Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis.
In 2006, the United States was estimated to have a production capacity of 11 million tons of hydrogen. 5 million tons of hydrogen were consumed on-site in oil refining, and in the production of ammonia (Haber process) and methanol (reduction of carbon monoxide). 0.4 million tons were an incidental by-product of the chlor-alkali process. Hydrogen production is an estimated $100 billion industry. According to the U.S. Department of Energy, only in 2004, 53 million metric tons were consumed worldwide. There are no natural hydrogen deposits, and for this reason the production of hydrogen plays a key role in modern society.
Currently, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming or partial oxidation of methane and coal gasification with only a small quantity by other routes such as biomass gasification or electrolysis of water.
- 1 Steam reforming
- 2 Other production methods from fossil fuels
- 3 From water
- 3.1 Electrolysis
- 3.2 Chemically assisted electrolysis
- 3.3 Radiolysis
- 3.4 Thermolysis
- 3.5 Thermochemical cycle
- 3.6 Ferrosilicon method
- 3.7 Photobiological water splitting
- 3.8 Photocatalytic water splitting
- 3.9 Biohydrogen routes
- 3.10 Xylose
- 4 Carbon neutral hydrogen
- 5 Use of hydrogen
- 6 See also
- 7 References
- 8 External links
There are four main sources for the commercial production of hydrogen: natural gas, oil, coal and electrolysis; which account for 48%, 30% 18% and 4% of the world’s hydrogen production respectively. Fossil fuels are the dominant source of industrial hydrogen. Hydrogen can be generated from natural gas with approximately 80% efficiency, or from other hydrocarbons to a varying degree of efficiency. Specifically, bulk hydrogen is usually produced by the steam reforming of methane or natural gas. The production of hydrogen from natural gas is the cheapest source of hydrogen nowadays. This process consists of heating the gas in the presence of steam and a nickel catalyst. The resulting exothermic reaction breaks up the methane molecules and forms carbon monoxide CO and hydrogen H2. The carbon monoxide gas can then be passed with steam over iron oxide or other oxides and undergo a water-gas shift reaction. This last reaction produces even more H2. The downside to this process is that its major byproducts are CO, CO2 and other greenhouse gases. Depending on the quality of the feedstock (natural gas, rich gases, naphtha, etc.), one ton of hydrogen produced will also produce 9 to 12 tons of CO2.
- CH4 + H2O → CO + 3 H2
In a second stage, additional hydrogen is generated through the lower-temperature, exothermic, water gas shift reaction, performed at about 360 °C:
- CO + H2O → CO2 + H2
Essentially, the oxygen (O) atom is stripped from the additional water (steam) to oxidize CO to CO2. This oxidation also provides energy to maintain the reaction. Additional heat required to drive the process is generally supplied by burning some portion of the methane.
Steam reforming generates carbon dioxide (CO2). Since the production is concentrated in one facility, it is possible to separate the CO2 and dispose of it without atmospheric release, for example by injecting it in an oil or gas reservoir (see carbon capture), although this is not currently done in most cases. A carbon dioxide injection project has been started by a Norwegian company StatoilHydro in the North Sea, at the Sleipner field.
Integrated steam reforming / co-generation - It is possible to combine steam reforming and co-generation of steam and power into a single plant. This can deliver benefits for an oil refinery because it is more efficient than separate hydrogen, steam and power plants. Air Products recently built an integrated steam reforming / co-generation plant in Port Arthur, Texas.
Other production methods from fossil fuels
The production of hydrogen from oil is achieved by partial oxidation. For this, a carefully controlled fuel-air mix is partially combusted, which results in an H2 rich gas. Like the previous process, the formation of hydrogen from oil is done with a water-gas shift reaction. The energy added to the process is achieved by the combustion of fuels, which also causes a negative impact to the environment.
