Estudio teórico de la reactividad de sistemas electroquímicos en función del potencial aplicado

Abstract

In the present work, a methodology is proposed to explain the difference in chemical reactivity of three metal oxide surfaces that are used in wastewater treatment as electrodes in the advanced electrochemical oxidation which consists in the generation of • OH to oxidize organic compounds in aqueous solution. The systems were three surfaces: SnO 2 , IrO 2 and PbO 2 , which were studied using the joint density functional theory in the grand canonical ensemble, employing CANDLE as the implicit solvation model and in the presence of two types of adsorbates: two water molecules and one OH molecule.When applying chemical potential, each system presented a different behavior in the variation of the average number of electrons and in the density of states. The chemical reactivity indexes that were evaluated were the global and local softness, obtaining that the softest system is the IrO 2 surface. In addition, using the methodology developed in this work, it was proposed the evaluation of another reactivity index that is related to the reduction potential of an electrochemical specie, this allowed the ordering of the systems on a potential scale that can be compared with experimental results since the values of the potential are referred to the standard hydrogen electrode.The effect of optimizing the ionic positions at applied chemical potential was evaluated for one of the systems, finding that it impacts the average number of electrons. Finally, for the systems with an OH molecule adsorbed, the grand adsorption energy was calculated as a function of the cehmical potential and it was found that it follows the trend IrO 2 > SnO 2 > PbO 2 , which is consistent with experimental results.