Hayden Brian E, Pletcher Derek, Suchsland Jens-Peter, Williams Laura J
School of Chemistry, University of Southampton, Southampton, UKSO17 1BJ.
Phys Chem Chem Phys. 2009 Mar 14;11(10):1564-70. doi: 10.1039/b817553e. Epub 2009 Jan 20.
A range of reduced titania (TiO(x)) supported platinum electrocatalysts have been synthesised using physical vapour deposition on arrays of electrodes. Surfaces with equivalent thicknesses of platinum in the range 0.2-2.5 nm on a uniform layer of TiO(x) have been synthesised on 10 x 10 arrays. The arrays have been used to study the surface redox chemistry of the supported platinum as well as the oxidation of a monolayer of carbon monoxide on the platinum. It is shown that below an equivalent thickness of 0.8 nm, there is a positive shift in the potential for the oxidation of the platinum surface and a negative shift for the reduction of the oxide with decrease in the platinum loading. These shifts show that it is the kinetics of the platinum/platinum oxide couple that change with platinum loading; the couple becomes increasingly irreversible with decreasing loading. The peak potential for the oxidation of the monolayer of carbon monoxide also shifts positive and broadens with decreasing platinum loading; these trends are again particularly marked below an equivalent thickness of 0.8 nm while below 0.4 nm no CO oxidation peak is observed although it could be confirmed that CO is adsorbed on such surfaces. Again, these changes with platinum loading are associated with the irreversibility of the platinum/platinum oxide couple. At low equivalent thicknesses, it is impossible to form the oxidised platinum species within the carbon monoxide monolayer essential to the commencement of oxidation of the CO monolayer.
通过物理气相沉积法在电极阵列上合成了一系列负载量降低的二氧化钛（TiO(x)）负载铂电催化剂。在10×10的阵列上，在均匀的TiO(x)层上合成了铂等效厚度在0.2 - 2.5 nm范围内的表面。这些阵列已被用于研究负载铂的表面氧化还原化学以及铂上一氧化碳单层的氧化。结果表明，在等效厚度低于0.8 nm时，铂表面氧化电位正向移动，氧化物还原电位负向移动，且随着铂负载量的降低而变化。这些变化表明，铂/铂氧化物偶合的动力学随铂负载量而改变；随着负载量降低，该偶合变得越来越不可逆。一氧化碳单层氧化的峰值电位也随着铂负载量的降低而正向移动并变宽；这些趋势在等效厚度低于0.8 nm时尤为明显，而在低于0.4 nm时，尽管可以确认一氧化碳吸附在这些表面上，但未观察到一氧化碳氧化峰。同样，这些随铂负载量的变化与铂/铂氧化物偶合的不可逆性有关。在低等效厚度下，不可能在一氧化碳单层内形成对于一氧化碳单层氧化开始至关重要的氧化铂物种。
