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Home , Gerhard Ertl, Nobel Prize in Chemistry, Wolf Prize in Chemistry

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The surface detective This year’s Nobel prize in has highlighted the importance of surface chemistry in modern life. Richard Van Noorden catches up with the winner,

46 | Chemistry World | November 2007 www.chemistryworld.org

CW.11.07.NOBEL.indd 46 18/10/2007 15:20:17 ‘This is the best birthday present you Langmuir, who could lay claim to be before meeting hydrogen. He also In short can give to somebody,’ a delighted the grandfather of modern surface explained why potassium (and other Gerhard Ertl told the Swedish chemistry, took the Nobel for his  2007 Nobel prize alkali metals) should promote the Academy of on learning he seminal studies into reactions at air- for chemistry goes to reaction, showing that the distorted had won the 2007 Nobel prize for water and air-solid interfaces. Gerhard Ertl, for his electron density between potassium chemistry on his 71st birthday. ‘As a young boy I was interested studies of chemical and encourages neighbouring After dabbling close to the shores in chemistry and , but only processes on solid nitrogen to break apart. of biology last year, the Nobel learned of the heroes of surface surfaces In doing so, he proved that clean, committee returned to later on,’ Ertl told  Ertl has investigated high-vacuum studies were relevant chemistry for this year’s award. Ertl Chemistry World. Son of a miller the Haber-Bosch to the commercial industrial process took the 10 million kroner (£755 000) and a tailor, he studied physics in process, and the reaction – a reality that some were prize for his detailed studies into , and before of carbon monoxide on struggling to believe. how chemical reactions take place securing as his mentor the physical A similarly memorable and on solid surfaces. Ertl, one of the Heinz Gerischer. He would  The next big challenge thorough analysis began in the fathers of modern surface chemistry, later succeed Gerischer as director of for surface chemistry 1980s, when Ertl tackled the more combines a gentle character with the department of physical chemistry will be in addressing complicated oxidation of carbon a deep understanding of at ’s institute, part more real-world monoxide on platinum (the reaction – qualities that have garnered of the society. situations, at ambient that is the basis of a car’s catalytic him international respect and In a 2002 lecture, Ertl approvingly pressures converter). The reactions here were widespread friendship. quotes Gerischer’s 1973 description more complicated, and Ertl showed Ertl’s prize-winning research was of the mysteries surrounding what that carbon monoxide and oxygen concerned with one fundamental happens at the surface of electrodes. molecules writhed in oscillatory question: what exactly goes on It could also summarise the waves over the platinum surface when molecules from the gas phase attitude of many chemists hoping to during the reaction, as surfaces hit a solid surface and react? The understand molecules reacting at reconstructed and incoming inquiry is not, perhaps, glamorous or surfaces: ‘It is like a detective story. molecules changed the balance of immediately startling, but pervades The kineticist knows the actors, electron density. a huge number of natural and present at the beginning, and he artificial chemical reactions. The sees the victims. He has to search for Winning technique -forming witnesses to reconstruct the course Ertl’s elegant experiments relied for making fertiliser; the exhaust- of events.’ strongly on combining the right cleaning catalytic converter in cars; methods for studying molecular the electronics industry’s production Molecules in court behaviour, and he was quick to of semiconductor materials by In the 1960s, the interrogators for pick up on whatever was available. chemical vapour deposition; the these witnesses were just appearing, Gerischer supplied him with the first breakdown of ozone on ice in in the form of new methods for commercial low-energy electron the atmosphere; these and thousands studying molecules on surfaces. diffraction (LEED) microscope of other reactions have surface Thanks partly to the growth in ; while in the 1980s he chemistry at their core. of semiconductor technology, was one of the first to recognise the ‘Ertl really pioneered the ability chemists were able to prepare potential of the scanning tunnelling to discover what was happening pristine surfaces in almost microscope, perfected by 1986 at surfaces on an atomic scale complete vacuum. Ultraviolet and physics Nobel prize winners Gerd – essentially, the physics behind why x-ray photoelectron , Binnig and . industrial processes happen,’ says which involve firing radiation ‘Progress either needs new ideas Charles Campbell, a surface chemist at molecules and measuring the (which are rare) or new techniques. at the University of Washington, characteristic energies of the ejected We had the techniques,’ he says Seattle, US. Ertl’s rigorous cross- electrons, were beginning to build modestly. But, as compatriot Ferdi examining of molecules at surfaces up characteristic signatures of Schüth, now at the Max Planck set a benchmark for all other studies molecules injected onto a surface. Institute of Coal Research, Mulheim, in the field: he showed it was possible Ertl took full advantage of the new points out, ‘If Ertl needs a technique to understand, and even to control, tools, first studying how hydrogen and there isn’t one available, then catalytic reactions. were organised on metals like he invents it.’ Schüth highlights the , platinum and nickel. In development of dynamic LEED Early activation the mid-1970s he moved on to look – monitoring how diffraction spots Long before Ertl was born in 1936 at the Haber-Bosch process, where move as a surface in Stuttgart, chemists understood nitrogen reacts with hydrogen to proceeds – while Ertl is proud of his the importance of solid surfaces form ammonia. This industrial adoption of photoemission electron to catalyse reactions. In 1912, Paul reaction now helps to make over 100 microscopy (PEEM) and tip- Sabatier was awarded the Nobel million tons of fertiliser a year. The enhanced . prize for his of commonly used catalyst consisted of ‘Ertl really Throughout this interplay of organic compounds ‘in the presence a witch’s brew of iron particles, with technology and fundamental science, of finely disintegrated metals, added potassium hydroxide, on a pioneered Ertl displayed ‘a unique ability to whereby the progress of organic support of alumina and silica, under the ability to distil out of a complex problem the chemistry has been greatly advanced pressure. essential simple questions,’ as his in recent years’. Fritz Haber’s How nitrogen and hydrogen were discover what Fritz Haber Institute colleague Hans discovery of ammonia synthesis behaving on the surface was unclear. was happening Freund puts it. Ertl’s methodology from nitrogen and hydrogen, using Ertl showed that nitrogen’s strong – showing how to use a formidable an iron catalyst, won him the 1918 triple bond cleaved on an iron surface at surfaces on set of tools to be certain of an answer Nobel prize. And in 1932, Irving so that the split into atoms an atomic scale’ – has influenced many surface www.chemistryworld.org Chemistry World | November 2007 | 47

