VOLUME 104, NUMBER 14, APRIL 13, 2000
© Copyright 2000 by the American Chemical Society
Gabor A. Somorjai†
Biography This issue of The Journal of Physical Chemistry is dedicated to Gabor A. Somorjai on the occasion of his 65th birthday. This collection of articles has been contributed by many of Gabor’s students, postdoctoral associates, collaborators, colleagues, and friends in recognition of his contributions to the development of the field of surface science and in honor of his scientific accomplishments over the past forty years. The articles collected here are indicative of the broad range of scientific interests, and the enthusiasm for surface science and the field of chemistry, that Gabor has exhibited and instilled in his colleagues and coworkers over these years. It is our pleasure to dedicate these articles to him in his honor.
Gabor A. Somorjai was born in Budapest, Hungary on May 4, 1935. He attended primary and secondary school in Budapest, and in 1953 entered the Technical University, Budapest to study chemical engineering. In the fall of 1956, just two months short of finishing his undergraduate work, the Hungarian Revolution began. By November 23, 1956, the Russians had put down the revolution and begun arresting people. Gabor joined the stream of refugees leaving Hungary at this point. He left Hungary, walking across the border to Austria with his sister Marietta and his future wife Judy Kaldor. In Vienna he began the process of trying to emigrate to the U.S. On January 2, 1957, he was †
Part of the special issue “Gabor Somorjai Festschrift”.
10.1021/jp993823n CCC: $19.00 © 2000 American Chemical Society Published on Web 02/25/2000
2938 J. Phys. Chem. B, Vol. 104, No. 14, 2000 sent to the U.S. and processed, along with Judy, at Camp Kilmer in central New Jersey. While at Camp Kilmer Gabor wrote a number of letters to universities in the U.S., inquiring about graduate studies. A rapid response from Charles Tobias and Ken Pitzer at the University of California at Berkeley resulted in Gabor’s entry into the chemistry Ph.D. program, on a probationary status, in February of 1957. Gabor was interested in pursuing research in polymer chemistry or catalysis, neither of which was represented on the Berkeley faculty at that time. In discussions with Richard Powell, an inorganic kineticist who had trained with Henry Eyring, a project was developed which focused on the use of small-angle X-ray scattering to characterize the particle size and size distribution of platinum on alumina catalysts. At that time Professor Powell shared the opinion of many in the university that federal support of academic research would spell the demise of independent research in the university. Thus, Gabor’s thesis project was not heavily funded, and he supported himself by teaching during the next three years while he finished his research. Samples for his research were provided via a collaboration with researchers at Chevron (Standard Oil of California at that time) and presaged Gabor’s strong and continued involvement with the chemical industry in his research work. Gabor finished his degree work by the end of 1959 and took a position with IBM Research, in their solid state materials research group at Poughkeepsie, NY in January of 1960. About a year later, IBM opened its Yorktown Heights facility, where Gabor carried out work on the properties of cadmium sulfide and other luminescent materials. At about this time, low energy electron diffraction using a post-acceleration apparatus was being developed by Germer and McRae at Bell Laboratories, and Gabor saw the power of this approach for investigating solid surfaces on the atomic scale. He persuaded IBM management to purchase the first commercially available low energy electron diffraction (LEED) apparatus from Varian, so that he could begin basic surface science studies on materials of interest to IBM. At this point IBM also promoted Gabor to manager of crystal growth, and he began looking for an academic position where he could more readily pursue his interests in surface chemistry and physics. Gabor accepted an offer of a faculty position in the Chemistry Department at Berkeley in July of 1964, and has been at Berkeley ever since. When he joined the faculty, the Inorganic Materials Research Division of LBL had just been established, and Gabor was offered a position as a Principal Investigator in IMRD. Building 62 was completed “on the hill” shortly after, and Gabor established laboratories there and on campus. His research group has been divided between the campus and the hill throughout his career at Berkeley, providing his students and postdocs the advantages of both the national laboratory infrastructure of LBL and the intellectual (and sometimes political) ferment of the Berkeley campus. This also led to a number of interesting vehicles (buses, bikes, and Cushman trikes) which allowed Gabor to be both places simultaneously (or so it seemed to his students). Gabor Somorjai has made an enormous number of contributions to the development of the molecular foundations of surface science, particularly the surface science of heterogeneous catalysis. While his contributions to the founding of this field are many and varied, three general and crucial lines of research characterize his contributions to this important field, and are indicative of his work and its impact on surface chemistry. The first is Gabor’s recognition that the detailed understanding of surface structure is key to the understanding of heterogeneous