The partial oxidation reaction occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas. A distinction is made between thermal partial oxidation (TPOX) and catalytic partial oxidation (CPOX). The chemical reaction takes the general form:
- CnHm + n/2 O2 → n CO + m/2 H2
Idealized examples for heating oil and coal, assuming compositions C12H24 and C24H12 respectively, are as follows:
- C12H24 + 6 O2 → 12 CO + 12 H2
- C24H12 + 12 O2 → 24 CO + 6 H2
The Kværner-process or Kvaerner carbon black & hydrogen process (CB&H) is a plasma reforming method, developed in the 1980s by a Norwegian company of the same name, for the production of hydrogen and carbon black from liquid hydrocarbons (CnHm). Of the available energy of the feed, approximately 48% is contained in the hydrogen, 40% is contained in activated carbon and 10% in superheated steam. CO2 is not produced in the process.
For the production of hydrogen from coal, coal gasification is used. The process of coal gasification uses steam and a carefully controlled concentration of gases to break molecular bonds in coal and form a gaseous mix of hydrogen and carbon monoxide. This source of hydrogen is advantageous since its main product is coal-derived gas which can be used for fuel. The gas obtained from coal gasification can later be used to produce electricity more efficiently and allow a better capture of greenhouse gases than the traditional burning of coal.
Similarly to coal, petroleum coke can also be converted in hydrogen rich syngas, via coal gasification. The syngas in this case consists mainly of hydrogen, carbon monoxide and H2S, depending on the sulfur content of the coke feed. Gasification is an attractive option for producing hydrogen from almost any carbon source, while providing attractive hydrogen utilization alternatives through process integration. 
Many technologies have been explored but it should be noted that as of 2007 "Thermal, thermochemical, biochemical and photochemical processes have so far not found industrial applications." High temperature electrolysis of alkaline solutions has been used for the industrial scale production of hydrogen (see Sable Chemicals) and there are now a number of small scale polymer electrolyte membrane (PEM) electrolysis units available commercially.
Electrolysis consists in using electricity to split water into hydrogen and oxygen. This source of hydrogen is by far the most expensive since the energy input required for water splitting is higher than the energy that could be obtained from the produced hydrogen. Due to their use of water, a readily available resource, electrolysis and similar water-splitting methods have attracted the interest of the scientific community. With the objective of reducing the cost of hydrogen production, renewable sources of energy have been targeted to allow electrolysis. There are three main types of cells, solid oxide electrolysis cells (SOECs), polymer electrolyte membrane cells (PEM) and alkaline electrolysis cells (AECs). SOECs operate at high temperatures, typically around 800 °C. At these high temperatures a significant amount of the energy required can be provided as thermal energy (heat), and as such is termed High temperature electrolysis. The heat energy can be provided from a number of different sources, including waste industrial heat, nuclear power stations or concentrated solar thermal plants. This has the potential to reduce the overall cost of the hydrogen produced by reducing the amount of electrical energy required for electrolysis. PEM electrolysis cells typically operate below 100 °C and are becoming increasingly available commercially. These cells have the advantage of being comparatively simple and can be designed to accept widely varying voltage inputs which makes them ideal for use with renewable sources of energy such as solar PV. AECs optimally operate at high concentrations electrolyte (KOH or potassium carbonate) and at high temperatures, often near 200 °C.
Chemically assisted electrolysis
In addition to reducing the voltage required for electrolysis via the increasing of the temperature of the electrolysis cell it is also possible to electrochemically consume the oxygen produced in an electrolyser via introducing a fuel (such as carbon) oxygen side of the reactor. This reduces the required electrical energy and has the potential to reduce the cost of hydrogen produced in this manner.
Nuclear radiation routinely breaks water bonds, in the Mponeng gold mine, South Africa, researchers found in a naturally high radiation zone a community dominated by a new phylotype of Desulfotomaculum, feeding on primarily radiolytically produced H2. Spent nuclear fuel/"nuclear waste" is also being looked at as a potential source of hydrogen.
Water spontaneously dissociates at around 2500 °C, but this thermolysis occurs at temperatures too high for usual process piping and equipment. Catalysts are required to reduce the dissociation temperature.
Thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled. If electricity is partially used as an input, the resulting thermochemical cycle is defined as a hybrid one.
