What is Hydrogen?

Hydrogen is a colorless, highly flammable gas. Like many other gases, hydrogen rarely appears in a pure form on Earth. Hydrogen is not a fuel or source of energy – by itself! Once hydrogen burns, it reacts with oxygen and creates tremendous heat. So the heat is used for energy then. Pure water and a few nitrogen oxides are the by-products only. Therefore, hydrogen is considered as an energy carrier.
Fortunately, there are ways of producing hydrogen fuel, such as electrolysis using hydroelectricity, solar, wind, and nuclear power. As a fuel, hydrogen has been used safely for many decades in a wide range of applications, including food products, metals, glass and chemical industries.

The global hydrogen industry is well established and produces more than 50 million tons a year these days.

A few characteristics:

  • Periodic table symbol “H”
  • Atomic number 1
  • Lightwightest chemical element
  • 75% of the universe by volume exists of Hydrogen

Excellent fuel source:

  • Carbon-free
  • Exceptionally clean
  • Lighter than air
  • Odourless
  • Non-toxic
  • Safe to produce, store and transport
  • Can be stored in large amounts
  • Easily produced from many different sources

Hydrogen's scope:

  • Refinement of petroleum
  • Soldering and brazing
  • Weather balloons
  • Rocket fuel
  • Clean fuel for automotive vehicles
  • Fertilizer production mainly (NH3)
  • Energy storage

Probably the most familiar use in the above list is as a clean fuel for automotive vehicles. Hydrogen can either be burnt in an internal combustion engine (like a conventional petrol car) or used in a fuel cell to produce electricity and drive electric motors. The latter option is the more efficient of the two but also the more expensive.

Hydrogen On Earth

Hydrogen is one of the widest spread elements on earth. In every 100 atoms of the earth’s crust, 17 are of hydrogen. It forms approximately 0,88% of our planet’s mass (including the atmosphere, lithosphere, and hydrosphere). Considering there is more than 1,510 m3 of water on earth, and the mass the hydrogen part inside water is 11,19%, you may understand there is unlimited raw material available on earth, you can obtain hydrogen from. Hydrogen itself is found in compositions of oil (10,9% – 13,8%), wood (6%), coal (brown coal up to 5,5%) and natural gas (25,13%). Hydrogen furthermore is within all compositions of animal and vegetative organisms. Also its within volcanic gases. The main mass of the hydrogen enters the atmosphere resulting from biological processes. Dissolution in anaerobic conditions, billions of tons of vegetative remains, a considerable amount of hydrogen goes into the air. This hydrogen quickly disperses and diffuses the upper layers of the atmosphere.

Centralized Hydrogen

Industrial hydrogen production in large quantities from all fossil fuels can be considered a commercial technology for industrial purposes, but not for utility companies. The potential in hydrogen production lies in the relatively low unit costs, although the costs for hydrogen production from natural gas in medium-sized plants can be reduced in the direction of the costs for large-scale production. An important challenge is the decarbonization of the hydrogen production process. Options for CO2 capture and storage have not yet been fully tested technically and commercially. They require research and development in relation to absorption or separation processes and the process design as well as the acceptance of CO2 storage. It is also important to increase plant efficiency, reduce capital costs, and increase reliability and operational flexibility.

There is also a further need for R&D in hydrogen purification (to generate H2 suitable for fuel cells) and in gas separation (to separate hydrogen or CO2 from gas mixtures). This includes the development of catalysts, adsorption materials, and gas separation membranes for the production and purification of hydrogen. The IGCC plant is the most advanced and efficient solution, where the carbon in the fuel is removed and the hydrogen is generated in a pre-combustion process.


However, successful centralized hydrogen production requires large market demand, as well as the construction of new infrastructure for hydrogen transmission and distribution, and a pipeline for CO2 storage. In the future, centralized hydrogen production from high-temperature processes based on renewable energies and waste heat may also be an option to improve sustainability and eliminate the need to capture and store CO2.

Hydrogen Facts

How does Hydrogen flow work?

