Abstract
Some paramagnetic superoxide ions detectable by electron paramagnetic resonance (EPR) can be generated on Au/ZnO catalyst by oxygen adsorption at room temperature as well as at 553
K. In both the cases, the O
2
− ions are present on the catalyst surface. The disappearance of the O
2
− signal by the introduction of carbon monoxide over the catalyst surface implies that the O
2
− ions are either the active oxygen species or the precursors of the active oxygen species. The CO
3
− species produced are also detected by EPR.