Zhu Xuebin, researcher of Solid State Institute of Chinese Academy of Sciences and his collaborators have made progress in the field of material preparation under strong magnetic field

Recently, researchers Zhu Xuebin, Dai Jianming and Liang Changhao from the Institute of solid state, Chinese Academy of Sciences, cooperated with the University of Wollongong in Australia to synthesize highly stable pure phase 1t-mos 2 materials by high magnetic field hydrothermal method The results were published in ACS Nano (DOI: 10.1021 / acsnano 8b07744) MX2 system, such as MoS 2, has potential applications in many fields due to its rich physical and chemical properties Generally speaking, there are several different crystal phases in MX2 system, such as 2h, 1t and so on Among them, 2h phase is semiconductor conductive and thermodynamic stable phase, while 1t phase is metal phase, which has good conductive properties It has excellent performance in energy storage such as electrocatalytic hydrogen production, lithium battery, sodium battery and super capacitor, but it is thermodynamic metastable phase, so it is very challenging to prepare stable pure phase 1t-mos 2 At present, 1t phase MX2 system can be obtained by alkali metal intercalation, mechanical stripping and electronic injection However, these methods have some shortcomings, such as heterogeneous metal pollution and low efficiency In addition, the 1t phase prepared by these methods will not be stable for a long time due to oxidation and stress relaxation As a thermodynamic parameter independent of temperature and pressure, magnetic field may play an important role in the synthesis of materials On the one hand, the magnetic field can transfer the high-strength energy to the molecular and atomic scale of the material without contact, leading to the corresponding chemical bond relaxation, the change of the valence state of the element, inducing new physical and chemical changes, changing the alignment, matching and migration of atoms and molecules, and affecting the microstructure and performance of the material On the other hand, the static magnetic energy produced by the material in a strong magnetic field will change the free energy of the material in the synthesis process, affect the nucleation rate and selectivity of the material, provide additional driving force for grain growth, and even obtain new material system or metastable phase In recent years, the synthesis of materials under strong magnetic field has become an important technical means to develop new materials The 4D electrons of 2h-mos 2 have no unpaired electrons and show diamagnetism; the 4D electrons of 1t-mos 2 have net magnetic moment Considering the different magnetic properties between 1t and 2H phases, the magnetic free energy caused by the different magnetic properties may effectively regulate the crystal phase of MoS 2, so as to realize the crystal phase engineering of MoS 2 system Based on this, the author has carried out the related research on the preparation of MoS 2 by hydrothermal method on the material synthesis platform under the self built 10t level strong magnetic field The results show that the crystal phase modulation of MoS 2 can be realized under the external enhanced magnetic field With the increase of the applied magnetic field, the proportion of 1t phase MoS 2 in the composite increases gradually When the applied magnetic field is 9t, the pure phase of 1t-mos 2 can be obtained What's more, 1t-mos 2 synthesized by high magnetic field hydrothermal method has high stability and no obvious degradation even after being placed in the atmosphere for one year This method provides an important way for the preparation of highly stable 1t phase transition metal disulfide compounds The above research was supported by the national key research and development plan, the 13th five year plan of Hefei Institute of material science, Chinese Academy of Sciences, and NSFC.