Potassium superoxide


Potassium superoxide is the inorganic compound with the formula KO2. It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide anion. Potassium superoxide is used as a scrubber, dehumidifier and generator in rebreathers, spacecraft, submarines and spacesuit life support systems.

Production and reactions

Potassium superoxide is produced by burning molten potassium in an atmosphere of oxygen.
The salt consists of and ions, linked by ionic bonding. The O−O distance is 1.28 Å.

Reactivity

Potassium superoxide is a strong oxidant, able to convert oxides into peroxides or molecular oxygen. Hydrolysis gives oxygen gas, hydrogen peroxide and potassium hydroxide:
Potassium hydroxide absorbing carbon dioxide produces carbonates:
Combining these two reactions produces:
Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents, crown ethers are typically used. The tetraethylammonium salt is also known. Representative reactions of these salts involve using superoxide as a nucleophile, e.g., in converting alkyl bromides to alcohols and acyl chlorides to diacyl peroxides.

Applications

The Russian Space Agency has had success using potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. has also been used in canisters for rebreathers for fire fighting and mine rescue work, but had limited use in scuba rebreathers because of its dangerously explosive reaction with water.
Theoretically, 1 kg of absorbs 0.310 kg of while releasing 0.338 kg of. One mole of absorbs 0.5 moles of but only releases 0.75 moles of oxygen gas molecules. The human body will produce fewer molecules than oxygen molecules needed because oxidation of food also needs oxygen to produce water and urea.

Hazards

Potassium superoxide is a potent oxidizer, and can produce explosive reactions when combined with a variety of substances and compounds, including water, acids, organics, or powdered graphite. Even dry superoxide can produce an impact-sensitive explosive compound when combined with organic oils such as kerosene. In 1999 at Oak Ridge National Laboratory, cleanup of potassium oxides from a NaK metal leak produced an impact-sensitive explosion while saturated with mineral oil.