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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Silicon microfabricated reactor for operando XAS/DRIFTS studies of heterogeneous catalytic reactions B. Venezia , E. Cao , Santhosh K. Matam , C. Waldron , G. Cibin , E. K. Gibson , S. Golunski , P. P. Wells , I. Silverwood , C. R. A. Catlow , G. Sankar , A. Gavriilidis Catalysis Science & Technology 39 DOI: 10.1039/D0CY01608J Diamond Proposal Number(s): [19359] Open Access Show Abstract ▼ Abstract: Operando X-ray absorption spectroscopy (XAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) provide complementary information on the catalyst structure, surface reaction mechanisms and activity relationships. The powerful combination of the techniques has been the driving force to design and engineer suitable spectroscopic operando reactors that can mitigate limitations inherent to conventional reaction cells and facilitate experiments under kinetic regimes. Microreactors have recently emerged as effective spectroscopic operando cells due to their plug-flow type operation with no dead volume and negligible mass and heat transfer resistances. Here we present a novel microfabricated reactor that can be used for both operando XAS and DRIFTS studies. The reactor has a glass–silicon–glass sandwich-like structure with a reaction channel (3000 μm × 600 μm; width × depth) packed with a catalyst bed (ca. 25 mg) and placed sideways to the X-ray beam, while the infrared beam illuminates the catalyst bed from the top. The outlet of the reactor is connected to MS for continuous monitoring of the reactor effluent. The feasibility of the microreactor is demonstrated by conducting two reactions: i) combustion of methane over 2 wt% Pd/Al2O3 studied by operando XAS at the Pd K-edge and ii) CO oxidation over 1 wt% Pt/Al2O3 catalyst studied by operando DRIFTS. The former shows that palladium is in an oxidised state at all studied temperatures, 250, 300, 350, 400 °C and the latter shows the presence of linearly adsorbed CO on the platinum surface. Furthermore, temperature-resolved reduction of palladium catalyst with methane and CO oxidation over platinum catalyst are also studied. Based on these results, the catalyst structure and surface reaction dynamics are discussed, which demonstrate not only the applicability and versatility of the microreactor for combined operando XAS and DRIFTS studies, but also illustrate the unique advantages of the microreactor for high space velocity and transient response experiments.	Oct 2020
B18-Core EXAFS	Carbidisation of Pd nanoparticles by ethene decomposition, with methane production Michael Bowker , Wilm Jones , Peter P. Wells , Emma K. Gibson , Arunabhiram Chutia , Ian P. Silverwood , C. Richard A. Catlow Chemcatchem DOI: 10.1002/cctc.201900795 Show Abstract ▼ Abstract: In the presence of oxygenated organic molecules pure Pd, which is widely used in chemicals processing and the pharmaceutical industry, tends to defunctionalise and dehydrogenate such molecules to H2, CO and surface/bulk carbon, in the form of a palladium carbide. We have investigated the formation of this carbide by ethene adsorption using a variety of techniques, including pulsed flow reaction measurements, XAS and DFT calculations of the lattice expansion during carbidisation. These experiments show that two main reactions take place above 500K, that is, both total dehydrogenation, but also disproportionation to methane and the carbide, after which the activity of the Pd is completely lost. We estimate the value of x in PdCx to be 0.28 (±0.03), and show by computer modelling that this fits the lattice expansion observed by XAFS, and that there is charge transfer to C from Pd of around 0.2‐0.4 e.	Jun 2019
I19-Small Molecule Single Crystal Diffraction	Modulating proton diffusion and conductivity in metal-organic frameworks by incorporation of accessible free carboxylic acid groups Peter Rought , Christopher Marsh , Simona Pili , Ian P. Silverwood , Victoria Garcia Sakai , Ming Li , Martyn Brown , Stephen P. Argent , Inigo Vitorica-yrezabal , George Whitehead , Mark R. Warren , Sihai Yang , Martin Schroeder Chemical Science DOI: 10.1039/C8SC03022G Diamond Proposal Number(s): [13650, 12517] Open Access Show Abstract ▼ Abstract: Three multi-carboxylic acid functionalised ligands have been designed, synthesised and utilised to synthesise the new barium-based MOFs, MFM-510, -511, and -512, which show excellent stability to water-vapour. MFM-510 and MFM-511 show moderate proton