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The sulfur–iodine cycle (S–I cycle) is a series of thermochemical processes used to produce hydrogen. The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The S–I process requires an efficient source of heat.
Water can be broken down into its constituent hydrogen and oxygen by metabolic or abiotic processes, and later recombined to become water again. While the water cycle is itself a biogeochemical cycle, flow of water over and beneath the Earth is a key component of the cycling of other biogeochemicals. [8]
The hydrogen cycle consists of hydrogen exchanges between biotic (living) and abiotic (non-living) sources and sinks of hydrogen-containing compounds. Hydrogen (H) is the most abundant element in the universe. [1] On Earth, common H-containing inorganic molecules include water (H 2 O), hydrogen gas (H 2), hydrogen sulfide (H 2 S), and ammonia ...
In chemistry, thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. [1] The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled. If work is partially used as an input, the ...
The ocean plays a key role in the water cycle as it is the source of 86% of global evaporation. [2] The water cycle involves the exchange of energy, which leads to temperature changes. When water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment.
The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O 2), as it is a common product or reactant of many biogeochemical redox reactions within the cycle. [2] Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O 2 ...
Oxygen-18 (18 O) occurs in approximately one oxygen atom in every five hundred and has a slightly higher mass than oxygen-16, as it has two extra neutrons. From a simple energy and bond breakage standpoint this results in a preference for evaporating the lighter 16 O containing water and leaving more of the 18 O water behind in the liquid state ...
The point of water electrolysis is to store energy in the form of hydrogen gas, a clean-burning fuel. The "oxygen evolution reaction (OER) is the major bottleneck [to water electrolysis] due to the sluggish kinetics of this four-electron transfer reaction." [6] All practical catalysts are heterogeneous. Diagram showing the overall chemical ...