Interview with the 2007 Nobel Laureate in Chemistry Gerhard Ertl on 6 December 2007. The interviewer is Adam Smith, Editor-in-Chief of Nobelprize.org.

Gerhard Ertl, welcome to this interview with Nobelprize.org. You are the 2007 Nobel Laureate in chemistry for your contributions to the science of surface chemistry and it may surprise people to know how much chemistry actually goes on at surfaces. When people think of chemical reactions, they tend to think of bubbling vessels and fluids and it all happening in liquids, but actually surface chemistry is everywhere.

Gerhard Ertl: Surface chemistry is taking place in almost all industrial plants. All chemicals are made through the operation of catalysts but also in biological systems. Many reactions take place at the surfaces of cells and so on, but the kind of surface chemistry I was studying was essentially with solid surfaces, and this is the basis of catalysis, which in turn is the basis of chemical industry but also of a lot of environmental chemistry.

Given how ubiquitous surface chemistry is, it might be thought to be a little surprising that this is the first Nobel Prize for surface chemistry since Irving Langmuir got it in 1932. Is part of the problem that it’s very difficult to study surface chemistry?

Gerhard Ertl: It’s certainly very difficult to study and as you mentioned Irving Langmuir, he was really groundbreaking, as his ideas, but many of these ideas couldn’t be studied at that time because we needed new techniques and /- – -/ This started only in the 1960s and ‘70s, that’s why surface chemistry is a relatively new field of chemistry in this sense.

What are the challenges, the difficulties in the instrumentation that one faces?

Gerhard Ertl: If you are interested to learn what is really taking place on an atomic scale on the surface, you have to keep in mind that the structure of a solid surface is usually very complex. It consists of different crystal planes, different defects, different compounds at the surfaces and if you expose it to an atmosphere, then impurities from the gas face will accumulate there, so it’s very badly defined. If you want to study really the elementary processes, you first have to start with preparation of clean and well defined surfaces. It needs very high vacuum and the use of single crystal surfaces. This was the event of surface science in the 1960s, when this whole field started.

Right. Taking it on from there, you have your single crystals, you have your vacuum …

Gerhard Ertl: Yes, and then you need the physical techniques to probe the properties of the surfaces because these are properties for one atomic layer, it’s not about properties. We need new techniques which are very surface sensitive and the first techniques which were developed in the ‘60s were based on the interaction of matter with low energy electrons. The mean free path in solid is very short, so we get really information from the topmost atomic layers. In the meantime, there are many other techniques which can probe also these properties in with direct atomic resolution with this scanning tunnelling microscope.

Right. I suppose that goes to explain why it was that one of the things that you did, which was to work out the precise mechanism of the Haber Bosch process in which nitrogen and hydrogen combine on an iron catalyst to form ammonia.

Gerhard Ertl: That’s right.

It was so difficult to do because that was a process that was around from the First World War onwards and has been used on a vast scale industrially around the world and yet nobody until you came along understood exactly how it worked.

Gerhard Ertl: It got realised in a laboratory in 1909 and transformed into an industrial plant in 1913 and I was attending a conference in Switzerland in 1974 where one of the great old men of catalysis research gave a lecture on the mechanism of ammonias and since is concluded. We still don’t know the mechanism. Especially we don’t know whether the nitrogen molecule first has to break up and then it’s reacting with the hydrogen or whether the nitrogen molecule reacts with the hydrogen. I came back from this conference and said to my students, This is a problem we should be able to solve. That’s how we became interested in that.

That’s a lovely challenge. Has it made any practical difference to the process, that you now understand?

Gerhard Ertl: With the knowledge about the process and about the rates of the individual steps, it was also possible to develop a kinetic model and this was done by people in Denmark working with Haldor Topsoe, the company who is one of the big manufacturer of plants for the ammonia synthesis. They tell me, now in the meantime, they developed their plants on the basis of data they have about the kinetics, so it makes it much, much easier for them also.

You defined the rate limiting steps for the reaction?

Gerhard Ertl: Yes, that’s right and we identified also other steps and with all this knowledge putting together, these people, Nørskov and his co-workers, they were able to develop this kinetic model.

One of the things that you’re known for is that you re-visit problems, when a new technology becomes available, you go back to an old problem that you studied previously and you’ll study it again using the new technology. Is the Haber Bosch process one of those that you have looked at more than once?

Gerhard Ertl: We continue to work on this because there was still the question is the iron catalyst the best catalyst? It was invented almost 100 years ago and, in the meantime, there are other catalysts being proposed, mainly by Japanese workers based on ruthenium and indeed it seems to be a better catalyst than iron but it’s very hard to transform this on an industrial scale and …

Iron is cheaper, I imagine.

Gerhard Ertl: Iron is cheaper and also the plants are available but that’s why we also continue to work now on the mechanism of the ruthenium catalyst, the mechanism which is very similar. In this way we continued our work on the ammonia catalyst, ammonia synthesis, to some extent.

Do you think it’s unusual that you re-visit problems?

Gerhard Ertl: I don’t think so. Whenever you solve a problem or answer a question, you are faced with two or three new ones so you are still left with open questions. I think it’s not very unusual that you go back to another question which you had left a couple of years ago.

