The kinetics and mechanism of methanol oxidation on Pt and PtRu catalysts in alkaline and acid media

Abstract

The kinetic of methanol electrochemical oxidation for a series of platinum and platinum-ruthenium catalysts was investigated. A correlation between the beginning of OHad adsorption and methanol oxidation was demonstrated on Pt single crystals and Pt nanocatalyst. The activity of the nano-structured Pt catalyst was compared with single crystal platinum electrodes assuming the Kinoshita model of nanoparticles. The ruthenium-containing catalysts shifted the onset of methanol oxidation to more negative potentials. The effect was more pronounced in acid than in alkaline media. Based on the established diagnostic criteria, the reaction between COad and OHad species according to the Langmuir-Hinshelwood mechanism was proposed as the rate determining step in alkaline and acid media on Pt and PtRu catalysts. .

Kinetika elektrohemijske oksidacije metanola je ispitivana na nizu katalizatora od platine i platine−rutenijuma. Pokazana je veza između početka adsorpcije OHad čestica i početka oksidacije metanola. Utvrđeno je da se nanostrukturni Pt katalizator po aktivnosti može porediti sa monokristalima platine, što je u skladu sa usvojenim modelom po kome se aktivnost Pt nanokatalizatora može povezati sa udelima niskoindeksnih ravni na površini nanočestice. Pokazano je da oksidacija metanola počinje na negativnijim potencijalima na katalizatorima koji sadrže rutenijum, pri čemu je taj efekat izraženiji u kiseloj nego u alkalnoj sredini. Ispitivan je uticaj pH, anjona i temperature, određeni su kinetički parametri, a za spori stupanj u oksidaciji metanola predložena je reakcija čestica COad i OHad prema Lengmir-Hinšelvudovom mehanizmu. .