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Hydrogen atom transfer hydrofunctionalization
Hydrogen atom transfer (HAT) hydrofunctionalization adds a hydrogen atom and a functional group across an alkene, typically via cobalt metal hydride catalysis, giving Markovnikov products.
Hydrogen atom transfer photocatalysis
Hydrogen atom transfer (HAT) photocatalysis is a strategy in organic synthesis that uses light-absorbing catalysts to abstract hydrogen atoms, converting C–H bonds into C–C and C–heteroatom bonds.
Hydrogen atom transfer/nickel catalysis
Hydrogen atom transfer/nickel (HAT/nickel) catalysis is a cross-coupling method in which a HAT catalyst generates carbon radicals from C–H bonds and nickel couples them with aryl or alkyl halides, introduced in 2016 by David MacMillan.
Hydrogen attack
Hydrogen attack is the irreversible deterioration of steel caused by hydrogen at high temperature, where hydrogen reacts with carbon to form methane inside the metal.
Hydrogen blending
Hydrogen blending is the injection of hydrogen into existing natural gas pipeline networks to transport and burn a hydrogen–natural gas mixture, cutting the carbon intensity of delivered gas.
Hydrogen blistering
Hydrogen blistering is hydrogen damage in which absorbed hydrogen forms gas pockets in a metal, raising surface blisters, typically in steels exposed to hydrogen sulfide.
Hydrogen bond
A hydrogen bond is an attractive interaction in which hydrogen attached to an electronegative atom is drawn toward an acceptor, proposed by Latimer and Rodebush in 1920.
Hydrogen bond network
A hydrogen bond network is the connected system of hydrogen bonds linking molecules or ions through a liquid, crystal, or biological structure, with liquid water as the archetype.
Hydrogen breath test
The hydrogen breath test is a non-invasive diagnostic procedure measuring hydrogen and methane in exhaled air after a sugar substrate, detecting carbohydrate malabsorption or small intestinal bacterial overgrowth.
Hydrogen bromide
Hydrogen bromide (HBr) is a colorless, corrosive gas discovered by Antoine Jérôme Balard in 1826 that dissolves in water to form hydrobromic acid, one of the strongest mineral acids.
Hydrogen burning
Hydrogen burning is the set of thermonuclear reactions by which stars convert hydrogen into helium, the dominant energy source for most of a star's life.
Hydrogen chloride
Hydrogen chloride (HCl), also called anhydrous hydrochloric acid, is a colorless, corrosive, nonflammable gas with a pungent odor that dissolves in water to form hydrochloric acid, used in steel pickling.
Hydrogen core network (Germany)
The hydrogen core network (Wasserstoff-Kernnetz) is a Germany-wide long-distance hydrogen pipeline network, approved by the Bundesnetzagentur in October 2024, connecting major hydrogen production, import, and storage locations by 2032.
Hydrogen Council
The Hydrogen Council is a CEO-led global non-profit hydrogen industry alliance founded at Davos in 2017, now uniting about 140 companies from over 20 countries.
Hydrogen crossover
Hydrogen crossover is the undesired transport of hydrogen through the polymer membrane of a PEM water electrolyzer into the oxygen-producing anode, lowering Faradaic efficiency and creating flammable hydrogen-oxygen mixtures.
Hydrogen cyanide
Hydrogen cyanide, also called prussic acid, is a colorless liquid or gas with a bitter almond odor that kills within minutes yet is produced industrially for nylon and gold mining.
Hydrogen detonation
Hydrogen detonation is the supersonic combustion of a hydrogen-air or hydrogen-oxygen mixture, a regime of hydrogen cloud explosion distinct from deflagration and from nuclear hydrogen bombs.
Hydrogen economy
The hydrogen economy is a proposed energy system in which low-emissions hydrogen serves as an energy carrier and industrial feedstock for refining, steel, shipping, and heavy transport.
Hydrogen embrittlement
Hydrogen embrittlement, also called hydrogen cracking, is the loss of ductility or load-bearing capacity in metals caused by atomic hydrogen, producing sudden brittle fracture below yield strength.
Hydrogen Energy Supply Chain
The Hydrogen Energy Supply Chain (HESC) is an Australian-Japanese pilot that produced hydrogen from Latrobe Valley brown coal and shipped it liquefied to Japan in 2022.
Hydrogen Epoch of Reionization Array
The Hydrogen Epoch of Reionization Array, or HERA, is a radio telescope of 14 m dishes in the South African Karoo measuring neutral hydrogen from cosmic dawn.
Hydrogen fluoride
Hydrogen fluoride, also known as fluorane, is a colorless, corrosive compound of hydrogen and fluorine that boils at 19.5 °C and forms hydrofluoric acid in water.
Hydrogen fuel
Hydrogen fuel is hydrogen used as an energy carrier, converted to energy in fuel cells or by combustion, emitting only water at the point of use in a fuel cell.
Hydrogen fuel cell bus
A hydrogen fuel cell bus is a zero-tailpipe-emission bus that generates its electricity onboard from hydrogen, distinguished by refueling in minutes and diesel-comparable range rather than overnight charging.
Hydrogen fueling station
A hydrogen fueling station, also called a hydrogen refueling station (HRS), dispenses hydrogen at high pressure to fuel cell vehicles, ranging from retail pumps to large fleet terminals.
Hydrogen hypothesis
Proposed by William Martin and Miklós Müller in 1998, the Hydrogen hypothesis posits that the eukaryotic cell originated from a metabolic symbiosis. This process involved an archaeal host and a hydrogen-producing alphaproteobacterial symbiont.
Hydrogen internal combustion engine
A hydrogen internal combustion engine is a piston engine that burns hydrogen like gasoline, emitting no carbon dioxide at the point of use, only water vapor and some nitrogen oxides.
Hydrogen internal combustion engine vehicle
A hydrogen internal combustion engine vehicle burns hydrogen instead of gasoline, producing no tailpipe carbon dioxide though still forming nitrogen oxides, and is aimed at heavy-duty trucks, buses, and off-road equipment.
Hydrogen iodide
Hydrogen iodide (HI) is a colorless diatomic gas with an acrid odor that fumes in moist air and dissolves in water to form hydroiodic acid, a strong mineral acid.
Hydrogen ion
The hydrogen ion, also called ionized hydrogen and formally named the hydron, is the positively charged ion of hydrogen, H⁺, which in water exists as hydronium and defines the pH scale.