Detection of radical species produced by catalytic decomposition of H_2, O_2 and their mixtures on heated Ir surfaces

摘要

Efficient production of H atoms, O atoms and OH radicals was confirmed by laser spectroscopic measurements in the catalytic decomposition of H_2,O_2 and their mixtures on a heated Ir filament No change in electric resistivity was observed when the filament was kept at 2350 K in the presence of 1.0 Pa of pure O_2, showing that oxidation is minor. Arrhenius-type temperature dependences were observed for the densities of H (0) atoms in pure H_2 (O_2) systems. In the H_2/O_2 mixed system, the H-atom density was almost independent of the O_2 partial pressure, although the 0-atom and OH-radical densities increased with the O_2 pressure. These O_2 pressure dependences are completely different from those observed for W. Ir is less poisoned by O_2 compared to W. In addition, direct production of H_2O molecules on Ir surfaces must take place besides the production of radical species.