The MXENE-CAT project is focused on two main objectives (i) the synthesis, functionalization and advanced characterization of new 2D transition metal carbides, so-called MXenes, and (ii) their development, including composites, for applications as noble-metal free electrocatalysts for key reactions of the energy transition: oxygen evolution and reduction reactions (OER and ORR).
The MXenes is among the newest and largest family of 2D materials with already demonstrated applications in diverse fields (e.g. energy storage and conversion or electromagnetic interference shielding). They are synthesized by selectively etching the A elements from Mn+1AXn phases, a family of 70-plus different members of layered ternary carbonitrides, where M is a transition metal, A is a group 13 or 14 (i.e. group IIIA or IVA) element, X is C and/or N, and n = 1 to 3. Beyond the possibility to tune the MXenes’ composition and related properties by changing the MAX phase precursor, the etching process is also a key step since it leads to the surface functionalization of the MXene sheets with different T terminal groups (F, OH or O), which also deeply modify the MXenes properties. Although crucial for many applications, the MXenes’ functionalization is still in its infancy because of the limited number of etching processes and the need for characterization protocols allowing the accurate determination of the nature and location of the T-groups.
Our first objective is thus to develop new etching protocols, beyond the classical acidic media, coupled to post-treatments (thermal, chemical) to control and optimize the MXenes’ surface functionalization for the target applications. In addition, we will also develop a complete characterization protocol based on the combination of long range (XRD) and short-range (STEM-EELS & NMR) orders, together with electronic structure characterization (XPS & STEM-EELS). The interpretation of the data obtained on these complex materials will be made quantitative thanks to a strong theoretical supports based on density functional theory simulations (RMN, XPS, EELS). This theoretical support is of utmost relevance in order to establish the chemistry/structure/properties relationship allowing to efficently guide the experimental works towards the most promissing MXene material for a given application (OER and ORR in the present context). In addition, the interplay between surface functionalization and chemical composition of the MX core will be scrutinize by synthesizing (Ti,M’)n+1CnTx solid solutions with M’ = Nb or Mo (i.e. relevant elements for OER and ORR) in order to evidence potential synergetic effects in terms of the electronic/catalytic properties that we aim at developing in the project.
Based on the fundamental knowledge concerning the synthesis of new functional MXenes, our second objective is to optimize MXene and MXene-based composites (functionalized with Co3O4) in order to propose a performant and stable noble metal-free catalyst formulation capable of activating OER or ORR (and potentially both reactions) at low overpotentials with high charge transfer kinetics. The performances of these catalysts will be evaluated by classical electrochemical techniques combined with original in situ and operando electrochemical characterizations down to the single nano-objet level, in order to determine, inter alia, the involved reaction mechanisms and the morpho-structural restructurations during the reactions.
Beyond the target applications, the findings and the deeper understanding regarding the synthesis of well-controlled functionalized MXene-based systems and their advanced characterization should benefit the entire, and rapidly growing, MXene community and we expect this fundamental project to open the way to a whole new field of research. We could then hope to emerge as one of the national and international leading consortia on MXene synthesis and characterization.
Monsieur Stéphane Célérier (Institut de Chimie des Milieux et des Matériaux de Poitiers)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IMN INSTITUT DES MATERIAUX JEAN ROUXEL
Pprime Institut P' : Recherche et Ingénierie en Matériaux, Mécanique et Energétique
CEMHTI Conditions Extrêmes et Matériaux : Haute température et Irradiation
IC2MP Institut de Chimie des Milieux et des Matériaux de Poitiers
Help of the ANR 462,848 euros
Beginning and duration of the scientific project: December 2018 - 48 Months