Hydrogen evolution reaction (HER) is a chemical reaction that yields H₂. The conversion of protons to H₂ requires reducing equivalents and usually a catalyst. In nature, HER is catalyzed by

hydrogenase A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2), as shown below: Hydrogen uptake () is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide (), and fumarat ...

enzymes. Commercial

electrolyzer In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

s typically employ

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Platinu ...

metal as the catalyst. HER is useful for producing hydrogen gas, providing a clean-burning fuel. HER, however, can also be an unwelcome side reaction that competes with other reductions such as

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

and

electrochemical reduction of carbon dioxide The electrochemical reduction of carbon dioxide, also known as electrolysis of carbon dioxide, is the conversion of carbon dioxide () to more reduction (chemistry), reduced chemical species using electrical energy. It is one possible step in the b ...

References

{{electrolysis Electrolysis Energy engineering