Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned.
Lavoisier produced hydrogen for his experiments on mass conservation by reacting a flux of steam with metallic
iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
through an incandescent iron tube heated in a fire. Anaerobic oxidation of iron by the protons of water at high temperature can be schematically represented by the set of following reactions:
:1)
:2)
:3)
Many metals such as
zirconium undergo a similar reaction with water leading to the production of hydrogen.
Hydrogen was
liquefied for the first time by
James Dewar in 1898 by using
regenerative cooling and his invention, the
vacuum flask
A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings. Invented by Sir James Dewa ...
.
He produced
solid hydrogen the next year.
Deuterium was discovered in December 1931 by
Harold Urey, and
tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of ...
was prepared in 1934 by
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics.
''Encyclopædia Britannica'' considers him to be the greatest ...
,
Mark Oliphant, and
Paul Harteck
Paul Karl Maria Harteck (20 July 190222 January 1985) was an Austrian physical chemist. In 1945 under Operation Epsilon in "the big sweep" throughout Germany, Harteck was arrested by the allied British and American Armed Forces for suspicion of ...
.
Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932.
François Isaac de Rivaz built the first
de Rivaz engine The de Rivaz engine was a pioneering reciprocating engine designed and developed from 1804 by the Franco-Swiss inventor Isaac de Rivaz. The engine has a claim to be the world's first internal combustion engine and contained some features of modern ...
, an internal combustion engine powered by a mixture of hydrogen and oxygen in 1806.
Edward Daniel Clarke invented the hydrogen gas blowpipe in 1819. The
Döbereiner's lamp and
limelight were invented in 1823.
The first hydrogen-filled
balloon was invented by
Jacques Charles
Jacques Alexandre César Charles (November 12, 1746 – April 7, 1823) was a French inventor, scientist, mathematician, and balloonist.
Charles wrote almost nothing about mathematics, and most of what has been credited to him was due to mistaking ...
in 1783.
Hydrogen provided the lift for the first reliable form of air-travel following the 1852 invention of the first hydrogen-lifted airship by
Henri Giffard
Baptiste Jules Henri Jacques Giffard (8 February 182514 April 1882) was a French engineer. In 1852 he invented the steam injector and the powered Giffard dirigible airship.
Career
Giffard was born in Paris in 1825. He invented the injector a ...
.
German count
Ferdinand von Zeppelin
Count Ferdinand von Zeppelin (german: Ferdinand Adolf Heinrich August Graf von Zeppelin; 8 July 1838 – 8 March 1917) was a German general and later inventor of the Zeppelin rigid airships. His name soon became synonymous with airships a ...
promoted the idea of rigid airships lifted by hydrogen that later were called
Zeppelins; the first of which had its maiden flight in 1900.
Regularly scheduled flights started in 1910 and by the outbreak of World War I in August 1914, they had carried 35,000 passengers without a serious incident. Hydrogen-lifted airships were used as observation platforms and bombers during the war.
The first non-stop transatlantic crossing was made by the British airship ''
R34'' in 1919. Regular passenger service resumed in the 1920s and the discovery of
helium reserves in the United States promised increased safety, but the U.S. government refused to sell the gas for this purpose. Therefore, was used in the
''Hindenburg'' airship, which was destroyed in a midair fire over
New Jersey on 6 May 1937.
The incident was broadcast live on radio and filmed. Ignition of leaking hydrogen is widely assumed to be the cause, but later investigations pointed to the ignition of the
aluminized fabric coating by
static electricity. But the damage to hydrogen's reputation as a
lifting gas was already done and commercial hydrogen airship travel
ceased. Hydrogen is still used, in preference to non-flammable but more expensive helium, as a lifting gas for
weather balloons.
In the same year, the first
hydrogen-cooled turbogenerator went into service with gaseous hydrogen as a
coolant
A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosi ...
in the rotor and the stator in 1937 at
Dayton, Ohio, by the Dayton Power & Light Co.; because of the thermal conductivity and very low viscosity of hydrogen gas, thus lower drag than air, this is the most common type in its field today for large generators (typically 60 MW and bigger; smaller generators are usually
air-cooled).
The
nickel hydrogen battery was used for the first time in 1977 aboard the U.S. Navy's Navigation technology satellite-2 (NTS-2). For example, the
ISS
The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (J ...
