Mathematical Modeling of Electrochemical Promotion and of Metal−Support Interactions

Abstract

A surface diffusion−reaction model is developed and solved to describe the effect of electrochemical promotion (also known as non-Faradaic electrochemical modification of catalytic activity, NEMCA effect) on porous conductive catalyst films on solid electrolyte supports. The model accounts for the migration (backspillover) of promoting anionic, Oδ-, species from the solid electrolyte onto the catalyst surface. The same type of model is then applied to describe the effect of metal−support interactions for the case of finely dispersed metal nanoparticles on ZrO2- and TiO2-based porous supports where the same type of Oδ- backspillover mechanism has recently been shown to be operative. Two basic dimensionless numbers are obtained that dictate the maximum allowable thickness of electrochemically promoted catalysts, or the maximum crystallite size in dispersed supported metal catalysts, to fully utilize the promoting species.