User:Chris Holtzman/sandbox

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Hydrogen synthesis refers to any process by which hydrogen gas is created by removing hydrogen molecules from other compounds. Hydrogen gas does not naturally occur on Earth. Instead, hydrogen is mostly found bound to carbon in the form of carbohydrates, to oxygen in the form of water, and to nitrogen in the form of ammonia. Hydrogen atoms bonded to other hydrogen atoms form hydrogen gas, which is burns very energetically when exposed to heat or flame. Methods for extracting hydrogen include electrolysis, biodegradation, sodium sulfate oxidation, carbon free tri-generation, the Cu-Cl cycle, and steam reformation of natural gas among others.

Electrolysis of Water

One common technique for synthesizing hydrogen is electrolysis. In this method, an electrified loop of wire carrying high amperage DC current is submerged in water . Electricity passing through water excites the H2O molecules to the point that the hydrogen separates from oxygen. The two gasses bubble to the surface where they are collected. One of the issues with electrolysis is the fact that more energy in the form of electricity is required to separate hydrogen from water than the hydrogen would yield in combustion . However, renewable resources such as wind, solar, or hydroelectricity are all viable sources for electricity required in electrolysis. One example of the full process in action has already been built on a small island in Utsira, Norway . At the site, an autonomous wind turbine produces electricity which is sent into a water electrolyzer. Hydrogen gas is gathered from the solution and compressed. The compressed hydrogen gas is then stored in a large collection tank. From that point, the hydrogen can either pass through a fuel cell and be converted into electricity or burned in a conventional engine.

Biohydrogen

Another method for hydrogen production relies on collecting hydrogen gas from decaying biomass. Organic matter decomposing with the help of certain bacteria yields H2 molecules. In nature, these molecules are taken up by other kinds of bacteria which coexist with the hydrogen producing bacteria. By removing the hydrogen fixing bacteria from the biomass, pure hydrogen gas is produced. Heat and acid treatments are the most effective methods of preparing biomass for this process . It takes several days for microbes to sufficiently deplete the matter of hydrogen.

Sodium Sulfate Oxidation

Yet another method of hydrogen production is called sodium sulfate oxidation. In this process, an aqueous Na2SO3 (sodium sulfite) solution is oxidized to Na2SO4 (sodium sulfate), while H2O is reduced to hydrogen using a low-pressure mercury lamp . When the solution is exposed to UV radiation, water molecules break down. The oxygen bonds with the sodium sulfite and the hydrogen bubbles out of solution. The resultant Na2SO4 produced during the chemical reaction is non toxic and inert. This process is less expensive than other methods of production because sodium sulfite is a naturally occurring salt found in many parts of the world.

Carbon Free Tri-Generation

In this method, two solid oxide cells (SOCs) work together to generate hydrogen gas and electricity at the same time. The two SOCs complement each other in this process. The SOCs are able to operate in two modes: (a) the Solid Oxide Fuel Cells (SOFCs) that produce electricity and heat and (b) the Solid Oxide Electrolyser Cells (SOEC) that consume electricity and heat to electrolyse H2O and produce hydrogen and oxygen. . The SOFC in this design is fed a combination of air, methane, and carbon dioxide to produce electricity which is then used to power the SOEC. The SOEC electrolyzes water and produces hydrogen. H2O produced by the system is recollected to be used by the SOEC. The reason the process is carbon free is the carbon dioxide is collected and fixed into solid material similar to how plants fix carbon dioxide into organic compounds.

The Cu-Cl Cycle

The Cu-Cl process is a set of chemical reactions by which copper and chlorine based compounds exchange hydrogen and oxygen molecules as shown:

1. 2CuCl (aq) + 2HCl (aq) → H2 (g) + 2CuCl2 (aq) (Ambient electrolysis)

2. CuCl2 (aq) → CuCl2 (s) (<100°C)

3. 2CuCl2 (s) + H2O (g) → CuO*CuCl2 (s) + 2HCl (g) (400°C)

4. CuO*CuCl2 (s) → 2CuCl (l) + 1/2O2 (g) (500°C)

Net reaction: 2 H2O → 2 H2 + O2

Copper and chlorine compounds are continuously recycled through the process and ultimately the inputs H2O and heat yield outputs of hydrogen gas and oxygen. The process is made more efficient by the recycling of heat generated in certain process back into other reactions where heat is required. This reaction produces much more hydrogen than existing methods. A 42% efficiency (electricity) with the Generation IV reactor (SCWR; Super-Critical Water Reactor) leads to about 30% net efficiency by electrolysis for hydrogen production . Ideally, a nuclear reactor or some similar exothermic generator would provide necessary heat and electricity to create a thermochemical power plant.

Steam Reformation of Natural Gas

Steam reformation incorporates large carbon-hydrogen chains most commonly found in fossil fuels with a device called a steam reformer. The steam reformer combines water vapor with fossil fuels at temperatures exceeding 1000°C. The carbon-hydrogen chains exchange hydrogen molecules with the water vapor to form CO2 and H2. Steam reformation operates at a chemical efficiency of roughly 70% with the remaining 30% being composed of energy lost in the reaction. This process is currently the most common form of hydrogen gas production for industrial applications due to the abundance and affordability of fossil fuels.

Significance

It is widely speculated that hydrogen will be used as a fuel source to replace fossil fuels (see hydrogen economy). Hydrogen burns very energetically and produces no CO2 during combustion. It can also be used in hydrogen fuel cells to produce electricity. Although it is stable at a range of temperatures, care must be taken in its storage as exposure to heat or flame can cause hydrogen tanks to explode. However, if stored properly, it has many applications. In addition to its uses as a power source, hydrogen has many industrial applications such as ammonia production, chemical processing, welding, and cryogenics.