The sulfur-iodine cycle (S-I cycle) is a thermochemical cycle processes which generates hydrogen from water with an efficiency of approximately 50%. The sulfur and iodine used in the process are recovered and reused, and not consumed by the process. The cycle can be performed with any source of very high temperatures, approximately 950 °C, such as by Concentrating solar power systems (CSP) and is regarded as being well suited to the production of hydrogen by high-temperature nuclear reactors, and as such, is being studied in the High Temperature Test Reactor in Japan. There are other hybrid cycles that use both high temperatures and some electricity, such as the Copper–chlorine cycle, it is classified as a hybrid thermochemical cycle because it uses an electrochemical reaction in one of the reaction steps, it operates at 530 °C and has an efficiency of 43 percent.
Ferrosilicon is used by the military to quickly produce hydrogen for balloons. The chemical reaction uses sodium hydroxide, ferrosilicon, and water. The generator is small enough to fit a truck and requires only a small amount of electric power, the materials are stable and not combustible, and they do not generate hydrogen until mixed. The method has been in use since World War I. A heavy steel pressure vessel is filled with sodium hydroxide and ferrosilicon, closed, and a controlled amount of water is added; the dissolving of the hydroxide heats the mixture to about 93 °C and starts the reaction; sodium silicate, hydrogen and steam are produced.
Photobiological water splitting
Biological hydrogen can be produced in an algae bioreactor. In the late 1990s it was discovered that if the algae are deprived of sulfur it will switch from the production of oxygen, i.e. normal photosynthesis, to the production of hydrogen. It seems that the production is now economically feasible by surpassing the 7–10 percent energy efficiency (the conversion of sunlight into hydrogen) barrier. with a hydrogen production rate of 10-12 ml per liter culture per hour.
Photocatalytic water splitting
The conversion of solar energy to hydrogen by means of water splitting process is one of the most interesting ways to achieve clean and renewable energy systems. However, if this process is assisted by photocatalysts suspended directly in water instead of using photovoltaic and an electrolytic system the reaction is in just one step, it can be made more efficient.
Biomass and waste streams can in principle be converted into biohydrogen with biomass gasification, steam reforming, or biological conversion like biocatalysed electrolysis or fermentative hydrogen production.
Fermentative hydrogen production
Fermentative hydrogen production is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of bacteria using multi enzyme systems involving three steps similar to anaerobic conversion. Dark fermentation reactions do not require light energy, so they are capable of constantly producing hydrogen from organic compounds throughout the day and night. Photofermentation differs from dark fermentation because it only proceeds in the presence of light. For example, photo-fermentation with Rhodobacter sphaeroides SH2C can be employed to convert small molecular fatty acids into hydrogen.
Fermentative hydrogen production can be done using direct biophotolysis by green algae, indirect biophotolysis by cyanobacteria, photo-fermentation by anaerobic photosynthetic bacteria and dark fermentation by anaerobic fermentative bacteria. For example, studies on hydrogen production using H. salinarium, an anaerobic photosynthetic bacteria, coupled to a hydrogenase donor like E. coli, are reported in literature.
Biohydrogen can be produced in bioreactors that utilize feedstocks, the most common feedstock being waste streams. The process involves bacteria feeding on hydrocarbons and exhaling hydrogen and CO2. The CO2 can be sequestered successfully by several methods, leaving hydrogen gas. A prototype hydrogen bioreactor using waste as a feedstock is in operation at Welch's grape juice factory in North East, Pennsylvania (U.S.).
Enzymatic hydrogen generation
Due to the Thauer limit (four H2/glucose) for dark fermentation, a non-natural enzymatic pathway was designed that can generate 12 moles of hydrogen per mole of glucose units of polysaccharides and water in 2007. The stoichiometric reaction is:
- C6H10O5 + 7 H2O → 12 H2 + 6 CO2
The key technology is cell-free synthetic enzymatic pathway biotransformation (SyPaB). A biochemist can understand it as "glucose oxidation by using water as oxidant". A chemist can describe it as "water splitting by energy in carbohydrate". A thermodynamics scientist can describe it as the first entropy-driving chemical reaction that can produce hydrogen by absorbing waste heat. In 2009, cellulosic materials were first used to generate high-yield hydrogen. Furthermore, the use of carbohydrate as a high-density hydrogen carrier was proposed so to solve the largest obstacle to the hydrogen economy and propose the concept of sugar fuel cell vehicles.
