Caesium superoxide

Caesium superoxide is a chemical compound with the chemical formula CsO2. It consists of caesium cations Cs+ and superoxide anions O2−. It is an orange solid.

Preparation
Burning caesium in excess oxygen will produce caesium superoxide.
 * Cs + O2 → CsO2

Properties
Caesium superoxide's crystal structure is same as calcium carbide. It contains direct oxygen-oxygen bonding.

It reacts with water to form hydrogen peroxide and caesium hydroxide.
 * 2 CsO2 + 2 H2O → O2↑ + H2O2 + 2 CsOH

Heating to approximately 400 °C induces thermal decomposition to caesium peroxide.

The standard enthalpy of formation ΔHf0 of caesium superoxide is −295 kJ/mol.

Caesium superoxide reacts with ozone to form caesium ozonide.
 * CsO2 + O3 → CsO3 + O2