Two‐Dimensional MXenes Derived from Medium/High‐Entropy MAX Phases M₂GaC (M = Ti/V/Nb/Ta/Mo) and their Electrochemical Performance

Abstract

Two‐dimensional (2D) transition metal carbides and/or nitrides, MXenes, are prepared by selective etching of the A‐site atomically thin metal layers from their MAX phase precursors. High entropy MXenes, the most recent subfamily of MXenes, are in their infancy and have attracted great interest recently. They are currently synthesized mainly through wet chemical etching of Al‐containing MAX phases, while various MAX phases with A‐sites elements other than Al have not been explored. It is important to embody non‐Al MAX phases as precursors for the high entropy MXenes synthesis to allow for new compositions. In this work, it is reported on the design and synthesis of Ga‐containing medium/high entropy MAX phases and then their corresponding medium/high entropy MXenes. Gallium atomic layer etching is carried out using a Lewis acid molten salt (CuCl2). The as‐prepared (Ti1/4V1/4Nb1/4Ta1/4)2CTx exhibits a Li+ specific capacity of ≈400 mAh g−1. For (Ti1/5V1/5Nb1/5Ta1/5Mo1/5)2CTx a specific capacity of 302 mAh g−1 is achieved after 300 cycles, and high cycling stability is observed at high current densities. This work is of great significance for expanding the family members of MXenes with tunable chemistries and structures.

Maximizing Potential Applications of MAX Phases: Sustainable Synthesis of Multielement Ti3AlC2

“…Such surface oxidation is an anticipated phenomenon due to the strong affinity toward oxygen by these metals . For the Ti 2.7 Nb 0.2 Mo 0.1 AlC 2 sample, HR core-level spectra exhibit asymmetric peaks that can be ascribed to Nb–C (Figure d) and Mo–C bonds (Figure e), aligning with binding energies reported in the literature . Noteworthy is that an additional peak pair is detected in the Nb 3d region (Figure d), at higher binding energies, which is attributed to the surface oxidation products of Nb, specifically Nb 2 O 5 , indicating its higher susceptibility to oxidation.…”

Atomic Scale Design of MXenes and Their Parent Materials─From Theoretical and Experimental Perspectives

“…In recent years there has been progress in the synthesis of MAX phases with more than two metals. ,,− ,− These so-called high-entropy MAX phases, schematically illustrated in Figure i–l, are composed of three to five metals (M′ + M′′ + M′′′ + ...) forming multielement solid solutions across the M layers. Corresponding MXenes have been demonstrated for n = 1, − n = 2, n = 3, , and n = 4 . The multielemental high-entropy MAX and MXenes will enable pathways for tuning the phase composition and ultimately the materials properties.…”

Environmental implications of metal–organic frameworks and MXenes in biomedical applications: a perspective

“…[4][5][6] These characteristics make them promising candidates for various biomedical applications, paving the way for innovative and efficient therapeutic and diagnostic approaches. [7][8][9] These materials are highly attractive for a wide range of biomedical applications, including drug delivery, 10,11 tissue engineering, 12,13 (bio)sensing, 8,[14][15][16] and imaging. 17,18 MOFs can be designed to encapsulate and deliver therapeutic agents, providing controlled release and targeted delivery to specic sites in the body.…”