Development of new anode materials for potassium-ion batteries

Classic Li-ion batteries are composed of a graphite anode and a cathode containing a lithiated layered oxide (formula LiNixMnyCozO2). The development and the generalization of the electric automobile market will generate stress on certain chemical elements source, especially for lithium, nickel, cobalt and copper. In addition, the production method consumes a lot of energy (multiple calcinations) and several solvents/products used are not respectful of the environment (NMP, ammonia).
The thesis aims to develop a battery technology based on potassium without using any critical element in order to significantly decrease the ecological footprint.
The insertion of potassium ion inside the graphite structure has been reported as an advantage in front of Na-ion batteries. However, due to the potassium size, the graphite structure expands (60%) and can limit the batterie cycle life.
The final target of the PhD thesis is to solve this issu following two approches : 1/ Find the link beetween graphites specifications and the resulting electrochemical performances in order to select the best graphite grade 2/ Develop new anode materials for K-ion application.

Melt grafting of polyolefin applied to reparable and recyclable photovoltaic panels

Solar panels are multi-materials assemblies constituted of photovoltaic cells that contains numerous precious metals (metal silicon, silver), high quality and therefore costly-to-manufacture glass that protects the cells, and a polymer film acting as binder, called encapsulant. These encapsulants are mostly thermoplastics that are reticulated during the manufacture of photovoltaic panels, which makes their dismantling and recycling difficult today.
CEA develops new materials to bring recyclability to renewable energy production systems, such as photovoltaic panels. The thesis revolves around the development of new encapsulants that allow improved recyclability of photovoltaic panels through a reversible reticulation system. In a first step, the melt grafting (extrusion, internal mixer) of polyolefins with molecules of interest will be studied in terms of grafting efficiency and kinetics, and impact on polyolefins properties such as thermal, optical, and structural properties. In a second step, a reversible reticulation will be triggered using the firstly grafted molecules. The impacts of this reticulation on the material thermal, mechanical, optical properties will be characterized. The application of the material as encapsulants will be the final aim of the thesis, and small demonstrators of photovoltaic modules using the material will be performed.

Model development and simulation of coupling between plume migration and chemical perturbations

The fate of chemicals in the environment is of importance in fields, including fuel-cycle or radioecology. Migration models describe the behaviour of radionuclides and relationships with properties: e.g. electrical charge, redox state. In addition, the retention on mineral surfaces strongly delays migration. This later mechanism may be described using various approaches and levels of complexity:
- Non-reactive approach, considering retention (Kd) without species chemistry,
- Reactive-transport, considering speciation in solution and on surfaces,
- Multi-component approaches, specifying diffusion for each compounds, e.g. NO3, EDTA, Th(IV), etc.
- Multi-species approaches, specifying the behaviour of each species for a given compound, e.g. [UO2] 2+, [CaUO2(CO3)3]2-, [Ca2UO2(CO3)3]0.
The work will focus on the development of multi-component and multi-species migration models. Models will be applied to assess more accurately the spread of chemical perturbations in natural barriers (soils, sediments). To this aim, available experimental data will be used as input data. A main objective is to quantify the differences between approaches and potential implications for radionuclide migration & corresponding mitigation strategies.

Novel membranes based on 2D nanosheets

This thesis project aims to exfoliate new nanostructured architectures based on two-dimensional inorganic phases. These nanostructures will be designed for filtration devices and tested using our microfluidic platform. The target application is water purification and the selective separation of metal ions. The doctoral student will interact with chemists, physicists and electrochemists in a real multidisciplinary environment, on a fundamental research subject directly connected to application needs. Thus, during his thesis, the student will be exposed to a multidisciplinary environment and brought to carry out experiments in various fields such as inorganic chemistry, physical chemistry, micro / nano-fabrication and nano-characterization methods. In In this context, this project should potentially lead to significant societal benefits.

For the realization of the latter, he will have access to a very wide and varied range of equipment ranging from optical microscopes to the latest generation synchrotron (ESRF), including field effect or electron microscopes and galvanostats.

This thesis is therefore an excellent opportunity for professional growth, both in terms of your knowledge and your skills.

