Carbon dioxide adsorption of two-dimensional Mo2C MXene

In this paper, the CO 2 adsorption behaviors of Mo 2 C MXene were explored for the first time. Two-dimensional (2D) Mo 2 C MXene samples were prepared by hydrothermal etching in four different solutions (LiF, NaF, KF or NH 4 F with HCl). The sample made by LiF + HCl etching exhibited the highest capacity of 3.66 mmol g −1 , which is consistent with theoretical calculation that Mo 2 CO 2 decorated by Li has stronger interaction with CO 2 than those of Na and K. Although Mo 2 C MXene has low specific surface area (SSA, 4.9–8.9 m 2  g −1 ) as compared with those of Ti 3 C 2 (21 m 2  g −1 ) and V 2 C (9 m 2  g −1 ) MXenes, Mo 2 C MXene possesses better performance on CO 2 capture than Ti 3 C 2 (1.33 mmol g −1 ) and V 2 C (0.52 mmol g −1 ) MXenes at 4 MPa. This is because the CO 2 adsorption of Mo 2 C MXene is mainly physical absorption formed by the capillary condensation in mixed pores (micropores and mesopores) and slitlike pores between two Mo 2 C MXene flakes. Besides, the CO 2 adsorption on the surface of Mo 2 C MXene with functional groups (O or F) shows a current of chemisorption feature. This work indicates that Mo 2 C MXene is a promising candidate for CO 2 capture and storage material.