Density functional theory in surface chemistry and catalysis

Abstract

Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future challenges. S urface chemistry is interesting and challenging for several reasons. It takes place at the border between the solid state and the liquid or gas phase and can be viewed as a meeting place between condensed-matter physics and chemistry. The phenomena at the solid-gas or solid-liquid interface are complicated for this reason. A chemical reaction at a metal surface, for instance, has all of the complexity of ordinary gas-phase reactions, but in addition the usual electron conservation rules do not apply because the metal provides a semi-infinite source of electrons at the Fermi level. A new set of concepts therefore needs to be developed to describe surface chemistry.An understanding of surface chemical reactions is necessary to describe a large number of surface phenomena including semiconductor processing, corrosion, electrochemistry, and heterogeneous catalysis. Heterogeneous catalysis alone has been estimated to be a prerequisite for more than 20% of all production in the industrial world (1), and it will most likely gain further importance in the years to come. The development of sustainable energy solutions represents one of the most important scientific and technical challenges of our time, and heterogeneous catalysis is at the heart of the problem. Most sustainable energy systems rely on the energy influx from the sun. Sunlight is diffuse and intermittent, and it is therefore essential to be able to store the energy, for example chemically as a fuel or in a battery. Such storage can then provide energy for the transportation sector and in decentralized applications, as it evens out temporal variations (2, 3). The key to providing an efficient transformation of energy to a chemical form or from one chemical form into another is the availability of suitable catalysts. In essentially all possible sustainable energy technologies, the lack of efficient and economically viable catalysts is a primary factor limiting their use (3, 4).In the present paper, we will discuss the status of the development of an understanding of surface chemistry. We will do this from a theoretical perspective, but it is important to stress that it is a close coupling between theory and experiment which has enabled the developments thus far. Surface science experiments have been invaluable in providing a quantitative description of a range of surface phenomena (5-14). This has been essential in benchmarking computational surface science based on density functional theory (DFT) calculations and in providing experimental guidance and verification of the concepts developed. This forms a good background for the development of an understanding of heterogeneous catalysis, which is the other part of this paper. We will show how the concepts dev...

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