​In 2018 we launched the ISIS Impact Awards for facility users, celebrating the scientific, social and economic impact generated by the user community. The winners of the three awards were announced at the UK Neutron and Muon Science and User Meeting (NMSUM) 2018.

The winner of the Economic Award was given to Dr. Andrea Lazzarini from the University of Oslo, for their work on activated carbons which are widely employed in industrial catalysis. Here we present the final case study​ from the winning Economic Award entry.

Activated carbons are widely employed in industrial catalysis, usually employed as a support for nanoparticle-based catalysts. Heterogeneous catalysis are manufactured by depositing a dispersed active phase (in the form of isolated ions or nanoparticles) on a high-surface-area support, which needs to cheap, inert and stable.

Despite their widespread use, the way in which activated carbons interact with the active phase of the catalyst and/or with the molecules involved in the reaction (reactants and products) is still far from understood. This is mainly due to the strong light-absorbing nature of activated carbons, which makes their investigation with traditional spectroscopic techniques extremely difficult.

Researchers used Inelastic Neutron Scattering (INS), coupled with several light-based spectroscopic techniques, to shed light on the role that the carbonaceous support has in the catalytic processes. The use of INS was fundamental to this study due to the nature of these materials, which are extremely rich in hydrogen terminations on their surface.

Thanks to neutron spectroscopy and to the multi-technique approach, researchers were able to discriminate the type and the behaviour of the different species present on the surface of the catalyst, and to describe how they influence the activity and selectivity of different hydrogenation processes.

This project had a strong impact on two different levels. Firstly, their industrial partner, Chimet S.p.A., provided both financial support and the samples that were investigated. The results achieved had a large impact on researchers understanding of the catalyst, from the support material through to the end of the lifecycle. Our industrial partner therefore has the opportunity to develop more efficient and more durable catalysts in the future.

Secondly, the team developed an exhaustive protocol for the characterization of activated carbons for catalytic purposes and for carbon-based materials in general. The use of inelastic neutron scattering  was essential for investigating the state of the hydrogen-rich surface of the support, which interacts with the active phase and reaction's substrate. Our INS measurements were complemented with other techniques (FT-IR spectroscopy, Raman spectroscopy, XRD, XPS, SEM and catalytic tests), establishing a full characterization protocol able to produce a complete picture of the material under analysis. The team shed light on the behaviour of the catalysts under reaction conditions and the influence that the support (the main target of the study) has during catalyst operation.

Underpinning research

1994-2004. Fillaux, Albers, Parker and their coworkers, extensively studied activated carbons-supported Pd nanoparticles catalysts for hydrogenation reactions. Their INS studies were focused on the H-containing terminations at the edge of graphitic domains of the carbon supports and their dynamical behavior in the presence or without the presence of the metal active phase [3.1-3.5].

2000. Ferrari and Robertson defined a new interpretation of Raman data, based on the intensity ratio between I(D)/I(G) signals, describing the average lateral dimension of the graphitic domains in activated carbons. According to Tuinstra-Koenig law, the larger is the ratio the higher is the structural disorder; however, it has been demonstrated that for domain size smaller than 20Å the I(D)/I(G) ratio follows an opposite behavior with respect to Tuinstra-Koenig law [3.6]. This work was fundamental in the interpretation of the controversial Raman data on our samples.

2005. Centrone and coworkers combined FT-IR spectroscopy and molecular modeling to ascribe to precise C-H species in condensed aromatic rings edges, the vibrations present in IR spectra of activated carbons in the 1000-700 cm⁻¹ region [3.7]. The ratio between those species reflects different levels of size and defectivity at the molecular level of the graphitic domains of the activated carbon supports.

2016: Smith and coworkers improved the deconvolution and interpretation of XPS data by means of molecular modeling. They proposed a 7-peaks fit of the C 1s signal instead of the traditional 6-peaks fit: this allows a better discrimination between structural defectivity of the carbon atoms in the graphene-like structure and the one arising from the presence of oxygenated functional groups, decorating the graphitic platelets edges [3.8].

