http://www.hinduonnet.com/fline/stories/20071116505410100.htm
NOBEL PRIZE
Surface of the matter
Excerpts from the article:
R. RAMACHANDRAN
This year’s Nobel Prize in Chemistry goes to the German scientist Gerhard Ertl for his work on surface chemistry.
 | “YOU should never give up. You should always try to solve the problem as far as possible. And you must be patient. You must be patient. That’s very important.” Indeed, it is this intense focus on a given problem and his dedication, perseverance and, above all, patience that brought this year’s Nobel Prize in Chemistry to the German chemist Gerhard Ertl. An Emeritus Professor at the Fritz-Haber Institute of Berlin’s Max-Planck Society for the Advancement of Science and its former director, Ertl won the award for his path-breaking and thorough investigations in surface chemistry that have enabled a detailed description of chemical reactions on solid surfaces. The award came as a birthday gift to Ertl on October 10 when he turned 71.
Surface chemistry, as the term implies, is essentially chemistry in two dimensions. Unlike the chemical reactions in bulk, with substances in test tubes, beakers and glass jars that one normally associates a chemistry laboratory with, surface chemistry has to do with the chemical processes that occur in the few atomic layers that constitute the interface between two phases, such as solid-liquid, solid-gas, solid-vacuum and liquid-gas interfaces. And two dimensions are better suited to probing reactions in greater detail at the atomic level than those in three-dimensional solutions because they are confined to the surface, but it is neither straightforward nor cheap to study how atoms and molecules react on solid surfaces. It involves painstaking and high-precision work, with advanced equipment such as high-vacuum systems, electron microscopes and spectroscopes, and clean rooms. And Ertl put these to innovative use in the past three decades and more. His work has chiefly been concerned with gas-solid interfaces. As Mark Peplow, the editor of Chemistry World, said, “he gave us the tools to understand why [oxygen] atoms do not bounce off [iron surfaces] but rather stick to them and turn into iron oxide”. |
The science of surface chemistry has important industrial applications, such as in the manufacture of artificial fertilizers, and the science is also key to understanding such diverse phenomena as the rusting of iron; the working of catalytic converters, which make automobile exhaust less polluting; the functioning of fuel cells; and the depletion of atmospheric ozone, which is owing to reactions on the surface of minute ice crystals in clouds.
In fact, the next long-standing problem that Ertl studied was the molecular mechanism in the catalytic reaction in the Haber-Bosch process, which captures nitrogen from air and is a basic step in the industrial production of nitrogenous fertilizers. The only natural processes that are known to bind or “fix” nitrogen in the soil in a form that can be taken up by plants – an important ingredient for crop productivity – include the work of certain bacteria at the roots of leguminous plants and atmospheric electricity such as lightning strikes. For the invention of the Haber-Bosch process, Fritz Haber – after whom, incidentally, the institute where Ertl works has been named – won the Nobel Prize in Chemistry in 1918.
In the Haber-Bosch process, nitrogen reacts with hydrogen to form ammonia (N{-2} + 3H{-2} <—> 2NH{-3}) at high pressure in the presence of a catalyst. The commonly used catalyst is finely dispersed iron particles with added potassium hydroxide on a substrate of alumina and silica. Nitrogen and hydrogen attach themselves to the surface of the iron grains, which enables the nitrogen-hydrogen bonding to take place more easily. Ertl’s work provided a detailed description of how the process works. When he took up the problem in the mid-1970s, it had already received the attention of numerous investigators given its enormous economic importance, but the underlying mechanism remained unclear. These investigations, which mainly looked at the problem from the perspective of kinetics, failed to throw light even on the form – atomic or molecular – in which the gases reacted.
