Молибден (IV) оксид

Химические свойства

Lead-gray, nonvolatile powder. Dapproximately 6.4. Insoluble in hydrochloric acidand hydrogen fluoride and alkalies, sparingly solu-ble in sulfuric acid.

Физические свойства

Molybdenum(IV) oxide can be prepared by several methods including controlled oxidation of Mo and controlled reduction of MoO3 with hydrogen. The pure oxide suitable for structure determination has been prepared by electrolysis of a polymolybdate (K2O5.MoO3) solution. Molybdenum(IV) oxide is insoluble in water: it is inert in solutions of nonoxidizing acids or bases, but is dissolved by oxidizing solutions. It dissociates to Mo and MoO3 at high temperatures (~ 1100°).
Crystalline MoO2 is violet or brown. Its deformed rutile structure consists of infinite chains of MoO6 octahedra sharing opposite edges along the chain direction with Mo-Mo distances alternately long (3.10 A) and short (2.50 A). It is diamagnetic and semiconducting ; metal-metal bonds are present. Some of its thermodynamic properties are as follows: G°f29% ~ 172.415 kcal/mole H°f29% -140.5 kcal/mole S°298 11.954 gibbs/mole.

Использование

Molybdenum(IV) oxide (MoO2) is a transition metal oxide with good electrical conductivity due to the presence of delocalized electrons in its valence band. It is traditionally prepared by reducing MoO3 in dry hydrogen in the temperature range of 450-550°C.
MoO2 can be used in a variety of energy based applications such as an anode material in rechargeable lithium batteries and fuel flexible solid oxide fuel cells.It can also be used as a catalyst in hydrogen reforming processes.

Подготовка

Molybdenum(IV) oxide is obtained by passing steam over red hot molybdenum:
Mo + 2H2O → MoO2 + 2H2
Alternatively, the oxide may be prepared by heating a molybdate salt, such as ammonium molybdate, with a reducing agent such as zinc. The dioxide also may be obtained along with other oxides of molybdenum when molybdenum metal is heated in air.
A brown-black suspension of MoO2 in hydrate form may be obtained by reducing a solution of ammonium molybdate with hydrogen in the presence of colloidal palladium.

Общее описание

Molybdenum(IV) oxide (MoO₂) is a transition metal oxide with good electrical conductivity due to the presence of delocalized electrons in its valence band. It is traditionally prepared by reducing MoO₃ in dry hydrogen in the temperature range of 450-550°C.

Опасность

Toxic material.

Профиль безопасности

Poison by subcutaneous route. Incandescent reaction with air. When heated to decomposition it emits toxic fumes of Mo.