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瑞典皇家科学院介绍2007年Nobel化学奖得主Gerhard Ertl教授主要成就
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Introduction The Nobel Prize in chemistry for 2007 is awarded to Gerhard Ertl for his thorough studies of fundamental molecular processes at the gas-solid interface. When a small molecule hits a solid surface from a gas phase there are a number of possible outcomes. The molecule may simply either bounce back or be adsorbed. It is the latter case that carries the most interesting possibilities. The interaction with the atoms of the surface can be so strong that the molecule dissociates into constituent groups or atoms. The molecule can also react directly with surface groups and change the chemical properties of the surface. A third possibility is that the adsorbed molecule encounters another previously adsorbed one and there is a binary chemical reaction on the surface. There are very important practical situations where these scenarios are the key chemical events. Heterogeneous catalysis has been a central process in the chemical industry for a century. The agriculture of the world has been supplied with fertilizers rich in nitrogen since 1913 due to the Haber-Bosch process, where the nitrogen of the air is converted to ammonia using an iron-based catalyst. Today every car produced has a catalyst system that converts carbon monoxide and hydrocarbons to carbon dioxide in the exhaust gases. Also the content of nitrous gases is reduced through the action of the catalyst. Thin semiconductor layers are produced by chemical vapor deposition (CVD) in large quantities in the microelectronics industry. Currently large resources are devoted to the development of efficient fuel cells that would enable the use of hydrogen as a standard vehicle fuel. Corrosion, which is caused by chemical reactions at surfaces, is a major problem both in everyday life and in more sophisticated industrial contexts such as in nuclear power plants and airplanes. Damage by corrosion may be reduced by adjusting the composition of the surface so that it is protected by an oxide layer formed in air. It is clear that chemical processes at surfaces play a central role in wide span of economically highly significant applications of chemical knowledge to the solution of practical problems. The study of chemical processes at surfaces also plays a significant role from the perspective of basic chemical research. In our theoretical description of chemical reactions the formation of a molecule in the gas phase provides the conceptually most simple case. Here it is possible to consider a reacting species affected only by the encounter with the reaction partner. However, in most applications of practical importance reactions occur in more complex environments, where the reacting species are constantly exchanging energy and momentum with other neighboring molecules. In a solution the environment is disordered and dynamic. In the description of such systems one typically has to rely on considering the effect of the environment through its average properties. The gas-solid interfaces provide one example of an environment that is intermediate between the relative simplicity of the gas phase and the molecular complexity of the liquid phase. At the surface of a solid an adsorbed molecule can exchange energy and momentum with the support, but in the most ideal cases the support has long-range order. The consequence is that the interaction between molecule and support is much more regular, which allows for more precise experiments and more detailed theoretical descriptions. Thus one can see the study of chemical reactions on surfaces as one route towards a deeper understanding of reactions in condensed phases in general. |
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