Plutonium hydride

Plutonium hydride is a non-stoichiometric chemical compound with the formula PuH$2+x$. It is one of two characterized hydrides of plutonium; the other is PuH$3$. PuH$2+x$ is non-stoichiometric with a composition range of PuH$2$ – PuH$2.7$. Metastable stoichiometries with an excess of hydrogen (PuH$2.7$ – PuH$3$) can also be formed. PuH$2$ has a cubic structure. It is readily formed from the elements at 1 atmosphere at 100–200°C: When the stoichiometry is close to PuH$2$ it has a silver appearance, but gets blacker as the hydrogen content increases, additionally the color change is associated with a reduction in conductivity.


 * Pu + H$2$ → PuH$2$

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 Pu$2$O$3$, PuO$2$ and a higher oxide identified by X-ray diffraction and X-ray photoelectron spectroscopy as the mixed-valence phase Pu$IV$$3−x$Pu$VI$$x$O$6+x$. Investigation of the reaction performed without heating suggests that the reaction of Pu metal and moist air the production of PuO$2$ and a higher oxide along with adsorbed hydrogen, which catalytically combines with O$2$ to form water.

Like the free metal, plutonium dihydride is pyrophoric. On the surface of hydrided plutonium, it acts as a catalyst for the oxidation of the metal with consumption of both O$2$ and N$2$ from air.