Destruction of NO during catalytic combustion on platinum and palladium

Mole fraction profiles of NO are obtained by laser-induced fluorescence in a catalytic combustion environment consisting of a stagnation flow of hydro gen, oxygen, and 150 ppm of NO over platinum and palladium substrates. For both catalysts under a wide range of equivalence ratios, including lean con ditions, diffusion limited destruction of the added NO is observed when cat alytic combustion occurs at the surface. With ignition in the gas-phase and a flow over the platinum surface, negligible NO destruction is observed un der fuel-lean conditions. The profiles are compared with the predictions of a flame model that includes complex gas-phase and surface chemistry. The r esults highlight the need for inclusion of heterogeneous NO removal steps i n surface modeling of catalytic combustion systems.