| he modification of Pt nanoparticles by adsorbing monolayers of phosphododecatungstic acid on their surfaces tends to activate them towards efficient electrocatalytic reduction of oxygen in acid medium. The modification steps were performed either before or after introduction of Pt nanoparticles onto the glassy carbon substrates. Formation of a stable colloidal suspension of phosphotungstate protected Pt-nanoparticles was required in the first case; whereas, in the second case, bare Pt nanoparticles had been deposited on glassy carbon before they were subsequently modified with H3PW12O40. Rotating disk voltammetry was used to probe the electroreduction of dioxygen in 0.5 mol dm-3 H2SO4 at 25 °C. H3PW12O40 could act as both effective mediator (e.g. for the reduction of the hydrogen peroxide intermediate) and the source of mobile protons at the electrocatalytic interface. The above concept of bifunctional catalytic system has been extended to the bioelectrocatalytic reduction of oxygen in neutral medium (0.1 mol dm-3 KCl) at the electrode modified with multi-walled carbon nanotube supported Co-protoporphyrin/horseradish peroxidase hybrid (composite) bioinorganic catalyst. |
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