Figure 2.

a) The schematic diagram illustrates the synthesis of Ti₄N₃T _x from Ti₄AlN₃ by molten salt treatment at 550 °C under Ar condition, followed by the dispersion of multilayer MXenes using TBAOH. Reproduced with permission.^{[ 41 ]} Copyright 2016, Royal Society of Chemistry. b) The picture on the left show magnetron sputtering of Ti, Al, and C to form several nanosized TiC incubation layers on a (0001) sapphire substrate, followed by the deposition of Ti₃AlC₂. The right diagram is that of Ti₃C₂ at —OH terminal after Al selective etching by Ti₃AlC₂ (Ti atom is yellow, C atom is black, O atom is red, and H atom is white). Reproduced with permission.^{[ 42 ]} Copyright 2014, American Chemical Society. c) Scanning electronic microscopy (SEM) picture of MAX phase treated with standard HF (left), SEM picture of MAX phase etched with EMIMBF₄ and BMIMPF₆ (right). Reproduced with permission.^{[ 44 ]} Copyright 2020, Royal Scoiety of Chemistry. d) Schematic diagram of spontaneous insertion of metal ions Ca²⁺, Mg²⁺, and Al³⁺ into MXene electrode. Inset on the left is a TEM image of a stripped Ti₃C₂T _x MXene nanosheet and the Tyndall scattering effect of the MXene dispersion. Reproduced with permission.^{[ 46 ]} Copyright 2020,Wiley‐VCH. e) Schematic of Ti₃C₂ MXene delamination and intercalation with phosphorus vapor. Reproduced with permission.^{[ 63 ]} Copyright 2021, Royal Scoiety of Chemistry.