'The Energy Cross-Functional Division of the Société Chimique de France (SCF) has awarded its Thesis Prize to Alexandre Terry, who graduated from the University of Le Mans in 2024.
This award recognises his doctoral thesis entitled ‘New mixed 3d-metal-based oxyfluoride materials as anode catalysts for water electrolysis: from synthesis to mechanistic studies'. During his PhD, he developed new oxyfluorinated materials based on abundant transition metals (iron, cobalt, nickel) and studied them as anodic catalysts for water electrolysis in an alkaline environment.The most efficient catalyst was also subjected to an in-depth study using electroanalytical methods, in situ/operando infrared and Raman spectroscopy, and mass spectrometry, in order to understand the origin of its electrocatalytic activity and to elucidate the mechanism of water oxidation on the surface of this material.
He wrote his doctoral thesis between 2021 and 2024 under the joint supervision of the University of Montréal, the University of Bonn and the University of Le Mans under the joint supervision of Nikolay Kornienko (Kornienko Lab, University of Montréal, later University of Bonn) and Jérôme LHOSTE (Institute for Molecules and Materials in Le Mans, University of Le Mans, UMR 6283).
Since April 2025, he has been working as a postdoctoral researcher at the LRCS in Amiens (EN), where he is involved in the synthesis and characterisation of new anode materials for high-performance lithium-ion batteries.'
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Abstract
If hydrogen is a promising energy vector for sustainable energy storage, its production must rely on carbon-free technologies. Water splitting powered by green electricity is ideal for producing a decarbonized energy carrier from water. However, this process is hampered by the sluggish kinetics of the oxidation evolution reaction (OER, 2H2O ⇋ O2 + 4H+ + 4e-) at the anode, requiring extra energy to ensure a suitable production rate. Catalysts, usually iridium and ruthenium oxides, are employed to reduce the energy requirement by facilitating electron and proton transfer involved in OER, but these metals are scarce, limiting the scalability of this technology. To overcome this, oxides and oxyhydroxides catalysts based on cost-effective and abundant 3d transition metal-based have been developed for alkaline water splitting, presenting high performance. In this way, this work presents the synthesis of new oxyfluorides with eco-compatible and affordable elements using a simple and straightforward two-step synthetic route for application as OER electrocatalyst in alkaline electrolyte.The initial study focuses on iron-enriched oxyfluoride catalysts from thermal decomposition under ambient air of (Co1-xFex)2+Fe3+F5(H2O)7 (0 ≤ x ≤ 0.72). Results show that cobalt content can be reduced by 20% without affecting OER performance, achieving an overpotential of 320 mV at 10 mA.cm-2, a mass activity of 110 A.g-1 at 1.55 V vs. RHE and high stability. The second part aims to enhanced the catalytic properties of Co0.5Fe0.5O0.5F1.5 reference by substituting cobalt with nickel, known for its OER activity. The (Co(1-x)/2Nix/2)2+Fe0.5O0.5F1.5-y(OH)y (y ≤ 0.3) solid solution have been obtained by thermal decomposition (Co1-xNix)2+FeF5(H2O)7 (0 ≤ x ≤ 1). The final section assesses the performance of these materials and studies their reaction mechanism. The x = 0.5 composition shows the best performance, with a low overpotential of 290 mV at 10 mA.cm-2 and a specific activity of 3.9 A.m-2 of BET surface area at 1.5 V vs. RHE. The origin of the exceptional catalytic properties of (Co0.25Ni0.25)2+Fe3+0.5O0.5F1.3(OH)0.2, highlighted via in-situ/operando analyses, among others, were employed, would stem from the synergy between Co and Ni, and the involvement of lattice oxygens in the mechanism (LOM), circumventing the theoretical limits linked to the conventional mechanism.