,
Mars Odyssey
''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectro ...
and the
Mars Global Surveyor
''Mars Global Surveyor'' (MGS) was an American robotic space probe developed by NASA's Jet Propulsion Laboratory and launched November 1996. MGS was a global mapping mission that examined the entire planet, from the ionosphere down through t ...
are equipped with nickel-hydrogen batteries. In the dark part of its orbit, the
Hubble Space Telescope is also powered by nickel-hydrogen batteries, which were finally replaced in May 2009, more than 19 years after launch and 13 years beyond their design life.
Role in quantum theory
Because of its simple atomic structure, consisting only of a proton and an electron, the
hydrogen atom, together with the spectrum of light produced from it or absorbed by it, has been central to the development of the theory of
atomic structure. Furthermore, study of the corresponding simplicity of the hydrogen molecule and the corresponding cation
brought understanding of the nature of the
chemical bond
A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of ...
, which followed shortly after the quantum mechanical treatment of the hydrogen atom had been developed in the mid-1920s.
One of the first quantum effects to be explicitly noticed (but not understood at the time) was a Maxwell observation involving hydrogen, half a century before full
quantum mechanical theory arrived. Maxwell observed that the
specific heat capacity of unaccountably departs from that of a
diatomic gas below room temperature and begins to increasingly resemble that of a monatomic gas at cryogenic temperatures. According to quantum theory, this behavior arises from the spacing of the (quantized) rotational energy levels, which are particularly wide-spaced in because of its low mass. These widely spaced levels inhibit equal partition of heat energy into rotational motion in hydrogen at low temperatures. Diatomic gases composed of heavier atoms do not have such widely spaced levels and do not exhibit the same effect.
Antihydrogen () is the
antimatter
In modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding particles in "ordinary" matter. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioac ...
counterpart to hydrogen. It consists of an
antiproton
The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.
The exis ...
with a
positron. Antihydrogen is the only type of antimatter atom to have been produced .
Cosmic prevalence and distribution
Hydrogen, as atomic H, is the most
abundant chemical element in the universe, making up 75 percent of
normal matter by
mass and more than 90 percent by number of atoms. (Most of the mass of the universe, however, is not in the form of chemical-element type matter, but rather is postulated to occur as yet-undetected forms of mass such as
dark matter and
dark energy.) This element is found in great abundance in stars and
gas giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
planets.
Molecular cloud
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydroge ...
s of are associated with
star formation. Hydrogen plays a vital role in powering
stars through the
proton-proton reaction in case of stars with very low to approximately 1 mass of the Sun and the
CNO cycle
The CNO cycle (for carbon–nitrogen–oxygen; sometimes called Bethe–Weizsäcker cycle after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, ...
of
nuclear fusion
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manife ...
in case of stars more massive than our
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
.
States
Throughout the universe, hydrogen is mostly found in the
atomic and
plasma states, with properties quite distinct from those of molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity and high emissivity (producing the light from the Sun and other stars). The charged particles are highly influenced by magnetic and electric fields. For example, in the
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
they interact with the Earth's
magnetosphere giving rise to
Birkeland current
A Birkeland current (also known as field-aligned current) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere. In the Earth's magnetosphere, the curr ...
s and the
aurora
An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...
.
Hydrogen is found in the neutral atomic state in the
interstellar medium because the atoms seldom collide and combine. They are the source of the
21-cm hydrogen line at 1420 MHz that is detected in order to probe primordial hydrogen. The large amount of neutral hydrogen found in the
damped Lyman-alpha systems is thought to dominate the
cosmological
Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher ...
baryonic density of the universe up to a
redshift of ''z'' = 4.
Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, . Hydrogen gas is very rare in the Earth's atmosphere (1
ppm by volume) because of its light weight, which enables it to
escape from the atmosphere more rapidly than heavier gases. However, hydrogen is the third most abundant element on the Earth's surface,
mostly in the form of
chemical compounds such as
hydrocarbons and water.
A molecular form called
protonated molecular hydrogen () is found in the interstellar medium, where it is generated by ionization of molecular hydrogen from
cosmic rays. This ion has also been observed in the upper atmosphere of the planet
Jupiter. The ion is relatively stable in the environment of outer space due to the low temperature and density. is one of the most abundant ions in the universe, and it plays a notable role in the chemistry of the interstellar medium. Neutral
triatomic hydrogen can exist only in an excited form and is unstable.
By contrast, the positive
hydrogen molecular ion () is a rare molecule in the universe.
