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Instruments / Technical Area	Publication Details	Published
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Understanding metal organic chemical vapour deposition of monolayer WS2 : the enhancing role of Au substrate for simple organosulfur precursors Ye Fan , Kenichi Nakanishi , Vlad P. Veigang-radulescu , Ryo Mizuta , J. Callum Stewart , Jack E. N. Swallow , Alice E. Dearle , Oliver J. Burton , Jack A. Alexander-webber , Pilar Ferrer , Georg Held , Barry Brennan , Andrew J. Pollard , Robert S Weatherup , Stephan Hofmann Nanoscale 7 DOI: 10.1039/D0NR06459A Diamond Proposal Number(s): [22123] Open Access Show Abstract ▼ Abstract: We find that the use of Au substrate allows fast, self-limited WS2 monolayer growth using a simple sequential exposure pattern of low cost, low toxicity precursors, namely tungsten hexacarbonyl and dimethylsulfide (DMS). We use this model reaction system to fingerprint the technologically important metal organic chemical vapour deposition process by operando X-ray photoelectron spectroscopy (XPS) to address the current lack of understanding of the underlying fundamental growth mechanisms for WS2 and related transition metal dichalcogenides. Au effectively promotes the sulfidation of W with simple organosulfides, enabling WS2 growth with low DMS pressure (<1 mbar) and a suppression of carbon contamination of as-grown WS2, which to date has been a major challenge with this precursor chemistry. Full WS2 coverage can be achieved by one exposure cycle of 10 minutes at 700 °C. We discuss our findings in the wider context of previous literature on heterogeneous catalysis, 2D crystal growth, and overlapping process technologies such as atomic layer deposition (ALD) and direct metal conversion, linking to future integrated manufacturing processes for transition metal dichalcogenide layers.	Oct 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Ambient-pressure endstation of the Versatile Soft X-ray (VerSoX) beamline at Diamond Light Source Georg Held , Federica Venturini , David C. Grinter , Pilar Ferrer , Rosa Arrigo , Liam Deacon , Wilson Quevedo Garzon , Kanak Roy , Alex Large , Christopher Stephens , Andrew Watts , Paul Larkin , Matthew Hand , Hongchang Wang , Linda Pratt , James J. Mudd , Thomas Richardson , Suren Patel , Michael Hillman , Stewart Scott Journal Of Synchrotron Radiation 27 DOI: 10.1107/S1600577520009157 Open Access Show Abstract ▼ Abstract: The ambient-pressure endstation and branchline of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source serves a very diverse user community studying heterogeneous catalysts, pharmaceuticals and biomaterials under realistic conditions, liquids and ices, and novel electronic, photonic and battery materials. The instrument facilitates studies of the near-surface chemical composition, electronic and geometric structure of a variety of samples using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy in the photon energy range from 170 eV to 2800 eV. The beamline provides a resolving power hν/Δ(hν) > 5000 at a photon flux > 1010 photons s−1 over most of its energy range. By operating the optical elements in a low-pressure oxygen atmosphere, carbon contamination can be almost completely eliminated, which makes the beamline particularly suitable for carbon K-edge NEXAFS. The endstation can be operated at pressures up to 100 mbar, whereby XPS can be routinely performed up to 30 mbar. A selection of typical data demonstrates the capability of the instrument to analyse details of the surface composition of solid samples under ambient-pressure conditions using XPS and NEXAFS. In addition, it offers a convenient way of analysing the gas phase through X-ray absorption spectroscopy. Short XPS spectra can be measured at a time scale of tens of seconds. The shortest data acquisition times for NEXAFS are around 0.5 s per data point.	