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NANO2021-Nanoteknologi og nye materiale

Perturbation-enhanced Atmospheric Pressure X-ray Photoelectron Spectroscopy (AP-XPS) combined with Temporal Analysis of Products (TAP)

Alternative title: Perturbation-forbedret Atmospheric Pressure X-ray Photoelectron Spectroscopy (AP-XPS)kombinert med Temporal Analysis of Products (TAP)

Awarded: NOK 5.1 mill.

Project Manager:

Project Number:

272266

Application Type:

Project Period:

2017 - 2020

Partner countries:

Catalytic materials accelerate chemical reactions, enabling industrial production of fuels, plastics, pharmaceuticals, and innumerable other compounds needed by modern society. We seek to understand how catalysts work on the molecular scale in order to develop more efficient and sustainable industrial processes. Broadly, catalysts work by binding the reagent molecules to specific active sites on their surfaces where reagents are able to convert into products with minimal energy costs. Newly formed product molecules subsequently detach from the catalyst, thereby freeing up the active sites for the next conversion cycle. However, the catalytic surfaces are not static and may drastically transform when brought into contact with reagents and products. Recent progress in catalysis science has revealed that the most active and selective catalytic sites can, in fact, be formed as a result of these transformations. For example, catalytic metal nanoclusters can change their oxidation state and form unique active sites at their interface with the underlying metal oxide support. In this project, we developed novel methods to investigate exactly how the interactions between catalysts and reactive molecules lead to new atomic arrangements on catalytic surfaces. TAPXPS explored synergies between very different, but complementary cutting-edge techniques to gain a deeper understanding of how different components of complex catalytic materials interact and evolve under reaction conditions. Temporal Analysis of Products (TAP) was employed to precisely measure the rates and selectivities of gas-surface reactions. When TAP experiments are combined with synchrotron-enabled Photoionization Mass-Spectrometry, rates and selectivities become available for different structural isomers of the same molecule, making this method more widely applicable to industrially-relevant hydrocarbon reactions. Ambient Pressure X-Ray Photoelectron Spectroscopy (AP-XPS) was used to probe the chemical state of catalytic surfaces at the atomic scale using powerful synchrotron light. These methods have never been combined before, and we expect their tandem application to unlock unprecedented levels of detail in catalytic chemistry. Throughout the project, different model and complex materials have been synthesized and fully characterized in the home laboratory, such as Cu nanoparticles on zirconia supports produced from Metal-Organic Frameworks (MOFs), PtCu alloyed nanoparticles produced by microwave-assisted synthesis, as well as Co- and Zn-containing MOFs uniquely grown out of the respective metal surfaces. These and other technologically-relevant materials from our laboratory were investigated during multiple experimental campaigns at MAX-IV laboratory in Lund, Sweden - the brightest and newest source of X-Rays in the world. Our findings have demonstrated that combining TAP and synchrotron-based photoelectron spectroscopies is a promising avenue for addressing outstanding questions in catalysis and materials science. We identified the limitations of the current scientific instruments and proposed several new experimental concepts to move beyond the state of the art in catalyst characterization. Some of these concepts were successfully implemented, and the first results were presented at the annual meeting of MAX-IV synchrotron users. Other, more ambitious developments are still in progress, and we look forward with excitement to testing the equipment prototypes for the next generation of experiments. The project team participated in organizing an InterReg workshop on synchrotron-based methods (TWF-2018, Oslo, June 2018) and the International Workshop of Transient Kinetic methods (NAM26, Denver, June 2019). We also contributed to several relevant research proposals, such as the proposal to incorporate the newly developed methods into the Norwegian national infrastructure (NICE-II). Overall, TAPXPS project has generated a unique expertise in combining the cutting-edge time-resolved kinetic and spectroscopic methodologies for better understanding of heterogeneous catalysts. We hope that the project outcomes will foster new research collaborations and innovative breakthroughs in this vibrant, sustainability-relevant field of knowledge.

The TAPXPS project explored potential synergies between synchrotron-based X-Ray spectroscopies and time-resolved kinetic measurements for advanced characterization of chemically-reactive materials such as heterogeneous catalysts. Several model materials and reactions were investigated, resulting in improved understanding of the dynamic surface restructuring of bimetallic catalysis in response to changes of gaseous environments. The most far-reaching implications of the project, however, are expected from the newly developed methodologies for materials characterization that take advantage of perturbation-enhanced experiments. For example, a prototype device was constructed and tested for unprecedented transient experiments in which both gas and surface species can be monitored with sub-second resolution during catalytic reactions. We expect that these developments will find a wide scope of applications in materials science and catalysis.

The central goal of this proposal is to develop a novel type of time-resolved Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) experiment at the MAX IV synchrotron for perturbation-enhanced interrogation of functional materials, primarily heterogeneous catalysts within reactive environments. Well-defined perturbations in the form of pulses and periodic modulations of reactant feeds will be imposed onto a catalytic sample to induce transient responses in XPS spectra. These novel spectroscopic experiments are inspired by and will be used in conjunction with Temporal Analysis of Products (TAP) kinetic experiments at the University of Oslo. Tandem TAPXPS data will illuminate molecular-scale details that underpin structure-performance relationships for technologically-relevant complex oxide surfaces. In order to enable this synergistic approach, innovative metal-oxide materials will be prepared with equivalent microstructures on 2D and 3D substrates via controlled decomposition of Metal-Organic Framework (MOF) films. TAPXPS will pioneer a novel synchrotron-based approach which reconciles high-fidelity spectral and kinetic data for the same functional state of a complex catalytic material. In accordance with SYKNOYT's strategic priority (i), TAPXPS will build a unique competence in synchrotron-based XPS among UiO and SINTEF researchers, which will facilitate their participation in advanced experiments at Max IV, ESRF, and other synchrotron facilities. Through SINTEF, this expertise will be made available and will be demonstrated to potential users from Norwegian industry. New collaborations will be fostered between researchers at the UiO-based TAP facility and various synchrotron-based researchers who will be interested in adopting the TAP-inspired methodologies. This will further facilitate the access of Norwegian research communities to synchrotron facilities and methodologies around the globe, in fulfillment of the primary objectives of the SYKNOYT program

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Funding scheme:

NANO2021-Nanoteknologi og nye materiale