Functionalized aluminosilicate nanotubes for photocatalysis

Rising energy demand and the need to reduce the use of fossil fuels to limit global warming have created an urgent need for clean energy collection technologies. One interesting solution is to use solar energy to produce fuels. Low-cost materials such as semiconductors have been the focus of numerous studies for photocatalytic reactions. Among them, 1D nanostructures are promising because of their interesting properties (high and accessible specific surface areas, confined environments, long-distance electron transport and facilitated charge separation). Imogolite, a natural hollow nanotubes clay, belongs to this category. Its particularity does not lies in its chemical composition (Al, O and Si) but in its intrinsic curvature, which induces a permanent polarization of the wall, effectively separating photo-induced charges. Several modifications of these materials are possible (coupling with metal nanoparticles, functionalization of the internal cavity), enabling their properties to be modulated.We have demonstrated that this clay is a nanoreactor for photocatalytic reactions (H2 production and CO2 reduction) under UV illumination. In order to obtain a useful photocatalyst, it is necessary to extend photon collection into the visible range. One strategy considered is to encapsulate and covalently graft dyes acting as antennae in the cavity. The aim of this thesis is to synthesize imogolites with different internal functionalizations, to study the encapsulation and grafting of dyes into the cavity of these functionalized imogolites, and finally to study the photocatalytic properties.

Use of Spray flash evaporation to Improve high explosives with crystal structuration

Thermally conductive yet electrically insulating polymer nanocomposite based on core-shell (nano)fillers oriented by magnetic field

Advances in power electronics, electric motors and batteries, for example, are leading to a significant increase in heat production during operation. This increase in power density combined with reduced heat exchange surfaces amplifies the challenges associated with heat dissipation. The absence of adequate dissipation leads to overheating of electronic components, impacting on their performance, durability and reliability. It is therefore essential to develop a new generation of heat dissipating materials incorporating a structure dedicated to this structure.

The objective and innovation of the PhD student's work will lie in the use of highly thermally conductive (nano)fillers that can be oriented in an epoxy resin in a magnetic field. The first area of work will therefore be to electrically isolate the thermally conductive (nano)charges with a high form factor (1D and 2D). The electrical insulation of these charges of interest will be achieved by a sol-gel process. The synthesis will be controlled and optimised with a view to correlating the homogeneity and thickness of the coating with the dielectric and thermal performance of the (nano)composite. The second part will focus on the grafting of magnetic nanoparticles (NPM) onto thermally conductive (nano)fillers. Commercial NPMs will be evaluated as well as grades synthesised in the laboratory. The (nano)composites must have a rheology compatible with the resin infusion process.

Brines for metal recycling

Critical metals are essential for a range of technologies that are vital to reduce our carbon dioxide emissions. However, the global recycling rate for metals contained in electronic waste is below 20%, indicating that electronic waste is a relatively untapped source of metals. Additionally, it is increasingly urgent to develop effective processes for recycling waste from products like solar panels, as the volume of waste solar pannels generated is set to rise significantly in the coming years. Currently, conventional hydrometallurgical methods often rely on toxic aqueous solutions to dissolve metals, which presents substantial environmental challenges.

This project proposes an innovative alternative by using concentrated brines (aqueous salt solutions) to oxidize and dissolve metals. This thesis will investigate the fundamental properties of brines and their ability to dissolve metals through various techniques, particularly electrochemical methods. Artificial intelligence methods developed within the lab will be employed to screen a wide range of brines that would allow metal dissolution. Subsequently, brine-based recycling processes will be developed to recover metals from printed circuit boards and solar panels. Finally, metal separation and the treatment of used brines will be explored using membrane and electrochemical processes.

Understanding the mechanisms of direct CO2 hydrogenation using (Na,K)FeOx catalysts via theoretical-experimental coupling

In the context of climate change, we need to reduce our CO2 emissions by using less energy. Another approach is to capture, store and use CO2, with the aim of moving towards a circular carbon economy and, ultimately, defossilization. With this in mind, the direct hydrogenation of CO2 enables it to be transformed into molecules of interest such as hydrocarbons, via the coupling of the reverse water gas shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS).

Computational operando catalysis has recently emerged as a reasoned alternative to the development of new catalysts, thanks to a multi-scale approach from the atom down to the active particle, to model catalyst selectivity and activity. New tools combining ab initio simulations (DFT) and molecular dynamics (MD) via machine learning algorithms bridge the gap between the precision of DFT calculations and the power of atomistic simulations. Current bifunctional catalysts (active for RWGS, and FTS) for direct CO2 hydrogenation are based on doped iron oxides (metal promoters).

The aim of this project is the theoretical study of Na-FeOx and K-FeOx catalysts doped with Cu, Mn, Zn and Co, in 4 stages: DFT simulations (adsorption energies, density of states, energy barriers, transition states), microkinetic modeling (reaction constants, TOF), construction of interatomic potentials by DFT/machine learning coupling, simulation of whole particles (selectivity, activity, microscopic quantities).

This theoretical study will go hand in hand with the synthesis and experimental measurements of the studied catalysts, and optimized catalysts emerging from the computational results. All the accumulated data (DFT, MD, catalytic properties) will be fed into a database, which can eventually be exploited to identify descriptors of interest for CO2 hydrogenation.

Perovskite devices for solar hydrogen production

Project Overview:
The PhD thesis is part of the ICARUS European project, aiming to develop efficient solar energy conversion systems for a carbon-neutral future. The project focuses on integrating photoelectrochemical (PEC) water splitting and photovoltaic (PV) power generation.

Key Objectives:
•Develop innovative metal halide perovskite solar cells with tunable bandgaps for broader light absorption.
•Optimize printed carbon-based solar cells and scaffolds for improved conductivity, mechanical resistance, and durability.
•Incorporate innovative carbon counter electrodes into perovskite devices.
•Upscale and manufacture solar modules.
•Integrate the developed modules into a final PEC prototype.