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3. References to the research

1. Journal article. F. Fillaux, R.Papoular, A.Lautié, J.Tomkinson, “Inelastic neutron-scattering study of the proton dynamics in carbons and coals", Carbon, 1994, vol. 32 (7), p. 1325-1331.
2. Journal article. P. Albers, G. Prescher, K. Seibold, D. K. Ross, F. Fillaux, "Inelastic neutron scattering study of proton dynamics in carbon blacks", Carbon, 1996, vol. 34 (7), p. 903-908.
3. Journal article. P. Albers, S. Bösing, H. Lansink Rotgerink, D. K. Ross, S. F. Parker, “Inelastic neutron scattering study on the influence of after-treatments on different technical cokes of varying impurity level and their sp²/sp³ character", Carbon, 2002, vol. 40 (9), p. 1549-1558.
4. Journal article. P. Albers, J. Pietsch, J. Krauter, S. F. Parker, “Investigations of activated carbon catalyst supports from different natural sources", Phys. Chem. Chem. Phys., 2003, vol. 5 (9), p. 1941-1949.
5. Journal article. P. Albers, M. Lopez, G. Sextl, G. Jeske, S. F. Parker, “Inelastic neutron scattering investigation on the site occupation of atomic hydrogen on platinum particles of different size", J. Catal., 2004, vol. 223 (1), p. 44-53.
6. Journal article. A. C. Ferrari, J. Robertson, “Interpretation of Raman spectra of disordered and amorphous carbon", Phys. Rev. B, 2000, vol. 61 (20), article n. 14095.
7. Journal article. A. Centrone, L. Brambilla, T. Renouard, L. Gherghel, C. Mathis, K. Müllen, G. Zerbi, “Structure of new carbonaceous materials: The role of vibrational spectroscopy", Carbon, 2005, vol. 43 (8), p. 1593-1609.
8. Journal article. M. Smith, L. Scudiero, J. Espinal, J.-S. McEwen, M. Garcia-Perez, “Improving the deconvolution and interpretation of XPS spectra from chars by ab initio calculations", Carbon, 2016, vol. 110, p. 155-171.

5. Sources to corroborate the impact

1. Progress in the Characterization of the Surface Species in Activated Carbons by means of INS Spectroscopy Coupled with Detailed DFT Calculations (DOI: 10.1155/2015/803267)
2. A comprehensive approach to investigate the structural and surface properties of activated carbons and related Pd-based catalysts (DOI: 10.1039/c6cy00159a)
3. Graphitization of activated carbons: a molecular-level investigation by INS, DRIFT, XRD and Raman techniques (DOI: 10.1016/j.phpro.2016.11.076)
4. Activated carbons for applications in catalysis: the point of view of a physical-chemist (DOI: 10.1007/s12210-017-0603-5)
5. The effect of surface chemistry on the performances of Pd-based catalysts supported on activated carbons (DOI: 10.1039/c7cy01005b)
6. “Vibrational characterization of high surface area carbons through DRIFT, Raman and INS: an innovative method", presented at ISIS Molecular Spectroscopy Science Meeting 2015, Abingdon (United Kingdom), January 29-30, 2015
7. “Vibrational characterisation of high surface area carbons through multitechnical tools: an innovative approach", presented at Annual World Conference on Carbon - CARBON 2015, Dresden (Germany), July 12-16, 2015
8. “Structural and surface characterisation of activated carbons through multitechnical tools", invited talk at College 7 topical days: Spectroscopy of carbon-based materials, Institut Laue-Langevin, Grenoble (France), January 26-27, 2016
9. “The importance of Inelastic Neutron Scattering for the study of carbon-based materials", presented at E-MRS Spring meeting 2016, Lille (France), May 4-6, 2016