The discovery of a nanocluster will protect precious metals

Scientists have created a new type of catalyst that will lead to new, sustainable ways of making and using molecules and protecting the supply of precious metals.

A research team from the University of Nottingham has designed a new type of catalyst that combines characteristics that were previously thought to be mutually exclusive and developed a process to fabricate metal nanoclusters on a mass scale.

In their new research, published today in Nature Communication, they demonstrate that the behavior of palladium nanoclusters does not conform to orthodox characteristics that define catalysts as homogeneous or heterogeneous.

Traditionally, catalysts are divided into homogeneous, where the catalytic centers are intimately mixed with reactive molecules, and heterogeneous, where the reactions take place on the surface of a catalyst. Usually, chemists have to make compromises when choosing one type or another, as homogeneous catalysts are more selective and active, and heterogeneous catalysts are more durable and reusable. However, nanoclusters of palladium atoms seem to defy traditional categories, as demonstrated by the study of their catalytic behavior in the cyclopropanation reaction of styrene.

Catalysts enable nearly 80% of industrial chemical processes to supply our economy’s most vital ingredients, from materials (such as polymers) and pharmaceuticals to agrochemicals, including fertilizers and crop protection. Strong demand for catalysts means that global supplies of many useful metals, including gold, platinum and palladium, are rapidly depleting. The challenge is to use each atom to its maximum potential. The exploitation of metals in the form of nanoclusters is one of the most powerful strategies to increase the active surface available for catalysis. In addition, when the dimensions of nanoclusters exceed the nanoscale, the properties of the metal can change drastically, leading to new phenomena otherwise inaccessible at the macroscopic scale.

The research team used analytical and imaging techniques to probe the structure, dynamics and chemical properties of nanoclusters, in order to reveal the inner workings of this unusual catalyst at the atomic level.

The team’s discovery holds the key to unlocking the full potential of catalysis in chemistry, leading to new ways to make and use molecules in the most efficient and energy-resilient ways.

The research was led by Dr Jesum Alves Fernandes, a researcher at Propulsion Futures Beacon Nottingham of the School of Chemistry, he said: Fast argon ions – a method called magnetron sputtering. Usually this method is used to make coatings or films, but we have adjusted it to produce metal nanoclusters which can be deposited on almost any surface. Importantly, the size of nanoclusters can be precisely controlled by experimental parameters, from a single atom to a few nanometers, so that a set of uniform nanoclusters can be generated on demand within seconds. ”

Dr Andreas Weilhard, postdoctoral fellow of Green Chemicals Beacon in the team added: “The surfaces of metal clusters produced by this method are completely ‘bare’, and therefore very active and accessible for chemical reactions leading to high catalytic activity. .

Professor Peter License, Director of the GSK Carbon Neutral Laboratory at the University of Nottingham added: “This method of catalyst fabrication is important not only because it enables the most economical use of rare metals, but it does. in the cleanest way, without any need. for solvents or chemical reagents, thus generating very low levels of waste, which is an increasingly important factor for green chemical technologies. ”

The University is about to embark on a large-scale project to expand this work with research that will lead to the protection of endangered elements.

MASI Principal Investigator Professor Andrei Khlobystov said: “Our project is intended to revolutionize the way metals are used in a wide range of technologies and to break our dependence on critically endangered elements. extinction. Specifically, MASI will make progress in: reducing carbon dioxide (CO₂) emissions and their valuation into useful chemicals; the production of “green” ammonia (NH₃) as a zero-emission alternative fuel and a new vehicle for storing hydrogen; and the provision of more sustainable fuel cells and electrolyzer technologies. ”

Metal nanoclusters are activated for reactions with molecules, which can be driven by heat, light or electric potential, while adjustable interactions with support materials ensure the durability and reuse of catalysts. In particular, MASI catalysts will be applied for the activation of molecules that are difficult to crack (for example N₂, H₂ and co₂) in reactions that form the backbone of the chemical industry, such as the Haber-Bosch process.