Production
is produced in chemistry and biology laboratories, often as a by-product of other reactions; in industry for the
hydrogenation of
unsaturated substrates; and in nature as a means of expelling
reducing equivalents in biochemical reactions.
Water electrolysis
The
electrolysis of water
Electrolysis of water, also known as electrochemical water splitting, is the process of using electricity to decompose water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, or remi ...
is a simple method of producing hydrogen. A current is run through the water, and gaseous oxygen forms at the
anode while gaseous hydrogen forms at the
cathode. Typically the cathode is made from platinum or another inert metal when producing hydrogen for storage. If, however, the gas is to be burnt on site, oxygen is desirable to assist the combustion, and so both electrodes would be made from inert metals. (Iron, for instance, would oxidize, and thus decrease the amount of oxygen given off.) The theoretical maximum efficiency (electricity used vs. energetic value of hydrogen produced) is in the range 88–94%.
:
Methane pyrolysis
Hydrogen production using natural gas methane
pyrolysis is a one-step process that produces no
greenhouse gases. Developing volume production using this method is the key to enabling faster carbon reduction by using hydrogen in industrial processes,
fuel cell electric heavy truck transportation, and in gas turbine electric power generation. Methane pyrolysis is performed by having
methane bubbled up through a molten metal catalyst containing dissolved
nickel at . This causes the methane to break down into hydrogen gas and solid
carbon, with no other byproducts.
: (ΔH° = 74 kJ/mol)
The industrial quality solid carbon may be sold as manufacturing feedstock or permanently landfilled; it is not released into the atmosphere and does not cause ground water pollution in landfill. Methane pyrolysis is in development and considered suitable for commercial bulk hydrogen production. Volume production is being evaluated in the
BASF
BASF SE () is a German multinational chemical company and the largest chemical producer in the world. Its headquarters is located in Ludwigshafen, Germany.
The BASF Group comprises subsidiaries and joint ventures in more than 80 countries ...
"methane pyrolysis at scale" pilot plant. Further research continues in several laboratories, including at Karlsruhe Liquid-metal Laboratory (KALLA) and the chemical engineering laboratory at University of California – Santa Barbara
Other industrial methods
Hydrogen is often produced by reacting water with
methane and
carbon monoxide, which causes the removal of hydrogen from hydrocarbons at very high temperatures, with 48% of hydrogen production coming from
steam reforming
Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen product ...
.
The water vapor is then reacted with the carbon monoxide produced by steam reforming to oxidize it to carbon dioxide and turn the water into hydrogen. Commercial bulk hydrogen is usually produced by the steam reforming of
natural gas with release of atmospheric greenhouse gas or with capture using
CCS and climate change mitigation. Steam reforming is also known as the
Bosch process and is widely used for the industrial preparation of hydrogen.
At high temperatures (1000–1400 K, 700–1100 °C or 1300–2000 °F), steam (water vapor) reacts with
methane to yield
carbon monoxide and .
:
This reaction is favored at low pressures but is nonetheless conducted at high pressures (2.0 MPa, 20 atm or 600
inHg). This is because high-pressure is the most marketable product, and
pressure swing adsorption
Pressure swing adsorption (PSA) is a technique used to separate some gas species from a mixture of gases (typically air) under pressure according to the species' molecular characteristics and affinity for an adsorbent material. It operates at ne ...
(PSA) purification systems work better at higher pressures. The product mixture is known as "
synthesis gas
Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principly used for producing ammonia or methanol. Syngas is combustible and can be used ...
" because it is often used directly for the production of
methanol and related compounds.
Hydrocarbons other than methane can be used to produce synthesis gas with varying product ratios. One of the many complications to this highly optimized technology is the formation of coke or carbon:
:
Consequently, steam reforming typically employs an excess of . Additional hydrogen can be recovered from the steam by use of carbon monoxide through the
water gas shift reaction
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...
, especially with an
iron oxide catalyst. This reaction is also a common industrial source of
carbon dioxide:
:
Other important methods for CO and production include partial oxidation of hydrocarbons:
:
and the coal reaction, which can serve as a prelude to the shift reaction above:
:
Hydrogen is sometimes produced and consumed in the same industrial process, without being separated. In the
Haber process
The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and ...
for the
production of ammonia, hydrogen is generated from natural gas.
Electrolysis of
brine to yield
chlorine also produces hydrogen as a co-product.
