(a) developed method for selective loading of nanocluster crystal facets (F-NCD; this method), (b) conventional nanocluster deposition (NCD), (c) photoelectrodeposition (PD), and (d) impregnation method (IMP) ). Credit: Yuichi Negishi et al.
Scientists are urgently seeking clean fuel sources, such as hydrogen, to help in the transition to carbon neutrality. A major breakthrough aimed at improving the efficiency of the photocatalytic reaction that splits water into hydrogen has been made by a team of researchers from Tohoku University, Tokyo University of Science and Mitsubishi Materials Corporation.
“Water-splitting photocatalysts can produce hydrogen (H2) only from sunlight and water,” explains Professor Yuichi Negishi, lead researcher of this project (Tohoku University), “However, the process has not been sufficiently optimized for practical applications. If we can improve this activity, hydrogen can be harnessed for the realization of a next generation energy society. »
The research team established a new method that uses an ultrafine mixed oxide of rhodium (Rh) and chromium (Cr) (Rh2-xCrxOh3) cocatalysts (the actual reaction site and a key component for stopping H2 reforming with oxygen to reconstitute water) with a particle size of approximately 1 nm. Then they are selectively loaded into crystal facets onto a photocatalyst (which uses sunlight and water to speed up the reactions).
The results are published in the Journal of the American Chemical Society.
Previous studies have failed to accomplish both feats in a single reaction: a tiny cocatalyst that can also be placed on specific regions of the photocatalyst.
A smaller particle size is important because the activity per amount of cocatalyst loaded is then greatly improved due to the increase in the specific surface area of the cocatalyst. Selective loading of facets is also important, because otherwise randomly placed cocatalysts could end up on crystal facets where the desired reaction does not occur.
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Schematic diagram of this method (F-NCD). The Rh complex is selectively adsorbed on the yellow-green zone (H2-evolution facet) in the figure using strategies 1) and 2). Subsequently, calcination is used to remove the ligands from the Rh complex and solidly solubilize it with Cr.2Oh3 layer. Finally, the desired photocatalyst is obtained by light irradiation. Credit: Yuichi Negishi et al.
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a) Strategy 1; protection of O2-evolution facet by addition of organic compounds (b) Strategy 2; improvement of the adsorption of Rh complexes by light irradiation under basic conditions. C) Comparison of photocatalytic water splitting activity of Rh2-xCrxOh3/18-STO photocatalysts prepared by developed conventional F-NCD, NCD, PD and IMP methods. Credit: Yuichi Negishi et al.
The particle size, loading position and electronic state of the cocatalyst in the photocatalyst prepared by the F-NCD method (Rh2-xCrxOh3/18-STO (F-NCD)) were compared with those prepared by the conventional method. Overall, the photocatalysts prepared by the new method achieved 2.6 times higher water-splitting photocatalytic activity. The resulting photocatalyst exhibits the highest apparent quantum yield achieved to date for strontium titanate.
This remarkable method has improved our ability to generate hydrogen without harmful byproducts such as carbon dioxide. This could allow us to harness hydrogen as a more abundant source of green energy so we can all breathe a little easier.
More information:
Daisuke Hirayama et al, Ultrathin rhodium-chromium mixed oxide cocatalyst with selective facet loading for excellent photocatalytic water splitting, Journal of the American Chemical Society (2024). DOI: 10.1021/jacs.4c07351
Provided by Tohoku University
Quote: New cocatalyst method improves water splitting efficiency (October 7, 2024) retrieved October 7, 2024 from
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