conductivities (2.1 x10-5 and 5.1 x10-5 S cm-1, respectively) at 99RH% and 298 K, attributed to the lack of free protons or hindered proton diffusion within the framework structures. In contrast, MFM-512, which incorporates a pendant carboxylic acid group directed into the pore of the framework, shows a two orders of magnitude enhancement in proton conductivity (2.9 x10-3 S cm-1). Quasi-elastic neutron scattering (QENS) suggests that the proton dynamics of MFM-512 are mediated by “free diffusion inside a sphere” confirming that incorporation of free carboxylic acid groups within the pores of MOFs is an efficient albeit a synthetically challenging strategy to improve proton conductivity.	Nov 2018
I11-High Resolution Powder Diffraction	Enhancement of proton conductivity in non-porous metal-organic frameworks: the role of framework proton density and humidity Simona Pili , Peter Rought , Daniil I. Kolokolov , Longfei Lin , Ivan Da Silva , Yongqiang Cheng , Christopher Marsh , Ian P. Silverwood , Victoria García-sakai , Ming Li , Jeremy J. Titman , Lyndsey Knight , Luke L. Daemen , Anibal J. Ramirez-cuesta , Chiu C. Tang , Alexander G. Stepanov , Sihai Yang , Martin Schroeder Chemistry Of Materials DOI: 10.1021/acs.chemmater.8b02765 Diamond Proposal Number(s): [13247] Show Abstract ▼ Abstract: Owing to their inherent pore structure, porous metal-organic frameworks (MOFs) can undergo post-synthetic modification, such as loading extra-framework proton carriers. However, strategies for improving the proton conductivity for non-porous MOFs are largely lacking, although increasing numbers of non-porous MOFs exhibit promising proton conductivities. Often, high humidity is required for non-porous MOFs to achieve high conductivities, but to date no clear mechanisms have been experimentally identified. Here we describe the new materials MFM-550(M), [M(HL1)], (H4L1 = biphenyl-4,4'-diphosphonic acid; M = La, Ce, Nd, Sm, Gd, Ho), MFM-550(Ba), [Ba(H2L1)], and MFM-555(M), [M(HL2)], (H4L2 = benzene-1,4-diphosphonic acid; M = La, Ce, Nd, Sm, Gd, Ho), and report enhanced proton conductivities in these non-porous materials by (i) replacing the metal ion to one with a lower oxidation state, (ii) reducing the length of the organic ligand, and (iii) introducing additional acidic protons on MOF surface. Increased framework proton density in these materials can lead to an enhancement in proton conductivity of up to four orders of magnitude. Additionally, we report a comprehensive investigation using in situ 2H NMR and neutron spectroscopy, coupled with molecular dynamic modelling, to elucidate the role of humidity in assembling interconnected networks for proton hopping. This study constructs a relationship between framework proton density and the corresponding proton conductivity in non-porous MOFs, and directly explains the role of both surface protons and external water in assembling the proton conducting pathways.	Sep 2018
	QENS study of methane diffusion in Mo/H-ZSM-5 used for the methane dehydroaromatisation reaction Ian P. Silverwood , Miren Agote-aran , Ines Lezcano González , Anna Kroner , Andrew M. Beale Proceedings of the Joint Conference on Quasielastic Neutron Scattering and the Workshop on Inelastic Neutron Spectrometers QENS/WINS 2016 DOI: 10.1063/1.5039294 Show Abstract ▼ Abstract: There is commercial interest in understanding the deactivation of Mo loaded H-ZSM-5 catalyst by coke fouling during the methane dehydroaromatization reaction (MDA). The effect of coke on methane diffusion inside the zeolite pores was studied by quasielastic neutron scattering (QENS) measurements on Mo/H-ZSM-5 samples reacted with methane for 0, 7, 25 and 60 min. Catalytic activity of the samples followed by mass spectrometry indicate that the induction period in which Mo species are carburized lasts for ∼9 min; after this period the material shows selectivity to aromatics. Characterization by TGA and N2 physisorption suggest that practically no carbon is deposited during the induction period. The ∼2 wt % of coke formed after one hour of reaction has a negligible effect in the zeolite crystal structurebut a small effect on the micropore volume. The QENS studies show that the methane transport by jump diffusion is however not measurably affected by the accumulated coke in the samples.	May 2018
