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The University of Southampton

Palladium nanoparticles could help drive cleaner vehicle exhausts

Published: 22 February 2019
Back of car, focus on exhaust
New research could help reduce nitrogen oxide emissions from diesel vehicles

Researchers at the University of Southampton have investigated variations of palladium nanoparticles that could help reduce nitrogen oxide emissions from diesel vehicles.

The collaborative research, led by the School of Chemistry’s Dr Peter Wells, analysed the performance of nanoparticle structures used in an emissions process known as selective ammonia oxidation.

Scientists have published findings from experiments in European synchrotron facilities in Nature Catalysis and will now seek to spearhead further research that will help drive the development of cleaner catalytic technologies.

“The development of highly active catalysts are crucial for the implementation of new sustainable chemical processes and better environmental protection, but before we can make significant strides in the development of these materials we first need to best understand how they work,” Peter explains.

“Using unique techniques made available through synchrotron radiation sources we have been able to establish links between palladium nanoparticle structures and catalytic selectivity. Moreover, we have identified a new palladium nitride nanoparticle that we believe has not been previously reported.”

The standard catalytic process utilised in diesel cars uses ammonia to convert nitrogen oxide to benign products of nitrogen and water. However, as the permissible levels of nitrogen oxide becomes ever tighter, more ammonia is used in the process. This can result in ammonia ending up in exhaust streams, an issue known as ‘ammonia slip’.

Ammonia selective catalytic oxidation aims to mitigate these emissions by using supported palladium nanoparticles to convert ammonia to nitrogen. Optimum conditions are crucial in the process, with incorrect temperatures potentially over-oxidising the ammonia and producing more nitrogen oxide. This latest research sought to understand how supported palladium nanoparticles direct the conversion of ammonia to different products.

Peter has been investigating this stream of inorganic chemistry since his PhD at Southampton, which he completed in 2007.

“Our current partnership with the UK Catalysis Hub and Diamond Light Source has been very successful in developing new methods and the tools used in this study” he says. “This research included a combined study at the Swiss Light Source, simultaneously collect X-ray absorption fine structure (XAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) data during ammonia oxidation.”

You can read more about Peter’s research in his blog on the Nature Research Chemistry Community website.


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