Methanol oxidation at platinum electrodes in acid solution: Comparison between model and real catalysts

Abstract

Methanol oxidation in acid solution was studied at platinum single crystals, Pt(hkl), as the model catalyst, and at nanostructural platinum supported on high surface area carbon, Pt/C, as the real catalyst. The linear extrapolation method was used to determine the beginning of hydroxyl anion adsorption. Structural sensitivity of the adsorption was proved and a correlation with the onset of the methanol oxidation current was established at all catalysts. Bisulfate and chloride anions were found to decrease the methanol oxidation rate, but probably did not influence the reaction parth. The specific activity for the reaction increased in the sequence Pt(110) LT Pt/C LT Pt(111), suggesting that the activity of the supported Pt catalyst can be correlated with the activities of the dominating crystal planes on its surface.

Oksidacija metanola ispitivana je na niskoindeksnim Pt monokristalnim elektrodama (model katalizator) i na nanokatalizatoru Pt dispergovanom na aktivnom uglju kao nosaču (realni katalizator) u kiseloj sredini. Metoda linearne ekstrapolacije krivih zavisnosti količine naelektrisanja adsorpcije kiseoničnih čestica od potencijala korišćena je za određivanje početka adsorpcije OH anjona. Potvrđeno je da je adsorpcija OH čestica strukturno osetljiva reakcija i pokazana je korelacija sa početkom reakcije oksidacije metanola. Utvrđeno je da bisulfatni i hloridni anjoni iz nosećeg elektrolita smanjuju brzinu oksidacije metanola, ali verovatno ne utiču na reakcioni put. Elektrokatalitička aktivnost ispitivanih katalizatora rasla je u nizu Pt(110) LT Pt/C LT Pt(111) ukazujući na to da se aktivnost Pt nanokatalizatora može povezati sa udelima niskoindeksnih ravni na površini Pt nanočestice.