Liu Song, Professor of Hunan University: one step synthesis of metal 1t '- sn0.3w0.7s2 nano sheet for hydrogen evolution reaction with template assisted

Introduction two dimensional (2D) layered metal sulfur compounds (LMD) have attracted great attention in the field of catalysis due to their ultra-thin structure, large specific surface area and fully exposed atoms However, the synthesis of LMD catalyst with high density active sites, excellent conductivity and high yield of her is still a great challenge The structure of metallic t 'phase has a profound influence on the enhancement of conductivity, active sites and inherent catalytic activity to enhance the performance of hydrogen evolution reaction (her) It is a great challenge to control the crystal phase structure to synthesize two-dimensional layered materials with different phase accurately Recently, by using 1t-sns2 as template, Liu Song's research group of Hunan University prepared Sn 0.3w 0.7s2 with distorted octahedral coordination metastable 1t 'phase structure by liquid-phase synthesis, which has high intrinsic conductivity and significantly improved her catalytic performance (adv funct mater 2019, 1906069 Doi: 10.1002 / ADFM 201906069) Profile of Professor Liu Song's research group: Professor Liu Song has 1 Professor, 1 associate professor and more than 10 doctoral students The research work of the research group is mainly focused on the controllable preparation of low dimensional nanomaterials and the research of functional devices The research content involves many interdisciplinary fields such as chemistry, materials science, biology and electronics The main research directions include: (1) controllable synthesis of low dimensional layered materials; (2) application research of functional devices; (3) nanobiology research More than 30 papers have been published in Nature Nanotechnology, angel Chem Int ed., nano lett., ACS Nano, nano energy, chem SCI., chem Mater And other international journals For details, please refer to http:// profile of Professor Liu Song, Professor Liu Song, School of chemistry and chemical engineering, Hunan University, State Key Laboratory of chemical biosensor and metrology, and professor of Institute of chemical biology and nanomedicine Graduated from Peking University in 2011 with a Ph.D in physical chemistry From 2011 to 2016, he was engaged in postdoctoral research at Case Western Reserve University and National University of Singapore In October 2016, he joined Hunan University and was elected to the "100 young people" program of Hunan Province in the same year Prof Feng Yexin, Associate Professor Feng Yexin, graduated from the school of physics of Nankai University in 2008, Ph.D from the school of physics of Nankai University in 2013, engaged in postdoctoral research in icqm of Peking University from 2013 to 2015, and joined the school of physics and microelectronics science of Hunan University in 2015 Research direction: computational condensed matter physics (path integral molecular dynamics simulation, surface physics, functional material design, etc.) Using high-performance parallel computing equipment and advanced computing methods, we are engaged in the research of condensed matter calculation, atomic and molecular simulation On the one hand, through in-depth understanding of the rich surface and interface characteristics of various functional materials, new material design and solve various complex technical problems that may be encountered in the process of material growth On the other hand, in the framework of quantum simulation, the phase transition of light element system, the structure of water on solid surface and the nucleation process are studied We focus on the role of nuclear quantum effects in these physical and chemical processes At present, he has published more than 40 research papers in science, science advances, nature sub journal, nano lett., J Phys Chem Lett., Phys Rev B, J chem Phys and other magazines As reviewer of J chem Phys, appl Phys Lett., ACS appl Mater Inter., scientific reports, Chinese Physics B and other journals Leading scientific research achievements: template assisted one-step synthesis of metallic 1t '- Sn 0.3w 0.7s 2 Nano chips for hydrogen evolution reaction Professor Liu Song's research group has done a series of work in the preparation and application of two-dimensional materials Firstly, salt assisted MoS 2 / WS 2 heterostructure was synthesized by two-step chemical vapor deposition method, and its growth mechanism was discussed It was found that diffusion plays an important role in the growth of anisotropic heterostructure materials (nano lett 2016, 16, 5129) In the aspect of morphology engineering, the addition of potassium halide effectively promoted the formation of 1t-sns2 in the atomic layer Compared with sodium halide, it can effectively promote the in-plane growth of single-layer SnS2 In addition, SnS2 (ACS Nano 2019, 13, 8265) with various morphologies were controlled by adjusting temperature, reactant molar ratio, time, gas flow, distance and other factors In the growth of Nb doped WS 2 monolayer, the transition from semiconductor to metallization was realized (chem Mater 2019, 31, 3534) At the same time, in the field of electrocatalysis, by etching the MoS 2 of the defect site with NaClO, the active site is effectively regulated and the performance of her is significantly improved (nano energy 2019, 57, 535) On the basis of these, the research group has developed a kind of her catalytic performance of metallic 1t '- Sn 0.3w 0.7s 2 by using stable T-phase SNS 2 as a template and doping metal atoms