Research Focus:
The PhD candidate will primarily focus on:
•Printed carbon-based solar cells: Optimizing ink properties, investigating the behavior of printed conductive ink under various conditions, and characterizing conductivity and mechanical resistance.
•Perovskite devices: Incorporating innovative carbon counter electrodes and evaluating their performance and stability.
•Module manufacturing: Upscaling and manufacturing solar modules based on the developed technologies.
•PEC prototype integration: Contributing to the final integration of the PEC prototype.

Expected Outcomes:
The research is expected to contribute to the development of highly efficient and sustainable solar energy conversion systems, supporting the transition to a carbon-neutral future. The findings will have implications for both academic research and industrial applications.

Thermoelectric energy conversion control via coordination chemistry of transition metal redox ions in ionic liquids

Thermoelectricity, a materials’ capability to convert heat in to electric energy has been known to exist in liquids for many decades. Unlike in solids, this conversion process liquids take several forms including the thermogalvanic reactions between the redox ions and the electrodes, the thermodiffusion of charged species and the temperature dependent formation of electrical double layer at the electrodes. The observed values of Seebeck coefficient (Se = - DV/DT, the ratio between the induced voltage (DV) and the applied temperature difference (DT)) are generally above 1 mV/K, an order of magnitude higher than those found in the solid (semiconductor) counterpart. The first working example of a liquid-based thermoelectric (TE) generator was reported in 1986 using Ferro/ferricyanide redox salts in water.

However, due to the low electrical conductivity of liquids, its conversion efficiency was very low, preventing their use in low-temperature waste-heat recovery applications. The outlook of liquid TE generators brightened in the last decade with the development of ionic liquids (ILs). ILs are molten salts that are liquid below 100 °C. Compared to classical liquids, they exhibit many favorable features such as high boiling points, low vapour pressure, high ionic conductivity and low thermal conductivity accompanied by higher Se values. More recently, an experimental study by IJCLab and SPEC revealed that the complexation of transition metal redox couples in ionic liquids can lead to enhancing their Se coefficient by more than a three-fold from -1.6 to -5.7 mV/K, one of the highest values reported in IL-based thermoelectric cells. A clear understanding and the precise control of the speciation of metal ions therefore is a gateway to the rational design of future thermoelectrochemical technology.

Based on these recent findings, we proposes to further study the coordination chemistry of transition metal redox ions in ILs and mixtures. A long-term goal associated to the present project is to demonstrate the application potential of liquid thermoelectrochemical cells based on affordable, abundant and environmentally safe materials for thermal energy harvesting as an energy efficiency tool.

Chemical recycling of oxgenated and nitrogenated plastic waste by reductive catalytic routes

Since the 1950s, the use of petroleum-based plastics has created a modern consumerist world based on the use of disposable products. Global production of plastic waste is therefore considerable, and has almost doubled 20 years, now reaching 468 million tons/year. This non-biodegradable plastic waste causes a great deal of environmental pollution (disturbance of flora and fauna, water and soil pollution, etc.). Barely 9% of this waste is recycled, the rest being burnt or landfilled. The health, climate and social problems inherent in this linear economy mean that we need to create a circularity for these materials by developing effective and robust recycling routes. While current recycling methods rely mainly on mechanical processes and are limited to specific types of waste (e.g. plastic water bottles), the development of chemical recycling methods seems promising for treating waste for which there are no recycling channels. Such chemical processes make it possible to recover the carbonaceous matter in plastics in order to regenerate new plastics.

Within this objective of material circularity, this doctoral project aims to develop new chemical recycling routes for mixed oxygen/nitrogen plastic waste such as polyurethanes (insulation foam, mattresses, etc.) and polyamides (textile fibres, circuit breaker boxes, etc.), for which recycling routes are virtually non-existent. This project is based on a strategy of depolymerizing these plastics by the selective cleavage of the carbon-oxygen and/or carbon-nitrogen bonds to form the corresponding monomers or their derivatives. To do that, catalytic systems involving metal catalysts coupled with abundant and inexpensive reducing agents, such as alcohols and formic acid, will be developed. The use of dihydrogen, an industrial reducing agent, will also be considered. In order to optimize these catalytic systems, we will seek to understand how they proceed and the mechanisms involved.

Synthesis and optical properties of quantum dots

Graphene as a constituent of graphite was close to us for almost 500 years. However, it is only in 2005 that A. Geim and K. Novoselov (Nobel Prize in 2010) reported for the first time the obtaining of a nanostructure composed by a single layer of carbon atom. The exceptional electronic properties of graphene make it a very promising material for applications in electronic and renewable energies.

For many applications, one should be able to modify and control precisely the electronic properties of graphene. In this context, we propose to synthesize chemically graphene nanoparticles and study their absorption and photoluminescence properties. We will focus on families of elongated nanoparticles, with the aim of studying how size can enable us to observe and control multiexcitonic processes in these materials. This project will be developed in collaboration with Physicists so the candidate will work in a multidisciplinary environment.

Porphyrin-based nanostructures

The aim of this project is the synthesis of new molecular structures based on porphyrins for the formation of 0D, 1D and 2D nanostructures. Porphyrins are an important class of molecules that are essential to life through oxygen transport or photosynthesis. Beyond, their importance in Nature, porphyrin derivatives exhibit outstanding optical, electronic, chemical and electrochemical properties that make them promising candidates for applications in catalysis, electrocatalysis, optoelectronics and medicine.

In this project, the porphyrins will be studied in collaboration with several groups of Physicists in order to fabricate 1D or 2D covalent networks on surface via the "bottom-up" approach and to study their electronic and optical properties.

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