by Staff Writers
Eindhoven, Netherlands (SPX) Feb 03, 2017
One of the main obstacles in the production of hydrogen through water splitting is that hydrogen peroxide is also formed, which affects the efficiency stability of the reaction and the stability of the production. Dutch and Israelian researchers from Eindhoven University of Technology and the Weizmann Institute have succeeded in controlling the spin of electrons in the reaction and thereby almost fully suppress the production of hydrogen peroxide.
They published these findings this week in the Journal of the American Chemical Society. The efficient production of hydrogen paves the way towards water splitting by solar energy.
Hydrogen has been referred to as the fuel of the future but its generation is still not efficient enough. One of the production methods is a photo-electrochemical cell whereby water is split into hydrogen and oxygen under the influence of light. Not only does the reaction require a lot of energy but also hydrogen peroxide is formed as a by-product, leading to the poisoning of one of the electrodes and thus reduced efficiency.
Their idea was that if both spins are aligned, the formation of hydrogen peroxide would not occur. That's because the ground state of hydrogen peroxide - a so-called singlet state - does not allow two electrons with opposite spins. Oxygen, with a triplet ground state, does.
This work followed former findings by the group of Naaman, that the transmission of electrons through chiral molecules depends on the electrons' spin.
"The effect on water splitting exceeded our expectations," Ron Naaman says. "The formation of hydrogen peroxide was almost entirely suppressed. We also saw a significant increase in the cell's current. And because chiral molecules are very common in nature, we expect great implications from this finding."
Stroke of luck
"In some ways, this was a stroke of luck because the supramolecular structures had not originally been intended for this purpose. It goes to show how important supramolecular chemistry is as a fundamental field of research, and we're very busy optimizing the process."
Eindhoven University of Technology
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