Hydrogen Production for Fuel Cells

Only small amounts of hydrogen occur naturally on Earth, yet the US Department of Energy estimates that the USA uses about 9 million tons per year, and, that this is set to grow if the "hydrogen economy" ever eventuates.

About 95% of the hydrogen in use is produced through steam reforming of natural gas, a catalytic process in which steam reacts with methane to yield carbon monoxide and hydrogen. This mixture is known as synthesis gas, or syngas, and is an intermediate in production processes for synthetic fuels, ammonia, methanol and other compounds.

Hydrogen is a high energy density fuel that is being considered as a cleaner source of future energy, particularly for low-temperature fuel-cell powered devices including vehicles. Fuel cells use electrochemical process to convert hydrogen and oxygen into water, producing current that powers a motor. Fuel cell vehicles require highly purified hydrogen such as is produced in the water-gas-shift reaction. This reaction strips residual carbon monoxide from the hydrogen generated through steam reforming of fossil fuels. Water-gas-shift catalysts decrease the amount of carbon monoxide in hydrogen and increase the hydrogen content by harvesting hydrogen from water molecules.

Currently, copper-based catalysts supported on zinc oxide and alumina are in use. Copper is pyrophoric, it can spontaneously ignite when exposed to air, so researchers have been looking for other more stable catalysts.

Platinum supported on cerium oxide is known to work, but platinum is expensive and cerium occurs in only a few places around the world. Scientists have discovered that sodium improves the platinum activity in the water-gas-shift reaction, which can now take place at low temperatures, even on inert materials such as silica. Less platinum is required, so the cost of hydrogen production should decrease.

Reference:
Yanping Zhai, Danny Pierre, Rui Si, Weiling Deng, Peter Ferrin, Anand U. Nilekar, Guowen Peng, Jeffrey A. Herron, David C. Bell, Howard Saltsburg, Manos Mavrikakis, and Maria Flytzani-Stephanopoulos. Alkali-Stabilized Pt-OHx Species Catalyze Low-Temperature Water-Gas Shift Reactions. Science, 24 September 2010: Vol. 329. no. 5999, pp. 1633 - 1636 DOI: 10.1126/science.1192449

Further Reading
Reaction Rates
Batteries and Fuel Cells

Study Questions

1. What are the 6 most abundant elements on Earth?
2. Natural Gas is the name given to a hydrocarbon. Give the IUPAC name and formula for this compound.
3. Write a balanced chemical reaction for the reaction between steam and natural gas to yield carbon monoxide and hydrogen.
4. Write equations to represent the electrochemical process to convert hydrogen and oxygen into water in a hydrogen fuel cell.
5. Cerium oxide is also known as ceria. Write a possible chemical formula for ceria.
6. Give the systematic name for alumina, and write its formula.
7. Give the systematic name for silica, and write its formula.
   

Pentane from Oil

Crude oil is refined by "cracking", the process in which large molecules are broken up into smaller molecules. The products of the cracking process include gasoline (petrol), kerosene, heating oil and lubricants. Catalysts can be used to further refine these hydrocarbons.

Rice University scientists have discovered that sub-nanometer clusters of active tungsten oxide lying on top of inert zirconium oxide (zirconia) are a highly efficient catalyst that turns straight-chain molecules of pentane, one of the many hydrocarbons present in gasoline (petrol), into better burning branched-chain hydrocarbons. This process of rearranging the carbon and hydrogen atoms in a molecule is referred to as isomerization.

Reference:
Nikolaos Soultanidis, Wu Zhou, Antonis C. Psarras, Alejandro J. Gonzalez, Eleni F. Iliopoulou, Christopher J. Kiely, Israel E. Wachs, Michael S. Wong. Relatingn-Pentane Isomerization Activity to the Tungsten Surface Density of WOx/ZrO2. Journal of the American Chemical Society, 2010; : 100903140709054 DOI: 10.1021/ja105519y

Further Reading
Organic Nomenclature
Naming Straight Chain Alkanes
Naming Branched-Chain Alkanes
Isomers of Alkanes
Uses of Hydrocarbons
Ethene

Study Questions

1. What is meant by the term hydrocarbon?
2. Give the names of 4 hydrocarbons.
3. Give the molecular formula for each of the hydrocarbons named above.
4. Give the molecular formula and the condensed molecular formula for pentane.
5. Draw the structural formula for pentane.
6. Draw the structural formula for all the possible isomers of pentane.
7. Name each of the isomers drawn above.
8. Why do you think that the branched-chain isomers of pentane are referred to as "better burning" hydrocarbons? Explain your answer.
   