Hydrogen is an efficient fuel that can be used to generate electricity. It is available in large quantities and has no negative effects such as harmful gas emissions or the “greenhouse” effect. This non-toxic gas is easily produced from many renewable energy sources.
Many studies have shown that hydrogen is the only alternative fuel that can reduce the world’s dependence on oil with a reduced greenhouse effect. This type of use of this renewable energy plays an important role in reducing future climate impacts.
Many organic compounds are rich in hydrogen, especially hydrocarbons, which are important sources for many fuels such as gasoline, natural gas, methanol, and propane.
A reforming process can separate hydrogen from hydrocarbons that are used to generate electricity.

A team of scientists at the Lawrence Berkeley National Laboratory (USA), Department of Energy (DoE), has discovered materials known as air-stable magnesium nanocomposites. This material helps store hydrogen with magnesium metal nanoparticles that are scattered through a matrix of polymethyl methacrylate. The material used with nanocomposites is able to absorb and release hydrogen at a normal temperature without oxidizing the metal. The same material is now used in hydrogen storage systems, hydrogen batteries, and hydrogen fuel cells.

Gaia Hydrogen - the new green

  • Uses unique efficient low-cost solid reactant
  • Chemical catalytic reaction to split water into oxygen and hydrogen
  • The water splits without light, heat, or electricity through oxidation
  • No use of hazardous material (no silicon, no acid, no aluminum, no zinc …)
  • Any kind of water is usable (fresh, brackish & seawater)
  • Sustainable green process, no negative environmental effects

Today's Green Hydrogen

Electrolysis from ressource water

Water electrolysis is a process in which water is split into hydrogen and oxygen through the use of electrical energy.

The total energy required for water electrolysis increases slightly with temperature, while the electrical energy required decreases.

A high-temperature electrolysis process may, therefore, be preferable in cases where high-temperature heat such as waste heat from other processes is available. This is particularly important globally, as most of the electricity generated worldwide is based on fossil fuels with relatively low levels of efficiency.

Future cost potentials for electrolytic hydrogen are shown in the following figure, whereby the possibilities for a considerable reduction in production costs are obvious.

Polymer Electrolyte Membrane Electrolysis

Polymer electrolyte membrane electrolysis (PEM) is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE), which is responsible for the conduction of protons, the separation of the product gases, and the electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the partial load, low current density, and low-pressure operation problems that currently plague the alkaline electrolyzer. Electrolysis is an important new technology for the production of hydrogen, which is to be used as an energy carrier. With fast dynamic response times, large operating ranges, high efficiencies, and very high gas purities (99.99%), PEM electrolysis is a promising alternative for energy storage in connection with renewable energy sources.

One of the greatest advantages of PEM electrolysis is its ability to operate at high current densities. This can lead to lower operating costs, especially in systems that are coupled to very dynamic energy sources such as wind and sun, where sudden peaks in energy input would otherwise lead to the energy that is not captured.

The polymer electrolyte enables the PEM electrolyzer to work with a very thin membrane (~100-200ìm) and still allow high pressures, which leads to low ohmic losses, which are primarily caused by the conduction of protons across the membrane (0,1 S/cm) and compressed hydrogen emission.

The polymer electrolyte membrane has a low gas transfer rate due to its solid structure, resulting in the following results with a very high product gas purity. Maintaining a high level of gas purity is important for storage safety and for direct use in a fuel cell. The safety limits for H2 in O2 under standard conditions are 4 mol% H2 in O2.

The ability of the PEM electrolyzer to operate not only under highly dynamic conditions but also under part load and overload conditions is one of the reasons for the recently renewed interest in this technology. The requirements of an electrical grid are relatively stable and predictable, but when coupled with energy sources such as wind and sun, the grid’s needs rarely match the generation of renewable energy. This means that energy generated from renewable sources such as wind and sun must have a buffer or a way to store energy outside of peak load times.

Electrolysis based on high temperatures

High-temperature electrolysis is based on a technology used for high-temperature fuel cells.

The electrical energy required to split water at 1000°C  is much lower than that for electrolysis at 100°C. This means that a high-temperature electrolyzer can work with significantly higher overall process efficiencies than a normal low-temperature electrolyzer.

A typical technology is a solid oxide electrolysis cell (SOEC). This electrolyzer is based on the solid oxide fuel cell (SOFC), which normally operates at 700 to 1000°C.