CW.11.07.NOBEL.indd 47 19/10/2007 16:42:44 Nobel prize

with the aid of basic research, many catalysts are best optimised by industry alone. The basic science often rationalises why a particular catalyst works so well, but can’t always make sufficiently useful predictions for improvement.

FRITZ HABER INSTITUTE, GERMANY INSTITUTE, HABER FRITZ Somorjai disagrees with this view, saying that once the original catalyst is found by trial and error, later permutations and refinements depend strongly on basic surface science research. This is increasingly true as fundamental research is taking place under conditions closer to the real world. As Somorjai puts it, ‘Real life is not an ultra-high vacuum system.’ So plenty of work is being done investigating how molecules behave on surfaces at ambient pressures – using the same techniques, such as x-ray photoelectron spectroscopy, that had to be restricted to low pressure in the 1960s and 70s, but have now benefited from improved instrument design. It’s also clear that, unsurprisingly, the surface of a real catalyst is dirtier scientists. He has ‘an uncanny insight prestigious Spiral waves of carbon and more confusing than a perfect into the central issues at work in in 1998, while Somorjai has recently monoxide occupation crystal. Molecules diffuse in and surface chemistry,’ according to been awarded the 2008 Priestley on a platinum out, rather than gliding over the John Yates, a surface chemist at the Medal by the American Chemical surface, captured by surface top; metal bonds restructure; University of Virginia, US. Society (ACS). Francisco Zaera, at photoelectron emission nano-sized lumps of catalyst can Ertl is also a renowned teacher, University of California, Riverside, microscopy (3D, false have catalytic activity greater than and has left a legacy of scientists has commented of the Priestley colour) their surface area would suggest; well-trained in surface chemistry. award that ‘Somorjai could be and even an inert silica support for ‘He is very inspiring for all students considered the father of modern a catalyst can affect the rate of a – a very generous person: gentle, surface chemistry, and to have almost reaction by binding substrates and friendly, and sympathetic,’ says single-handedly set the molecular intermediates. Schüth. John Vickerman, of the foundations of heterogeneous Key areas for advance in surface University of Manchester, who ’. , of the science, says Somorjai, include worked in Ertl’s group in Munich for University of Cambridge, UK, was understanding selectivity in surface a year in 1979, remembers how he another potential Nobel candidate, catalysts – why some reactions are invited colleagues to musical soirees; some surface scientists suggested. preferred over others when there Ertl is a keen pianist, fond of Mozart Nonetheless, chemists were all are very small energetic differences and Bach, and enjoys German pleased that surface science had between them – and the effects of literature. finally got the nod from the Nobel nanocatalysis. Moving away from committee. As ACS president Katie speeding up industrial reactions, Surface tension Hunt said: ‘I am delighted that the bio-interfaces – those in bone While the surface science prize recognises a field of chemistry implants and contact lenses – are community praises Ertl’s that often receives little public taking over the field, with issues of achievements, some are surprised attention, and yet has transformed biocompatibility still unsolved. that other eminent surface chemists lives in so many ways.’ But none of this work could be missed out on a share of the prize. considered without Ertl’s pioneering ‘All the main names of the field Future imperfect beginnings. As Ortwin Hess, a were considered,’ Nobel prize Thanks to the efforts of Ertl, condensed matter theorist working committee member Anders Liljas Somorjai, King, and many others, at the University of Surrey, sums up: told Chemistry World, but ‘it was felt surface science is now a mature ‘Ertl’s lifelong work has lifted the most appropriate to give the award to discipline. But some argument subject of molecular chemistry at one single person’. remains about the transition from surfaces from to cutting- University of California, Berkeley, fundamental research to the real edge 21st century science.’ chemist Gabor Somorjai, who world goal of developing better praised Ertl’s Nobel as ‘well deserved catalysts, says Vickerman. Further reading – he is a good colleague and a good ‘Funding agencies are asking ● G Ertl et al, Appl. Surf. Sci., 1981, 8, 373 friend’, was mentioned by many questions – how directly applicable ‘Real life is not ● M Kim et al, Science, 2001, 292, 1357 (DOI: chemists contacted by Chemistry is this to catalysis?’ he says. 10.1126/science.1059478) an ultra-high ● R Imbihl, R J Behm and R Schlögl, Phys. World as equally deserving of the Detractors argue that while the Chem. Chem. Phys., 2007, 9, 3459 (DOI: award. Somorjai and Ertl shared the catalytic converter was developed vacuum system’ 10.1039/b706675a) 48 | Chemistry World | November 2007 www.chemistryworld.org

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