Advancements in the local reaction center electron transfer theory and the transition state structure in the first step of oxygen reduction over platinum

This paper demonstrates the importance of calculating both the reduction and oxidation electrode potential-dependent activation energy curves, E-a(U), and then evaluating the respective derived E-a(U) curves from them when using constrained variation theory for electron transfer to a local reaction center, an approach developed in this lab. A structure parameter averaging is introduced for calculating improved results if the calculated and derived results are not in satisfactory agreement. This averaging technique is used to improve upon a previous study of the first step of O-2 reduction to hydrogen peroxide or water when bonded to platinum and to show the role that twisting of Pt-O-O-H+ can play by increasing its electron affinity and lowering the activation energy. By the same token, oxidation of peroxide proceeds with a higher barrier when the molecule is allowed to be twisted, which is its stable structure. (c) 2005 Elsevier B.V. All rights reserved.