Selective oxidation of ammonia over Ir(1 1 0)

The interaction of NH3 with Ir(1 1 0) and the NH3–O2 reaction on that surface have been studied in the temperature range from 300 up to 800 K. Decomposition of NH3 at room temperature and combination of N-atoms to form N2 was observed. The products were N2, H2O and N2O. NO was not observed. Inhibition of the reaction by N species seems to exist until a certain temperature (between 550 and 650 K, depending on the NH3/O2 ratio). Above those temperatures the reaction starts as manifested by a sharp decrease in NH3 and O2 pressures and a simultaneous sharp increase in H2O and N2O pressures. N2 seems to follow a somehow independent pattern. Reaction orders with respect to NH3 and O2 were found to have values between 0.36 and 0.54.