Introduction Pef
The particular importance ofsurface effects in hydrogen adsorption and absorption by metals, for getters, permanent magnets, in catalytic reactions, battery electrode reaction, H embrittlement and plasma-wall interaction in fusion stems from two facts The first relates to the surface itself.The sharp discontinuity of matter with electric charges and potentials of electrons and atom cores at the surface together with the loss of periodicity in the direction orthogonal to the surface leads to...
Chemisorption on Metal Surfaces
The electronic properties of elemental metals, ordered and disordered alloys and metal hydrides, and the experimental and theoretical methods to study them are described in Chapter 4.3 by I. Chorkendorf.Here we restrict ourselves to a short overview. The isolated H2 molecule possesses an occupied 1ag, bonding level well below the bottom of most metal bands and a 1au, antibonding level above EF. At large distances from the metal surface, the electronic structure of H2 is little affected by the...
A Survey of Effects Phenomena and Models
The adsorption of H is conveniently described in terms of simplified one-dimensional potential energy curves for an H plus a molecule and for two H atoms on a clean metal surface Figure 4.11 . Far from the surface the two curves are separated by the heat of dissociation D 218 kJ mol H 1 4.746eV 51 . The first attractive interaction of the hydrogen molecule approaching the metal surface is the Van der Waals force leading to the physisorbed state Phys 5 kJ mol H -1 approximately one hydrogen...
Chemisorption on Metal Oxides
The surfaces of metal oxides and their H2 chemisorption characteristics have been far less studied than the surfaces of elemental metals and semiconductors 113,133 . Cation surface states are formed on ideal oxide surfaces at about 2 eV below the bottom ofthe conduction band. The charge of the surface ions is found to be reduced compared with that of the bulk ions and this leads to an enhanced covalency at the surface. The reduction amounts to less than 10 for oxides of simple metals such as...
Hydrogen in the Twenty First Century
During the twenty first century, the world pattern ofenergy usage has to be transformed. To continue our ever increasing dependence on fossil fuels is futile and will accelerate the onset of further extreme climatic events. Hydrogen has the potential to be a key factor in this transformation. This chapter has outlined the hydrogen cycle-based principles, by which the change from fossil fuel dominance to a sustainable global energy system can be achieved. The penetration and growth ofhydrogen...
Physical Properties
In hydrogen, the interaction between molecules is weak as compared to other gases, therefore the critical temperature is low Tc 33.0 K . The melting curve, the solid-liquid boundary in a p-T diagram, has been determined by several groups 11 for p-H2 and n-D2. The following functions were determined by least-squares Table 4.3 Vapor pressure and density of p-hydrogen at low temperatures Temperature K Vapor pressure kPa pS p l pc aTriple point. b 101.3 kPa. c Critical point. pm -51.49 0.1702 Tm...
The Carbon Cycle
Living systems are characterized by a continuous exchange ofmaterial and energy with their environment. The chemical energy responsible for maintaining life on the planet is produced by complex photochemical reactions involving the photochemical reduction of CO2 with water to organic forms of carbon and molecular oxygen. The process is referred to as photosynthesis. The photosynthetic conversion of CO2 and water to glucose and oxygen absorbs an energy equivalent of 2800 kJ mol-1 The reverse...
Hydrogen Isotopes
Hydrogen 1 hydrogenium, vhrnp the water, yevveiv to give birth is the first element in the periodic table of the elements having the atomic number 1 and the electron configuration 1s1. Hydrogen was prepared many years before it was recognized as a distinct substance by Cavendish in 1766 and it was named by Lavoisier. Hydrogen is the most abundant of all elements in the universe and it is thought that the heavier elements were, and still are, built from hydrogen and helium. It has been estimated...
Hydrogen Molecule
The isotopes H, D and T form diatomic molecules. The interaction potential energy of two hydrogen atoms goes through a minimum at a certain interatomic distance when two electrons form a singlet state1 Eg , namely, the state with a total electron spin equal to zero the combination of two electrons with opposite spin . The energy of the triplet state 3Eu , having a total electron spin of unity, increases when two hydrogen atoms with parallel spin approach each other. Hydrogen atoms of opposite...
Carbon Reservoirs
Human beings developed on Earth on the basis of plants, that is biomass, as the only energy carrier. The average power consumed by a human body at rest is 0.1 kW and approximately 0.4 kW for a hard working body, delivering about 0.1 kW of work. The consumption of plants by humans and animals did not change the atmosphere because the carbon dioxide liberated by humans and animals was reabsorbed by the plants in the photosynthesis process. The only mechanical work available from nonliving systems...
Equation of State
Among the most fundamental knowledge about the thermodynamic properties of hydrogen is the equation of state EoS , namely, the volume as a function of pressure and temperature V p,T . Once the EoS is known, all the thermodynamic quantities can be calculated. The Gibbs energy G p,T and entropy S p,T can be obtained by integration Table 4.5 Physical properties of liquid and gaseous para-hydrogen p-H2 and normal-hydrogen n-H2 Table 4.5 Physical properties of liquid and gaseous para-hydrogen p-H2...
The Theoretical Approach
When a H2 molecule approaches a metal surface, as indicated in Figure 4.14 it will first feel the van der Waals interaction. This is a weak interaction due to polarization effects, which typically amounts to only 10 kJ mol-1 for H2 and thus only leads to adsorption at very low temperatures or high pressures. When approaching even closer there may be an exchange between the hydrogen electrons and the electrons in the metal leading to associative chemisorption, that is the H2 molecule remians...