At these temperatures, the electrode reactions are more reversible and the fuel cell reaction can be more easily converted into an electrolysis reaction.

Attempts are now being made to develop systems in which some of the electricity consumed by the electrolyzer can be replaced by heat available from geothermal, solar or natural gas sources, which can significantly reduce electricity consumption. Similar to the main challenges for SOFCs, the main research and development needs for SOECs relate to material development and the thermomechanical stress within the functional ceramic materials.

Electrolysis based on photovoltaic

Photovoltaic (PV) systems coupled to electrolyzers are commercially available. The systems offer some flexibility as the output can be electricity from photovoltaic cells or hydrogen from the electrolyzer.

Direct photoelectrolysis is an advanced alternative to a PV electrolysis system by combining both processes in a single device.

Photoelectrolysis of water is the process in which light is used to split water directly into hydrogen and oxygen. Such systems offer great potential for reducing the cost of electrolytic hydrogen compared to traditional two-stage technologies.

Fundamental and applied R&D efforts in materials science and systems engineering for photoelectrochemical cells (PEC) are currently underway around the world, with at least 13 OECD countries running PEC-related R&D projects and/or entire programs. The IEA-HIA coordinates and manages a significant part of these R&D efforts in a collaborative, task-sharing annex.

In the past few years, various PEC devices have been developed on a laboratory scale, which so far has solar-hydrogen conversion efficiencies of up to 16%. The main challenges to bring PEC cell innovation to market relate to advancement in materials science and technology. Since no “ideal” photoelectrode material for water splitting exists commercially, tailor-made materials must be developed.

Photobiological Production (Biophotolysis)

The biological evolution of hydrogen offers a sustainable and environmentally friendly way to generate clean energy from renewable resources. Biologically produced hydrogen or biohydrogen is considered a renewable, CO2 neutral form of energy.

The photobiological production of hydrogen is based on two steps: photosynthesis and hydrogen production, which is catalyzed by hydrogenases, e.g. green algae, and cyanobacteria. Under special conditions, cyanobacteria and green microalgae split water into molecular hydrogen and oxygen with the help of sunlight.

Advances have been made in solving the intrinsic intolerance of the simultaneous evolution of hydrogen and oxygen gas in photoautotrophic cells, particularly the adverse effects on the key enzymes of hydrogen (hydrogenase and nitrogenase).

A large number of microbial species evolve hydrogen when they grow on renewable resources under special anaerobic conditions with low hydrogen pressure. Depending on the carbon and energy sources, three different mechanisms are involved in microbial hydrogen evolution, which poses unique technical challenges for hydrogen production.

Heterotrophic obligate or facultative anaerobes (e.g. Clostridium) gain both carbon and energy from carbohydrates such as glucose and deposit the excess reducing power in fermentative products and hydrogen. The hydrogen yield, therefore, depends on the profile of the fermentation products and ranges from 0.3 to 4 mol of hydrogen per mol of glucose used.

Photosynthetic bacteria (e.g. Rhodobactor) can use broad organic substrates such as lactic and acetic acid as a source of energy and carbon when exposed to light. Light energy is essential for the evolution of hydrogen by photosynthetic cells.

Biophotolysis is the action of light on biological systems, which leads to the dissociation of water into molecular hydrogen and oxygen: H2O H2 + ½ O2.

High-temperature decomposition

The high-temperature splitting of water occurs at around 3000°C. At this temperature, 10% of the water is decomposed and the remaining 90% can be recycled. To lower the temperature, other methods of high-temperature splitting of water have been proposed:

  • Thermo-chemical cycles
  • Hybrid systems that couple thermal decomposition and electrolytic decomposition.
  • Direct catalytic decomposition of water with separation via a ceramic membrane (“thermophysical cycle”).
  • Plasma-chemical decomposition of water in a two-stage CO2 cycle

For these processes, efficiencies of over 50% are to be expected and could potentially lead to a considerable reduction in hydrogen production costs. The most important technical questions for these high-temperature processes relate to the material development for corrosion resistance at high temperatures, high-temperature membrane and separation processes, heat exchangers, and heat storage media, but design aspects and safety are also important in high-temperature processes.

