Selective oxidation of ammonia over Ir(1 1 0)

Abstract

The interaction of NH 3 with Ir(1 1 0) and the NH 3–O 2 reaction on that surface have been studied in the temperature range from 300 up to 800 K. Decomposition of NH 3 at room temperature and combination of N-atoms to form N 2 was observed. The products were N 2, H 2O and N 2O. 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 NH 3/O 2 ratio). Above those temperatures the reaction starts as manifested by a sharp decrease in NH 3 and O 2 pressures and a simultaneous sharp increase in H 2O and N 2O pressures. N 2 seems to follow a somehow independent pattern. Reaction orders with respect to NH 3 and O 2 were found to have values between 0.36 and 0.54.