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DS: Fachverband Dünne Schichten

DS 9: Focus Session: 2D Transition Metal Carbides, Nitrides and Carbonitrides I (joint session DS/MM/O)

DS 9.2: Talk

Wednesday, March 20, 2024, 15:45–16:00, A 053

Tuning the molten salt etching process by in situ XRD — •Julian T. Müller, Aleksander Gurlo, and Maged F. Bekheet — Technische Universität Berlin, Faculty III Process Sciences, Institute of Material Science and Technology, Chair of Advanced Ceramic Materials, Straße des 17. Juni 135, 10623 Berlin, Germany

MXenes, whose properties are mainly defined by their chemical composition and surface terminations, could be synthesized by etching an A element (A = Al, Si, etc.) from the parent MAX phase using hydrofluoric acid. This acid is of high risk to human health and leads to fluorine terminations on the surface of MXene, which are difficult to alter and may be detrimental for certain applications, e.g. electrodes in different battery systems. Etching via molten salt formation offers an alternative, less harmful way. By sophisticated selection of salts, it is possible to adjust the surface terminations and pave the way for a new generation of tailored MXenes. Gaining insight into the molten salt etching process and tuning its process parameters such as temperature, duration, and precursor ratio are keys to ensuring a qualitative MXene and saving time, energy, and cost. To support this, we are currently establishing an in situ XRD setup at the Advanced Light Source of the Lawrence Berkeley National Laboratory. It will allow measurements under various gas atmospheres up to 1450 °C and 50 bars, including a vapour phase. In the first molten salt etching experiments, we successfully gained knowledge on the etching onset, duration, and phase composition. With this measurement setup, the synthesis of MAX phases and many MXene and salt combinations await to be explored.

Keywords: MXene; in situ XRD; etching; molten salt