Australian University of New South Wales (UNSW) chemists have invented a new, cheap catalyst for splitting water with an electrical current to efficiently produce hydrogen fuel. Usually splitting water requires two different catalysts, but this catalyst can drive both of the reactions required to separate water into oxygen and hydrogen. The technology is based on the creation of ultrathin slices of porous metal-organic complex materials coated onto a foam electrode.

Metal salts and substrate are firstly mixed together in an aqueous solution, and then introduces the organic ligand. Next, the MOF nanosheet array grows on the surface of substrate via a dissolution-crystallization mechanism. Image Credit: Chuan Zhao, UNSW. Click image for the largest view.

Study leader Associate Professor Chuan Zhao said, “Splitting water usually requires two different catalysts, but our catalyst can drive both of the reactions required to separate water into its two constituents, oxygen and hydrogen. Our fabrication method is simple and universal, so we can adapt it to produce ultrathin nanosheet arrays of a variety of these materials, called metal-organic frameworks. Compared to other water-splitting electro-catalysts reported to date, our catalyst is also among the most efficient.”

The research paper by Zhao, Dr Sheng Chen and Dr Jingjing Duan has been published in the journal Nature Communications.

Hydrogen is a very good carrier for renewable energy because it is abundant, generates zero emissions, and can be easier to store as fuel than some other energy sources, like solar or wind energy.

But the cost of producing hydrogen by using electricity to split water is still high, because the most efficient catalysts developed so far are often made with precious metals, like platinum, ruthenium and iridium.

The UNSW developed catalysts are made of abundant, non-precious metals like nickel, iron and copper. They belong to a family of versatile porous materials called metal organic frameworks, which have a wide variety of other potential applications.

So far metal-organic frameworks have been considered poor conductors and not very useful for electrochemical reactions. In current common usage they are made in the form of bulk powders, with their catalytic sites deeply embedded inside the pores of the material, where it is difficult for the water to reach.

Zhao’s team was able to expose the pores and increase the surface area for electrical contact with the water by creating nanometer-thick arrays of the metal-organic frameworks.

Zhao said, “With nanoengineering, we made a unique metal-organic framework structure that solves the big problems of conductivity, and access to (the) active sites. It is ground-breaking. We were able to demonstrate that metal-organic frameworks can be highly conductive, challenging the common concept of these materials as inert electro-catalysts.”

Metal-organic frameworks have the potential for a large range of applications, including fuel storage, drug delivery, and carbon capture. The UNSW team’s demonstration that they can also be highly conductive introduces a host of new applications for this class of material beyond electro-catalysis.

One would think that with all the breakthroughs in hydrogen that there would be something to buy and use. But this technology is still in the chicken versus egg conundrum, who will buy something that uses a fuel the isn’t available and who will produce a fuel that has no customers to use it. Something big, like a disaster, might need to happen to set off the market build out.


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