It indicates a nice open mindedness about things, though, that you don’t want to just close things off and finish.

Gerhard Ertl: Definitely, and of course you always need some fantasy to imagine what could be the answer to this question because this defines the line along which you are doing your new research.

What led you to surface chemistry in the first place? What was your path that ended up there?

Gerhard Ertl: I am not a chemist, I am a physicist, but I was always interested in both chemistry and physics and that’s why I did my first degree where the diploma work was a physical chemist and he was a famous electro-chemist. Electrochemistry is the science of solid/liquid interface, with charge transfer. I did my first work on the reactions in liquid fase but then I wanted to continue for my PhD and I asked my thesis advisor, Is there anything else I could do – everybody here in the laboratory is working on electro-chemical systems? He told me, We know quite a bit about solid/liquid interfaces, but very little about solid/gas interfaces. There is no electrochemistry. If you think you could start with that, you can do it as you like. He gave me completely free way and this was the advantage. He was not an expert in this field but he just trusted me and that’s how I came interested in that.

You must have had considerable self-confidence.

Gerhard Ertl: Yes, definitely, obviously. Yes. No, I owe him very much.

Where did the original interest in science come from? Before you started studying physics at university, what were you …

Gerhard Ertl: I started doing experiments in chemistry when I was a boy at age of about 12 or 13. In these days, no computers were available. I was always very bad in sports, so I was playing the piano. I was interested in music but apart from that, I was interested in science. That’s why I started these chemical experiments. I had a wonderful book called Chemical Experiments That Work and it listed all the chemicals you needed and all the instruments and you could buy them in a drug store and there were no regulations concerning safety, was there, in those days? I started to do these experiments in my bedroom and …

Did they work?

Gerhard Ertl: They worked, yes. Yes, of course, including little fireworks and all these things, but one day my mother said, You should stop that. It smells always so terrible and I am afraid one day in the morning you will not wake up any more. That’s why I stopped the chemical experiments and moved into physics. The alternative to chemistry was electronics radio, all boys at my age were working with radio. That’s how I became interested in physics and since I was very good in mathematics at school, I started physics and not chemistry. We had also a very good teacher in physics and a not so good teacher in chemistry, so that’s why I became a physicist.

But it sounds like it was your mother’s influence, really.

Gerhard Ertl: At the beginning there, certainly. One of my friends in school, a classmate, he started chemistry and he was always interested in the beginning in this large organic molecules which I was not very fond of. They looked too complicated to me and that was the reason why I decided to go away into physics and more fundamental science.

Well, there still seems to be enough to learn about nitrogen and hydrogen.

Gerhard Ertl: Definitely. These are small molecules. I never worked with these large organic.

When you yourself recruit students to your lab, and you’ve recruited many, what do you look for in them? What are you trying to identify in a new student?

Gerhard Ertl: First of all, I had about the same number of students from physics and chemistry and this is very advantageous because both parts have their pros and contrasts and their collaboration was always very fruitful. Then I always check if they are really motivated and interested. It’s not so much the marks they got in their examinations but are they curious enough and also brave enough to take a new problem? You can recognise that very early and I think that was, shall we say, a recipe which worked.

You can recognise their passion for the science?

Gerhard Ertl: Definitely, yes. If somebody really gets interested in a problem, you’ll explain to him.

You say you have an equal mix of chemists and physicists. Is it easy to get the physicists to come across to what is essentially a chemistry environment?

Gerhard Ertl: Yes, because the methods we are applying are physical methods, so many, many physics students are really interested to see what they can do with the physical techniques. These are problems they are usually not faced with, so I never have problems to get good students from physics.

Ok, that’s what you look for in them. What do you think that they look for in you? What are they hoping to get from you as a mentor?

Gerhard Ertl: I think there is a lot of networking between the students. They know in advance what kind of professor is that. They told me that many years later, very often, I went to you because my friend said you should go there and so, yes, and obviously …

It works.

Gerhard Ertl: It works.

But what sort of professor are you? How do you treat your students? How much latitude do you give them? Are you like your doctoral supervisor and just say …

Gerhard Ertl: I think you are very much influenced by the mentor which brings you on on your pass and my mentor Heinz Gerischer was such a perfect person, I must say. Let you complete freedom and give you all the support you need, and I think this was also the way I wanted to treat my students.

And in the main they respond well to that?

Gerhard Ertl: Oh yes. This is just the kind of responsibilities they get in this way. Of course I was told later that very often I had convinced them to do something else than they had in mind but they always agreed that later this was the right decisions I made.

Your students must have gone off and inhabited many, many other departments?

Gerhard Ertl: I’ve many students now who are professors at universities or in leading positions. I’m very proud about that, I must say.

The citation from the committee suggests that really you’ve changed the shape of surface chemistry by seeding all these different environments.

Gerhard Ertl: This is a quotation from the Nobel Committee. I do not want to comment on that. But I agree, there are many, many of my students now working at universities and are professors there.

A question that I often ask, but what is it that you enjoy the most about the practice of science? About the science that you do?