Besides dark fermentation, electrohydrogenesis (electrolysis using microbes) is another possibility. Using microbial fuel cells, wastewater or plants can be used to generate power. Biocatalysed electrolysis should not be confused with biological hydrogen production, as the latter only uses algae and with the latter, the algae itself generates the hydrogen instantly, where with biocatalysed electrolysis, this happens after running through the microbial fuel cell and a variety of aquatic plants can be used. These include reed sweetgrass, cordgrass, rice, tomatoes, lupines and algae.
In 2014 a low-temperature 50 °C (122 °F), atmospheric-pressure enzyme-driven process to convert xylose into hydrogen with nearly 100% of the theoretical yield was announced. The process employs 13 enzymes, including a novel polyphosphatexylulokinase (XK).
Carbon neutral hydrogen
Currently there are two practical ways of producing hydrogen in a renewable industrial process. One is to use power to gas where electric power is used to produce hydrogen from electrolysis and the other is landfill gas to produce hydrogen in a steam reformer. Hydrogen fuel, when produced by renewable sources of energy like wind or solar power, is a renewable fuel.
In 2014, it was demonstrated that it is possible to synthesize synthetic fuel that is also a carbon-neutral fuel from elemental carbon and hydrogen, with both the carbon and hydrogen being derived from seawater, which contains a much more economical source of Carbon dioxide than the air. With researchers estimating that carbon extraction from seawater would cost about $50 per ton. The U.S. Navy estimates that their typical naval nuclear reactor generating 100 megawatts of electricity could, in theory, produce 41,000 US gallons of jet fuel per day and shipboard production from nuclear power would cost about $6 per gallon. While that was about twice the petroleum fuel cost in 2010, it is expected to be much less than the market price in less than five years if recent trends continue. Moreover, since the delivery of normal jet fuel to the aircraft carrier battle group costs about $8 per gallon, shipboard production would be much less expensive. This method of synthesizing jet fuel is currently only experimental.
Use of hydrogen
Hydrogen is mainly used for the conversion of heavy petroleum fractions into lighter ones via the process of hydrocracking and other petroleum fractions (dehydrocyclization and the aromatization process). It is also required for cleaning fossil fuels via hydrodesulfurization.
Hydrogen is also produced as a by-product of industrial chlorine production by electrolysis. Although requiring expensive technologies, hydrogen can be cooled, compressed and purified for use in other processes on site or sold to a customer via pipeline, cylinders or trucks. The discovery and development of less expensive methods of production of bulk hydrogen is relevant to the establishment of a hydrogen economy.
- Ammonia production
- Biological hydrogen production (Algae)
- Hydrogen analyzer
- Hydrogen compressor
- Hydrogen economy
- Hydrogen embrittlement
- Hydrogen leak testing
- Hydrogen pipeline transport
- Hydrogen piping
- Hydrogen purifier
- Hydrogen purity
- Hydrogen safety
- Hydrogen sensor
- Hydrogen storage
- Hydrogen station
- Hydrogen tank
- Hydrogen tanker
- Hydrogen technologies
- Hydrogen valve
- Industrial gas
- Liquid Hydrogen
- Next Generation Nuclear Plant (partly for hydrogen production)
- The Phoenix Project: Shifting from Oil To Hydrogen (book)
- Renewable energy
- The Hype about Hydrogen
- Lane hydrogen producer
- Linde-Frank-Caro process
- Liquid nitrogen production
- Underground hydrogen storage
- "Appendix C. Existing Hydrogen Production Capacity". The Impact of Increased Use of Hydrogen on Petroleum Consumption and Carbon Dioxide Emissions. U.S. Energy Information Administration. August 2008.
- Barlow, Zeke. "Breakthrough in hydrogen fuel production could revolutionize alternative energy market". Virginia Tech News. Virginia Tech. Retrieved 5 April 2013.
- Template:Cite report Energy, U. S. D. o. The Impact of Increased Use of Hydrogen on Petroleum Consumption and Carbon Dioxide Emissions. 84 (Energy Information Administration, Washington, DC, 2008)
- Ogden, J.M. (1999). "Prospects for building a hydrogen energy infrastructure". Annual Review of Energy and the Environment 24: 227–279. doi:10.1146/annurev.energy.24.1.227.
