The 2007 Nobel Prize in Chemistry has been awarded to German scientist Gerhard Ertl, on his 71^st birthday. Ertl's groundbreaking research showed chemists it was possible to understand the fine details of what gas molecules do at the solid surfaces of metals. He worked out the role of metal catalysts in industrial reactions such as the making of artificial fertilizer. But he also pioneered the study of surfaces in many chemical processes: from ozone destruction in the atmosphere and cars' exhaust-cleaning catalytic converters, to the manufacture of pharmaceuticals, and materials for the electronics industry. 

'Ertl's lifelong work has lifted the subject of molecular chemistry at surfaces from alchemy to cutting edge 21st century science,' said Ortwin Hess of the University of Surrey, UK.   

Well before Ertl was born, chemists knew solid surfaces were key to catalysing reactions: as far back as 1912, Paul Sabatier shared the Nobel Prize for using nickel to help hydrogenate organic compounds. But the precise details of how molecules and atoms interacted with a surface evaded scientists: they didn't have the technology to look closely enough. 

In the 1960s, the right tools fell within reach, thanks to methods developed by the semiconductor industry, such as the ability to handle clean surfaces under almost perfect vacuum. An array of sophisticated techniques were developed by chemists, Ertl among them: injecting gas molecules onto surfaces and firing electrons, UV, infrared and x-rays at them in order to probe their structures using microscopy, spectroscopy and diffraction. 

Ertl began by looking at how hydrogen atoms were organised on the surface of metals such as palladium, platinum and nickel. In the 1980s he studied the Haber-Bosch process, where ammonia is made by nitrogen and hydrogen gas molecules reacting on an iron surface. Ertl explained that nitrogen molecules split apart into atoms on the surface; where the atoms were adsorbed; why potassium promoted the reaction, and the step-by-step mechanism of ammonia production. In doing so he laid down a model of how to unravel any solid-gas catalytic mechanism.   

In the 1980s and 90s Ertl tackled another classic reaction: how carbon monoxide is oxidised on a platinum surface to form carbon dioxide - one of the key reactions in the catalytic converter. This one was more complicated, since the kinetics of reaction were not dominated by one slow step. Again, he picked his way through a formidable series of methods to a comprehensive understanding; showing how molecules moved around on the platinum in complicated rhythms and patterns during the reaction.   

Ertl, now emeritus professor at Berlin's Fritz Haber Institute, part of the Max Planck Society, was delighted with his award. 'This is the best birthday present you can give to somebody,' he told the Swedish Academy of Sciences. 

Surface scientists were pleased with the recognition of their field, but at the same time surprised that other surface science pioneers, including David King, of Cambridge University, UK and Gabor Somorjai, of the University of California, Berkeley, had missed out. 

'No doubt there will be disappointment in some quarters that the prize was not more widely shared,' said Andrea Sella, of University College London. But many surface scientists agreed with American Chemical Society President Katie Hunt: 'I am delighted that the prize recognizes a field of chemistry that often receives little public attention, and yet has transformed lives in so many ways.' 

Richard Van Noorden