Caesium peroxide or cesium peroxide is an inorganic compound of caesium and oxygen with the chemical formula . 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 ðC, the compound will decompose to caesium monoxide and atomic oxygen:
Caesium peroxide shows a Raman vibration at 743 cm<sup>âÂÂ1</sup>, due to the presence of the peroxide ions. The compound is often used as a coating for photocathodes, due to its low work function.