- Template:Roman J. Press, K. S. V. S., Massoud J. Miri, Alla V. Bailey, Gerald A. Takacs. Introduction to hydrogen Technology. 307 (John Wiley & Sons, Inc., 2008).
- Häussinger, Peter; Lohmüller, Reiner; Watson, Allan M. (2011). "Hydrogen, 1. Properties and Occurrence". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a13_297.pub2. ISBN 978-3-527-30673-2.
- Fossil fuel processor
- Collodi, Guido (2010-03-11). "Hydrogen Production via Steam Reforming with CO2 Capture" (PDF). http://www.aidic.it/CISAP4/. Retrieved 2015-11-28. External link in
- "HFCIT Hydrogen Production: Natural Gas Reforming". U.S. Department of Energy. 2008-12-15.
- Port Arthur II Integrated Hydrogen/Cogeneration Facility, Port Arthur, Texas Power magazine, September 2007
- https://www.hfpeurope.org/infotools/energyinfos__e/hydrogen/main03.html[full citation needed]
- Kværner-process with plasma arc waste disposal technology
- Hordeski, M. F. Alternative fuels: the future of hydrogen. 171-199 (The Fairmont Press, inc., 2007).
- Lee, Woon-Jae; Lee, Yong-Kuk (2001). "Internal Gas Pressure Characteristics Generated during Coal Carbonization in a Coke Oven". Energy & Fuels 15 (3): 618–23. doi:10.1021/ef990178a.
- El Gemayel, Jimmy. "Simulation of the integration of a bitumen upgrading facility and an IGCC process with carbon capture". FUEL Journal. Retrieved 2014-01-30.
- "HYDROFILL PRO".
- "HyLYZER™ PEM Electrolyser".
- "ITM power products page".
- Badwal, Sukhvinder P.S.; Giddey, Sarbjit; Munnings, Christopher. "Hydrogen production via solid electrolytic routes". Wiley Interdisciplinary Reviews: Energy and Environment 2 (5): 473–487. doi:10.1002/wene.50.
- Hauch, Anne; Ebbesen, Sune Dalgaard; Jensen, Søren Højgaard; Mogensen, Mogens (2008). "Highly efficient high temperature electrolysis". Journal of Materials Chemistry 18 (20): 2331–40. doi:10.1039/b718822f.
- In the laboratory, water electrolysis can be done with a simple apparatus like a Hofmann voltameter:"Electrolysis of water and the concept of charge".
- "Nuclear power plants can produce hydrogen to fuel the 'hydrogen economy'" (Press release). American Chemical Society. March 25, 2012. Retrieved March 9, 2013.
- Clarke, R.E.; Giddey, S.; Ciacchi, F.T.; Badwal, S.P.S.; Paul, B.; Andrews, J. (2009). "Direct coupling of an electrolyser to a solar PV system for generating hydrogen". International Journal of Hydrogen Energy 34 (6): 2531–42. doi:10.1016/j.ijhydene.2009.01.053.
- Badwal, Sukhvinder P. S.; Giddey, Sarbjit S.; Munnings, Christopher; Bhatt, Anand I.; Hollenkamp, Anthony F. (24 September 2014). "Emerging electrochemical energy conversion and storage technologies (open access)". Frontiers in Chemistry 2. doi:10.3389/fchem.2014.00079.
- Li-Hung Lin, Pei-Ling Wang, Douglas Rumble, Johanna Lippmann-Pipke, Erik Boice, Lisa M. Pratt, Barbara Sherwood Lollar, Eoin L. Brodie, Terry C. Hazen, Gary L. Andersen, Todd Z. DeSantis, Duane P. Moser, Dave Kershaw, and T. C. Onstott (2006). "Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome". Science 314 (5798): 479–82. Bibcode:2006Sci...314..479L. doi:10.1126/science.1127376. PMID 17053150.
- Producing hydrogen: The Thermochemical cycles
- IEA Energy Technology Essentials - Hydrogen Production & Distribution, April 2007
- "HTTR High Temperature engineering Test Reactor". Httr.jaea.go.jp. Retrieved 2014-01-23.
