Reaction of oxygen at lithium oxide surfaces

Abstract

The uptake of oxygen by lithium oxide has been studied from 0 to 450°C. Results are reported for Li₂O outgassed at 450 and at 700°C respectively. In both cases the temperature dependence of the uptake of oxygen gas is similar, with a marked acceleration of the uptake above ∼200°. It is proposed that below 200° the reaction is limited to chemisorption, but that above this temperature oxygen is able to diffuse into the bulk of the oxide, being incorporated as peroxide ions.

Experiments with nitrous oxide have also been made. It is shown that N₂O does not react with Li₂O below ∼200°, but above this temperature it decomposes to yield nitrogen, the oxygen produced being retained by the solid. The rate of uptake of oxygen in this reaction compares closely with that observed when oxygen gas is used as oxidant. It is concluded that the uptake in both cases is limited by the same solid-state process. The results have a bearing on the use of lithium-doped oxides in chemisorption and catalysis. They establish the behaviour to be expected towards oxygen when Li₂O is incompletely dissolved.