Thermo-chemical process water splitting

Thermo-chemical water splitting is the conversion of water into hydrogen and oxygen by a  series of thermally driven chemical reactions. Thermo-chemical water-splitting cycles have been known for the past 35 years. They were extensively studied in the late 1970s and 1980s,  but have been of little interest in the past 10 years.

While there is no question about the technical feasibility and the potential for high efficiency, cycles with proven low cost and high efficiency have yet to be developed commercially.

An example of a thermo-chemical process is the Iodine/Sulphur cycle, outlined in equations (5.), (6.), (7.), and the figure below. For this process, the research and development needs are to capture the thermally split H2, to avoid side reactions, and to eliminate the use of noxious substances.

The corrosion problems associated with the handling of such materials are likely to be extremely serious.

5. (850 °C):  H2SO4 SO2 + H2O + 1/2 O2

6. (120 °C):  I2 + SO2 + 2 H2O  H2SO4 + 2 HI

7. (450 °C):  2 HI  I2 + H2  SUM:  H2O  H2 + 1/2 O2

Sulfur-Iodine Cycle

Gray Hydrogen

Production from natural gas

The industry is currently able to produce hydrogen from natural gas using three different chemical processes:

  • Steam reforming (steam methane reforming – SMR)

  • Partial Oxidation (POX)

  • Autothermal Reforming (ATR)

Even though many new process concepts have been developed, none of them are close to commercialization!

Comparison of technologies for H2 production from natural gas

POX: “Partial oxidation” of natural gas means that hydrogen is created by partially burning methane with oxygen to provide carbon monoxide and hydrogen: CH4 + 1/2 O2 CO + 2 H2 + Heat.

In this process, heat is generated in an exothermic reaction and a more compact design is possible since no external heating of the reactor is required. The CO produced is further converted into H2, as described in the above reaction.

SMR: “Steam reforming”, includes the endothermic conversion of methane and water vapor into hydrogen and carbon monoxide CH4 + H2O + Heat CO + 3 H2.

The heat is often provided by burning some of the methane feed gas.

The process typically takes place at temperatures of 700 to 850 ° C and pressure between 3 to 25 bar. The gas produced contains around 12% CO, which can be further converted into CO2 and H2 by the water-gas shift reaction CO + H2O ➔ CO2 + H2 + Heat.

ATR: “Auto-Thermo-Reforming” is a combination of steam reforming and partial oxidation.

The entire reaction is exothermic and releases heat. The outlet temperature from the reactor is in the range from 950 to 1100 ° C. and the gas pressure can be up to 100 bar. Here, too, the CO generated is converted into H2 by the water-gas shift reaction. The need to purify the source gases adds significantly to plant costs and reduces overall efficiency.

Production from coal

Hydrogen can be produced from coal by a variety of gasification processes (e.g. fixed bed, fluidized bed or entrained flow). In practice, high temperature entrained flow processes are preferred in order to maximize the conversion of carbon to gas and thus avoid the formation of significant amounts of charcoal, tars, and phenols.

A typical reaction for the process is C (s) + H2O + Heat CO + H2, in which carbon is converted into carbon monoxide and hydrogen.

As this reaction is endothermic, additional heat is required as with methane reforming.

The CO is further converted into CO2 and H2 by the water-gas shift reaction. Hydrogen production from coal is commercially mature, but it is more complex than producing hydrogen from natural gas. The costs for the resulting hydrogen are also higher. However, since coal is abundant in many parts of the world and is likely to be used independently as a source of energy, it is worth studying the development of clean technologies for its use.

Production from Alkaline

Alkaline electrolyzers use an aqueous KOH (lye) solution as the electrolyte, which normally circulates through the electrolytic cells. Alkaline electrolyzers are suitable for stationary applications and are available for operating pressures of up to 25 bar.

Alkaline electrolysis is a mature technology with a significant operating history in industrial applications that enables remote-controlled operation.

Commercial electrolyzers usually consist of a number of electrolysis cells that are arranged in a cell stack.

