Theory guided synthesis of MXenes with magnetic ordering

• Applicants: Professorin Dr. Christina Birkel; Dr. Jochen Rohrer
• Subject Area: Synthesis and Properties of Functional Materials ; Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 501386284

MXenes represent a family of two-dimensional materials with the general chemical composition Mn+1XnTx (M = transition metal, X = C, N, C/N, Tx = functional groups, typically -F, -OH, -O) that can be chemically exfoliated from three-dimensional MAX phases (Mn+1AXn, A = group IIIA /IVA element) and whose properties can be tuned both by means of their composition and by surface functionalisation. This variability, together with their unique properties (metallic conductivity, hydrophilic, mechanical stability) has led to many potential applications within various technological fields (energy storage, (photo) catalysis, gas detection etc.). On the other hand, despite the many, in principle possible compositions and the large number of existing precursor MAX phases, only about 30 MXenes have been successfully synthesised so far. The goal of the here proposed project is the preparation of novel, ideally magnetic MXenes based on extensive theoretical calculations of the stability and exfoliability of respective precursor MAX phases. So far, only a limited number of two-dimensional materials with magnetic ordering exist, that are, however, highly interesting for potential spintronic applications and as quantum materials. Based on their chemical diversity (composition and surface functionalisation), the expected new materials promise to significantly extend this class of materials while adding beneficial properties (e.g. form stable colloidal solutions), particularly for their processing and applications. In order to explore the space of chemical compositions, that will allow for magnetic ordering, as fully as possible, we will combine experimental and theoretical methods. On the basis of high-throughput electronic-structure calculations and established thermodynamic models we will systematically investigate and predict the stability of MAX phases and their exfoliability into MXenes. Feedback from the experimental part of the project will be used to successively refine the thermodynamic models and improve predictions, if applicable. Promising precursor MAX phases will be synthesised by diverse solid-state and wet chemical methods, such as microwave heating and sol-gel chemistry. This will lead to ternary and quaternary MAX phases that will subsequently be treated with different etchants, and, if successful, exfoliated, into their two-dimensional analogs.

• DFG Programme: Research Grants