1. Element distribution of the MAX phases known to date. The M-site elements (orange color) have been extended to lanthanides, A-site elements (blue color) have been extended to subgroup element with unsaturated d-orbitals, and boron has been added into X-site elements (green color)

2. HR-STEM images showing the atomic positions of MAX phase (a), i-MAX phase (b), and o-MAX phase (c)^[8,16-17]

3. A schematic diagram showing the process of producing MXene by using ZnCl₂ to etch MAX phase (a), scanning electron microscopy(SEM) image showing the microstructure of Ti₃C₂Cl₂ MXene (b), and HR-STEM image showing the atomic positions of Ti₃C₂Cl₂ MXene (c)^[8]

4. HR-STEM image showing the atomic positions of Ti₃(Al_xCu_1-x)C₂ (a), a schematic diagram showing the H₂O₂ detecting mechanism of Ti₃(Al_xCu_1-x)C₂ (b), and comparison of the H₂O₂ detecting ability between Ti₃(Al_xCu_1-x)C₂ and Ti₃AlC₂ (c)^[9]