Like a successful dinner party, productive chemical reactions depend upon getting the right components to mingle in the right surroundings, and often the best environment for chemistry turns out to be a solid surface. From the cleaning of exhaust fumes in factory chimneys to the reduction of ozone on the outside of ice crystals in the clouds, surface chemistry surrounds us constantly. Developing ways to better understand the detailed dynamics of chemistry at these interfaces has been Gerhard Ertl’s life work.

Studying surface chemistry is a painstaking process, requiring intricate preparation of samples and great precision in visualizing the reactive species that are undergoing chemical reactions in regions just a few atoms deep. The challenges Ertl set himself were bold, for instance to understand the Haber-Bosch process, a reaction of huge industrial importance that has been used since the first world war without anyone knowing precisely how it worked. This process generates ammonia, primarily needed for agriculture, from its constituent elements, hydrogen and nitrogen, on the surface of an iron catalyst. Using an astonishing variety of techniques, Ertl was able to piece together the step-by-step interplay between the hydrogen and nitrogen atoms bound to the face of the iron particles during the reaction, solving a sixty-year old mystery.

Another of Ertl’s longstanding areas of interest, and one where his investigations have also revealed previously unknown phenomena, is the conversion of carbon monoxide to carbon dioxide on platinum catalysts, one of the reactions performed by catalytic converters in cars. A hallmark of Ertl’s approach has been his willingness to return to the same research questions whenever technology became available that opened new avenues for investigating an old problem in a fresh way. This intense focus on particular problems, combined with his patient approach to solving them, hold part of the key to his success in exposing events at chemistry’s hidden face.