Tungsten oxide as active matrix for dispersed carbon-supported RuSex nanoparticles: Enhancement of the electrocatalytic oxygen reduction

Modification of carbon-supported RuSex nanoparticles with ultra-thin WO3 films results in the enhancement of their electrocatalytic properties towards electroreduction of dioxygen in acid medium (0.5 mol dm−3 H2SO4) as evidenced from the positive shift of the O2 reduction potential (ca. 150 mV) and the higher heterogeneous rate constant (ca. 3 times). An important issue is that the mixed-valent tungsten(VI,V) oxide support is characterized by good electronic and protonic conductivities. Further, not only RuSex is catalytic but tungsten oxide itself is also capable of promoting the reduction of hydrogen peroxide. This bifunctional activity of the WO3-modified system has been the most pronounced at rather low loadings (e.g. 80 μg cm−2) of RuSex nanoparticles. To facilitate attachment of catalytic particles to glassy carbon substrate, they have been over-coated with Nafion.