilizing neither reduced graphene oxide nor
tungsten oxide component. By over-coating the reduced-graphene-oxide support
with WO3 nanorods, the electrocatalytic activity of the system toward the
reduction of oxygen in acid medium has been enhanced even at the low Pt loading
of 30 microg cm-2. The RRDE data are consistent with decreased formation of
hydrogen peroxide in the presence of WO3. Among important issues are such
features of the oxide as porosity, large population of hydroxyl groups, high
Broensted acidity, as well as fast electron transfers coupled to unimpeded
proton displacements. The conclusions are supported with mechanistic and
kinetic studies involving double-potential-step chronocoulometry as an
alternative diagnostic tool to rotating ring-disk voltammetry.
