Biohydrogen is H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass, including biological waste. Furthermore some photosynthetic microorganisms are capable to produce H2 directly from water splitting using light as energy source.
Besides the promising possibilities of biological hydrogen production, many challenges characterize this technology. First challenges include those intrinsic to H2, such as storage and transportation of an explosive noncondensible gas. Additionally, hydrogen producing organisms are poisoned by O2 and yields of H2 are often low.
The main reactions driving hydrogen formation involve the oxidation of substrates to obtain electrons. Then, these electrons are transferred to free protons to form molecular hydrogen. This proton reduction reaction is normally performed by an enzyme family known as hydrogenases.
In heterotrophic organisms, electrons are produced during the fermentation of sugars.Hydrogen gas is produced in many types of fermentation as a way to regenerate NAD+ from NADH. Electrons are transferred to ferredoxin, or can be directly accepted from NADH by a hydrogenase, producing H2. Because of this most of the reactions start with glucose, which is converted to acetic acid.
C6H12O6 + 2 H2O -> 2 CH3COOH + 2 CO2 + 4 H2
A related reaction gives formate instead of carbon dioxide:
C6H12O6 + 2 H2O -> 2 CH3COOH + 2 HCOOH + 2 H2
These reactions are exergonic by 216 and 209 kcal/mol, respectively.
It has been estimated that 99% of all organisms utilize or produce dihydrogen (H2). Most of these species are microbes and their ability to use or produce H2 as a metabolite arises from the expression of H2 metalloenzymes known as hydrogenases. Enzymes within this widely diverse family are commonly sub-classified into three different types based on the active site metal content: [FeFe]-hydrogenases (iron-iron), [NiFe]-hydrogenases (nickel-iron) hydrogenases, and [Fe]-hydrogenases (iron-only).
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Green hydrogen (GH2 or GH2) is hydrogen generated by renewable energy or from low-carbon power. Green hydrogen has significantly lower carbon emissions than grey hydrogen, which is derived from fossil fuels without carbon capture. Green hydrogen may be used to decarbonize sectors that are hard to electrify, such as cement and iron production. Green hydrogen can be used to produce green ammonia, the main constituent of synthetic fertilizer. It can also be used for long-duration grid energy storage, and for long-duration seasonal energy storage.
Biohydrogen is H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass, including biological waste. Furthermore some photosynthetic microorganisms are capable to produce H2 directly from water splitting using light as energy source. Besides the promising possibilities of biological hydrogen production, many challenges characterize this technology. First challenges include those intrinsic to H2, such as storage and transportation of an explosive noncondensible gas.
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: 2 H2O → 2 H2 + O2 Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy, based on green hydrogen. A version of water splitting occurs in photosynthesis, but hydrogen is not produced. The reverse of water splitting is the basis of the hydrogen fuel cell. Electrolysis of water Electrolysis of water is the decomposition of water (H2O) into oxygen (O2) and hydrogen (H2) due to an electric current being passed through the water.
This course covers the fundamental and applied aspects of electrocatalysis related to renewable energy conversion and storage. The focus is on catalysis for hydrogen evolution, oxygen evolution, and C