Projects

Area A: SCALMS (Supported Catalytically Active Liquid Metal Solutions)

A01 aims at understanding the catalytic properties of SCALMS and the dynamic behaviour of the active sites at the gas/liquid interface to enable their knowledge-based improvement. We will study model and real-world catalysts in UHV and near-ambient pressure to technical operating conditions. Towards providing a full “depth-resolved” picture, we will employ laboratory- and synchrotron-based X-ray spectroscopic techniques with specific surface or bulk sensitivity. The fundamental studies will reveal details such as the metal distribution in the liquid alloy, its (de-)wetting behaviour on supports, its electronic structure, as well as its behaviour and surface chemistry as a function of temperature and pressure.

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The atomic dynamics of metal and alloy droplets of SCALMS systems will be studied in this Project. Using coherent and incoherent quasielastic neutron scattering (QENS), time (pico- to nanoseconds) and length (nanometers) scales relevant for single atom catalysis at the gas/liquid interface will be addressed. The applied methodology allows for decoupling the observation of the atomic dynamics from the slower convection processes and the solid support material hardly contributes to the QENS signal. The QENS data are perfectly suited for validation of atomistic simulations in this CRC. Adapted scattering techniques (XRR, XRD, and (GI)SAXS/SANS) will contribute to structure determination for the whole CRC.

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Project A03 addresses the temperature-dependent phase stability of SCALMS, the liquid alloy distribution, the surface composition, and the wetting behaviour in porous support materials. For this purpose, we will use analytical and in situ transmission electron microscopy (TEM) as well as scale-bridging tomography techniques, ranging from atom probe tomography (APT) and electron tomography (ET) to X-ray nanotomography (NanoCT). The project includes in situ studies with high spatial resolution of model nanoalloys at near operation conditions, three-dimensional chemical and structural analysis of SCALMS with high-resolution through correlative TEM/APT, and scale-bridging correlative 3D analysis of SCALMS after catalytic operation.

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Catalysis in SCALMS takes place at the gas/liquid interface. However, standard pre­pa­ration methods for SCALMS do not control the liquid interface area and, thus, this parameter is mostly unknown, at least under reaction conditions. Project A04 targets the preparation and catalytic application of SCALMS materials with ordered, regularly spaced liquid metal droplets of uniform size. For this purpo­se, dimples (radius of curvature between 10 and 200 nm depending on preparation) will be prepared on planar Al or Ti substrates by anodisation and filled with alloy droplets. Their size will be varied to generate model systems applicable to theoretical description and SCALMS microreactors with optimised specific surface areas.

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Project A05 deals with experimental studies to understand and optimise the wetting of liquid alloys on porous support materials. We explore how structure and catalytic performance of SCALMS are affected by the interplay between preparation, surface chemical properties and support texture. For this, we will develop targeted, adsorption-based methodologies and novel liquid intrusion techniques for (i) a reliable textural characterisation of SCALMS and meso-macroporous supports and (ii) for assessing the wetting behaviour of liquid metal solutions in the supports. This information will enable a knowledge-based selection of support materials and pore structures for maximising the gas/alloy interface of SCALMS and, thereby, the volumetric productivity.

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A06 focuses on the technical dimension of SCALMS by exploring quantitatively the expected enhanced poisoning resistance and stability in dehydrogenation catalysis. For the specific case of isobutane dehydrogenation, we will perform systematic poisoning experiments under surface science and technical conditions. The data will be compared to traditional catalysts. Spectroscopic and reaction engineering studies will be applied to determine the concentration, reactivity, and regenerability of active sites of the SCALMS systems after contact with defined amounts of traditional poisons or after exposure to conditions favouring coke formation. We will also investigate ternary SCALMS to elucidate the effect of further alloying and dissolution on the adsorption strengths, reactivity, and stability.

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Area B: Interface-enhanced SILP (Supported Ionic Liquid Phase)

Project B01 focuses on the design and synthesis of functionalised and task-specific ILs, with the aim (i) to tailor support/IL interfaces and (ii) to develop electrocatalytically active interface-enhanced SILPs. The latter concept will combine catalytic functionalities operating at both the gas/IL and the IL/solid interfaces for the electro­chemical production of hydrogen from water (or protons) and the hydrogenation of divers C=C and C=O moieties in selected substrates. These two processes shall be controlled by the incorpora­tion of identical task-specific structural motifs in the IL and in the active transition metal catalyst. The long-term objective will be the direct electro­catalytic hydrogenation of substrates in a ‘tandem-like’ system.

