Surface reactivity trends

This is in principle all we need to understand chemical bonding on surfaces and trends in reactivity. For a more accurate description of molecular orbital theory we refer to P.W. Atkins, Molecular Quantum Mechanics (1983), Oxford University Press, Oxford. The main results from molecular orbital theory are summarized in Fig. 6.8 below. 

By combining the results of the Newns-Andersons model and the considerations from the tight binding model it is now possible to explain a number of trends in surface reactivity. This has been done extensively by Norskov and coworkers and for a thorough review of this work we refer to B. Hammer and J.K. Norskov, Adv. Catal. 45 (2000) 71. We will discuss the adsorption of atoms and molecules in separate sections. 

Such calculations have also been performed for isolated impurities of late transition metals alloyed into the surface of other transition metals, and the trends are the same. The accuracy of the numbers in Fig. 6.33 is limited since many approximations had to be made to calculate them. Nevertheless, they reflect trends very well and give useful insight into reactivity trends that have actually been measured for a number of pseudomorfic overlayers [J.A. Rodriquez and D.W. Goodman, Science 257 (1992) 897]. 

Are there fields other than catalysis where trends in surface reactivity may be of value ... 

Nalewajski, R. F. and A. Michalak. 1998. Charge sensitivity/bond-order analysis of reactivity trends in allyl-[Mo03] chemisorption systems A comparison between (010)- and (100)-surfaces. J. Phys. Chem. A 102 636-640. 

General Trends in Metal Complex/Surface Reactivity, and Further Requirements for Metal-Supported Catalyst Preparation... 

Because of our ignorance about the stoichiometries of surface complexes, comparisons between dissolved complexes and surfaces work only at the scale of reactivity trends and then only in tightly constrained conditions. One could use the relative dissociation rates of (H20)4Cr( X-0H)2Cr(0H2)4] (aq) and (en)(H20)2Cr( i-0H)2Cr(H20)2(en) (aq) complexes, for example, to gauge the effect that coordination of two -NH2 ligands to a metal site has on the dissolution rates of a Cr(0H)3(s) mineral if amine ligands could be induced to adsorb in a structurally simple manner (11,12). 

Reactivity Trends for Dissociation of Oligomers. Rules useful for assigning reactivities to oxygens in dissolved multimers that may apply to surfaces include ... 

Most of the theoretical methods used to correlate chemical reactivity trends implicitly (or in some cases explicitly) use a model of interacting diabatic surfaces in which the transition structure is associated with an avoided crossing of a reactant-like or a product-like diabatic surface. In the molecular-orbital correlation diagram approach of Woodward and Hoffmann or the frontier orbital method of Fukui, the molecular orbitals of the fragments are first mixed to form the MO of the supermolecule and then the electrons are assigned to various configurations of these supermolecule MO. We shall refer... 

Skoplyak O, Menning CA, Barteau MA, Chen JG (2007) Experimental and theoretieal study of reactivity trends for methanol on Co/Pt(l 11) and Ni/Pt(l 11) bimetallic surfaces. J Chem Phys... 

This overall trend of TMNs in structure and physical properties is also consistent with the observation that these interstitial compounds exhibit surface reactivity and catalytic properties resembling those of noble metals, although the difference between carbides and nitrides is not always clear. The bonding in TMNs can be described as a mixture of metallic, covalent, and ionic components like TMCs. 

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