Sep 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS E01-JEM ARM 200CF	Elucidating the mechanism of the methanation reaction over Ni-hydrotalcite-derived catalysts via surface-sensitive in situ XPS and NEXAFS Gianfranco Giorgianni , Chalachew Mebrahtu , Manfred E. Schuster , Alexander I. Large , Georg Held , Pilar Ferrer , Federica Venturini , David Grinter , Regina Palkovits , Siglinda Perathoner , Gabriele Centi , Salvatore Abate , Rosa Arrigo Physical Chemistry Chemical Physics DOI: 10.1039/D0CP00622J Diamond Proposal Number(s): [19472] Show Abstract ▼ Abstract: Hydrotalcite-derived Ni and Fe-promoted hydrotalcite-derived Ni catalysts were found to outperform industrial catalysts in the CO2 methanation reaction, however the origin of the improved activity and selectivity of these catalysts is not clear. Here, we report a study of these systems by means of in situ X-ray photoelectron spectroscopy and near-edge X-ray absorption spectroscopy elucidating the chemical nature of the catalysts` surface under reaction conditions and revealing the mechanism by which Fe promotes activity and selectivity towards methane. We show that the increase of the conversion leads to hydroxylation of the Ni surface following the formation of water during the reaction. This excessive Ni surface hydroxylation has however a detrimental effect as shown by a controlled study. A dominant metallic Ni surface exists in conditions of higher selectivity towards methane whereas if an increase of the Ni surface hydroxylation occurs, a higher selectivity towards carbon monoxide is observed. The electronic structure analysis of the Fe species under reaction conditions reveals the existence of predominantly Fe(III) species at the surface, whereas a mixture of Fe(II)/Fe(III) species is present underneath the surface. Our results highlight that Fe(II) exerts a beneficial effect on maintaining Ni in a metallic state, whereas the extension of the Fe oxidation front from the surface towards the bulk is accompanied by a more extended Ni surface hydroxylation with a negative impact on the selectivity towards methane.	Apr 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS B18-Core EXAFS E01-JEM ARM 200CF	Influence of synthesis conditions on the structure of nickel nanoparticles and their reactivity in selective asymmetric hydrogenation Rosa Arrigo , Simone Gallarati , Manfred E. Schuster , Jake Seymour , Diego Gianolio , Ivan Da Silva , June Callison , Haosheng Feng , John E. Proctor , Pilar Ferrer , Federica Venturini , Dave Grinter , Georg Held Chemcatchem DOI: 10.1002/cctc.201901955 Open Access Show Abstract ▼ Abstract: Unsupported and SiO 2 ‐supported Ni nanoparticles (NPs), were synthesised via hot‐injection colloidal route using oleylamine (OAm) and trioctylphosphine (TOP) as reducing and protective agents, respectively. By adopting a multi‐length scale structural characterization, it was found that by changing equivalents of OAM and TOP not only the size of the nanoparticles is affected but also the Ni electronic structure. The synthetized NPs were modified with ( R , R )‐tartaric acid (TA) and investigated in the asymmetric hydrogenation of methyl acetoacetate to chiral methyl‐3‐hydroxy butyrate. The comparative analysis of structure and catalytic performance for the synthetized catalysts has enabled us to identify a Ni metallic active surface, whereby the activity increases with the size of the metallic domains. Conversely, at the high conversion obtained for the unsupported NPs there was no impact of particle size on the selectivity. ( R )‐selectivity was very high only on catalysts containing positively charged Ni species such as over the SiO 2 ‐supported NiO NPs. This work shows that the chiral modification of metallic Ni NPs with TA is insufficient to maintain high selectivity towards the ( R )‐enantiomer at long reaction time and provide guidance for the engineering of long‐term stable enantioselective catalysts.	Dec 2019
	Testing the self-cleaning properties of a coordination polymer surface Artur P. Terzyk , Grzegorz S. Szymański , Emil D. Korczeniewski , Paweł Bryk , Adam Bieniek , Paulina Bolibok , Michał Chodkowski , Piotr Kowalczyk , Marek Wiśniewski , Pilar Ferrer , Ivan Da Silva Adsorption 25, 33 - 39 DOI: 10.1007/s10450-018-9987-5 Open Access Show Abstract ▼ Abstract: It is well established that self-cleaning can be related to the hydrophobic or hydrophilic nature of a surface. Using adsorption chromatography, molecular simulations and wetting dynamics measurements, the self-cleaning properties of a new, strongly water resistant and hydrophilic cystine-containing coordination polymer (CP) were tested. Adsorption isotherms of n-octane and methanol were determined in the range of 313–343 K. Next the isosteric enthalpy of adsorption and the change in adsorption entropy were calculated to explain higher adsorption of methanol than n-butane. Performed chromatographic tests, molecular dynamics simulations and wetting dynamics experiments additionally prove that the Zn(Cys)2 CP is a promising material for the application in the preperation of self-cleaning surfaces or coatings.	Jan 2019

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