Study of metal oxide catalysts by temperature programmed desorption. 1. Chemisorption of oxygen on nickel oxide

Abstract

The chemisorption of oxygen on nickel oxide was investigated over a wide range of temperature (0-600 °C) by means of the temperature programmed desorption (TPD) technique. At least four different states of adsorbed oxygen were indicated by the appearance of four TPD peaks, with peak maxima located at 30-~40 (a), 320~360 (ß), 420~450 ( ), and 520~550 °C (6), respectively. Taking into account their adsorptive characteristics, the corresponding adsorbed species were tentatively assigned to 02 ( ), 02~(ß), and -( and ). Experimental facts that none of the ß, y, and oxygen retarded the chemisorption of the'others suggested that these chemisorptions took place on different surface sites, while the chemisorption site for a was estimated to be common to ß oxygen. The activation energies of adsorption for ß and y were 12.8 and 17.5 kcal/mol, respectively, and that of desorption for ß was 23 kcal/mol. Adsorbed oxygen in various forms amounted altogether to ca. 3 X 1013 molecules/(cm2 of NiO surface). The corresponding surface coverage was estimated to be ca. 4% with respect to surface nickel atoms, suggesting adsorptions on some sorts of surface defects. Discussions of these results are presented in relation to the oxidation power distribution of the surface excess oxygen, the oxygen isotopic exchange reaction, the binding energy of oxygen, etc.

Modeling CO Oxidation on Silica-Supported Iron Oxide under Transient Conditions

“…By investigating the formation of adsorbed oxygen on Fe 2 O 3 and NiO by temperature-programmed desorption, Iwamoto et al (1976Iwamoto et al ( , 1978a have demonstrated the existence of at least four states of adsorbed oxygen, the maxima of which appeared at 50-300 (R), 350-360 ( ), 480-490 (γ), and >600°C (δ), respectively. γ and δ oxygen were assigned to O -species adsorbed on different surface sites.…”

Charge Polarization at Catalytic Metal–Support Junctions, Part A: Kelvin Probe Force Microscopy Results of Noble Metal Nanoparticles

“…However, in oxygen atmosphere or in air, oxygen molecules may adsorb at the oxide surface and act as low energy traps for excess electrons, including those transferred from the metal particle. This leads to the formation of superoxide radical anions, 24,25 and it provides a possible mechanism for an explanation of the observed p-type behavior and the direction of polarization. The presence of electron donating metals may further support the formation of such species.…”

Carbon monoxide gas sensing properties of Ga-doped ZnO film grown by ion plating with DC arc discharge

“…The temperature of the sample films was controlled at between 230 and 330 • C using a ceramic heater set beneath the sample. These temperatures are slightly higher than the desorption temperatures of oxygen from metal oxide (Iwamoto et al, 1978). The sample chamber was flowed continuously with nitrogen gas at a flow rate of 400 sccm.…”