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Methods to produce hydrogen without the use of fossil fuels involve the process of water splitting, or splitting the water molecule (H 2 O) into its components oxygen and hydrogen. When the source of energy for water splitting is renewable or low-carbon, the hydrogen produced is sometimes referred to as green hydrogen.
Hydrogen can be deployed as a fuel in two distinct ways: in fuel cells which produce electricity, and via combustion to generate heat. [58] When hydrogen is consumed in fuel cells, the only emission at the point of use is water vapor. [58] Combustion of hydrogen can lead to the thermal formation of harmful nitrogen oxides emissions. [58]
For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. The overarching challenge is the very low boiling point of H 2: it boils around 20.268 K (−252.882 °C or −423.188 °F).
In contrast, direct seawater electrolysis skips the pre-treatment step and introduces seawater directly into the electrolyzer to produce hydrogen. This approach is seen as more promising due to limited freshwater resources, the need to prioritize basic human needs, and the potential to reduce energy consumption and costs.
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: [1] Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy. A version of water splitting occurs in photosynthesis, but hydrogen is not produced. The reverse of water splitting is the ...
Heat of combustion. The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard ...
Hydrogen technologies are applicable for many uses. Some hydrogen technologies are carbon neutral and could have a role in preventing climate change and a possible future hydrogen economy . Hydrogen is a chemical widely used in various applications including ammonia production, oil refining and energy. [ 1 ]
The molecule leaves the surface. Hydrogenation is a chemical reaction between molecular hydrogen (H 2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds.