• Solar hydrogen: Better photoelectrodes t

    From ScienceDaily@1:317/3 to All on Monday, April 04, 2022 22:30:44
    Solar hydrogen: Better photoelectrodes through flash heating

    Date:
    April 4, 2022
    Source:
    Helmholtz-Zentrum Berlin fu"r Materialien und Energie
    Summary:
    Producing low-cost metal-oxide thin films with high electronic
    quality for solar water splitting is not an easy task. Especially
    since quality improvements of the upper metal oxide thin films
    need thermal processing at high temperatures, which would melt
    the underlying glass substrate.

    Now, a team has solved this dilemma: A high intensity and rapid
    light pulse directly heats the semiconducting metal-oxide thin
    film, allowing it to reach the optimal temperature without damaging
    the substrate.



    FULL STORY ========================================================================== Solar energy can directly drive electrochemical reactions at the surface
    of photoelectrodes. Photoelectrodes consist of semiconducting thin
    films on transparent conductive-glass substrates that convert light
    into electricity.

    Most photoelectrochemical studies have focused on water splitting, a thermodynamically uphill reaction that could offer an attractive pathway
    for the long-term capture and storage of solar energy by producing
    'green' hydrogen.


    ========================================================================== Metal-oxide thin film photoelectrodes are particularly promising for
    these diverse functions. They comprise abundant elements, potentially
    offering infinite tunability to achieve the desired properties -- at potentially low costs.

    Made from plasma At the HZB Institute for Solar Fuels, several teams
    focus on developing such photoelectrodes. The usual method to produce
    them is pulsed laser deposition: an intense laser pulse hits a target containing the material and ablates it into a highly energetic plasma
    deposited on a substrate.

    Quality needs heat Further steps are needed to improve the quality
    of the deposited thin film. In particular thermal processing of the
    metal-oxide thin-film reduces defects and imperfections. However, this
    creates a dilemma: Reducing atomic defects concentration and improvements
    in crystalline order of the metal-oxide thin films would require thermal processing temperatures between 850 and 1000 degrees Celsius -- but the
    problem is that the glass substrate melts at 550 degrees Celsius.

    Flash-heating the thin film Dr. Ronen Gottesman from the HZB Institute
    for Solar Fuels has now solved this problem: After deposition, using high-powered lamps, he flash-heats the metal- oxide thin film. This
    heats it up to 850 degrees Celsius without melting the underlying glass substrate.

    "The heat efficiently reduces structural defects, trap states,
    grain boundaries, and phase impurities, which would become more
    challenging to mitigate with an increasing number of elements in
    the metal-oxides. Therefore, new innovative synthesis approaches are
    essential. We have now demonstrated this on photoelectrodes made of
    Ta2O5, TiO2, and WO3, which we heated to 850 DEGC without damaging the substrates," says Gottesman.

    Record performance for a-SnWO4 The new method was also successful with
    a photoelectrode material that is considered a very good candidate for
    solar water splitting: a-SnWO4.

    Conventional furnace heating leaves behind phase impurities. Rapid thermal processing (RTP) heating improved crystallinity, electronic properties,
    and performance, leading to a new record performance of 1 mA/cm2 for
    this material, higher by 25% than the previous record.

    "This is also interesting for the production of quantum dots or halide perovskites, which are also temperature-sensitive," explains Gottesman.


    ========================================================================== Story Source: Materials provided by Helmholtz-Zentrum_Berlin_fu"r_Materialien_und_Energie.

    Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Ronen Gottesman, Isabella Peracchi, Jason L. Gerke, Rowshanak Irani,
    Fatwa F. Abdi, Roel van de Krol. Shining a Hot Light on Emerging
    Photoabsorber Materials: The Power of Rapid Radiative Heating in
    Developing Oxide Thin-Film Photoelectrodes. ACS Energy Letters,
    2022; 7 (1): 514 DOI: 10.1021/acsenergylett.1c02220 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220404120534.htm

    --- up 5 weeks, 10 hours, 51 minutes
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)