Polyoxometallate-assisted integration of nanostructures of Au and ZrO2 to form supports for electrocatalytic PtRu nanoparticles: enhancement of their activity toward oxidation of ethanol

Abstract

Heteropolymolybdate (PMo12O403−) modified gold nanocarriers (diameters, ca. 30–40nm) were integrated with ZrO2 nanostructures (sizes, ca. 15–20nm) to form hybrid supports (on glassy carbon electrodes) for bimetallic platinum-ruthenium (PtRu) electrocatalytic nanoparticles. The anionic heteropolymolybdate monolayers covering Au surfaces not only stabilized gold nanoclusters but also tended to attract electrostatically zirconium oxo cations that were expected to exist on zirconia surfaces in acid medium. By dispersing PtRu nanoparticles over such hybrid integrated supports, the electrocatalytic activity of PtRu toward the oxidation of ethanol was enhanced. When compared to the behavior of bare PtRu nanoparticles (deposited on glassy carbon at the same loading of 100μgcm−2), the enhancement effect was demonstrated in terms of remarkable increases of electrocatalytic (voltammetric, chronoamperometric) currents recorded at room temperature (22°C) in 0.5moldm−3 H2SO4 containing 0.5moldm−3 ethanol. The effect was even more evident at low potentials, particularly below 0.35V (vs. RHE). Introduction of the metal oxide (zirconia and heteropolymolybdate) nanostructures, and their integration with gold nanoparticles, led to formation of the hybrid electrocatalytic supports characterized by improved distribution of electrons as well as by the high population of reactiveOH groups favoring mobility of protons and inducing the oxidative removal of poisoning (methanolic and, indirectly, CO-type intermediates) at ruthenium sites of the deposited bimetallic PtRu nanoparticles.