Etching Mechanism of Ti₃C₂Cl₂ MXene Phases by CuCl₂-Lewis Molten Salt Method

Abstract

We described a method for obtaining fluorine-free Ti₃C₂Cl₂ MXene phases by melting copper in CuCl₂ instead of aluminum in Ti₃AlC₂. XRD results show that when molten salt CuCl₂ etches Ti₃AlC₂, it forms an intermediate product Ti₃CuC₂, and then reacts with Ti₃CuC₂ to obtain Ti₃C₂Cl₂. The reaction of Ti₃AlC₂ and CuCl₂ at a temperature of 800 °C for 2 h to obtain Ti₃C₂Cl₂ with an optimal lamellar structure is shown in SEM results. The pseudopotential plane-wave (PP-PW) method is used to calculate on the electronic structure. The etching mechanism is investigated by the total energies of each substance. The chemical reaction of Ti₃AlC₂ and CuCl₂ will first become Ti₃CuC₂ and Cu, and then become Ti₃C₂Cl₂ during the Lewis acid etching process, which are consistent with the experimental results.

Keywords

molten salt method / CuCl₂ / MXene / first-principles calculations / etching mechanism

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