Mathematical modeling of electrochemical promotion and of metal-support interactions

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