Diacetylene in Space

Diacetylene, C₄H₂, has previously been discovered in the atmosphere of Titan and on the Moon. Polish scientists have recently observed it in translucent interstellar clouds.

The density of translucent interstellar clouds is extremely small, much less than the best vacuum we can produce in a laboratory, but because they are huge in size their gas molecules have a chance to interact with penetrating radiation, so scientists can use spectroscopy to study the composition of these translucent interstellar clouds.

Molecules absorb and emit photons of specific energies, and therefore wavelengths, corresponding to the differences between energy levels in their atomic structure. The light from stars that reaches the Earth is slightly changed as a result of interactions with gas particles in translucent clouds, it lacks the wavelengths absorbed by intervening interstellar atoms and molecules. Until now, compounds composed of no more than a few atoms have been found in these clouds, molecules such as C₃ andH₃⁺. It is possible that diacetylene is quite a common component of the interstellar medium, having now been located in two carbon-rich galaxy regions and in the averaged data coming from a dozen other lines of sight.

Reference
Institute of Physical Chemistry of the Polish Academy of Sciences (2010, September 17). Surprisingly complicated molecule found in outer space. ScienceDaily. Retrieved September 18, 2010, from http://www.sciencedaily.com­ /releases/2010/09/100915084456.htm

Further Reading
Spectroscopy : http://www.ausetute.com.au/spectros.html
Nomenclature : http://www.ausetute.com.au/namctut1.html
Alkynes : http://www.ausetute.com.au/namsynes.html

Study Questions:

1. Draw the structural formula for diacetylene, C₄H₂.
2. Give the systematic IUPAC name for diacetylene.
3. To which homologous series does the diacetylene molecule belong?
4. Give the empirical formula for the diacetylene molecule.
   
5. Is diacetylene an example of a saturated or unsaturated hydrocarbon? Explain your answer.
6. In Titan's atmosphere, diacetylene could be produced from the reaction between acetylene, C₂H₂, and the ethynyl radical C₂H. Write a possible chemical equation to represent this reaction.
7. Would you expect diacetylene to react with bromine water? Explain your answer.
8. Would you expect diacetylene to be easily oxidized? Explain your answer.
   

Looking Inside Lithium Ion Batteries

Lithium-ion batteries are used to power electronic devices such as mobile phones (cell phones) and are widely used because of their low weight, high energy density and recharging ability. If scientists could see the batteries working at the nanoscale, observing the functionality of the batteries at the level of a single grain or an extended defect, they could determine what makes one battery work and another one fail.
Department of Energy's Oak Ridge National Laboratory (ORNL) scientists have developed a new type of scanning probe microscopy called electrochemical strain microscopy (ESM) to examine the movement of lithium ions through a battery's cathode material. They showed that the lithium ion flow could concentrate along grain boundaries, leading to cracking and battery failure.

Reference:
N. Balke, S. Jesse, A. N. Morozovska, E. Eliseev, D. W. Chung, Y. Kim, L. Adamczyk, R. E. García, N. Dudney, S. V. Kalinin. Nanoscale mapping of ion diffusion in a lithium-ion battery cathode. Nature Nanotechnology, 2010; DOI: 10.1038/nnano.2010.174

Further Reading:
Batteries
Galvanic Cells
Oxidation and Reduction

Study Questions

1. What is the difference between a battery and an electrochemical (galvanic or voltaic) cell?
2. Is the lithium-ion battery described in the article an example of a primary or secondary cell? Explain your answer.
3. Draw a sketch of a galvanic (voltaic) cell. Label the anode, cathode, and electrolyte. Clearly show the direction of electron flow through the cell.
4. Explain how the galvanic (voltaic) cell above could be recharged.
5. In the lithium-ion battery in the article above, will lithium ions be produced at the anode or the cathode while the battery is being discharged?
6. Describe the movement of lithium ions in the lithium-ion battery described above during the process of recharging the battery.
   

Bilirubin

Bilirubin is the compound responsible for the yellow colour of bruises and urine. It is formed during the breakdown of red blood cells in animals.

Scientists at the Florida International University have now identified bilirubin in the Bird of Paradise plant. Using high-performance liquid chromatography (HPLC) and HPLC/electrospray ionization-tandem mass spectrometry, the scientists discovered bilirubin in the seeds and sepals of the plant.

