Kinetic interpretation of catalytic activity patterns based on theoretical chemical descriptors

We introduce descriptors of bond energies, calculated at the DFT level for bulk crystalline structures. We show the relevance of these descriptors for surface bonds, insofar as they are well correlated with experimental heats of adsorption. Based on these correlations, and combining adapted Bronsted-Evans-Polanyi free energy relationships and simple Langmuir-Hinshelwood rate expressions, we show that the trends in experimental activity patterns across the periodic table can be explained by a single variable, the relevant bond energy descriptor. We obtain volcano curves with strong maxima, at bond energies that indicate optimal chemical properties. Activities of metallic formulations involving binary alloys in hydrogenation and hydrogenolysis reactions, as well as of ternary sulfides in hydrodesulfurization, are correctly predicted by the metal-carbon or metal-sulfur bond energy descriptors calculated for simple structural models. Our approach therefore provides useful exploratory guidelines. (C) 2003 Elsevier Science (USA). All rights reserved.