Olefin production units may produce substantial quantities of byproduct hydrogen particularly from cracking light feedstocks like
ethane
Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petroc ...
or
propane.
Metal-acid
Many metals react with water to produce , but the rate of hydrogen evolution depends on the metal, the pH, and the presence alloying agents. Most commonly, hydrogen evolution is induced by acids. The alkali and alkaline earth metals, aluminium, zinc, manganese, and iron react readily with aqueous acids. This reaction is the basis of the
Kipp's apparatus, which once was used as a laboratory gas source:
:
In the absence of acid, the evolution of is slower. Because iron is widely used structural material, its
anaerobic corrosion is of technological significance:
:
Many metals, such as
aluminium, are slow to react with water because they form passivated coatings of oxides. An alloy of aluminium and
gallium, however, does react with water. At high pH, aluminium can produce :
:
Some metal-containing compounds react with acids to evolve . Under anaerobic conditions,
ferrous hydroxide () can be oxidized by the protons of water to form
magnetite and . This process is described by the
Schikorr reaction:
:
This process occurs during the anaerobic corrosion of
iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
and
steel in
oxygen-free groundwater and in reducing
soils below the
water table.
Thermochemical
More than 200 thermochemical cycles can be used for
water splitting. Many of these cycles such as the
iron oxide cycle
For chemical reactions, the iron oxide cycle (Fe3O4/FeO) is the original two-step thermochemical cycle proposed for use for hydrogen production.
It is based on the reduction and subsequent oxidation of iron ions, particularly the reduction and oxid ...
,
cerium(IV) oxide–cerium(III) oxide cycle
The cerium(IV) oxide–cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two-step thermochemical process that employs cerium(IV) oxide and cerium(III) oxide for hydrogen production. The cerium-based cycle allows the separation of H2 and O2 in two s ...
,
zinc zinc-oxide cycle,
sulfur-iodine cycle,
copper-chlorine cycle and
hybrid sulfur cycle
The hybrid sulfur cycle (HyS) is a two-step water-splitting process intended to be used for hydrogen production. Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (inste ...
have been evaluated for their commercial potential to produce hydrogen and oxygen from water and heat without using electricity. A number of laboratories (including in
France,
Germany,
Greece,
Japan, and the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
) are developing thermochemical methods to produce hydrogen from solar energy and water.
Serpentinization reaction
In deep geological conditions prevailing far away from the Earth's atmosphere, hydrogen () is produced during the process of
serpentinization
Serpentinization is a hydration and metamorphic transformation of ferromagnesian minerals, such as olivine and pyroxene, in mafic and ultramafic rock to produce serpentinite. Minerals formed by serpentinization include the serpentine group mine ...
. In this process, water protons () are reduced by ferrous () ions provided by
fayalite
Fayalite (, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system (space group ''Pbnm'') with cell parame ...
(). The reaction forms
magnetite (),
quartz (), and hydrogen ():
:
:''fayalite + water → magnetite + quartz + hydrogen''
This reaction closely resembles the
Schikorr reaction observed in anaerobic oxidation of
ferrous hydroxide in contact with water.
Applications
Petrochemical industry
Large quantities of are used in the "upgrading" of fossil fuels. Key consumers of include
hydrodealkylation,
hydrodesulfurization, and
hydrocracking. Many of these reactions can be classified as
hydrogenolysis, i.e., the cleavage of bonds to carbon. Illustrative is the separation of sulfur from liquid fossil fuels:
:
Hydrogenation
Hydrogenation, the addition of to various substrates is conducted on a large scale. The hydrogenation of to produce ammonia by the
Haber–Bosch process
The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and C ...
consumes a few percent of the energy budget in the entire industry. The resulting ammonia is used to supply the majority of the protein consumed by humans.
Hydrogenation is used to convert
unsaturated fats and
oils
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...
to saturated fats and oils. The major application is the production of
margarine.
Methanol is produced by hydrogenation of carbon dioxide. It is similarly the source of hydrogen in the manufacture of
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
. is also used as a
reducing agent for the conversion of some
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
s to the metals.
Coolant
Hydrogen is commonly used in power stations as a coolant in generators due to a number of favorable properties that are a direct result of its light diatomic molecules. These include low
density, low
viscosity, and the highest
specific heat and
thermal conductivity of all gases.
Energy carrier
Elemental hydrogen has been widely discussed in the context of energy, as a possible future carrier of energy on an economy-wide scale. Hydrogen is a
''carrier'' of energy rather than an energy resource, because there is no naturally occurring source of hydrogen in useful quantities.