Reference:
Pirone, Cary, Johnson, Jodie V., Quirke, J. Martin E., Priestap, Horacio A., Lee, David. The Animal Pigment Bilirubin Identified in Strelitzia reginae, the Bird of Paradise Flower. HortScience, 2010; 45: 1411-1415

Further Reading
Organic nomenclature
Functional groups
Chromatography

Study Questions

1. Give the molecular formula for the bilirubin molecule.
   
2. Identify the functional groups present in a molecule of bilirubin by circling them on the structure.
3. Name each of the functional groups above.
4. Is bilirubin an example of a saturated or an unsaturated organic molecule? Explain your answer.
5. Would you expect bilirubin to undergo a reaction with a mild oxidizing agent? Explain your answer.
6. Why do you think that bilirubin is a coloured compound?
7. Why do you think that scientists were initially surprised to find bilirubin in plants?
   

Magic Numbers

Scientists who study the nuclei of atoms apply the "magic" moniker to elements with a certain number of protons or combinations of protons and neutrons. At the magic numbers of 2, 8, 20, 28, 50, 82 and 126 the protons and neutrons are tightly bound together, giving many "magic" elements a high degree of nuclear stability.

Rutgers scientists have been studying an isotope of tin that is "doubly magic", it contains 50 protons and 82 neutrons. Unlike other magic nuclei that are stable, this isotope of tin is very unstable with a half-life of 40 seconds.

The scientists believe that this isotope of tin may be formed in supernova explosions or collisions of neutron stars, and could be part of the process that forms heavier elements.

Reference:
K. L. Jones, A. S. Adekola, D. W. Bardayan, J. C. Blackmon, K. Y. Chae, K. A. Chipps, J. A. Cizewski, L. Erikson, C. Harlin, R. Hatarik, R. Kapler, R. L. Kozub, J. F. Liang, R. Livesay, Z. Ma, B. H. Moazen, C. D. Nesaraja, F. M. Nunes, S. D. Pain, N. P. Patterson, D. Shapira, J. F. Shriner, M. S. Smith, T. P. Swan, J. S. Thomas. The magic nature of ¹³²Sn explored through the single-particle states of ¹³³Sn. Nature, 2010; 465 (7297): 454 DOI: 10.1038/nature09048

Further Reading
Isotopes
Nuclear Decay
Half-life

Study Questions

1. Explain what is meant by the term isotope.
2. What is the atomic number for the tin isotope described in the article above?
3. What is the mass number for the tin isotope described in the article above?
4. What are the names of the elements that have a nucleus containing the following "magic" numbers of protons:
   
• 2
• 8
• 20
• 28
• 50
• 82
5. Explain what is meant by the term half-life.
6. The half-life of the tin isotope described above is 40 seconds.
   
   • If the original sample had a mass of 0.1g, what mass of tin isotope would be present in the sample after 2 minutes?
   • What percentage of the mass of the original sample would be present after 80 seconds?
   
   

Phosphorus

Phosphorus deposits come from fossilized animals skeletons. Purifying these deposits produces white phosphorus, a tetrahedral P₄ molecule.

Organophosphorus compounds such as those found in pesticides are produced commercially in a two step process:

1. three of the atoms in P₄ are replaced with chlorine atoms to produce PCl₃
2. chlorine atoms are then displaced by organic molecules

This process is both wasteful and dangerous, chlorine is a toxic gas. It would be very beneficial if scientists could find a way of producing organophosphorus compounds without the need for chlorine.

It has been known since 1937 that P₄ can be broken into two molecules of P₂ using ultraviolet light and that the P₂ will polymerize into red phosphorus.

Massachusetts Institute of Technology (MIT) Chemists have just used UV light to break P4 molecules apart in the presence of unsaturated organic molecules in order to form tetra-organo diphosphane, a molecule made up of 2 atoms of phosphorus attached to 2 molecules of the organic compound.

Reference:
Daniel Tofan, Christopher C. Cummins. Photochemical Incorporation of Diphosphorus Units into Organic Molecules. Angewandte Chemie International Edition, 2010; DOI: 10.1002/anie.201004385

Further Reading
Allotropes

Study Questions

1. Name the allotropes of phosphorus
2. Explain the ways in which these allotropes of phosphorus are similar and the ways in which they are different to each other.
3. Write a sequence of chemical equations to represent the series of stages in the two step process to produce commercial organophosphorus compounds.
4. Write a chemical equation to represent the breaking up of P₄ molecules into P₂ molecules using UV light.
5. Explain what is meant by the term polymerize.
6. Explain the difference between saturated and unsaturated organic compounds.
   
7. Why do you think that MIT chemists used unsaturated rather than saturated organic compounds in their experiment with P₄?