Colmati Flavio, Tremiliosi-Filho Germano, Gonzalez Ernesto R, Berná Antonio, Herrero Enrique, Feliu Juan M
Instituto de Química de São, Carlos Universidade de São Paulo, Av. Trab. Sãdocarlense 400, São Carlos, SP 13560-970, Brazil.
Faraday Discuss. 2008;140:379-97; discussion 417-37. doi: 10.1039/b802160k.
Ethanol oxidation has been studied on Pt(111), Pt(100) and Pt(110) electrodes in order to investigate the effect of the surface structure and adsorbing anions using electrochemical and FTIR techniques. The results indicate that the surface structure and anion adsorption affect significantly the reactivity of the electrode. Thus, the main product of the oxidation of ethanol on the Pt(111) electrode is acetic acid, and acetaldehyde is formed as secondary product. Moreover, the amount of CO formed is very small, and probably associated with the defects present on the electrode surface. For that reason, the amount of CO2 is also small. This electrode has the highest catalytic activity for the formation of acetic acid in perchloric acid. However, the formation of acetic acid is inhibited by the presence of specifically adsorbed anions, such as (bi)sulfate or acetate, which is the result of the formation of acetic acid. On the other hand, CO is readily formed at low potentials on the Pt(100) electrode, blocking completely the surface. Between 0.65 and 0.80 V, the CO layer is oxidized and the production of acetaldehyde and acetic acid is detected. The Pt(110) electrode displays the highest catalytic activity for the splitting of the C-C bond. Reactions giving rise to CO formation, from either ethanol or acetaldehyde, occur at high rate at any potential. On the other hand, the oxidation of acetaldehyde to acetic acid has probably the lower reaction rate of the three basal planes.
为了利用电化学和傅里叶变换红外光谱（FTIR）技术研究表面结构和吸附阴离子的影响，人们对乙醇在Pt(111)、Pt(100)和Pt(110)电极上的氧化过程进行了研究。结果表明，表面结构和阴离子吸附对电极的反应活性有显著影响。因此，乙醇在Pt(111)电极上氧化的主要产物是乙酸，乙醛作为次要产物生成。此外，生成的CO量非常少，可能与电极表面存在的缺陷有关。因此，CO2的量也很少。该电极在高氯酸中对乙酸的生成具有最高的催化活性。然而，特定吸附阴离子（如硫酸氢根或乙酸根）的存在会抑制乙酸的生成，这是乙酸形成的结果。另一方面，在Pt(100)电极上，低电位时很容易形成CO，从而完全阻塞表面。在0.65至0.80 V之间，CO层被氧化，并检测到乙醛和乙酸的生成。Pt(110)电极对C-C键的断裂显示出最高的催化活性。由乙醇或乙醛生成CO的反应在任何电位下都以高速率发生。另一方面，乙醛氧化为乙酸的反应速率可能是三个基面中最低的。
