Gas hydrates are crystalline solids consisting of gas molecules trapped within a water lattice. They are stable under conditions of high pressure and low temperature, and can be found in marine sediments and permafrost. Gas hydrates have the potential to be an important energy resource, as they can store large amounts of methane gas. However, exploitation of gas hydrates is challenging due to the difficult conditions under which they occur.
Gas hydrates were first discovered in the late 18th century by Swiss naturalist Horace-Benedict de Saussure. However, it was not until the mid-20th century that their structure was elucidated by American chemist Irving Langmuir. Gas hydrates occur naturally in a variety of environments, including marine sediments, permafrost, and even in some laboratory settings.
Under normal conditions, methane is a gas at ambient temperature and pressure. However, when methane comes into contact with water at high pressures and low temperatures, it can become trapped within a water lattice to form a gas hydrate. The resulting solid is known as a clathrate hydrate or cage hydrate. The structure of methane clathrates consists of a framework of water molecules with methane molecules occupying the cavities within this framework (Figure 1).