Mixed terminal MXenes react with SF6 in aqueous solution: reaction mechanism and pathway

Abstract

Abstract The search for an ecofriendly treatment for the strong greenhouse gas SF 6 has become a global hot issue. Herein, the mixed-terminal Ti 3 C 2 T x MXene catalyzing conversion of SF 6 in aqueous solution was explored. The catalytic network on realistic Ti 3 C 2 T x was constructed. By theoretical calculations, target products and the microscopic reaction mechanism were studied. Firstly, SF 6 exhibited different degrees of chemisorption on the constructed Ti 3 C 2 T x surfaces of three varying terminal proportions, with different terminals showing synergistic effects. Secondly, taking the effect of H 2 O and surface hydroxyl into account, the catalytic conversion system of SF 6 on a Ti 3 C 2 (OH) 0.66 O 1.33 surface was constructed, containing 25 sub-reactions with H 2 S as one of the final products. SF 6 went through successive defluorination on the Ti 3 C 2 (OH) 0.66 O 1.33 surface to form low-fluorine sulfide SF x ( x = 5, 4, 3, 2, 1), with energy of 80.685 kcal mol −1 released during the whole process. The energy barriers of all the SF 6 decomposition sub-reactions were significantly lower than that in free space. Besides, O terminals were regarded as potential hydroxyl terminals in aqueous solution, which continuously provided active hydroxyl groups for the Ti 3 C 2 (OH) 0.66 O 1.33 surface. Thus, SF 6 conversion in aqueous solution will not result in deactivation of Ti 3 C 2 T x catalyst. This work provides a theoretical basis for MXene to catalyze SF 6 decomposition in an efficient way.