NITRIC-OXIDE ADSORPTION AND DECOMPOSITION ON THE (111) AND (110) SURFACES OF IRIDIUM

Ultraviolet and X-ray photoelectron spectroscopies, UPS and XPS, have been used to study the adsorption states of NO on the Ir(111) and Ir(110) surfaces. Two states of approximately equal population are found on Ir(111), whereas one state predominates on Ir(110). The predominant state on Ir(110) decomposes thermally at a significantly higher temperature than the two states on Ir(111). Steady-state NO decomposition studies demonstrate that Ir is a better decomposition catalyst than a reduction catalyst, and the presence of CO is required to prevent poisoning by a surface oxide. The formation of a surface oxide of low chemical reactivity begins at a significantly lower temperature with NO as the oxidizing agent than with O2. © 1979.