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We aim to design functionalised redox active metal complexes to control their enrichment and orientation at ILs interfaces, i.e. the exposure of active sites to the reactants and thus, control their reactivity. Targeted will be binding and hydrogenation/reduction of CO2 or other C=O functionalities by Pt, Pd, Ru and Ni complexes of bi-, tri- and tetradentate pincer-like or macrocyclic ligands. Systematic variation of substituents will tune charge, polarity, coordination equilibria and redox properties of complexes, affecting interactions with ILs and reactants, leading to catalytic activity. We will also study kinetics and thermodynamics of processes in ILs and, for comparison, conventional solvents by variety of techniques, including high-pressure and cryo-methodology.

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Project B03 will develop silica-based support materials with tailored porosity and surface properties to explore the catalytic potential of interface-enhanced SILPs. We will control the wettability and film formation of the ILs on the solid support via surface functionalisation and the introduction of hierarchical porosity. These tailored supports will maximise the IL wettability and film stability while ensuring efficient mass transport by preventing pore flooding, also under reaction conditions. We will take advantage of the homogeneous IL films with controlled thickness and tailored surface functionality to control the catalyst position relative to the gas/liquid and liquid/solid interface to elucidate differences in activity and fundamentally understand SILP performance.

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We aim at understanding the fundamental processes that determine the properties of the gas/liquid interface of Interface-enhanced SILPs. Towards this aim, the Steinrück and Koller groups will apply X-ray photoelectron spectroscopy under ultraclean conditions and the pendant drop method as well as surface light scattering under reaction conditions. This enables to develop relationships between the surface properties on the nanometre scale and the macroscopic properties surface tension, viscosity and dynamics of surface fluctuations. Based on this concerted characterisation, we envisage to identify those factors which are responsible for the enrichment of catalytic metal complexes at IL interfaces.

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Project B05 aims at understanding the properties of the liquid/solid interface of Interface-enhanced SILPs using solid-state NMR spectroscopy. We will determine the dynamics of the IL and its interactions with the support, as well as the distance between the catalyst and the support by implementing advanced solid-state NMR methods, including 2D heteronuclear correlation and REDOR techniques. Ultimately, Parahydrogen Induced Polarisation (PHIP) in a Magic Angle Spinning probe will be developed as a novel tool to probe with enhanced sensitivity hydrogenation reactions in SILP catalysts in situ and operando. Active catalyst components, reaction intermediates and side products can thus be identified.

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In Project B06, we will elucidate the relation between the position of the active molecular complex in the SILP material and the resulting activity, selectivity, and stability of the catalyst. We envisage that for e.g poorly soluble substrates the reaction is still fast if the active species is located at the gas/IL interface and slow if the active species is located in the IL bulk or at the IL/support interface. We will determine solubility of different substrates in ILs and test competitive conversion of mixed feeds containing substrates with strongly differing solubility. Systematic kinetic tests will be performed varying the IL (chain length and functionalisation), the catalyst (ligand variation) and the operation conditions.

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Area C: Advanced SCILL (Solid Catalysts with Ionic Liquid Layer)

Project C01 deals with the modification of alumina-supported Pt and Pd catalysts with ILs that carry one or several functionalities. By specific interaction of the IL and its functionalities with the solid catalyst, a ligand-like IL effect is expected which strongly alters activity and selectivity of the active sites of the supported nanoparticles. The ILs will be prepared in highest purity and are also provided to the partner projects C02C05. The prepared catalysts will be tested in competitive gas phase hydrogenation reactions comparing SCILL systems with non-functionalised ILs, functionalised ILs and IL mixtures. This project will provide de-tailed kinetic data (activity, selectivity, chemoselectivity) of Advanced SCILL catalysts and will explore the stability of IL functionalities under reaction conditions.

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We aim at understanding the fundamental processes and the chemical/morphological stability of IL/solid interfaces in Advanced SCILLs. We will proceed in three steps: for non-functionalised and functionalised ILs, we will investigate (a) the chemical interaction and the wetting behaviour of (ultra)thin IL films on the supporting solid on a wide range of well-defined substrates, (b)the stability of Advanced SCILL systems from the point of view of interface chemistry and morphology, and finally, (c) strategies to control and to switch the adsorption and wetting behaviour. Using ARXPS, STM, and AFM, we will extract interface compositions, depth profiles, chemical states, adsorption geometries and growth behaviour.

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In Project C03, we will elucidate the fundamental interaction mechanisms between functionalised ILs and catalytically active surfaces and their role in catalytic hydrogenation. To this aim, we will combine in situ studies at single crystals and atomically defined model catalysts in UHV with operando spectroscopy on real SCILLs under true working conditions. Our key tools will be vibrational spectroscopy (IRAS, PM-IRAS, DRIFTS) in combination with online analytics of products (MB experiments, TPD, TPR, online GC, online QMS). Specifically, we will identify interaction mechanisms at the surface, the orientation of IL ions, conformational changes, specific interactions with co-adsorbates, reaction intermediates and selectivity patterns.