Gerhard Ertl: I think it’s always an adventure to ask a question and to enter a new field where you don’t know the answer in advance. If you then get an answer and if this answer is really surprising, this creates a great joy, always. And this continues, yes.

I’ve had other answers that have suggested that the pleasure is in realising that something is possible and then practically carrying it out, so that’s almost the opposite, that it’s not getting the surprise, it’s getting the confirmation.

Gerhard Ertl: Of course. Very often you have an idea what could be the answer to this question and this is of course also a source of joy, if you get confirmation of what you had expected, but it’s even more rewarding if you get a new answer which was unexpected.

And do you enjoy the lab work very much?

Gerhard Ertl: That’s right, yes. I have spent quite some time with the laboratory. I’m no longer working with my hands but just discussing with the people there and so on. It’s very rewarding also to see how the results come out.

Why do you no longer work with your hands?

Gerhard Ertl: I’m retired. I retired three years ago, so I no longer have a laboratory any more. The more advanced you get, the more other responsibilities you have. You are no longer able to really spend hours in the laboratory, that’s correct. You have to rely on your co-workers and I had always the luck to have excellent co-workers.

Talking of the other responsibilities, how have you enjoyed the building of departments as well and the interplay with …

Gerhard Ertl: Yes. Whenever you come into positions that you are at a somewhat advanced level, of course, others ask you for your advice and since you are part of the system, this is also responsible. I served with the German Science Foundation as vice president for a couple of years and I served as a dean of the department in Munich, so there were many different positions I took over and I think this is also part of our duties we have to fulfil.

What are your feelings about the future of German, European science? Are you optimistic about the way things are going?

Gerhard Ertl: I think the research going on in Europe is not of the same quality as the research going on in the United States. Also funding, of course, that would need better funding for research but this is not the main issue. The main problem of our universities is the structure, the undergraduate training and the structure of the universities. There are many, many students who leave the university after two or three years or so and there is no real challenge for them. They’re just there and of course many professors are a little bit frustrated because they don’t get the support for their teaching which would be necessary. This is something which has to be reformed, quite obviously.

Are you saying that the students are using the universities as a sort of finishing school but not getting anything?

Gerhard Ertl: Yes, yes.

What’s wrong with the structure? Why is that happening, do you think?

Gerhard Ertl: We don’t have any tuition fees in our German system so there are many students, after finishing high school, that really don’t know what to do, so they enter university and they start with some subject and then they do something else. Then eventually they find a job and then they leave again, so yes, there is no real challenge for them to really study a certain subject and bring it to an end.

Right, and tuition fees would add that driving force?

Gerhard Ertl: Yes, of course. As soon as you have to pay something … If you don’t pay for something it’s not worthwhile. We have a long standing debate on this issue in our country at the moment and some parts of Germany now have introduced small tuition fees and I think that will help.

I suppose it must be very important for Germany that they had two new Nobel Laureates this year. Indeed, when I phoned you immediately after the announcement for the telephone interview, I was getting in the way, you were waiting for a call from Angela Merkel.

Gerhard Ertl: That’s right.. She called me the same evening.

Oh, she did? She did.

Gerhard Ertl: I know her personally so I was very happy that she called me in the evening.

That’s nice. But presumably there is perhaps now a pressure to take part in further planning for the future of German science, as a Nobel Laureate?

Gerhard Ertl: So far, I was not approached directly in this respect but, as I told you, I was for many years vice president of the German Science Foundation. I was always involved in the planning of the research funding in Germany so I am familiar with the attempts to improve the situation for German research and I’m sure that I will also be approached in the future again.

On the subject of being a Laureate, how are you finding it? How have you found the last couple of months since the announcement?

Gerhard Ertl: Hectic and chaotic, so it still needs some time for me to really recover from the announcement, I must say, because now many, many people approach you and want answers to questions you never had thought before and on quite different things.

I can imagine, yes.

Gerhard Ertl: And you must be very careful with your answers because they can be used and brought to /- – -/ and then they are completely turned around. An experience which I never had before.

The economics Laureate, von Hayek, in his banquet speech said that, in economics, not in the physical sciences but in economics, he thought that Laureates should take a vow not to speak about anything beyond their competence.

Gerhard Ertl: Of course, but that’s not so easy.

Exactly, if people ask you the questions, yes.

Gerhard Ertl: I got a call from China from a journalist – what shall we do to get Nobel Prizes in China? What do you answer?

What did you answer?

Gerhard Ertl: Don’t copy, that was my answer.

Hopefully they were satisfied.

Gerhard Ertl: I’m not so sure.

Do you have any intentions of how to use the status of being Nobel Laureate in the future or is it too early to say?

Gerhard Ertl: I still have to recover from all these hectic weeks now, so after Christmas, I will retreat into my resort and stay there for a week or so and just think over the whole situation.

Thank you very much indeed and I wish you an extremely enjoyable Nobel week.

Gerhard Ertl: Thank you very much.

Did you find any typos in this text? We would appreciate your assistance in identifying any errors and to let us know. Thank you for taking the time to report the errors by sending us an e-mail.