Huang Junxiao, Pan Xuelei, Liao Xiaobin, Yan Mengyu, Dunn Bruce, Luo Wen, Mai Liqiang
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
Nanoscale. 2020 Apr 30;12(16):9246-9254. doi: 10.1039/d0nr02161j.
1T-MoS2 is widely used in the hydrogen evolution reaction (HER) due to its abundant active sites and good conductivity. However, 1T-MoS2 is thermodynamically metastable due to the distorted crystal structure. Recently, researchers have detected the J1 and A1g Raman peaks after the HER process and confirmed that the 2H-1T phase possesses good stability. Therefore, continuous HER is likely to transform 1T-MoS2 into a stable 2H-1T mixed phase. The in situ characterization of 1T-MoS2 individual nanosheets in the HER process is important to understand the intrinsic electrocatalytic behaviour at confined nanoscale, which has rarely been investigated. Herein, we built an individual 1T-MoS2 nanosheet micro-nano device by the intercalation of N-butyllithium into 2H-MoS2. Then, the device was kept at an overpotential (η) of 450 mV, which was much lower than the onset potential, for 20 minutes to ensure continuous HER. Through this electrochemical treatment, we successfully obtained a mixed phase of 2H-1T and monitored the electrochemical phase transition by in situ Raman mapping and atomic force microscopy (AFM). The HER performance of the 2H-1T phase was superior to that of 1T-MoS2 and 2H-MoS2. Additionally, computational simulations demonstrated that the 2H-1T phase exhibited optimal hydrogen adsorption energy. The presented work displays the excellent catalysis of the mixed phase obtained by the electrochemical phase transition, which provides new directions for improving the catalytic activity of TMDs.
1T型二硫化钼（1T-MoS2）因其丰富的活性位点和良好的导电性而被广泛应用于析氢反应（HER）。然而，由于晶体结构扭曲，1T-MoS2在热力学上是亚稳态的。最近，研究人员在析氢反应过程后检测到了J1和A1g拉曼峰，并证实2H-1T相具有良好的稳定性。因此，持续的析氢反应可能会将1T-MoS2转变为稳定的2H-1T混合相。在析氢反应过程中对1T-MoS2单个纳米片进行原位表征，对于理解受限纳米尺度下的本征电催化行为非常重要，但这方面的研究很少。在此，我们通过将正丁基锂插入2H-MoS2中构建了一个单个的1T-MoS2纳米片微纳器件。然后，将该器件保持在450 mV的过电位（η）下20分钟，该过电位远低于起始电位，以确保持续的析氢反应。通过这种电化学处理，我们成功获得了2H-1T混合相，并通过原位拉曼映射和原子力显微镜（AFM）监测了电化学相变。2H-1T相的析氢反应性能优于1T-MoS2和2H-MoS2。此外，计算模拟表明2H-1T相表现出最佳的氢吸附能。所展示的工作显示了通过电化学相变获得的混合相具有优异的催化性能，这为提高过渡金属二硫属化物（TMDs）的催化活性提供了新的方向。
