【作者】 温飞；

【导师】 H.Boennemann； 金子林；

【作者基本信息】 大连理工大学 ， 应用化学， 2004， 博士

【摘要】 近年来,烷基铝对过渡金属盐的“还原稳定法”被成功用于制备纳米单金属和双金属胶体,该方法主要有两个优点:(1)不需要表面活性剂即可制得高分散过渡金属胶体;(2)制得的纳米颗粒表面存在高活性烷基铝基团,可以进一步通过化学改性改善纳米颗粒的分散性能,或者构建二维或二维的纳米粒子网络。 本论文将“还原稳定法”的起始原料由过渡金属盐扩展至低价态过渡金属配合物,制得具有烷基铝保护基团的单分散(<15%)过渡金属胶体(铂,镍,铂钉),通过改变分应条件可以对胶体的粒径在一定范围内进行控制。基于烷基铝路线,提出了制备单分散镍胶体的烷基硼路线。 由于制得的金属铂和金属镍胶体表面存在具有反应活性的烷基铝或烷基硼基团,可以通过醇解反应进一步构建铂和镍的纳米粒子网络。采用不同分子长度的二元醇交联剂可以达到控制粒子间距的目的。 基于“前体概念”(Precursor concept),烷基铝稳定的铂和铂钉胶体被用于制备碳载电化学催化剂。本工作采用薄膜旋转圆盘电极法(Thin-film rotating disk electrode)对催化剂的一氧化碳和甲醇电化学氧化活性进行了考察,并对胶体表面烷基铝保护层于电化学活性的影响进行了探讨。 此外,本论文对温控相转移催化过程中原位生成的铑胶体进行了研究,发现生成的铑胶体在进一步的反应循环中表现出奥斯特瓦德熟化(Ostwald ripening)特征,其不稳定性可能是造成催化体系多次循环后失活的原因。更多还原

【Abstract】 Previous work has shown that aluminium trialkyls can be used successfully to prepare colloidal mono- and bimetallic nanoparticles by "reductive stabilization". Two major advantages of this methodology are that: (1) no surfactant is required for the preparation of nearly monodisperse transition metal colloids, and (2) these nanoparticles have highly reactive organo-Al groups as colloidal stabilizers, which can then be chemically modified to tailor their dispersion characteristics and even to develop 2-D or 3-D nanoparticle networks.The present work extends the "reductive stabilization" to low-valeht organometallics with the aim of obtaining monodisperse transition metal colloids (Pt, Ni, Pt-Ru) having reactive protective shells. The size-selective syntheses of these transition metal colloids were explored.By analogy with the aluminium organic route, organoborane compounds were applied to the preparation of Ni colloids stabilized by B-organic shells.The reactive organo-Al or organo-B groups in the stabilizers of Pt and Ni colloids allow nanoparticle networks to be formed via protonolytic action of bifunctional "spacers". Control of the inter-particle distance can be achieved by using spacer molecules with different lengths.Based on the "precursor concept", Pt and Pt-Ru colloid precursors stabilized by Al-organyls were used to prepare fuel cell catalysts on Vulcan XC-72. The electrochemical activity in the oxidation of CO or methanol was investigated by the thin-film rotating disk electrode (RDE) method. In particular, leaching effect, i.e., the removal of Al protective shells, was discovered.With respect to homogeneous catalysis, the thermoregulated Rh complex catalyst was shown to form colloidal Rh after the repeated catalytic cycles. Ultimately, as a result of Ostwald ripening, the colloids grow and form metal precipitates, causing them to lose their activity.更多还原