Hydrogen can be burned to produce heat or combined with oxygen in
fuel cells to generate electricity directly, with water being the only emissions at the point of usage. The overall lifecycle emissions of hydrogen depend on how it is produced. Nearly all of the world's current supply of hydrogen is created from fossil fuels. The main method is
steam methane reforming, in which hydrogen is produced from a chemical reaction between steam and
methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide.
While
carbon capture and storage
Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
can remove a large fraction of these emissions, the overall carbon footprint of hydrogen from natural gas is difficult to assess , in part because of emissions created in the production of the natural gas itself.
Electricity can be used to split water molecules, producing sustainable hydrogen provided the electricity was generated sustainably. However, this
electrolysis process is currently more expensive than creating hydrogen from methane and the efficiency of energy conversion is inherently low.
Hydrogen can be produced when there is a surplus of
variable renewable electricity, then stored and used to generate heat or to re-generate electricity. It can be further transformed into
synthetic fuel
Synthetic fuel or synfuel is a liquid fuel, or sometimes gaseous fuel, obtained from syngas, a mixture of carbon monoxide and hydrogen, in which the syngas was derived from gasification of solid feedstocks such as coal or biomass or by refo ...
s such as
ammonia and
methanol.
Innovation in
hydrogen electrolysers could make large-scale production of hydrogen from electricity more cost-competitive. There is potential for hydrogen to play a significant role in decarbonising energy systems because in certain sectors, replacing fossil fuels with direct use of electricity would be very difficult.
Hydrogen fuel can produce the intense heat required for industrial production of steel, cement, glass, and chemicals. For steelmaking, hydrogen can function as a clean energy carrier and simultaneously as a low-carbon catalyst replacing coal-derived
coke. Hydrogen used in transportation would burn relatively cleanly, with some
emissions, but without carbon emissions.
Disadvantages of hydrogen as an energy carrier include high costs of storage and distribution due to hydrogen's explosivity, its large volume compared to other fuels, and its tendency to make pipes brittle.
The infrastructure costs associated with full conversion to a hydrogen economy would be substantial.
Semiconductor industry
Hydrogen is employed to saturate broken ("dangling") bonds of
amorphous silicon
Amorphous silicon (a-Si) is the non-crystalline form of silicon used for solar cells and thin-film transistors in LCDs.
Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films ont ...
and
amorphous carbon Amorphous carbon is free, reactive carbon that has no crystalline structure. Amorphous carbon materials may be stabilized by terminating dangling-π bonds with hydrogen. As with other amorphous solids, some short-range order can be observed. Amor ...
that helps stabilizing material properties. It is also a potential
electron donor
In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process.
Typical reducing agents undergo permanent chemi ...
in various oxide materials, including
ZnO,
,
CdO,
MgO,
,
,
,
,
,
,
,
,
,
,
, and
.
Aerospace
Liquid hydrogen and
liquid oxygen together serve as
cryogenic fuel
Cryogenic fuels are fuels that require storage at extremely low temperatures in order to maintain them in a liquid state. These fuels are used in machinery that operates in space (e.g. rockets and satellites) where ordinary fuel cannot be used, d ...
in
liquid-propellant rockets, as in the
Space Shuttle main engines.
Niche and evolving uses
*Shielding gas: Hydrogen is used as a
shielding gas in
welding methods such as
atomic hydrogen welding.
*Cryogenic research: Liquid is used in
cryogenic research, including
superconductivity studies.
*Buoyant lifting: Because is lighter than air, having only 7% of the density of air, it was once widely used as a
lifting gas in balloons and
airships.
*Leak detection: Pure or mixed with nitrogen (sometimes called
forming gas), hydrogen is a
tracer gas
A tracer-gas leak testing method is a nondestructive testing method that detects gas leaks. A variety of methods with different sensitivities exist. Tracer-gas leak testing is used in the petrochemical industry, the automotive industry, and in the ...
for
detection {{Unreferenced, date=March 2018
In general, detection is the action of accessing information without specific cooperation from with the sender.
In the history of radio communications, the term " detector" was first used for a device that detected ...
of minute leaks. Applications can be found in the automotive, chemical, power generation, aerospace, and telecommunications industries. Hydrogen is an authorized food additive (E 949) that allows food package leak testing, as well as having anti-oxidizing properties.
