Chinese researchers found a material to catalyze the water-splitting reaction and gather hydrogen.
2D Janus Materials Could Split Water Molecules
Previous studies predicted that a particular group of 2D materials could activate the splitting of molecules in water. Researchers from Shandong Normal University in China discovered a promising group named 2D Janus materials, whose two sides feature different molecular compositions.
Junfeng Ren and colleagues presented a new group of four 2D Janus materials through recent calculations detailed in The European Physical Journal B. Since hydrogen releases abundant energy when combusted with only water as a byproduct, they considered the discovery an excellent alternative to fossil fuels, Phys.org reported.
The splitting of water molecules involves a redox reaction, where electrons and holes participate in reduction and oxidation reactions.
2D Janus materials are excellent semiconductors making them perfect catalysts. When the electron in a semiconductor's insulating valence band absorbs a photon, it is excited to the material's conduction band, leaving behind a positively charged hole. In turn, the materials become sources and acceptors of electrons allowing redox reactions to occur.
How Did The Study Go?
Ren and his colleagues examined a group of four 2D Janus materials with one surface composed of selenium or tellurium and the other from bromine or iodine. Both sides sandwich a middle layer of arsenic.
The energies of the valence and conduction bands were far enough to prevent electrons and holes from readily recombining, allowing them to combine electrons and holes to produce hydrogen and oxygen.
All four materials display excellent stability and light absorption. The researchers were convinced they could catalyze the water-splitting reaction if the results could be reproduced in experiments.
Ren and his colleagues hoped the four materials could be a key element in reducing carbon emissions in the new decades.
The study was published in the journal The European Physical Journal B.
What Are Janus 2D Materials?
Janus 2D materials are a novel class of 2D materials in which two faces are either asymmetrically functionalized or are exposed to a different local environment. Due to the diverse properties of the two opposing sides, it allows the design of new multi-functional materials for various applications, including optoelectronics, energy storage, and catalysis, according to a study by Verónica Montes-García and Paolo Samorì published in the journal Chemical Science.
Another study published in 2021 also discovered that Janus 2D exhibits high dynamical stability and band gaps between 0.89 to 2.03 eV. It shows appropriate band edge positions, strong light absorptions in the visible light region, high energy conversion efficiencies, effective spatial separation, and fast transfer of carriers, making them a promising candidate for photocatalytic water splitting.
The previous study added that aside from being an efficient photocatalyst, Janus 2D materials are also piezoelectric.
According to Nanomotion, Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress. The piezoelectric effect is reversible, meaning the materials exhibiting it also exhibit the converse piezoelectric effect (the generation of stress when an electric field is applied).
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