Lehrstuhl Technische Chemie, Ruhr-Universität Bochum, P.O. Box 102148, 44780 Bochum (Germany).
Angew Chem Int Ed Engl. 2014 Mar 17;53(12):3245-9. doi: 10.1002/anie.201308206. Epub 2014 Feb 19.
Au/TiO2 catalysts prepared by a deposition-precipitation process and used for CO oxidation without previous calcination exhibited high, largely temperature-independent conversions at low temperatures, with apparent activation energies of about zero. Thermal treatments, such as He at 623 K, changed the conversion-temperature characteristics to the well-known S-shape, with activation energies slightly below 30 kJ mol(-1). Sample characterization by XAFS and electron microscopy and a low-temperature IR study of CO adsorption and oxidation showed that CO can be oxidized by gas-phase O2 at 90 K already over the freeze-dried catalyst in the initial state that contained Au exclusively in the +3 oxidation state. CO conversion after activation in the feed at 303 K is due to Au(III)-containing sites at low temperatures, while Au(0) dominates conversion at higher temperatures. After thermal treatments, CO conversion in the whole investigated temperature range results from sites containing exclusively Au(0).
通过沉积沉淀法制备的 Au/TiO2 催化剂无需预先煅烧即可用于 CO 氧化，在低温下表现出高转化率，且基本与温度无关，表观活化能约为零。热处理（例如在 623 K 下用 He）会使转化率-温度特性转变为熟知的 S 形，活化能略低于 30 kJ/mol。通过 XAFS 和电子显微镜对样品进行表征以及对 CO 吸附和氧化的低温 IR 研究表明，在初始状态下，即在仅含有 Au+3 价态的冷冻干燥催化剂中，CO 已经可以在 90 K 时通过气相 O2 氧化。在 303 K 下进料中进行活化后，CO 的转化率归因于低温下含 Au(III)的位，而 Au(0)在较高温度下占主导地位。经过热处理后，整个考察温度范围内的 CO 转化率均来自仅含 Au(0)的位。
