Tungsten disulfide

Tungsten disulfide is the chemical compound with the formula WS2. It occurs naturally as the rare mineral tungstenite. This material is a component of certain catalysts used for hydrodesulfurization and hydrodenitrification.Bulk WS2 forms dark gray hexagonal crystals with a layered structure. Like the closely related MoS2, it exhibits properties of a dry lubricant. It is chemically fairly inert but is attacked by a mixture of nitric and hydrofluoric acids. When heated in oxygen-containing atmosphere, WS2 converts to tungsten trioxide. When heated in absence of oxygen, WS2 does not melt but decomposes to tungsten and sulfur, but only at 1250 °C.WS2 is produced by a number of methods. Many of these methods involve treating oxides with sources of sulfide or hydrosulfide, supplied as hydrogen sulfide or generated in situ. Other routes entail thermolysis of tungsten(VI) sulfides (e.g., (R4N)2WS4) or the equivalent (e.g., WS3).WS2 is used, in conjunction with other materials, as catalyst for hydrotreating of crude oil.Like MoS2, nanostructured WS2 is actively studied for potential applications, such as storage of hydrogen and lithium. WS2 also catalyses hydrogenation of carbon dioxide: