The reactivity and auger chemical shift of oxygen adsorbed on platinum

The reaction of carbon monoxide with oxygen chemisorbcd on polycrystalline platinum has been studied using Auger spectroscopy. Two types of chemisorbed oxygen are distinguished on the basis of Auger electron chemical shifts and reactivity towards carbon monoxide. When the substrate is below 800 K, a single very reactive type of chemisorbed oxygen is formed. Above 800 K a new species begins to form which is characterized by an Auger chemical shift of about 6 eV and by low reactivity. The decay of the oxygen Auger signal using several fixed pressures of carbon monoxide was measured. The reaction is first order in carbon monoxide pressure but no clear decision can be made about the order with respect to oxygen coverage. With the reaction $\text{CO +}\text{1}\text{20}{}_2\text{→ CO}{}_2$ operating at steady-state, the oxygen coverage was measured as a function of CO pressure. In the region 363–600 K, the steady state oxygen coverage began to decline measurably when reached 0.1. When p_CO>p_O2the oxygen coverage became immeasurably small. A simple model is used to relate these phenomena to observed carbon dioxide production rates.