Predicting new catalysts for fixing dinitrogen

New chemical approaches for conversion of N2 to NH3, as an alternative to the energy- and CO2-intensive Haber-Bosch process, are of high interest for improved fertilizer production and the potential of NH3 as a zero-carbon fuel. Catalytic N2 fixation, however, is an extremely difficult reaction with few successes. Previous attempts show low turnover rates, insufficient selectivity or too negative potentials required. A breakthrough in molecular N2 fixation was recently described (J. C. Peters and co. Nature, 2022). By combining coupled proton-electron transfer mediator, CPET, with simple Fe/Mo/W complexes in solution, selective catalysis was demonstrated (-1.2 V vs. Fc0/+). This proof-of-principle experiment implicates CPET mediation as a general N2 fixation strategy when combined with N2-binding metal complexes. However, design principles for improving catalytic N2 fixation activity under CPET conditions are not known. We propose here a multiscale simulation strategy to uncover these catalyst design principles and aid synthetic efforts. Our previous expertise in studying biological N2 fixation, multiscale modelling of redox processes and high-level calculations of redox mediators will be of benefit in this project.

Exploring the reactivity of oxide based catalysts by radiolysis

In the context of the search for processes that are less polluting and more energy-efficient than current processes, it is interesting to produce high-stake molecules such as C2H4 by developing alternative synthesis routes to steam cracking, which is used in the majority of cases, but is energy-intensive and based on fossil resources. Processes such as photocatalysis, which relies on the use of light energy, seem an attractive way of generating these molecules of interest. In this context, we have already shown that the use of TiO2-based photocatalysts decorated with copper particles enables the production of ethylene from an aqueous solution of propionic acid, with a selectivity (C2H4/other carbonaceous products) of up to 85%.

However, photocatalysis kinetics can be slow, and it can take a long time to identify the best catalysts or catalyst/reagent pairs for a given reaction. So, in order to determine whether radiolysis, which relies on the use of radiation to ionize matter, can be an effective method of screening catalysts, initial experiments have already been carried out on catalyst (TiO2 or Cu TiO2)/reagent (propionic acid more or less concentrated) pairs, previously studied in photocatalysis. Initial results obtained by radiolysis are encouraging. In these experiments, only dihydrogen production was measured. A significant difference was observed in this production depending on the system: it was high during radiolysis of propionic acid with TiO2 nanoparticles, and significantly lower in the presence of Cu TiO2 nanoparticles, suggesting a different reaction path in the latter case, in line with observations made during photocatalysis experiments.

The aim of this thesis work will be to extend these initial results by synthesizing nanoparticles (catalysts), preparing reagent/catalyst mixtures, then irradiating them and measuring the various gases produced by gas-phase micro-chromatography, with special attention on ethylene. Particular attention will be paid to determining the species formed, especially transient ones, in order to ultimately propose reaction mechanisms accounting for the differences observed for the different reagent/catalyst pairs. Comparisons will also be made with results obtained by photocatalysis.

Porous materials integrated into devices for glycomic analysis in hospitals.

Glycomics involves identifying oligosaccharides (OS) present in a biological fluid as a source of biomarkers for diagnosing various pathologies (cancers, Alzheimer's disease, etc.). To study these OS, sample preparation involves 2 key phases, enzymatic cleavage (breaking the bond between OS and proteins) followed by purification and extraction (separation of OS and proteins). However, the materials currently used in the protocols impose numerous manual and time-consuming steps, incompatible with high-throughput analysis.

In this context, the LEDNA laboratory specialized in materials science has recently developed a sol-gel process for the manufacture of Hierarchical Porosity Monoliths (HPMs) in miniaturized devices. These materials have provided a proof of concept demonstrating their value for the second stage of glycomic analysis, i.e. the purification and extraction of oligosaccharides. The LEDNA is now looking to improve the first step, corresponding to enzymatic cleavage, which has become a limiting factor in the glycomics analysis process. Functionalization of porous materials, in particular HPMs, with enzyme would enable simple sample preparation in just a few hours with a single step.

The aim of this thesis is therefore to show that the use of porous materials with a dual function - catalytic and filtration - applied to the preparation of samples for glycomic analysis is a relevant means of simplifying and accelerating glycomic analysis, as well as employing them in hospital-related studies to identify new biomarkers of pathologies.

The research project will involve developing a device incorporating porous materials with catalytic and filtration functions. Several aspects will be addressed, ranging from the synthesis and shaping of these materials to characterization of their textural and physico-chemical properties. Particular emphasis will be placed on enzyme immobilization. The most promising prototype(s) will be evaluated in a glycomic analysis protocol, verifying the oligosaccharide profiles obtained from human biofluids (plasma, milk). Physico-chemical characterization will involve a variety of techniques (SEM, TEM, etc.), as well as characterization of porosity parameters (nitrogen adsorption, Hg porosimeter). Oligosaccharides will be analyzed by high-resolution mass spectrometry (mainly MALDI-TOF).

