PhD position: Elaboration of 3D electrodes by additive manufacturing: numerical optimization and application to the electrosynthesis of ammonia

Duration: 3 years (start: October 1, 2024)

Funding: Université Toulouse 3, Paul Sabatier, FRANCE

Doctoral school: Mechanics, Energetics, Civil & Process Engineering, MEGEP

Lab: Laboratoire de Génie Chimique, LGC

Keywords: hydrodynamics, mass transfer, electrochemistry, modeling, additive manufacturing, electrosynthesis I electrification, energy, environment, decarbonisation, hydrogen

Electrochemical reactors play a key role in several areas such as i) the production and recycling of raw materials (electrosynthesis, chlor-alkali, H₂, metals, etc.), ii) environmental protection (degradation of pollutant compounds, carbon-free processes, CO₂ recovery, etc.) and iii) energy transformation and storage (fuel cells, redox flow batteries). They are also crucial for the development of carbon-free solutions based on electrification (renewable energy storage, electrosynthesis). New electrochemical applications in these areas (contributing to achieving carbon neutrality in 2050 [1]) require optimal and rapid design of efficient electrochemical reactors. In this context, this thesis aims to implement Additive Manufacturing (AM) for the development of new electrodes of the reactor. The full geometry control offered by AM allows the production of 3D/porous electrodes with complex shapes, which are not achievable by conventional manufacturing methods, and which lead to greatly improved electrochemical (mass flux/current and selectivity/potential distribution) and hydraulics (resistance to flow) performances. As the structure is numerically designed, it is possible to simulate the flow, and the transfers of mass and charges, through a 3D electrode produced by AM. This opens the way to the numerical optimization of the structure of the electrodes in order to design and produce more quickly an electrochemical reactor adapted, optimized and selective for a given application; thus avoiding the long and costly experimental optimization phase. AM represents a paradigm shift from the “classic” development of electrodes. However, no optimization method has yet been developed. In addition, the contribution of 3D electrodes produced by AM has not yet been evaluated and exploited for electrochemical applications of current interest.

In this context, the main objectives of this thesis are:

-  Develop a method to numerically optimize the structure of 3D electrodes: selection and implementation of a numerical simulation of the flow and potential/current distribution taking into account electrochemical kinetics and mass transfer (direct CFD simulation, continuous effective model, porous medium), optimization

-  Experimental validation of the performance of numerically optimized 3D electrodes: production of 3D electrodes by metallic AM LPBF (Laser Powder Bed Fusion), determination of AM parameters, electrochemical measurements on a filter-press reactor integrating the electrodes (voltammetry, electrolysis, measurement of the limiting current, etc.)

-  Application to the electrosynthesis of ammonia NH₃ which is considered today as a way to store hydrogen and whose production, without using H₂ of fossil origin (alternative to the Haber-Bosch process), is an important topic of decarbonisation: use of the 3D electrodes produced by AM to enhance the flux and the yield of NH₃ production (electrolysis, chemical analysis, NH₃ dosage).

This research work will be carried out at Laboratoire de Génie Chimique (LGC) in the Electre team of the Electrochemical Processes department. The Electre team specializes in the design, modeling and implementation of electrochemical reactors and microreactors (electrosynthesis, depollution, redox flow batteries). The LGC has all the required analytical and numerical resources. During this project, the Electre team will collaborate with Laboratoire d’Études des Microstructures et de Mécanique des Matériaux (LEM3) in Metz (France) for aspects related to the metallic AM of the electrodes.

[1] IEA (2021), Net Zero by 2050, IEA, Paris https://www.iea.org/reports/net-zero-by-2050

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