B18-Core EXAFS	Adsorption of formate species on Cu(h,k,l) low index surfaces Arunabhiram Chutia , Ian P. Silverwood , Matthew R. Farrow , David O. Scanlon , Peter P. Wells , Michael Bowker , Stewart F. Parker , C. Richard A. Catlow Surface Science 653, 45 - 54 DOI: 10.1016/j.susc.2016.05.002 Open Access Show Abstract ▼ Abstract: We report a density functional theory study on the relative stability of formate species on Cu(h,k,l) low index surfaces using a range of exchange-correlation functionals. We find that these functionals predict similar geometries for the formate molecule adsorbed on the Cu surface. A comparison of the calculated vibrational transition energies of a perpendicular configuration of formate on Cu surface shows an excellent agreement with the experimental spectrum obtained from inelastic neutron spectroscopy. From the calculations on adsorption energy we find that formate is most stable on the Cu(110) surface as compared to Cu(111) and Cu(100) surfaces. Bader analysis shows that this feature could be related to the higher charge transfer from the Cu(110) surface and optimum charge density at the interfacial region due to bidirectional electron transfer between the formate and the Cu surface. Analysis of the partial density of states finds that in the –5.5 eV to –4.0 eV region, hybridization between O p and the non-axial Cu dyz and dxz orbitals takes place on the Cu(110) surface, which is energetically more favourable than on the other surfaces.	Nov 2016
I11-High Resolution Powder Diffraction I19-Small Molecule Single Crystal Diffraction	Proton Conduction in a Phosphonate-Based Metal–Organic Framework Mediated by Intrinsic “Free Diffusion inside a Sphere” Simona Pili , Stephen Argent , Christopher Morris , Peter Rought , Victoria García-sakai , Ian Silverwood , Timothy Easun , Ming Li , Mark Warren , Claire Murray , Chiu Tang , Sihai Yang , Martin Schroeder Journal Of The American Chemical Society DOI: 10.1021/jacs.6b02194 Show Abstract ▼ Abstract: Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metal–organic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 × 10–4 S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic “free diffusion inside a sphere”, representing the first example of such a mechanism observed in MOFs.	May 2016
B22-Multimode InfraRed imaging And Microspectroscopy	Towards microfluidic reactors for in situ synchrotron infrared studies I. Silverwood , N. Al-rifai , E. Cao , D. Nelson , A. Chutia , P. Wells , S. P. Nolan , M. D. Frogley , G. Cinque , A. Gavriilidis , C. R. A. Catlow Review Of Scientific Instruments 87 DOI: 10.1063/1.4941825 PMID: 26931867 Diamond Proposal Number(s): [8962] Show Abstract ▼ Abstract: Anodically bonded etched siliconmicrofluidic devices that allow infrared spectroscopic measurement of solutions are reported. These extend spatially well-resolved in situ infrared measurement to higher temperatures and pressures than previously reported, making them useful for effectively time-resolved measurement of realistic catalytic processes. A data processing technique necessary for the mitigation of interference fringes caused by multiple reflections of the probe beam is also described.	Feb 2016
B18-Core EXAFS	In situ spectroscopic investigations of MoOx/Fe2O3 catalysts for the selective oxidation of methanol Catherine Brookes , Peter Wells , Emma Gibson , Diego Gianolio , Khaled Mohammed , Stephen Parry , Scott Rogers , Ian Silverwood , Michael Bowker Catalysis Science & Technology DOI: 10.1039/C5CY01175B Diamond Proposal Number(s): [8071] Open Access Show Abstract ▼ Abstract: Multicomponent oxide shell@core catalysts have been prepared, affording overlayers of MoOx on Fe2O3. This design approach allows bulk characterization techniques, such as X-ray Absorption Fine Structure (XAFS), to provide surface sensitive information. Coupling this approach with in situ methodologies provides insights during crucial catalytic processes. Calcination studies were followed by a combination of XAFS and Raman, and demonstrate that amorphous multi-layers of MoOx are first converted to MoO3 before formation of Fe2(MoO4)3. However, a single overlayer of Oh Mo units remains at the surface at all times. In situ catalysis studies during formaldehyde production identified that Mo6+ was present throughout, confirming that gas phase oxygen transfer to molybdenum is rapid under reaction conditions. Reduction studies in the presence of MeOH resulted in the formation of reduced Mo-Mo clusters with a bonding distance of 2.6 Å. It is proposed that the presence of the clusters indicates that the selective conversion of MeOH to formaldehyde requires multiple Mo sites.	Aug 2015

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