Enhancing Faradaic Efficiency in Protonic Ceramic Electrolysis Cells (PCCELs) through Electrolyte and Electrode–Electrolyte Interface Engineering
Proton conducting ceramic electrolysis cells (PCCELs), an advanced variant of solid oxide electrolysis cells (SOECs), enable the direct production of hydrogen through steam electrolysis using proton-conducting electrolytes. Unlike conventional SOECs, which rely on oxygen ion (O²?) conductors, PCCELs operate at lower temperatures (~400–600?°C vs. 750–850?°C for SOECs) due to their higher proton conductivity. This lower operating temperature helps reduce material degradation and overall system costs. While SOEC technology has reached industrial maturity, with large-scale deployment projects underway, the development of PCCELs remains limited by several scientific challenges. These include the difficulty of densifying electrolytes (such as BaCeO3–BaZrO3) without barium volatilization during high-temperature sintering; the proton transport limitations posed by grain boundaries; and the poor control of electrode–electrolyte interfaces. This thesis aims to improve the faradaic efficiency of PCCELs by optimizing the microstructure of the electrolyte and engineering high-quality interfaces through targeted surface treatments. The methodology includes cell fabrication, interface engineering, and electrochemical evaluation. The ultimate goal is to establish robust and scalable processing protocols that enable PCCELs to achieve faradaic efficiencies above 95%, compatible with industrial-scale deployment.
Controlling the composition and microstructure to achieve high magnetic performance in 1–12 rare earth-poor magnets
Permanent magnets based on rare earth elements (REEs), particularly neodymium-iron-boron (Nd-Fe-B) magnets, are strategically important for the development of more efficient motors and generators (electric vehicles, wind turbines). However, REEs, particularly Nd, are critical materials, with a high risk of supply disruption in the coming years. The growing demand for high-performance magnets requires the development of new types of magnets with reduce RE content. Iron-rich compounds, such as Sm-Fe12 (commonly known as phase 1-12), have very interesting intrinsic magnetic properties and are considered the best alternative to NdFeB magnets, allowing for a TR saving of around 35% by weight. However, achieving sufficient magnetic performance (remanence > 1 T and coercivity > 800 kA/m) depends on obtaining a suitable microstructure and remains the main challenge in the development of Sm-Fe12 magnets.
The aim of the thesis is therefore to improve the magnetic performance of this new family of magnets, in particular by controlling the composition and distribution of phases at grain boundaries. The doctoral work will combine an advanced experimental approach (development of Sm-Fe12 alloys, characterization of equilibrium phases, magnet manufacturing, magnetic characterization) with knowledge of phase diagrams to define compositions and optimal manufacturing conditions to achieve the targeted magnetic performances.
Potential synergy between NH3 and NaBH4 for improved H2 density and enhanced safety
The thesis focuses on the study of the hybrid ammonia–sodium borohydride system (NH3–NaBH4) as an innovative chemical energy carrier. The objective is to investigate the combination of ammonia (NH3), recognised for its high hydrogen density and mature industrial infrastructure, with sodium borohydride (NaBH4), a high-capacity chemical hydrogen storage material, in order to overcome certain limitations associated with each vector when considered separately.
The proposed work specifically addresses the safer storage and transport of ammonia through its coupling with sodium borohydride, enabling a reduction in vapour pressure (compared to 8.88 bar at 21 °C for liquid ammonia) and less restrictive operating conditions. In parallel, the thesis aims to improve the stability (relative to the H2O–NaBH4 system) and operability of sodium borohydride which, when combined with ammonia molecules (acting as inert species), forms stable liquid or viscous phases that are potentially pumpable, thereby facilitating integration into energy-related processes.
The fundamental goal of the thesis is to understand the physicochemical mechanisms governing this hybrid system, particularly the role of dihydrogen interactions between the N–H bonds of ammonia and the B–H bonds of borohydride, and their influence on stability, reactivity, transport properties, and hydrogen release pathways (thermal and/or hydrolytic).
Beyond its storage function, the thesis also explores the potential of the NH3–NaBH4 system as a novel hybrid material with high gravimetric and volumetric hydrogen capacity, while considering realistic operational constraints relevant to energy applications in a dual-use context. At this stage, exhaustive optimisation is not the primary objective.
High-throughput screening of catalysts for the direct conversion of CO2 into synthetic fuels
This doctoral project aims to develop an innovative high-throughput screening approach for catalysts for the direct conversion of CO2 into synthetic fuels, known as CO2-FTS. This approach will combine a catalyst screening platform with in situ/operando characterization techniques and artificial intelligence methods to accelerate the discovery and optimization of high-performance catalysts. It aims to identify doped FeOx-type catalysts for the CO2-FTS reaction (>50% conversion, high selectivity towards C8-C16). Several high-throughput screening campaigns will allow for iterative optimization of compositions and reactive conditions. A numerical model of the parametric landscape will then be developed. This model will subsequently be coupled with multi-scale modeling from the active site to the reactor level. The developed catalysts will contribute to the energy transition by enabling a circular carbon economy.
Understanding Lithium Recovery Mechanisms through the Application of Electrochemical Pumping on Battery Leachates
The economical, environmental and geopolitical context recently pushed Europe to issue a regulation on battery recycling. By 2031, 80% of lithium in batteries should be recovered. In this context, CEA is interested in Electrochemical Lithium-Ion Pumping (ELIP): this process uses battery electrodes to selectively insert and disinsert lithium, allowing to extract it from a complex solution. Unlike more common lithium recovery processes, ELIP allies a high selectivity towards lithium, does not require the use of toxic chemicals during the process and offers the possibility to be used in a continuous flow mode, practical for industrial applications. A first PhD work on the subject, in our team, evidenced for the relevance of such a process for the separation of lithium from other alkali cations (sodium and potassium). Real battery leachates are however more complex and can include transition metal cations and organic species besides alkaline cations. The proposed PhD subject has the aim to precisely understand the effect of these solutions on the ELIP process in order to choose the best position in the recycling loop (upstream or downstream), and to adapt to adverse effects encountered in such conditions. The impact of the other species present in solution will be evaluated on selectivity, efficiency and durability at different scales: material, electrode and membrane. Chemical (ICP-AES, EDX), structural (XRD) and morphological (SEM, TEM) characterizations will be correlated with electrochemical results in order to identify side reactions and species which impact the most the performances. Based on these results, the PhD student will have to test different improvement protocols (additive incorporation, pH control, change of the electrochemical method, etc...) and to understand the physico-chemical reasons governing these improvements. The PhD work will allow to propose a thoughtful integration of the ELIP process in conventional battery recycling steps, as well as highlighting the relevance, or not, of such a process for lithium extraction from real leachates.