Operando coupling of Steady-State Isotopic Transient Kinetic Analysis (SSITKA) and Fourier Transform InfraRed (FTIR) spectroscopy has evolved as one of the most powerful combination to investigate reaction mechanisms under real conditions. Information regarding catalytic surfaces, active sites and true intermediate species are necessary to design new catalysts able to achieve higher conversion and selectivity. However, “grey zones” about very fast reaction elementary steps (spillover, molecule flip, deoxygenation) have yet to be revealed. In this project, the innovative combination of SSITKA with time resolved FTIR methodology (ms-µs time scale) will help us to remove scientific barriers to define more detailed heterogeneous catalytic oxidation mechanisms. In practice, the ultimate scientific and technical barriers to be lifted and the results expected during the TRAIE project are: (i) The optimization of a new combined SSITKA/Time-resolved IR (rapid and step-scan modes) set-up able to acquire reliable kinetics data and and new insights about the nature of fast elementary steps, active intermediate species and catalyst reactivity. (ii) The test and validation of the operando SSITKA/Time-resolved IR methodology using model reactants and previous literature results. A particular attention will be paid to the amount of data collected and to develop a proper method of data treatment and interconnection. (iii) The investigation of the fast elementary steps of CO and CH4 oxidation reactions over Pt and Pd supported on alumina, respectively, using the SSITKA/Time resolved IR newly developed methodology to establish a more relevant surface-site reactivity relationships and thus, fully depict the different routes of the reaction mechanisms. (iv) The extend of the methodology and result to other relevant catalytic systems using other nature of metallic particles (Rh or Ag), metal-free oxide materials or fully dispersed metallic phase as single atoms. The use of the latter is expected to emphasize the not well-understood differences in the reaction intermediates and/or mechanistic routes from supported large metal nanoparticles. The TRAIE project tackles an important scientific issue in catalysis in order to obtain significant breakthrough in heterogeneous mechanisms understanding. In our knowledge, the combination of these powerful techniques will be achieved for the first time. Ultimately, the fundamental knowledge acquired during the fulfillment of the TRAIE project goals could be apply to catalyst material selection and/or design able to succeed high selectivity to desired products with low energy cost. The realization of the 42 month JCJC project will be ensured by a young researcher and the recruitment of a Ph.D. student in UCCS laboratory. The data and results of this project will be disseminated as much as possible in open-access sources for the scientific community and the general public.

As hydrogen slowly becomes an increasingly popular carbon free energy vector; fuel cells, electrochemical devices able to convert H2 in electricity, gradually appear as a key component of the smart electrical grid of tomorrow. In particular, Solid Oxide Fuel Cells (SOFC) based on an oxygen ion conducting electrolyte are of special interest due to their very high yield in heat/electricity co-generation mode and the absence of noble metal on the electrodes. Yttria Stabilized Zirconia (YSZ), the dominant electrolyte used in SOFC does not allow high power output below 700 °C, driving the research efforts towards high temperature systems. However, durable and flexible high temperature SOFCs are extremely difficult to engineer due to the restrictions on materials set by the temperature range. A recently developed bi-layered electrolyte composed of stabilized ceria (GDC) and bismuth oxide (ESB) offers sufficient ionic conductivity to operate at temperatures as low as 350 °C, however there is still the need to find efficient cathodes to realize the full potential of this electrolyte. Hence, this proposal is focused on the search for new cathode materials and assembly procedures compatible with bi-layer GDC/ESB electrolytes. The goal of this project is to investigate the possibility of assembling solid oxide fuel cells using this new generation of bismuth based bilayer electrolytes, able to operate at temperatures of 400 °C and lower. We will focus on the design of cathode materials to be deposited on the “bismuth layer” of the electrolyte. For this purpose, we propose to look at the assembly of composite air electrodes made with materials with outstanding properties that are usually out of the scope of SOFC research due to chemical/mechanical compatibility. The considerably reduced temperature range will allow us to investigate oxides with metallic behavior such as high-Tc superconductors or SrFeO3-deta. High oxygen ionic conduction will be provided by structure deriving from delta-Bi2O3 such as ESB, DWSB or BiMeVOXs, usually not applicable to higher temperature range due to the reactivity and low melting point. Finally, the oxygen reduction catalytic properties of structures like LnBaCo4O7+delta and LnFe2O4+delta that are able to reversibly insert oxygen into the bulk of their structure at T < 400°C will be tested. By combining two materials with auspicious properties we hope to understand finely the parameters limiting the cathode performance at reduced temperature. To reach our goal an important work of characterization of the compatibility of the different phases of interest coupled to the measurement of their transport properties will allow the rational design of innovative electrodes specifically design to operate at reduced temperature. The performance of the electrodes will be evaluated on symmetrical cells using electrochemical impedance spectroscopy. Detailed understanding of the mechanisms impeding the low temperature operation of the air electrode will lead to electrode optimization. Ultimately these new compounds will be tested in full cell using GDC/ESB bi-layer electrolytes to demonstrate the full potential of these electrodes.

