The study of phase transition of MoS2 regulated by H+

Abstract

The mixed-phase MoS2 (1T/2H MoS2) with heterostructure exhibited high catalytic activity. The specific ratios of 1T/2H could exhibit optimal performance in various applications. Therefore, more methods need be developed for synthesizing 1T/2H mixed-phase MoS2. Herein, a viable route was studied for the phase transition of 1T/2H MoS2 regulated by H+. Briefly, the commercially available bulk MoS2 was used to obtain 1T/2H MoS2 via chemical intercalation of Li+. Then the residual Li+ around 1T/2H MoS2 was replaced by H+ in acidic electrolytes, owing to the extremely higher charge-to-volume ratio of H+. Thus, the thermodynamically unstable 1T phase lost the protection of residual Li+ and could be re-transforming into the relatively stable 2H phase. The change of the 2H/(2H+1T) ratio was measured using novel extinction spectroscopy, which provides a rapid identification method in comparison with x-ray photoelectron spectroscopy (XPS). The experimental results revealed that the concentration of H+ influenced the phase transition velocity of MoS2. In particular, the phase transition from 1T to 2H phase in the H+ solution was faster at the beginning, and the higher the H+ concentration in an acidic solution, the faster the increase in 2H content. For an instant, the ratio of the 2H phase was increased by 7.08% in an acidic solution (CH + = 2.00 M) after 1 h, which was several times greater than the case in the distilled water. This finding provides a promising method to easily obtain different ratios of 1T/2H MoS2, which is beneficial for further development of catalytic performance especially in energy generation and storage.