Abstract: A process for reducing the oxides of nitrogen in exhaust gases from an internal combustion engine comprising contacting the exhaust gases with a self supporting catalytic structure in the form of an expanded thin metal foil. The expanded metal foil comprises a corrosion resistant metallic substrate having an NO.sub.x reducing catalyst on the surface layer. The corrosion resistance substrate may be a nickel/chromium alloy, and the NO.sub.x catalytic surface may be a nickel/copper alloy.