The greatest R&D challenge for the future is to design and manufacture electrolyzer equipment at a lower cost, with higher energy efficiency and greater shutdown rates.
Alkaline electrolyzers usually contain the following main components:

Methanol Decomposition

The process can be described as follows (heat of reaction at 298 K in KJ / mol):

CH3 OH ➔ CO + 2 H2

The catalyst in this process is a mixed copper-nickel or nickel-aluminum catalyst which is applied to the refractory support. The composition of the gas obtained after the first stage of the process is 61% Í2, 31% NI, and 2% NI2. With an overpressure of 2 MPa, the process can be carried out in one stage:

CH3 OH + H2O  ➔ 3 H2 + CO2

Copper-zinc-chromium catalyst at 530-570 E causes an almost complete conversion of methanol to I2 and NI2 with a considerable volume flow.

Blue Hydrogen

Capture and Storage of CO2

Carbon dioxide is a major exhaust in any production of hydrogen from fossil fuels. The amount of CO2 varies depending on the hydrogen content of the starting material. In order to achieve sustainable (emission-free) production of hydrogen, the CO2 should be captured and stored. This process is known as decarbonization. There are three (3) different ways to capture CO2 in a combustion process:

1. the afterburning. The CO2 can be removed from the exhaust gas of the combustion process in a conventional steam turbine or a combined cycle power plant (gas and steam turbine power plant). This can be done via the “amine” process, for example. In addition to water vapor, CO2 and CO, the exhaust gas will contain large amounts of nitrogen and some amounts of nitrogen oxides.

2. Pre-combustion. During the production of hydrogen, CO2 is captured using one of the processes described above.

3. Oxyfuel combustion. The fossil fuel is converted into heat in a combustion process using a conventional steam turbine or CCGT power plant. This is done with pure oxygen as the oxidizing agent. Usually, CO2 and water vapor are formed in the exhaust gas or in the flue gases, and CO2 can be easily separated by condensation of the water vapor.

In post-combustion and oxyfuel combustion systems, electricity is turned into near-conventional steam and combined cycle power plants. The electricity generated could then be used for water electrolysis.

If CO2 is captured and stored in an energy conversion process with relatively low efficiency and the electricity is used to electrolyze water, then the overall efficiency from fuel to hydrogen would not exceed 30%.

The captured CO2 can be found in geological formations such as oil and gas fields as well as in aquifers, but the feasibility and evidence of permanent CO2 storage are critical to the success of decarbonization.

The choice of the transport system for the CO2 (pipeline, ship or combined) will largely depend on the choice of the location of the production facility and the location chosen for storage.

Turquoise Hydrogen

Hydrogen from Biomass

In biomass conversion processes, a hydrogen-containing gas is normally produced, similar to the gasification of coal. However, there are no commercial plants for the production of hydrogen from biomass.

Steam gasification (direct or indirect), entrained flow gasification, and more advanced concepts such as gasification in supercritical water, the application of thermo-chemical cycles or the conversion of intermediate products (e.g. ethanol, bio-oil or torrefied wood) are currently being pursued. None of the concepts has reached a demonstration phase for hydrogen production.

The gasification of biomass is a research and development area that shares H2 production and the production of biofuels.

Gasification and pyrolysis are considered to be the most promising medium-term technologies for commercializing H2 production from biomass.

A typical flow diagram for the production of hydrogen from biomass is shown in the figure below.

In terms of its energy requirements, the drying of biomass may not be justifiable; therefore, other approaches based on moist biomass are also being sought.

Biomass raw materials are unrefined products with inconsistent quality and poor quality control.

The production methods vary depending on the type of plant, location, and climatic fluctuations. Irregular fuels have contributed to the difficulties in technological innovation, as less homogeneous and poor quality fuels require more sophisticated conversion systems. There is a need to streamline the production and processing of fuels in order to produce more consistent, higher-quality fuels that can be described by common standards. Large plants are more suitable for cheaper and inferior fuels, while smaller plants tend to require higher fuel quality and better fuel homogeneity.

Necessary development:

  • Feed preparation and identification of the properties of the raw materials that allow the development of the technologies.

  • Gasification of biomass. This is not specific to hydrogen but relates to general pathways and research in biomass and renewable energy.

  • Handling and cleaning of raw gas.

  • Interface issues and system integration. One should also examine the relationship between the scale of production and the fuel quality requirements and tolerances that can be considered for each technology.