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RESEARCHERS in the US and Europe have developed a new palladium catalyst which ensures the complete combustion of methane, a potent greenhouse gas.

Methane is a very stable molecule and the best catalysts currently available, which consist of palladium nanoparticles deposited on oxides such as cerium oxide, can only ensure complete combustion at temperatures of at least 600°C and beyond 800°C in a power station gas turbine. However, whilst ensuring that no methane enters the atmosphere, high temperatures cause the formation of other damaging byproducts, such as nitrogen oxides, sulphur oxides and carbon monoxide.

The team of chemical engineers and chemists, based at the University of Pennsylvania, US, with collaborators from Italy’s University of Trieste and the Universidad de Cádiz in Spain, says that its catalyst, also based on palladium, works at temperatures of around 400°C, and is 30 times more efficient. It offers a way to reduce emissions from vehicles which run on natural gas and means that the maximum amount of energy can be gained from gas burned in turbines.

The catalyst consists of a palladium core surrounded by a porous cerium oxide shell. The researchers assembled the catalyst using a nanoparticle self-assembly technique. The palladium cores, which have a diameter of 1.8 nm, were assembled first before being surrounded with the shell. The catalyst particles were deposited on a hydrophobic aluminium oxide surface to prevent them clumping together, which reduces efficiency.

“We can use this assembly method to test different types of metals and oxides,” says Matteo Cargnello, a postdoctoral chemistry fellow at Pennsylvania. “That will allow us to prepare a whole library of materials, some of which might be very good at catalysing reactions besides methane combustion.”

Science DOI: 10.1126/science.1222887