Electrochemical promotion of NO reduction by CO and by propene

Abstract

Electrochemical promotion (EP) provides an efficacious means of catalyst promotion. The effects are reversible and the phenomenon provides a uniquely effective and controllable means for in situ tuning of the working catalytic system. EP studies of the catalytic chemistry of NO reduction by CO and by propene over Pt films supported on β″-alumina (a sodium ion conductor) demonstrate that major enhancements in activity are possible when Na is electrochemically pumped to the catalyst surface. Both reactions exhibit strong electrochemical promotion under appropiate conditions of temperature, gas composition and catalyst potential. The data indicate that Na increases the strength of NO chemisorption relative to CO or propene, a process that is accompanied by weakening of the N-O bond, thus facilitating NO dissociation, thought to be the reaction initiating step. The overall kinetic behaviour and the selectivity towards N 2 formation on catalyst potential are in agreement with this hypothesis. XP spectroscopy data confirm that the mode of operation of the electrochemically promoted Pt film does indeed involve reversible pumping of Na to or from the solid electrolyte.