University of Innsbruck, Austria, scientists and colleagues have now devised a method of using copper as a catalyst in the reaction designed to split water and produce hydrogen in gaseous form. The new model explains interactions between small copper clusters used as low-cost catalysts in the production of hydrogen by breaking down water molecules.

Adsorption of water molecules on the surface of copper nanoparticles could produce hydrogen faster and more efficiently. Image Credit: Stefan Raggl, University of Innsbruck. Click image for the largest view.

Copper nanoparticles dispersed in water or in the form of coatings have a range of promising applications, including lubrication, ink jet printing, as luminescent probes, exploiting their antimicrobial and antifungal activity, and in fuel cells.

Another promising application is using copper as a catalyst to split water molecules and form molecular hydrogen in gaseous form. At the heart of the reaction, copper-water complexes are synthesized in ultra-cold helium nanodroplets as part of the hydrogen production process.

The groups study paper has been published in EPJ D.

Previous work has shown that at the molecular level, water oxidizes copper nanoparticles until their surface is saturated with molecules carrying hydrogen (called hydroxyl groups). Theoretical work further showed that a monolayer of water, once adsorbed on the copper particles, spontaneously converts to a half-monolayer of hydroxide (OH) plus half a monolayer of water while releasing hydrogen gas.

In their study, Stefan Raggl of the University of Innsbruck and colleagues synthesized neutral copper-water complexes by successively doping helium nano-droplets – which are kept at the ultra-cold temperature of 0.37 K in a state referred to as superfluid – with copper atoms and water molecules.

These droplets are then ionized by electrons. The authors show that the composition of the most prominent ions depends on the partial copper and water pressures in the cell where the reaction occurs. They observe ions containing several copper atoms and several dozen water molecules.

The authors recognize that they failed to directly observe the predicted hydrogen formation because their instrument is not designed to detect electrically neutral entities.

So far, so good. But there is a very long way to go, indeed. The battle to avoid the rare earth and dreadfully expensive common catalysts such as platinum is well underway. Lots of ideas have been published here and we can expect many more.

One day an idea is not only going to be low enough cost, but last a long time and use a pittance of energy to work. Maybe tomorrow, maybe years out, but its coming.


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