Investigation of chloride ion adsorption onto Ti2C MXene monolayers by first-principles calculations

Abstract

Chloride ion adsorption on Ti₂C monolayers was theoretically investigated. Electrochemical parameters, including specific capacity, chloride ion (Cl⁻) diffusion barrier, and discharge voltage profile, were studied via first-principles calculations. The most favorable Cl⁻ adsorption configuration was identified using a partial particle swarm optimization algorithm and the results showed that Cl⁻ adsorption onto Ti₂C monolayers achieved a large theoretical capacity (331 mA h g⁻¹), high working voltage (4.0–3.5 V), and low diffusion barrier (0.22 eV). This resulted in excellent rate capability and a large specific energy of 1269 W h kg⁻¹ at the material level. The effects of terminal O, F, and OH groups on Cl⁻ adsorption onto Ti₂C monolayer were also studied, which showed that Cl⁻ could not be adsorbed onto O and F terminated Ti₂C monolayers. In comparison, Cl⁻ adsorption onto OH terminated Ti₂C was allowed but generated a smaller specific capacity (126 mA h g⁻¹) and lower working voltage (3.5–1.5 V) than a bare Ti₂C monolayer.