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 hydrogen, oxygen, and 150 ppm of NO over platinum and palladium substrates. For both catalysts under a wide range of equivalence ratios, including lean conditions, diffusion limited destruction of the added NO is observed when catalytic combustion occurs at the surface. With ignition in the gas-phase and a flow over the platinum surface, negligible NO destruction is observed under fuel-lean conditions. The profiles are compared with the predictions of a flame model that includes complex gas-phase and surface chemistry. The results highlight the need for inclusion of heterogeneous NO removal steps in surface modeling of catalytic combustion systems.