For this multidisciplinary thesis project, we are looking for a student chemist or physical chemist, interested in materials chemistry and motivated by the applications of fundamental research in the field of new technologies for health. The thesis will be carried out in two laboratories, LEDNA for the materials part and LI-MS for the use of materials in glycomics analysis. The research activity will be carried out at the Saclay research center (91).

Nano- and micropatterned biomineral-based materials: Orientation-specific assembly of coccoliths into arrays

Coccoliths of coccolithophorid algae are anisotropically-shaped microparticles consisting of calcite (CaCO3) crystals with unusual morphologies arranged in complex 3D structures. Their unique micro- and nanoscale features make coccoliths attractive for various applications in nanotechnology. It is anticipated that the range of applications of coccoliths can be further extended by (bio)chemical modification and functionalization as well as possibilities for their arrangement into 2D and 3D arrays. However, methods for both aspects are still lacking.
The aim of this project is thus to develop methods for regioselective functionalization of coccoliths and their assembly into arrays. Regioselective functionalization of the margin area and central area of coccoliths will be achieved by exploitation of local differences in the composition of the insoluble organic matrix of coccoliths. The existence of local differences in the composition of biomacromolecules within this matrix has only very recently been demonstrated. In particular, we will regioselectively introduce proteins/(poly-)peptides that can serve as “anchoring points” for in vitro modifications into the insoluble organic matrix of coccoliths by genetic engineering of a coccolithophore. These engineered coccoliths form the basis for the construction of coccolith arrays. Three independent approaches for the assembly of such arrays will be pursued. The structural and physico-chemical properties of the coccolith-based magnetite-calcite hybrid material will be determined by means of a number of analytical methods.
This interdisciplinary project will benefit greatly from the complementary expertise of the binational groups. In the long term, we aim to create an advanced pool of methods to regioselectively endow coccoliths with desired properties and to develop new biomineral-based materials for nanotechnological applications.

Catalytic cleavage of C-O and C-N bonds applied to the transformation or reductive depolymerization of waste plastics

The recycling and chemical recovery of plastics are necessary and crucialsteps to accelerate the transition to a circular economy and reduce the pollution associated with these materials.

The aim of this project is to develop catalytic systems for depolymerizing oxygenated and nitrogenous plastics into their monomers or derivatives (alcohols, amines, halides or even hydrocarbons). These methods, which enable the carbonaceous matter in polymers to be recovered under mild conditions in the form of chemical products useful to the chemical industry, are still underdeveloped and will, in the future, be virtuous processing routes for recycling certain plastics.

The aim of this doctoral project is to develop and use new metal molecular complexes (aluminium, zirconium, rare earths, etc.) and organic catalysts (boron-based), which

- are simple, inexpensive, recyclable and more selective than current catalysts (composed of iridium, ruthenium and boron), to depolymerize different types of plastics (polyesters, polycarbonates, polyurethanes and polyamides),
- allow, in the case of reductive catalysis, the use of hydrosilanes and hydroboranes, as well as the use of new reducing agents acting by transfer hydrogenation routes.

Finally, we will also consider the use of organic anhydrides to transform plastics into reactive organic compounds useful in organic chemistry.

Study of the CHON-UNEX process for the removal of high heat-emitters from spent fuel

The removal of high heat emitters from spent fuels allows to reduce the volume necessary for a safe storage in deep repository. Some of these isotopes can also be recycled, for instance 241Am as fuel for fast-breeder reactors and 137Cs as a gamma source (radiotherapy, sterilization). A new process called CHON-UNEX has been recently proposed, whose ligands and diluents are composed of only C, H, O and N elements so that the effluents can be eventually vaporized and do not form secondary wastes. It consists in a co-extraction of all high heat emitters followed by successive stripping steps to enable the recycling of these elements. The Sr, Am and Ln extractant is a diglycolamide (DGA) that also serves as modifier for the Cs extractant, a calixarene crown-ether (CC) insoluble in kerosene.
At first, the Ph.D. student will study several commercially available DGAs in combination with 2 CCs to assess their extraction efficiency and selectivity, followed by the determination of the speciation and the supramolecular assemblies of these systems by various analytical tools. Then, the student will perform the selective stripping of Am by phenanthroline-based hydrosoluble ligands previously tested on Lns by an other student.
The student will eventually gain knowledge on the nuclear fuel cycle, hydrometallurgy and analytical tools that can lead to pursue academic work or to a job in the hydrometallurgy industry.
The candidate is M.Sc. with chemistry as major. A solid basis in analytical chemistry is recommended.