- https://smr.inl.gov/Document.ashx?path=DOCS%2FGCR-Int%2FNHDDELDER.pdf. Progress in Nuclear Energy Nuclear heat for hydrogen production: Coupling a very high/high temperature reactor to a hydrogen production plant. 2009
- Status report 101 - Gas Turbine High Temperature Reactor (GTHTR300C)
- JAEA’S VHTR FOR HYDROGEN AND ELECTRICITY COGENERATION : GTHTR300C
- Chukwu, C., Naterer, G. F., Rosen, M. A., "Process Simulation of Nuclear-Produced Hydrogen with a Cu-Cl Cycle", 29th Conference of the Canadian Nuclear Society, Toronto, Ontario, Canada, June 1–4, 2008. 
- Report No 40: The ferrosilicon process for the generation of hydrogen
- Candid science: conversations with famous chemists, István Hargittai, Magdolna Hargittai, p. 261, Imperial College Press (2000) ISBN 1-86094-228-8
- Hemschemeier, Anja; Melis, Anastasios; Happe, Thomas (2009). "Analytical approaches to photobiological hydrogen production in unicellular green algae". Photosynthesis Research 102 (2–3): 523–40. doi:10.1007/s11120-009-9415-5. PMC 2777220. PMID 19291418.
- DOE 2008 Report 25 %
- Jenvanitpanjakul, Peesamai (February 3–4, 2010). Renewable Energy Technology And Prospect On Biohydrogen Study In Thailand (PDF). Steering Committee Meeting and Workshop of APEC Research Network for Advanced Biohydrogen Technology. Taichung: Feng Chia University.
- Navarro Yerga, Rufino M.; Álvarez Galván, M. Consuelo; Del Valle, F.; Villoria De La Mano, José A.; Fierro, José L. G. (2009). "Water Splitting on Semiconductor Catalysts under Visible-Light Irradiation". ChemSusChem 2 (6): 471–85. doi:10.1002/cssc.200900018. PMID 19536754.
- Navarro, R.M.; Del Valle, F.; Villoria De La Mano, J.A.; Álvarez-Galván, M.C.; Fierro, J.L.G. (2009). "Photocatalytic Water Splitting Under Visible Light: Concept and Catalysts Development". Photocatalytic Technologies. Advances in Chemical Engineering 36. pp. 111–43. doi:10.1016/S0065-2377(09)00404-9. ISBN 978-0-12-374763-1.
- Tao, Y; Chen, Y; Wu, Y; He, Y; Zhou, Z (2007). "High hydrogen yield from a two-step process of dark- and photo-fermentation of sucrose". International Journal of Hydrogen Energy 32 (2): 200–6. doi:10.1016/j.ijhydene.2006.06.034.
- Rajanandam, Brijesh; Kiran, Siva (2011). "Optimization of hydrogen production by Halobacterium salinarium coupled with E coli using milk plasma as fermentative substrate". Journal of Biochemical Technology 3 (2): 242–4.
- Percival Zhang, Y.-H.; Evans, Barbara R.; Mielenz, Jonathan R.; Hopkins, Robert C.; Adams, Michael W.W. (2007). Melis, Anastasios, ed. "High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic Pathway". PLoS ONE 2 (5): e456. doi:10.1371/journal.pone.0000456. PMC 1866174. PMID 17520015.
- Percival Zhang, Y.-H. (2010). "Production of biocommodities and bioelectricity by cell-free synthetic enzymatic pathway biotransformations: Challenges and opportunities". Biotechnology and Bioengineering 105 (4): 663–77. doi:10.1002/bit.22630. PMID 19998281.
- Percival Zhang, Y-H; Sun, Jibin; Zhong, Jian-Jiang (2010). "Biofuel production by in vitro synthetic enzymatic pathway biotransformation". Current Opinion in Biotechnology 21 (5): 663–9. doi:10.1016/j.copbio.2010.05.005. PMID 20566280.
- Ye, Xinhao; Wang, Yiran; Hopkins, Robert C.; Adams, Michael W. W.; Evans, Barbara R.; Mielenz, Jonathan R.; Percival Zhang, Y.-H. (2009). "Spontaneous High-Yield Production of Hydrogen from Cellulosic Materials and Water Catalyzed by Enzyme Cocktails". ChemSusChem 2 (2): 149–52. doi:10.1002/cssc.200900017. PMID 19185036.
