Oxidation of methanol at an electrocatalytic film containing platinum and polynuclear oxocyanoruthenium microcenters dispersed within tungsten oxide matrix

We propose a composite bifunctional electrocatalytic film that contains pla tinum microparticles and oxocyanoruthenium microstructures dispersed in the reactive matrix of non-stochiometric tungsten(VI,V) oxides. Polynuclear ox ocyanoruthenium can be viewed as a ruthenium analogue of Prussian blue or, more precisely, ruthenium(II,III,IV) hexacyanoruthenate(II,III), that featu res ruthenium oxo species within the cyanide bridged network. The composite film was fabricated by sequential electrodeposition starting from the prep aration of tungsten oxide film into which oxocyanoruthenium and metallic pl atinum (from chloroplatinate) centers were introduced. To evaluate the reac tivity of such a hybrid system toward the oxidation of methanol at fairly l ow potentials (0.1 -0.3 V vs. SCE), cyclic voltammetric and chronoamperomet ric measurements have been performed at 22 and 60 degreesC. With approximat ely the same platinum loading and under analogous conditions, the composite film shows higher catalytic activity than a simple platinized tungsten oxi de. It is possible that ruthenium hydroxo species generated within polynucl ear oxocyanoruthenium microstructures exhibit an activating effect on neigh boring dispersed platinum microparticles. An alternative explanation may in volve the possibility of different morphologies of the catalytic films in t he presence and absence of oxocyanoruthenium species. At higher potentials, ruthenium(IV)-oxo centers participate directly in the oxidation of methano l. The protonically/electronically conducting and physicochemically stable tungsten oxide/hydrogen bronze matrix is expected to support the activity o f platinum and ruthenium centers. (C) 2001 Elsevier Science B.V. All rights reserved.