• Scientists observe record high hydride i

    From ScienceDaily@1:317/3 to All on Tue Jan 25 21:30:44 2022
    Scientists observe record high hydride ion conductivity using modified lanthanum trihydride

    Date:
    January 25, 2022
    Source:
    Tokyo Institute of Technology
    Summary:
    Lanthanum trihydride, a compound of lanthanum and hydrogen, when
    lightly doped with oxygen shows potential as an efficient hydrogen
    carrier, according to a new study. Hydride ion (H--) conductors
    are expected to be used in chemical reactors and energy storage
    systems. However, the low H- - conductivity at room temperature
    introduces certain technical limitations. These limitations may
    now be overcome with this latest innovation by the researchers.



    FULL STORY ========================================================================== Fossil fuels such as coal, oil, and natural gas cannot last
    forever. Therefore, gradually decreasing our dependency on fossil fuels
    seems critical. Whereas alternative sources of energy such as solar or
    tidal energy can fill in the gap to some extent, they come with certain practical limitations. For example, utilizing solar energy requires the
    use of solar panels with large surface areas, thus making it a relatively expensive energy alternative.


    ==========================================================================
    In the recent past, scientists have explored multiple possibilities in an attempt to harness energy from various other sources. One such example
    includes the use of hydrogen-based energy systems. In this regard,
    lanthanum hydride, a compound of hydrogen and the metallic element
    lanthanum, has attracted quite a lot of attention. Because of its unique material properties, lanthanum hydride allows for superior hydride ion
    (H-) conductivity under certain conditions, which is the prerequisite
    for the efficient operation of chemical reactors and energy storage
    systems. However, most H-conductors show low H-conductivity at room temperature, which limits their application.

    In a new study, researchers from Tokyo Institute of Technology (Tokyo
    Tech) have now come up with a technological innovation that can be used
    to overcome this limitation and design the next generation of energy
    carriers. The research team, led by Prof. Hideo Hosono, senior author of
    the study and Honorary Professor, Tokyo Tech, has successfully prepared
    and characterized a hydrogen- rich lanthanum hydride, with the chemical
    formula "LaH3-2xOx," which shows a H- conductivity that is higher by three orders of magnitude when compared with the best conductor available. Their trick was to control the concentration of oxygen in LaH3-2xOx.

    The researchers used a two-step process to prepare LaH3-2xOx. The
    high-density LaH3-2xOx pellet prepared using the first high-pressure
    synthesis step had a large amount of hydrogen deficiency. Next, the
    researchers exposed these pellets to hydrogen gas atmosphere at an
    elevated temperature (400 DEGC) for an extended duration (10 hours) to
    fill the hydrogen vacancy. It resulted in the formation of "LaH2.8O0.1,"
    a novel material showing high ionic conductivity even at room temperature.

    Elaborating the concept behind their research, which is all set to be
    published in the Journal of the American Chemical Society, Prof. Hosono
    says, "Our study was driven by the idea that minimizing the amount of substituted O2- used to suppress the electronic conduction in LaH3-y
    should ideally make fast H- conduction in LaH3-2xOx at room temperature possible." Quite interestingly, the hydrogen-rich LaH3-2xOx also
    exhibited a low activation barrier -- an energy hurdle that it must
    overcome to successfully function as an efficient ionic conductor. In
    terms of the actual measurement, this low activation barrier was
    somewhere between 0.3 and 0.4 eV. Moreover, the low activation barrier was independently confirmed using computerized simulations. The simulations
    also showed that the H- ions far from O2- ions were highly mobile and some
    of them traveled long distances by knocking each other out, suggesting
    the presence of strong repulsive Coulombic interactions ideal for fast
    H- conduction.

    It seems there is good reason for Prof. Hosono to observe optimistically, "Hydrogen-rich LaH3-2xOx is a promising candidate for next-generation
    hydrogen carriers and can promote fossil fuel replacement!" ========================================================================== Story Source: Materials provided by Tokyo_Institute_of_Technology. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Keiga Fukui, Soshi Iimura, Albert Iskandarov, Tomofumi Tada, Hideo
    Hosono. Room-Temperature Fast H- Conduction in Oxygen-Substituted
    Lanthanum Hydride. Journal of the American Chemical Society, 2022;
    DOI: 10.1021/jacs.1c11353 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/01/220125112519.htm

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