Theoretical study on the first step of oxygen reaction reduction

NOELIA LUQUE; PETER HINDELANG; PAOLA QUAINO; WOLFGANG SCHMICKLER

Alicante

Congreso; Electrocatalysis: present and future and ELCAT meeting; 2011

ELCAT

Oxygen reduction and its reverse reaction, oxygen evolution, are amongst the most important electrochemical reactions. They are also of great practical importance. Indeed, the most pressing problem of fuel cell technology is to find a better catalyst for oxygen reduction, since the slow speed with which this reaction proceeds even on good catalysts like platinum greatly reduces their efficiency; and in spite of much theoretical work, the role of the first and rate-determining step, which is the transfer of an electron to the molecule, is not understood.In this context, our present work is oriented to investigate the first step of the reaction by density functional calculations and the theory of electrocatalysis developed in our own group. The theory, which has to be adapted to this case, presents a unified model for electrochemical electron transfer reactions which explicitly accounts for the electronic structure of the electrode and provides a framework describing the whole course of bond-breaking electron transfer, which explains catalytic effects caused by the presence of surface d-bands.As a starting point, we centered our studies in the following reaction O2+e- = O2-, which is suspected to be the rate determining step for some number of electrode materials. In our case, the reaction was explore on Au(100) surface and since the product is an adsorbed ion interacting strongly with the adjacent water, the adsorption phenomena was investigated in the presence of water molecules. In particular, we try to determine both the free energy and the energy of activation of this first step, the role of the solvent, and the binding of the product to the substrate.