*Neutron moderation:
Deuterium (hydrogen-2) is used in
nuclear fission applications as a
moderator to slow
neutrons.
*Nuclear fusion fuel: Deuterium is used in
nuclear fusion
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manife ...
reactions.
*Isotopic labeling: Deuterium compounds have applications in chemistry and biology in studies of
isotope effects on reaction rates.
*Rocket propellant:
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...
has investigated the use of
rocket propellant made from atomic hydrogen, boron or carbon that is frozen into solid molecular hydrogen particles that are suspended in liquid helium. Upon warming, the mixture vaporizes to allow the atomic species to recombine, heating the mixture to high temperature.
*Tritium uses:
Tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of ...
(hydrogen-3), produced in
nuclear reactors, is used in the production of
hydrogen bombs, as an isotopic label in the biosciences,
and as a source of
beta radiation
A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β� ...
in
radioluminescent paint for instrument dials and emergency signage.
Biological reactions
is a product of some types of
anaerobic metabolism
Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.
In aerobic organisms undergoing r ...
and is produced by several
microorganisms, usually via reactions
catalyzed by
iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
- or
nickel-containing
enzymes called
hydrogenases. These enzymes catalyze the reversible
redox reaction between and its component two protons and two electrons. Creation of hydrogen gas occurs in the transfer of reducing equivalents produced during
pyruvate fermentation to water. The natural cycle of hydrogen production and consumption by organisms is called the
hydrogen cycle.
Hydrogen is the most abundant element in the human body in terms of numbers of
atoms of the element but, it is the 3rd most abundant element by mass, because hydrogen is so light. occurs in the breath of humans due to the metabolic activity of hydrogenase-containing microorganisms in the
large intestine
The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before bein ...
. The concentration in fasted people at rest is typically less than 5
parts per million
In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, th ...
(ppm) but can be 50 ppm when people with intestinal disorders consume molecules they cannot absorb during diagnostic
hydrogen breath test
A hydrogen breath test (or HBT) is used as a diagnostic tool for small intestine bacterial overgrowth and carbohydrate malabsorption, such as lactose, fructose, and sorbitol malabsorption.
The test is simple, non-invasive, and is performed after ...
s.
Hydrogen gas is produced by some bacteria and
algae and is a natural component of
flatus
Flatulence, in humans, is the expulsion of gas from the intestines via the anus, commonly referred to as farting. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swallowed environm ...
, as is
methane, itself a hydrogen source of increasing importance.
Water splitting, in which water is decomposed into its component protons, electrons, and oxygen, occurs in the
light reactions in all
photosynthetic organisms. Some such organisms, including the alga ''
Chlamydomonas reinhardtii
''Chlamydomonas reinhardtii'' is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an eye ...
'' and
cyanobacteria, have evolved a second step in the
dark reactions in which protons and electrons are reduced to form gas by specialized hydrogenases in the
chloroplast. Efforts have been undertaken to genetically modify cyanobacterial hydrogenases to efficiently synthesize gas even in the presence of oxygen. Efforts have also been undertaken with genetically modified
alga in a bioreactor.
Safety and precautions
Hydrogen poses a number of hazards to human safety, from potential
detonation
Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with s ...
s and fires when mixed with air to being an
asphyxiant in its pure,
oxygen-free form.
In addition, liquid hydrogen is a
cryogen
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
and presents dangers (such as
frostbite) associated with very cold liquids. Hydrogen dissolves in many metals and in addition to leaking out, may have adverse effects on them, such as
hydrogen embrittlement, leading to cracks and explosions.
Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns.
Even interpreting the hydrogen data (including safety data) is confounded by a number of phenomena. Many physical and chemical properties of hydrogen depend on the
parahydrogen/orthohydrogen ratio (it often takes days or weeks at a given temperature to reach the equilibrium ratio, for which the data is usually given). Hydrogen detonation parameters, such as critical detonation pressure and temperature, strongly depend on the container geometry.
See also
*
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*
* (for hydrogen)
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*
Notes
References
Further reading
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Hydrogen safety covers the safe production, handling and use
External links
Basic Hydrogen Calculations of Quantum Mechanicsat ''
The Periodic Table of Videos
''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
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Chemical elements
Reactive nonmetals
Diatomic nonmetals
Nuclear fusion fuels
Airship technology
Reducing agents
Refrigerants
Gaseous signaling molecules
E-number additives