Microporous hybrid materials, such as metal-organic frameworks (MOFs), are promising for numerous applications (energy, health, environment), since they combine high surface areas and tunable pore dimensions. However, little is known about the water stability of the MOFs, even if it represents a critical issue for many applications, including gas storage, radionuclides capture, drug delivery or water purification. The rational improvement of MOFs water stability requires the development of suitable characterization methods since diffraction techniques are not able to detect local defects or change in the organization of extra-framework species caused by hydration. This project aims at analysing water stability of MOFs through advanced solid-state NMR characterization of structural modifications caused by water. By its local character, solid-state NMR is a promising method to probe the structural alterations of MOFs resulting from water adsorption. The final deliverables of this project are (i) standardized NMR protocols to assess water stability of MOFs and (ii) the identification of the most water stable MOFs. In a first step, we will investigate Al containing MOFs, since they benefit from high water and thermal stability (up to 500°C for MIL-53) as well as low cost, density and toxicity. Furthermore, they are promising systems for the capture of radionuclides and heterogeneous catalysis. In a second step, scandium and gallium containing MOFs will be investigated in order to determine the influence of the metal on the water stability. A major stumbling block for the NMR characterization of MOFs is the inability to probe 13C-27Al, 13C-45Sc and 13C-69,71Ga using common solid-state NMR probes since these isotopes exhibit close Larmor frequencies. In this project, we will develop high-performance diplexers and new NMR sequences to circumvent this limitation. These new diplexers will benefit from higher sensitivity and extended tuning range with respect to the existing diplexers, while these devices must be fully compatible with commercial NMR probes. These instrumental developments will be conducted in close collaborations with NMR Service Company and are in line with the strategy of UCCS to contribute to high-field NMR instrumentation for the future installation of 1.2 GHz NMR spectrometer at the University of Lille 1. In this project, we will also develop advanced heteronuclear NMR methods suitable for isotopes of close Larmor frequencies and compatible with the use of diplexers. These NMR methods include two- and three-dimensional heteronuclear correlation experiments to probe 13C-27Al, 13C-45Sc and 13C-69,71Ga proximities. We will also use high magnetic field and/or Dynamic Nuclear Polarization (DNP) to improve the sensitivity of these experiments. The combination of instrumental and methodological developments with conventional NMR characterization (1H, 13C, 17O) will allow determining structural alterations caused by water adsorption and clarifying the mechanisms and the kinetics of the processes involved in water adsorption in MOFs. Besides MOFs, this project is expected to have a broad impact on solid-state NMR and materials science. The developed diplexers will open new avenues for NMR of other isotopes with close Larmor frequencies (31P-7Li, 1H-19F...), which are present in important systems, such as glasses, polymers, soils, biomolecules, organometallics…

In the construction industry, the use of a fibre reinforcement in a mineral matrix (concrete, mortar, gypsum) is often used to improve the mechanical characteristics of the material: the fibres increase the tensile strength of the composite and limits the development of cracks due to the shrinkage of concrete in the early-age. In the hardened state, fibres also play an important role in the crack opening and propagation in concrete. However, the fibres usually used in these materials are derived from non-renewable resources (steel, polypropylene, glass, etc.). The economic issues linked to the rising costs of fossil resources, their increasing scarcity, and the environmental impacts inherent to their manufacturing lead to the exploration of other sources of materials and/or production processes. From this point of view, plant fibres, due to their natural and renewable nature, seem very promising. Many plant fibers are available, and have different morphological and physicochemical characteristics, which strongly influence the functional properties of the composites. This project aims to better identify the phenomena influencing the properties of plant-reinforced cement composites, during their manufacturing, in the hardening state (early-age) and in the hardened state (medium and long term). This will help to better identify and select plant fibers adapted to a required composite characteristics (limitation of shrinkage, cracking at a realy-age, improved toughness, maximum strength, durability, etc.). The ambition of this project is to enhance the use of plant fibers in mortars and concretes to replace traditional fibres, throught recommendations for the use of these fibers for specific applications.

Silica nanoparticles (NPs) with fibrous morphology (KCC-1) coated with TiO2 and functionalized with amine chains (KCC-1-TiO2-NH2) are promising materials for the integrated capture of CO2 and its photoconversion into fuels or chemicals. Such nanocatalysts should combine high surface area, high accessibility, efficient CO2 capture and good water stability. However, there are still unsettled questions about the structure and the activity of this type of nanophotocatalysts, including (i) the structure of the TiO2 surface and its interaction with reactants (CO2 and H2O); (ii) the structure of TiO2 phases supported on silica and the SiO2-TiO2 interactions; and (iii) the orientation and the mobility of the grafted amine chains. The EOS project aims at obtaining such information by developing innovative high-field solid-state (DNP)-NMR instruments and methods since this spectroscopy is suited to the characterization of heterogeneous and/or disordered materials. The techniques developed in the project will open new avenues for the detection of insensitive quadrupolar nuclei (47/49Ti, 14N, 17O) near surface. We will notably design innovative instrumentation for the observation of these isotopes using 1.2 GHz NMR spectrometers. We will also explore novel approaches to improve the sensitivity of 800 MHz DNP-NMR. NMR methods will also be introduced to selectively observe the insensitive quadrupolar nuclei near surfaces and to probe their interactions with the reactants (H2O, CO2). These novel (DNP)-NMR techniques will lead to a better understanding of the structure and the dynamcis of KCC-1-TiO2-NH2 surface and its interactions with reactants. This new knowledge will be used to rationally improve the conception of the nanocatalysts and their performances. This project addresses important questions in NMR, heterogeneous catalysis and material sciences. It will open new horizons for the conception of photocatalysts, which is a crucial technology for the clean energy challenge.