Katarzyna Karnicka

New Strategies to Activation and Assembling of Catalytic Metal Nanoparticles through Modification with Polyoxometallate Monolayers

The modification of Pt nanoparticles of ca. 8 nm diameter by adsorbing monolayers of phosphododecatungstic acid (H3PW12O40) on their surfaces tends to activate them towards efficient electrocatalytic reduction of oxygen in acid medium. The modification steps were be performed either before or after introduction of catalytic nanoparticles onto the glassy carbon substrates. Formation of a stable colloidal suspension of phosphotungstate protected Pt-nanoparticles as a source of activated catalytic centers 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 ultrathin films of H3PW12O40. Rotating disk voltammetry was used to probe the electroreduction of dioxygen in 0.5 mol dm H2SO4 at 25C. In addition to the usual reactivity towards the oxygen reduction, 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.