Effect of bismuth surface coverage on the kinetics of quinone¨Chydroquinone at polycrystalline platinum electrodes

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• 作者：Eunice Mercado^a ; Margarita Rodrí ; guez-Ló ; pez^b ; ^d ; Omar Ló ; pez^a ; Glenda Rodrí ; guez^a ; Estevao R. Fachini^c ; Paulino Tu&ntilde ; ó ; n Blanco^d ; Arnaldo Carrasquillo Jr.^a ; ^{carrasa@uprm.edu}
• 关键词：Kinetics ; Platinum ; Hydroquinone ; Bismuth ; AES ; Cyclic voltammetry
• 刊名：Journal of Electroanalytical Chemistry
• 出版年：2007
• 出版时间：1 June 2007
• 年：2007
• 卷：604
• 期：1
• 页码：26-32
• 全文大小：226 K

文摘

Auger electron spectroscopy (AES), linear sweep voltammetry and coulometry have been used to investigate the effect of bismuth surface coverage over the electron-transfer kinetics of the quinone/hydroquinone (Q_(aq)/H₂Q_(aq)) redox couple at Bi-coated polycrystalline platinum (Pt_poly) electrodes. In 0.5 M HClO₄ acid solutions, the observed rate of electron-transfer is controlled by the relative bismuth surface coverage present at the Pt_poly electrode surface. At full bismuth monolayer coverages, the reversibility of the Q_(aq)/H₂Q_(aq) redox couple is considerably enhanced. Continued potentiodynamic cycling of the Q_(aq)/H₂Q_(aq) couple at a Bi-coated Pt_poly electrode leads to a decrease in the Q_(aq)/H₂Q_(aq) redox rates. The decrease in redox rates is accompanied by the simultaneous decrease in Bi_(ad) surface coverage and a concomitant increase in the chemisorption of hydroquinone-derived adspecies. Eventually, all Bi_(ad) is displaced and electron-transfer takes place slowly, through a spontaneously adsorbed hydroquinone-derived adlayer. In sharp contrast, in the presence of 1 mM , no changes are observed during potentiodynamic cycling of the Q_(aq)/H₂Q_(aq) redox couple and the reaction rates remain fast.