Caesium peroxide

Caesium peroxide or cesium peroxide is an inorganic compound of caesium and oxygen with the chemical formula Cs₂O₂. It can be formed from caesium metal by adding a stoichiometric amount in ammonia solution, or oxidizing the solid metal directly.

It can also be formed by the thermal decomposition of caesium superoxide:

Upon heating until 650 °C, the compound will decompose to caesium monoxide and atomic oxygen:

Caesium peroxide shows a Raman vibration at 743 cm⁻¹, due to the presence of the peroxide ions. The compound is often used as a coating for photocathodes, due to its low work function.