Defect-Free Few-Layer M4C3Tx (M = V, Nb, Ta) MXene Nanosheets: Synthesis, Characterization, and Physicochemical Properties

High-quality few-layer M4C3Tx (M = V, Nb, Ta) MXenes are very important for applications and are necessary for clarifying their physicochemical properties. However, the difficulty in etching for themselves and the existence of MC/MC1-& delta; and M-Al alloy impurities in their M4AlC3 precursors seriously hinder the achievement of defect-free few-layer M4C3Tx (M = V, Nb, Ta) MXenes nanosheets. Herein, three different defect-free few-layer M4C3Tx (M = V, Nb, Ta) nanosheets are obtained by using a universal synthesis strategy of calcination, selective etching, intercalation, and exfoliation. Comprehensive characterizations confirm their defect-free few-layer structure feature, large interlayer spacing (1.702-1.955 nm), types of functional groups (-OH, -F, -O), and abundant valance states (M5+, M4+, M3+, M2+, M-0). M4C3Tx (M = V, Nb, Ta) free-standing films obtained by vacuum filtration of few-layer M4C3Tx inks show good hydrophilia, high thermostability, and conductivity. A roadmap on synthesis of defect-free few-layer M4C3Tx (M = V, Nb, Ta) nanosheets are proposed and three key points are summarized. This work provides detailed guidelines for the synthesis of other defect-free few-layer MXenes nanosheets, but also will stimulate extensive functional explorations for M4C3Tx (M = V, Nb, Ta) MXenes nanosheets in the future.

Automated summary

In this study, three different defect-free few-layer M4C3Tx (M = V, Nb, Ta) nanosheets were successfully obtained by a universal synthesis strategy of calcination, selective etching, intercalation, and exfoliation. Comprehensive characterizations confirmed their defect-free few-layer structure, large interlayer spacing, types of functional groups, and abundant valance states. M4C3Tx (M = V, Nb, Ta) free-standing films derived from these nanosheets exhibited good hydrophilia, high thermostability, and conductivity. This work not only provides detailed guidelines for the synthesis of other defect-free few-layer MXenes nanosheets, but also encourages extensive functional explorations for M4C3Tx (M = V, Nb, Ta) MXenes nanosheets in the future.