Electrochemical promotion of bimetallic RhAg/YSZ catalysts for the reduction of NO under lean burn conditions

Abstract

At positive overpotentials, RhAg bimetallic electrodes interfaced with yttria-stabilised zirconia (YSZ) exhibit strong electrochemical promotion in the catalytic reduction of NO by propene, even in the presence of a large excess of gaseous oxygen. Compared with the unpromoted system, at positive overpotentials, the N 2 production rate can be accelerated by a factor of eight: this is the key figure of merit. In addition the N 2 selectivity improves from 28 to 55%. The effect on reaction rates is strongly non-faradaic and persists to a significant degree in the absence of applied potential. At negative overpotentials the nitrogen-containing products exhibit faradaic behaviour, possibly reflecting self-poisoning of the system due to excessive adsorption of oxygen. The overall performance of the RhAg/YSZ bimetallic system is substantially better than that of Rh/YSZ, suggesting that the former are promising candidates for use in novel approaches to NO x reduction under fuel lean conditions.