Advancing catalysis through long-standing academic-industrial collaborative research

Chimet S.p.A is a world-leading specialist in the recovery of noble metals from industrial waste, which are then refined and recycled to produce a number of different catalysts. A chance discussion more than 20 years ago between Riccardo Pellegrini of Chimet S.p.A and Carlo Lamberti, then professor at the University of Turin, revealed the potential of collaborative academic-industrial research to advance understanding of the physico-chemical properties of these catalysts.

While Chimet S.p.A provides the industry-relevant questions, necessary samples and financial support, the University of Turin contributes expertise in a number of different experimental techniques, both laboratory-based (such as infrared spectroscopy, transmission electron microscopy and microcalorimetry) and at large-scale research facilities (synchrotron X-ray absorption spectroscopy in particular). This multi-technique approach is necessary in order to obtain a comprehensive understanding of the system, composed of metal nanoparticles (palladium and platinum in particular) deposited on a supporting material made of either activated carbon or aluminium oxide.

When Andrea Piovano, previously involved in the collaboration as a postdoctoral researcher at the University of Turin, began work in 2011 as a scientist with responsibility for the IN8 instrument at the Institut Laue Langevin (ILL), he realized the huge contribution that neutrons could make to the research. “The palladium and platinum catalysts studied are both widely used in hydrogenation reactions, in which hydrogen plays a major role,” explains Piovano. “Neutrons are one of the most powerful probes to directly observe the dynamics of hydrogen, making it the ideal technique to investigate the dynamic interaction of hydrogen with the system’s metal nanoparticles and supporting material.”

The vibrational frequencies measured as a function of energy by inelastic neutron scattering spectroscopy offer the additional advantage of being closely related to the data acquired by optical spectroscopy techniques (such as Raman and infrared), facilitating the synergistic approach. It is also relatively straightforward to couple inelastic neutron scattering with advanced density functional theory simulations. “The neutron data provides a spectrum but without a model, it’s very difficult to interpret the different features and assign them to specific species in the sample,” explains Eleonora Vottero, postdoctoral researcher at the University of Turin, following a joint ILL - University of Turin PhD. “A model simulates the dynamic interaction between hydrogen and the system, enabling a decomposition of the different vibrations and a full understanding of the various contributors to each part of the spectrum. What you observe in the experimentally acquired neutron spectrum can then be interpreted with a relatively high level of confidence.”

Initial results, obtained from the first neutron experiment carried out at the ISIS Neutron and Muon Source (UK), were promising and a number of experiments have since been performed at the ILL using IN1-LAGRANGE, with the support of instrument responsible Monica Jimenez. “The LAGRANGE instrument is a recent upgrade that provided a significant intensity increase. Very subtle spectral modifications can now be detected and a decent spectrum obtained with only a very low number of hydrogen atoms,” explains Piovano. The ILL also offers unique sample environment capabilities. “Most of our sample environment is made of aluminium due to its high neutron transparency which enables us to detect the very small changes we’re trying to observe. Considerable work was carried out at the ILL to develop a sample cell that could be connected to a gas injection device and capable of withstanding both a vacuum externally and high gas pressures internally while minimising background signal,” explains Piovano.

The partnership formed by the ILL, University of Turin and Chimet S.p.A has enabled the realisation of synergistic research combining multiple techniques across laboratories and large-scale research facilities and resulting in the generation of both industrially valuable information and a number of notable scientific publications. “The metal nanoparticles were one of the first aspects investigated and X-rays were used due to their particular sensitivity to elements with a high number of electrons. Then the properties of the supporting material were explored, revealing their impact on the catalytic properties of the system as a whole. [1] Neutrons have enabled the interaction of hydrogen with the catalyst to be explored in unprecedented detail allowing the ductility of metal nanoparticles at different hydrogen partial pressures to be demonstrated. [2] We are now also investigating the interaction between the nanoparticles and the supporting material. This multi-technique approach combines the specific information provided by each technique in order to form a complete picture and understand, at the fundamental level, how the catalyst works,” explains Vottero. The approach is demonstrated in the most recently published article, Inelastic neutron scattering study of the H₂ interaction with carbon-supported Pt and Pd catalysts in Catalysis Today, which brings together all previous work in order to uncover previously unexplained aspects of the palladium and platinum catalysts. [3]

With extensive expertise acquired in palladium and research advancing well in platinum, the researchers are turning their attention to a new metal catalyst – ruthenium, with a first exploratory experiment planned at the ILL in May 2023.