Chemists develop a new method for splitting water

Researchers from the University of Münster have developed a new photocatalytic process for activating water using tri-aryl phosphinate, making it easier to produce hydrogen from water. This innovative approach uses light energy to drive the reaction and shows potential for exploring new chemical processes using hydrogen atoms in synthesis.

The photocatalytic process enables water to be activated.

Hydrogen is often touted as the energy solution of the future, especially when it is generated in environmentally friendly ways. In addition to its energy potential, hydrogen plays a crucial role in the production of active ingredients and various basic compounds. To generate hydrogen, water (H2O) can be converted into hydrogen gas (H2) through a series of chemical reactions.

However, because water molecules are so stable, splitting them into hydrogen and oxygen is a big challenge for chemists. For it to work at all, the water must first be activated with a catalyst – then it reacts more easily.

A team of researchers led by Professor Armido Studer at the Institute of Organic Chemistry at the University of Münster (Germany) has developed a photocatalytic process in which, under mild reaction conditions, water is activated by triarylphosphines and not, as in most other processes, by complexes transition metal.

split water

A hydrogen atom (H) is transferred from water (H2O) to the phosphine radical cation and water under the supply of light energy (LED). This important radical intermediate can transfer a (white) hydrogen atom to the substrate. The blue regions indicate the electron spin distribution. Credit: Christian Mok Lichtenfeld

This strategy, which was recently published in the journal natureThe team says this discovery will open a new chapter in a very active area of ​​research related to radical chemistry. Radicals are, as a rule, highly reactive intermediates. The team uses a special medium – the radical cation of water and phosphine – as activated water, with which hydrogen atoms from H2O can easily be separated and transferred to another substrate.

The reaction is carried out by light energy. “Our system provides an ideal platform for studying unstudied chemical processes that use hydrogen,” says Armido Studer corn as a reagent in the synthesis.

“The hydrogen-oxygen bond in this medium is very weak, which makes it possible to transfer a hydrogen atom into different compounds,” says Dr. Christian Mok-Lichtenfeld, who analyzed doped water complexes using theoretical methods. “Hydrogen atoms in activated water can transfer to alkenes and arenes under very mild conditions, in so-called hydrogenation reactions,” adds Dr. Jingjing Zhang, who did the experimental work.

Hydrogenation reactions are of great importance in pharmaceutical research, in the agrochemical industry, and in materials science.

Reference: “Photophosphine-mediated Water Activation for Radical Hydrogenation” by Jing Jing Zhang, Christian Mok Lichtenfeld, and Armido Studer, June 28, 2023, Available here. nature.
doi: 10.1038/s41586-023-06141-1

The study was funded by the Alexander von Humboldt Foundation.

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