catalysis. The second is his insistence on using characterizable model systems to probe the important questions of catalysis, under conditions that are appropriate to catalytic practice. The third is Gabor’s ability and success at developing the infrastructure of tools and methods which allow microscopic information about surface reaction processes to be obtained. Gabor’s first important contributions to the emerging field of surface chemistry were his studies in the middle 1960s which showed that the clean surface of the Pt(100) single crystal exhibited a reconstruction. This clean surface reconstruction was very controversial at the time, most researchers assuming that a clean metal surface should exhibit a structure which is just the termination of the bulk structure. His was the first work to propose and demonstrate this possibility of reconstruction, and subsequently many other systems have been found which exhibit complex reconstructions. In fact, clean surface reconstructions are no longer surprising, but rather expected. This work relied on the use of LEED, a method whose promise Gabor was early in recognizing, and one which Gabor was has been key in developing. In the early years of the development of LEED, when many were abandoning it as impractical for detailed structural analysis, Gabor continued pushing experimental and theoretical developments which make it the accepted form of surface structural analysis today. During this developmental period, Somorjai and co-workers investigated many important systems, applying the method to more and more complex and interesting surfaces. The first studies of adsorption on stepped surfaces, the first use of LEED to probe vibrational motion of surface atoms, the first study of organic monolayers by LEED, the first study of surface melting and freezing using LEED, the first surface structural studies of molecular crystals, the first structural characterization of an adsorbed organic molecule by LEED, the first report of adsorbate-induced surface restructuring, and the first structural characterization of an oxide film grown on a foreign substrate by LEED all resulted from Gabor’s insistence on the primacy of structure in developing an understanding of surface chemical reactions. This insistence on structural information continues in his present work, where he is using other methods in addition to LEED. Of most specific interest is his recent use of scanning tunneling microscopy (STM) to probe the structure of surfaces, including adsorbate-induced restructuring of surfaces. Gabor has also been recently active in the use of sum frequency generation (SFG) methods for probing molecular structure at surfaces in a high pressure environment. In addition to this emphasis on surface structure, Gabor’s work has been characterized by his novel use of model systems to probe heterogeneous catalytic processes. His early use of single-crystal metal substrates for studies of chemisorption and reactions pioneered this approach, providing much of the first atomic level information available about heterogeneous reactions. His contributions in this area are illustrated by two key studies in the 70s. The first compared the reactivity of low index and stepped platinum surfaces for the adsorption and decomposition of simple small molecules. The second study used molecular beam scattering methods to directly show that steps on the platinum surface are essential for the dissociation of hydrogen, a key process in many heterogeneous catalytic reactions. This work was followed up with several other studies of the hydrogen dissociation reaction, detailing the mechanism and dynamics of this process on the stepped platinum surface. These studies, directly showing the importance of steps and kinks in the reactivity of catalytically important metal surfaces,
J. Phys. Chem. B, Vol. 104, No. 14, 2000 2939 have stimulated many further studies, both in Gabor’s laboratory and in many others around the world. At about this time, Gabor and his group also pioneered the use of model single crystal catalysts operating at high pressure to investigate the kinetics and mechanisms of heterogeneous reactions. His development of a high pressure catalytic reactor which could be isolated from the ultrahigh vacuum (UHV) electron spectroscopic chamber, allowed the use of standard UHV electron spectroscopic probes for characterizing the single crystal catalyst surface. The characterized surface could then be exposed to high pressure gas phase reactants, and the products of the reaction monitored gas chromatographically. This approach couples the investigation of the atmospheric pressure kinetics of catalytic reactions with the structural and compositional characterization of the catalyst surface before and after reaction. This pioneering approach again provided much of the first atomic level information about the connection between surface structure and surface reaction kinetics, and has been extensively used by many other groups. This high pressurelow pressure method was first applied by the Somorjai group to many important catalytic systems, ranging from the ammonia synthesis reaction to detailed studies of hydrocarbon conversion reactions over platinum. Somorjai’s emphasis on model systems is also well illustrated by his studies of coadsorption effects in surface reactions of catalytic interest. Studies of the coadsorption of potassium with CO on the platinum surface illustrated the effect of coadsorbates on binding site and adsorption energy. The effects of atomic adsorption on the restructuring of the metallic substrate and the consequences of this restructuring for surface bond breaking and catalysis were first identified in his work. Similarly, the first evidence that organic molecular adsorbates could cause extensive restructuring of the metallic substrate was also obtained by Gabor and co-workers. The implications of this sort of restructuring on the mechanism of heterogeneous catalytic processes cannot be overstated. The entire concept of the active site as a “template” for a surface reaction process is modified by these observations. This adsorption-induced restructuring is much more like enzymatic catalytic action, where the enzyme accommodates the reaction substrate, than the common view of the reactive site in heterogeneous catalysis. Emphasis on the study of reactivity of model systems continues in Gabor’s group, with recent studies of catalysis on ordered arrays of nanoclusters fabricated by electron beam lithography, as well as the use of STM to probe surface restructuring and its effect on reaction. The third thread of contribution to the development of the surface science of heterogeneous