Biomass and Hydrogen
The chemical composition of biomass with respect to carbon, hydrogen and oxygen can be approximated by the formula C6H9O4, that is biomass contains a little less Fossil fuel consumption 5.3 Solar radiation hitting earth surface 4.67 1021 based on glucose as primary product of photosynthesis 2.33 1021 Ref. 27 oxygen than the primary product of photosynthesis, glucose C6Hi2O lt s , but much more than fossil fuels CH2 to CH4 . The oxidation state of carbon in biomass is close to zero while for...
Ignition and Detonation Performance
Hydrogen reacts, when the ignition energy thermal activation energy of 0.02 mJ is provided, violently with oxidizing agents such as oxygen air , fluorine or chlorine and N2O. Combustion, deflagration or detonation may occur, depending on the conditions. The ignition and detonation properties of hydrogen-air mixtures are particularly important from the safety aspect. The flammability limits i.e. the minimum and the maximum concentration of hydrogen in air are exceptionally wide for hydrogen....
Hydrogen in Transportation
Cavendish, who called hydrogen inflammable air, was also the first to measure its density. He reported in his 1766 paper that hydrogen is 7 to 11 times lighter than air the correct value is 14.4 . Cavendish's results not only opened up a new chapter in the history of gases, but also attracted attention to hydrogen as an alternative to hot air as a buoyant gas. Jacques Alexandre Cesar Charles was the first to take advantage of this, soon after the first public demonstration by the Mongolfier...
JouleThomson Effect Inversion Curve
The differential coefficient was first investigated by James Joule and William Thomson in the 1850s 23 , before Thomson was elevated to the peerage, to become the first Lord Kelvin. So it is also referred to as the Joule-Kelvin coefficient. It is a measure of the effect of the throttling process on a gas, when it is forced through a porous plug, or a small aperture or nozzle. The drop in pressure, at constant enthalpy H, has an effect on temperature. The enthalpy of hydrogen as a Van der Waals...
Potential Hazards ofthe Hydrogen Economy
Effects on the Environment Until recently, it was assumed that migration to a hydrogen fuel economy would have no negative aspects for the environment. However, in mid-2002, it was proposed that the widespread use of hydrogen could lead to hitherto unknown environmental impacts due to hydrogen emissions 56 , the central claim being there will be substantial leakage of hydrogen associated with the production, transportation and storage of hydrogen. It is estimated that the total anthropogenic...
References 1
1 In photosynthesis, water is split, releasing oxygen as a by-product. The hydrogen is used to produce ATP and NADPH, the energy carriers of the living cell. See Purves, W.K., Savada, D., Orians, G.H., Heller, H.C. 2003 Life The Science of Biology, Sinauer Associates, Inc. Publishers, Sunderland, USA. 4 David, J.-L., Painter, F. 1748-1825 Neo-classicism Portrait of Monsieur Lavoisier 5 Weber, R. 1988 Der sauberste Brennstoff, Band 3 der OLYNTHUS-Reihe, Oberb zberg, ISBN 3-907175-10-7....
Preface
Thermodynamically speaking a human being, like any animal, is an engine combusting an energy carrier like food into work. In other words, the difference between living matter and dead matter is the ability to convert energy. Therefore, energy is essential for our existence and development. Natural processes led to a spontaneous accumulation of carbon- and hydrogen-based energy carriers - the so-called fossil fuels. A large amount of fossil fuels was given by nature, which allowed us to start...
The Hindenburg and Challenger Disasters
The LZ-129 Hindenburg and her sister-ship LZ-130 Graf Zeppelin II were the two largest aircrafts ever built. The Hindenburg was named after the President of Germany, Paul von Hindenburg. It was a brand new all-aluminum design 245 m long, 41 m in diameter, containing 211 890 m3 of gas in 16 bags or cells, with a Fig. 2.6 On May 6, 1937, at 19 25 the German zeppelin Hindenburg caught fire and was utterly destroyed within a minute while attempting to dock with its mooring mast at Lakehurst Naval...
Introduction Cfg
Global energy demand is forecast to double by 2050. By persisting in our use of current energy technologies most of this demand will be met by the increased use of our rapidly dwindling supplies of petrochemicals. In Europe alone, the oil import dependence is set to grow from 50 currently, to 70 or more, by 2025. Even more serious, the European Community is already dependent on oil for 90 of its transport needs. A central theme of this volume is that the Western economies must take the lead in...
Klaus Yvon
University of Geneva Laboratoire de Cristallographie 24 Quai Ernest Ansermet 1211 Geneve 4 Switzerland XIV List of Contributors Andreas Zuttel Empa Swiss Federal Laboratories for Materials Research and Testing, an ETH Domain Institute Laboratory for Hydrogen amp Energy 8600 DUbendorf Switzerland University of Fribourg Physics Department Condensed Matter Physics Perolles 1700 Fribourg Switzerland
Chemical Properties and Diffusion
Hydrogen is the element with the highest diffusion capacity because of its small size and small mass. Some diffusion coefficients 25 of hydrogen in gases and liquids are listed in Table 4.10 . In metals with a high hydrogen solubility a high hydrogen diffusion rate is also usually found. The diffusion coefficients are in the same range as for hydrogen ions in water 10-4 cm2 s-1 at 25 C . Table 4.10 Diffusion coefficients of hydrogen in gases p 101.3 kPa and liquids Table 4.10 Diffusion...
Timeline of the History of Hydrogen
Jan Baptista van Helmont 1577 to 1644 was one of the first to reject the basic elements ofAristoteles. He discovered that air is not an element and that another air with different properties exists. He called it, based on the Greek word chaos which means empty space, according to the Dutch spelling gas. In the Middle Ages Paracelsus 1493 to 1541 is reported to have noted that a gas is yielded when iron is dissolved in spirit of vitriole. Turquet De Mayerne 1573-1655 noted that this gas was...