Hydrogen Production and Utilization: Challenges and Opportunities

Dear Colleague,

Hydrogen is a surprising material. In its elemental state, it forms two-atomic molecules, H₂, that are expectedly very stable, given their high bonding energy of 440 kJ/mol. Molecular hydrogen is indeed not very active, and for its numerous applications, the H₂ molecules first need to be subjected to dissociation into atomic hydrogen. The single hydrogen atoms, in contrast, are considered to be extremely active and cannot be stored in a gaseous form, as they undergo immediate recombination. One solution to this predicament is to produce atomic hydrogen immediately before use, for which case the chemists of old have coined the term “in statu nascendi” hydrogen, meaning in Latin “at the moment of birth”. Another way is to fill voids in the crystal structure with guest hydrogen atoms in certain solid materials, applying them as the host lattice. Still, such intercalation must be preceded by an act of H₂ dissociation, which usually occurs upon contact between gaseous hydrogen and certain metals, mostly the noble, Pt, Pd, or the semiprecious, including Ni and Cu. Here comes the surprising moment: in spite of its apparent stability, the dissociation of H₂ proceeds rapidly at rather mild conditions and, moreover, turns out to be an exothermic process, despite the large barrier of its 440 kJ/mol bonding energy to be overcome. So, it is not always totally clear where the energy for splitting the H–H bond comes from during dissociation, since the atomic hydrogen species produced do not seem to form any strong bonds, or indeed any bonds at all, within the structure of their eventual host lattice. This seems to be a paradox, often ignored. Hydrogen is undoubtedly far too important an energy vector, and a material of too great industrial relevance for us, to let the progress of its technology to be slowed down by any scientific uncertainties. Only certain rare events, like exceptionally strong hydrogen explosions, or surprisingly anomalous scientific outcomes, like low-energy nuclear reaction (LENR) effects, still act as a reminder that we do not know everything about hydrogen yet. But if there is a hidden source of energy in hydrogen, how can it be harvested?

Hydrogen is not a natural resource; it does not appear in nature in its elemental form. It has to be produced from non-renewable resources like natural gas, and currently, the process of steam methane reforming (SMR) is the most widely used technology, covering around half of the global demand. The alternatives are legion. Various other hydrocarbons and alcohols may also be steam reformed. In particular, ethanol steam reforming (ESR), utilizing bioethanol as a renewable resource material, may be a way to limit the depletion of the finite resources. Other alternatives include the pyrolysis of hydrocarbons and the electrolysis of water. However, all of those methods consume high amounts of energy. Moreover, raw hydrogen contains impurities (like CO) and has to be carefully purified before it is usable for certain, more refined applications, like fuel cells, which consumes even more energy. Perhaps it is worthwhile to search for a way to apply the LENR effects, if still unconventional and indeed barely emerging from the scientific underground, in an effort to mitigate the high energy cost of hydrogen production.

This Special Issue welcomes contributions focused on hydrogen production and purification, as well as its energetic and environmentally friendly uses. Both conventional and less conventional aspects will be considered, but efforts to specifically gain insight into the energetic effects of investigated reactions will be appreciated. Manuscripts reporting any experimental or theoretical approaches will be considered.

Dr. Erwin Lalik
Guest Editor

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• catalytic stem reforming of methane (MSR) and other hydrocarbons
• catalytic stem reforming of alcohols, including bio-alcohols
• hydrogen purification methods and processes
• catalytic hydrogenation reactions
• catalytic hydrogen-assisted processes
• electrochemical systems, such as fuel cells or electrolytic hydrogen evolution processes
• catalytic oxidation of hydrogen
• low-energy nuclear reactions (LENR)
• hydrogen evolution reactions
• pseudocapacitive materials
• electrochemical energy storage systems
• application of hydrogen as fuel