Plutonium hydride

Plutonium hydride is a non-stoichiometric chemical compound with the formula PuH_2+x. It is one of two characterised hydrides of plutonium, the other is PuH₃. PuH₂ is non-stoichiometric with a composition range of PuH₂ – PuH_2.7. Additionally metastable stoichiometries with an excess of hydrogen (PuH_2.7 – PuH₃) can be formed. PuH₂ has a cubic structure. It is readily formed from the elements at 1 atmosphere at 100–200 °C: When the stoichiometry is close to PuH₂ it has a silver appearance, but gets blacker as the hydrogen content increases, additionally the color change is associated with a reduction in conductivity.

Studies of the reaction of plutonium metal with moist air at 200–350 °C showed the presence of cubic plutonium hydride on the surface along with Pu₂O₃, PuO₂ and a higher oxide identified by X-ray diffraction and X-ray photoelectron spectroscopy as the mixed-valence phase Pu^IV_3−xPu^VI_xO_6+x. Investigation of the reaction performed without heating suggests that the reaction of Pu metal and moist air the production of PuO₂ and a higher oxide along with adsorbed hydrogen, which catalytically combines with O₂ to form water.

Plutonium dihydride on the surface of hydrided plutonium acts as a catalyst for the oxidation of the metal with consumption of both O₂ and N₂ from air.