catalysis from Gabor’s work is his continuing development of the tools that are needed to provide the atomic level understanding of surface processes. Several of these important developments have already been mentioned. Gabor’s insistence on structural characterization of the surface has led to many advances in the theory and experimental practice of LEED. Early advances included photographic LEED data collection and densitometer analysis, real time video data collection, and sensitive diffraction optics based on position-sensitive detector technology. All of these experimental advances moved forward simultaneously with theoretical developments for the determination of surface structure, many of which also came from the Somorjai laboratory. The high pressure catalytic reactor coupled with a UHV electron spectroscopic system has been mentioned. This approach has also been successfully adapted to the use of STM surface characterization, as well as the use of optical probes of surface processes such as sum frequency generation. In addition,
Gabor’s group was the first to use radiotracer methods to determine absolute hydrocarbon coverages for the examination of surface reaction kinetics on single-crystal surfaces. He also developed methods for preparing characterizable oxide thin films for surface studies, an approach which is widely used in other laboratories as well. In all of this work, Gabor’s very effective approach has been to create the tools which have been needed to obtain the atomic level information required. Too often in surface science, because of the cost and difficulty of experiments, a researcher will become “attached” to a particular method. One of the hallmarks of Gabor’s work is to use what methods are best to provide the important atomic level information, and to invent the needed methods if the best is not already available. Recently Gabor has revisited his early interest in polymer chemistry by initiating molecular studies of the surface properties of polymeric materials. By combining SFG methods with the atomic force microscope, Gabor has examined the polymer surface structure and its unique chemical and mechanical properties. Molecular understanding of polymer surface properties such as biocompatibility, wear, and lubrication, as well as the science of polymerization catalysis form a current focus of research in Gabor’s laboratory. In addition to his long-standing interest in catalysis, Gabor has pioneered the application of the tools and thinking of surface chemistry to the fields of tribology, electrochemistry, and biological materials. Comments must also be made about Gabor’s other, and really overarching, contribution to the development of the field of surface chemistry. That is his contribution as teacher and effective spokesman for the field. Over the past thirty-five years he has trained more than ninety graduate students and more than one hundred postdoctoral associates. These students and research associates have had an enormous impact on the practice of this science and its development as a research field. Many have gone on to develop active research programs investigating the atomic level mechanisms of heterogeneous catalysis, corrosion, wear and lubrication, electronic device processing, and sensor development. A selection of this range of research is reflected in the articles which make up this special issue. Gabor’s unflagging enthusiasm for his science, his devotion to his students, and his ability to clearly express his ideas in the literature and in lectures around the world have really identified the field of surface chemistry with him. Gabor Somorjai has published over 750 articles and reviews concerning surface science, heterogeneous catalysis, and solidstate chemistry. He has authored three textbooks, starting with Principles of Surface Chemistry published in 1972, Chemistry in Two Dimensions: Surfaces in 1981, and Introduction to Surface Chemistry and Catalysis, which was published in 1994. All three textbooks have been widely used by generations of surface science students and are indispensable references used by those practicing in the field. Gabor’s professional contributions outside of the laboratory are also enormous, both as a spokesman for the field of surface chemistry and catalysis and as an advocate for international scientific interactions. He serves on the editorial boards of fourteen journals in surface science, catalysis, and physical chemistry, and is Co-Editor in Chief of Catalysis Letters. Honorary degrees from five universities, including his undergraduate alma mater, the Technical University of Budapest, head his extensive list of honors and awards. Included among these honors are the Wolf Prize in Chemistry, the Von Hippel Award of the MRS, the Adamson, Debye, and Colloid and Surface Chemistry Awards of the ACS, Senior Distinguished
2940 J. Phys. Chem. B, Vol. 104, No. 14, 2000 Scientist Award of the Alexander von Humboldt Foundation, the Henry Albert Palladium Medal, and the ACS 2000 Award for Creative Research in Catalysis. Gabor is a member of the National Academy of Sciences, a Fellow of AAAS, and an Honorary Member of the Hungarian Academy of Sciences. These awards and honors are just a reflection of the considerable contribution his career has been to the establishment and growth of the field of surface chemistry, and its contribution to the study and practice of chemistry in general. It has been a great honor for us to be counted among the students and colleagues of Gabor Somorjai. His influence on our own scientific ideas, his constant interest in our work and in our careers, and his infectious enthusiasm for surface science have made our lives and those of his many colleagues
considerably brighter. It is with great pleasure that we dedicate this special issue of The Journal of Physical Chemistry to Gabor A. Somorjai on the occasion of his 65th birthday. Steven J. Baldelli Lawrence Berkeley National Laboratory Steven L. Bernasek Princeton University Peter C. Stair Northwestern University Francisco Zaera University of California, Riverside Guest Editors