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Project C04 will target the stability of advanced SCILLs in hydrogenation reactions both with and without potential control. Depending on the catalyst material, reaction, and operation conditions, functionalised ILs may have a beneficial or a detrimental effect on the stability of the active NPs. Therefore, we will study the dynamic evolution of the catalytic interface over extended operation periods, in dependence of parameters such as the EC potential, composition, structure, morphology, and the chemical nature of the interface, and investigate the effect on the reactions in Projects C01 and C05. The project will benefit from the complementary expertise of the Mayrhofer and Virtanen groups, bringing together a broad range of methods to study dissolution, degradation and corrosion mechanisms.

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In Project C05, we will explore the potential of Advanced SCILLs in electrocatalytic hydrogenation. Using a broad range of EC in situ spectroscopies, microscopies, and advanced EC characterisation methods, we will scrutinise the selective hydroge­na­tion of unsaturated ketones and nitriles on a broad range of test electrodes (single crystals, atomically defined model electrodes, complex alloys and supported nanoalloys). At the electrified interface, we will explore (i) how ILs interact with specific sites at the electrode, (ii) how ILs interact with reactants during the electrocatalytic re­ac­tion, (iii) how these interactions affect the mechanism and kinetics, and (iv) how ILs can be tailored to enhance the selectivity of electrohydrogenation.

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Area M: Modelling and simulation

The project aims at a microscopic quantum mechanical description of catalytic materials and processes in the three Areas A, B, and C (SCALMS, Interface-enhanced SILP, and Advanced SCILL). We will interpret and explain experimental data and develop and suggest strategies to optimise catalytic materials and processes. Based on conventional and newly developed density-functional methods (i) ab initio molecular dynamics simulations will be performed and (ii) slab and cluster models as well as (iii) molecular systems will be studied. Detailed atomistic information on catalytic sites, reaction steps, and diffusion and segregation processes as well as input for other theory projects in Area M will be provided.

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Project M02 focusses on multi-scale simulations in the field of SILP and SCILL catalysis for tuning of the catalytic complex, the IL, and the support material in order to maximise efficiency of reactions studied in C01 and B06. This requires the development of hybrid quantum mechanics/ molecular mechanics approaches to embed the local quantum description of the reactive centre into the surrounding IL film. Molecular dynamics simulations will be used to enhance the spatial coordination of the reactants with the interfaces, by investigation of the structural and transport properties of IL and reactants. Molecular simulations of IL interface dynamics shall be used to parametrise the lattice-Boltzmann models in M04.

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Project M03 will perform molecular dynamics simulations for the in-depth understanding of effects that occur at the nanometre scale such as the self-organisation of IL layers and films (Kawska-Zahn approach). To account for charge polarisation in metal droplets and nanoparticles, the MM models will be extended by QeQ approaches. This effectively expands QM characterisation to MD simulations reaching the million atoms scale. Using multi-state MM models triggered by QM/MM calculations, the relaxation dynamics of deactivation and self-healing reactions of the catalyst will be elucidated.

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Project M04 will address mesoscale phenomena relevant to all experimental areas by means of lattice-Boltzmann simulations. The dynamics of wetting and dewetting of substrates by IL films and metal droplets will be elucidated driven by heat formation and mass transport during catalyst operation. M04 will assess contact angles and their variation depending on the geometry of porous supports, the dynamics of spreading and imbibition of ILs and liquid metals in such supports, the accessibility of surface sites, the heat flux, and the resulting turnover rates. Understanding the combination of these effects, we will rationalise experimental findings and propose strategies for the improvement of materials and processes.

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Central Projects

Project Z01 comprises the scientific coordination of CLINT. The project targets include the administrative management, reporting, proposal preparation, measures related to internationalisation, public relations and outreach, science communication and dissemination. Furthermore, the project will provide professional quality assurance, will help to protect our inventions by IP rights, will act as central coordination point between all institutions, and will organise seminars by invited speakers, area meetings, workshops, retreats and conferences. We will place special emphasis on equal opportunity at all levels of qualification in accordance with our gender equality targets.

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The primary goal of the CLINTiRTG is to ensure a profound academic education and to provide qualifications that go beyond the usual training of young researchers. While primarily addressing doctoral students, CLINTiRTG will also support postdoctoral researchers and undergraduate students. For its participants, CLINTiRTG will provide a comprehensive training and networking programme that foremost expands their multidisciplinary academic competences in catalysis and related fields. A soft skills program will enable improving their capacities to lead, organise and communicate while promoting a progressive and diverse working environment. CLINTiRTG will boost the knowledge and independence of young researchers to create a next generation of experts working on the executive level in industry and academia.

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