- Percival Zhang, Y.-H. (2009). "A sweet out-of-the-box solution to the hydrogen economy: Is the sugar-powered car science fiction?". Energy & Environmental Science 2 (3): 272–82. doi:10.1039/b818694d.
- "Gassed up: A new, green way to make hydrogen". The Economist. May 24, 2007. Retrieved March 9, 2013.
- Edwards, Chris (June 18, 2008). "Synthetic biology aims to solve energy conundrum". The Guardian. Retrieved March 9, 2013.
- "Synthetic Biology Department: Aims". Lawrence Berkeley National Laboratory. Archived from the original on July 5, 2007.
- Strik, David P. B. T. B.; Hamelers (Bert), H. V. M.; Snel, Jan F. H.; Buisman, Cees J. N. (2008). "Green electricity production with living plants and bacteria in a fuel cell". International Journal of Energy Research 32 (9): 870–6. doi:10.1002/er.1397. Lay summary – Wageningen University and Research Centre.
- Timmers, Ruud (2012). Electricity generation by living plants in a plant microbial fuel cell (PhD Thesis). ISBN 978-94-6191-282-4.[page needed]
- "Virginia Tech team develops process for high-yield production of hydrogen from xylose under mild conditions". Green Car Congress. 2013-04-03. doi:10.1002/anie.201300766. Retrieved 2014-01-22.
- Martín Del Campo, J. S.; Rollin, J.; Myung, S.; Chun, Y.; Chandrayan, S.; Patiño, R.; Adams, M. W.; Zhang, Y. -H. P. (2013). "High-Yield Production of Dihydrogen from Xylose by Using a Synthetic Enzyme Cascade in a Cell-Free System". Angewandte Chemie International Edition 52 (17): 4587. doi:10.1002/anie.201300766.
- "New Horizons for Hydrogen" (PDF). Research Review (National Renewable Energy Laboratory) (2): 2–9. April 2004.
- DiMascio, Felice; Willauer, Heather D. ; Hardy, Dennis R. ; Lewis, M. Kathleen ; Williams, Frederick W. (July 23, 2010). Extraction of Carbon Dioxide from Seawater by an Electrochemical Acidification Cell. Part 1 – Initial Feasibility Studies (PDF) (memorandum report). Washington, DC: Chemistry Division, Navy Technology Center for Safety and Survivability, U.S. Naval Research Laboratory. Retrieved September 7, 2012. Cite uses deprecated parameter
- Willauer, Heather D.; DiMascio, Felice ; Hardy, Dennis R. ; Lewis, M. Kathleen ; Williams, Frederick W. (April 11, 2011). Extraction of Carbon Dioxide from Seawater by an Electrochemical Acidification Cell. Part 2 – Laboratory Scaling Studies (PDF) (memorandum report). Washington, DC: Chemistry Division, Navy Technology Center for Safety and Survivability, U.S. Naval Research Laboratory. Retrieved September 7, 2012. Cite uses deprecated parameter
- Eisaman, Matthew D.; et al. (2012). "CO2 extraction from seawater using bipolar membrane electrodialysis" (PDF). Energy and Environmental Science 5 (6): 7346–52. doi:10.1039/C2EE03393C. Retrieved September 7, 2012.
- Willauer, Heather D.; Hardy, Dennis R.; Williams, Frederick W. (September 29, 2010). Feasibility and Current Estimated Capital Costs of Producing Jet Fuel at Sea (PDF) (memorandum report). Washington, DC: Chemistry Division, Navy Technology Center for Safety and Survivability, U.S. Naval Research Laboratory. Retrieved September 7, 2012.
|Wikimedia Commons has media related to Hydrogen production.|
- U.S. DOE 2012-Technical progress in hydrogen production
- U.S. NREL article on hydrogen production
- Komatsu, Teruyuki; Wang, Rong-Min; Zunszain, Patricia A.; Curry, Stephen; Tsuchida, Eishun (2006). "Photosensitized Reduction of Water to Hydrogen Using Human Serum Albumin Complexed with Zinc−Protoporphyrin IX". Journal of the American Chemical Society 128 (50): 16297–301. doi:10.1021/ja0656806. PMID 17165784. Lay summary – Imperial College London (December 1, 2006).