Air pollution hotspots in Europe

Big cities beset with gridlocked traffic, major regions producing coal, pockets of heavy industry encased by mountains—Europe's air pollution hotspots are clearly visible from space on most sunny weekdays.

Single-atom nanozymes

Nanozymes are catalytic nanomaterials with enzyme-like characteristics that have attracted enormous recent research interest. The catalytic nanomaterials offer unique advantages of low cost, high stability, tunable catalytic ...

Colorful solution to a chemical industry bottleneck

The nanoscale water channels that nature has evolved to rapidly shuttle water molecules into and out of cells could inspire new materials to clean up chemical and pharmaceutical production. KAUST researchers have tailored ...

A superior, low-cost catalyst for water-splitting

In a significant step toward large-scale hydrogen production, researchers at the Indian Institute of Science (IISc) have developed a low-cost catalyst that can speed up the splitting of water to produce hydrogen gas.

A new view of wintertime air pollution

The processes that create ozone pollution in the summer can also trigger the formation of wintertime air pollution, according to a new study from researchers at the University of Colorado Boulder and NOAA, in partnership ...

Transforming waste heat into clean energy

Do you feel the warmth coming off your computer or cell phone? That's wasted energy radiating from the device. With automobiles, it is estimated that 60% of fuel efficiency is lost due to waste heat. Is it possible to capture ...

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Oxide

An oxide ( /ˈɒksaɪd/) is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2.

Most of the Earth's crust consists of solid oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are considered to be pure elements often contain a coating of oxides. For example, aluminium foil has a thin skin of Al2O3 that protects the foil from further corrosion.

Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements—lithium, sodium, potassium, rubidium, caesium, strontium and barium—react rapidly, even dangerously, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, and solutions of potassium and sodium, so called NaK are used to deoxygenate and dehydrate some organic solvents. The surface of most metals consists of oxides and hydroxides in the presence of air. A well known example is aluminium foil, which is coated with a thin film of aluminium oxide that passivates the metal, slowing further corrosion. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising. Although solid magnesium and aluminium react slowly with oxygen at STP, they, like most metals, will burn in air, generating very high temperatures. Finely grained powders of most metals can be dangerously explosive in air. Consequently, they are often used in Solid-fuel rockets.

In dry oxygen, iron readily forms iron(II) oxide, but the formation of the hydrated ferric oxides, Fe2O3−2x(OH)x, that mainly comprise rust, typically requires oxygen and water. The production of free oxygen by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe2O3 in the economically important iron ore hematite.

Due to its electronegativity, oxygen forms chemical bonds with almost all elements to give the corresponding oxides. Noble metals (such as gold or platinum) resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes.

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