A new family of water-splitting catalyst materials developed at MIT could make fuel cells and advanced batteries more viable.
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Fuel cells can turn hydrogen and oxygen into water and energy very efficiently - but splitting water to make the gases in the first place is much more difficult. New catalysts developed at MIT could change that, and make energy storage based on hydrogen and water, as in the concept above, much more viable. (Image credit: Photos.com)
A research group led by Yang Shao-Horn, Professor of Mechanical Engineering and Materials Science have tested a new group of catalysts to assess their ability to promote the water-splitting reaction, producing oxygen and hydrogen gas. Their work has been published in Nature Communications.
This would allow the two gases to be separated and stored, so that they can be recombined in a fuel cell to produce energy.
Fuel cells are a very efficient way to generate electricity, and hydrogen gas is one of the best ways to store energy if it can be produced efficiently.
Efficient storage is particularly important for renewable sources of electricity, as the power they generate often comes in surges (from periods of bright sunshine or high winds) which cannot be timed to coincide with demand. Efficient storage would allow this energy to be stored until it is needed, without too much being wasted.
However, existing technologies to produce hydrogen by electrochemically splitting water are expensive, and not very efficient. Many scientists are hunting for an ideal catalyst, which is made out of inexpensive materials and makes turning water into hydrogen as easy as charging a battery.
Shao-Horn's team previously held the record for the best performing water-splitting catalyst, but even this has been overshadowed by their new advances in both performance and durability - the previous material's structure altered quite rapidly during the reaction.
The new material has a double perovskite structure - a derivative of the perovskite structure shared by many naturally occuring minerals. Synthetic perovskites have been found to possess such properties as superconductivity, ferroelectricity, and colossal magnetoresistance, so it is no great surprise to find yet another ground-breaking material in this family.
The term "double-perovskite" comes from the fact that there are two distinct sites in the crystal structure, one for barium, and another for a lanthanide element (praseodymium, samarium, holmium or gadolinium in this case).
The structure allows for many variations, which the MIT team showed had a large range of catalytic activity for the water-splitting reaction.
The strongest catalysts were those containing praseodymium - in fact, they had the highest activity of any material ever tested, and were also more chemically stable.
This is just the beginning for this new family of catalysts, as postdoc researcher Alexis Grimaud insists:
“We figured out what physical parameters could control the activity and stability, which will provide guidance for future research. The family is very large, and the work so far is just scratching the surface. With the methods that we have developed, we can screen them and search for active catalysts systematically."
These compounds could pave the way to commercial use of hydrogen fuel cells, advanced rechargeable metal-air batteries, and direct-solar splitting of water.
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