to adjust the phase structure, which realizes the transition from semiconductor to metallicity, and greatly improves the her catalytic performance of metallicity 1T' - Sn 0.3w 0.7s 2 First of all, Feng Yexin, a teacher from the College of physics and microelectronics science, Hunan University, who is a collaborator of the research group, used the density functional theory to study the Gibbs free energy (Δ g h *) of hydrogen adsorbed by several commonly used dopants (i.e W, Ru, Au and Ag) to express her activity through theoretical calculation The results show that W-doped SnS2 is a promising potential her catalyst In addition to optimizing the hydrogen adsorption (Δ g h *), the embedded w atom can also affect the electronic and transport properties of SnS2 The density of states (DOS) and the integrated DOS near Fermi level of Sn 1-x W x s 2 alloy with different w ratios are calculated Doping w can cause the transition from semiconductor to metal in SN 1-x W x s 2 DFT calculation shows that metal 1t '- Sn x W 1-x s 2 may provide more active sites on the base surface and have better conductivity Figure 1 Theoretical calculation for metallic properties of Sn 1-x W x s 2 The SN 1-x W x s 2 alloy with different W ratio was obtained by adjusting the mole ratio of snbr 2 and Na 2WO 4 The crystal composition and stoichiometric ratio of the corresponding products at different reaction ratios (snbr2: Na2WO4) were studied by EDX The relationship between the x value of these sn1-xwxs2 alloys and the molar ratio of reactants was quantitatively analyzed SEM showed that the morphology of the sample changed from hexagonal nano sheet to folded sheet When x reaches 0.65, only three main peaks (9.2 °, 15.6 °, 31.5 °) remain It is worth noting that there is a new (002) peak at 9.2 ° in the XRD spectrum of Sn 0.35 w 0.65 s 2 alloy This change is due to the large amount of W atoms doped into SnS2 lattice, resulting in the deformation of T-phase crystal structure, and then forming a new crystal structure (t 'phase) In addition, with x = 0.7, the peak intensity at 9.2 ° becomes stronger due to the more stable structure and higher phase purity between W and Sn in the T 'phase The characteristic peaks at 9.2 ° and 15.6 ° correspond to (002) and (004) crystal faces, respectively, and the diffraction peaks at 31.50 ° correspond to (022) reflective crystal faces of 1t 'phase metallic nanoflakes The edge of the synthesized Sn 0.3w 0.7s 2 is curly and ultrathin The tem of the side view clearly shows that the thin film becomes thinner to several layers towards the edge The thickness of Sn 0.3w 0.7s 2 nanoflakes is about 4.2nm, almost six layers, measured by AFM The high angle dark field scanning transmission electron microscope (HAADF-STEM) image and the corresponding EDX element mapping further revealed the uniform distribution of Sn, W and s in typical Sn 0.3w 0.7s 2 samples At the same time, by comparing the mapping intensity, the amount of Sn is much lower than that of W All these results indicate that the stoichiometric 2D Sn 0.3w 0.7s 2 nanoflakes have been successfully prepared Figure 2 Basic characterizations of 2D Sn 1-x W x S 2 alloys a) W ratio value of these products with different molar ratios ofreactants (SnBr 2 :Na 2 WO 4 ) b) XRD data of these Sn 1-x W x S 2
alloys c-f) SEM image, Low-magnification side-view TEM image, AFM image and stem-edxelement mappings of typical 2D Sn 0.3w0.7s2 (source: adv funct Mater.) the author characterized the atomic structure of the synthesized products (SnS2 and sn0.3w0.7s2) by stem HAADF image reveals the lattice structure of SnS2 with hexagonal T-phase The measured lattice distance is about 0.321nm, corresponding to the (100) crystal surface of SnS2 Interestingly, stem measurements of Sn 0.3 w 0.7 s 2 nanowafers show that these wafers have a 1t 'phase structure, and the clear zigzag chain shows that the shortest W-W distance is 2.80 μ M According to ADF comparison, Sn (n = 50, green circle) and w (n = 74, blue circle) atoms are distinguished Heavy atom w looks brighter XPS analysis further confirmed that twisted 1t 'phase was dominant By w4f calculation, the composition of twisted 1t 'and 2H phases is 81% and 19%, respectively In addition, XPS results show that the ratio of SN to W is about 0.29:0.71, which is basically consistent with EDX analysis In order to further verify the metal properties of 1t '- Sn 0.3w 0.7s 2, the field effect transistor (FET) was fabricated and the electrical properties of SNS 2 and 1t' - Sn 0.3w 0.7s 2 were tested The current voltage (I-V) curve of 1t '- Sn 0.3w 0.7s 2 is almost insensitive to the grid voltage, while the conductivity of Sn 0.3w 0.7s 2 is almost three orders of magnitude higher than that of SNS 2, which shows that the metal Sn 0.3w 0.7s 2 Nano chip can effectively carry out charge transfer This finding provides direct evidence for efficient electron transport of 1t '- Sn 0.3w 0.7s 2 in her In order to confirm the metal characteristics of 1t '- Sn 0.3w 0.7s 2, the UV-Vis spectrum was measured in ethanol solution, showing a smooth line without any obvious absorption band, and the ethanol solution of Sn 0.3w 0.7s 2 showed gray black Figure 3 Stem and metallic property of 2D Sn 0.3 w 0.7 s 2 (source: adv funct Mater.) in order to evaluate the electrocatalytic properties of the prepared Sn 1-x W x s 2 alloy, the linear sweep voltammetry (LSV) scanning of the prepared material was carried out by three electrode system electrochemical workstation It is found that Sn 0.3w 0.7s 2 + CB can significantly enhance the catalytic performance of her Compared with pure SNS 2 (at - 0.350 V), the current density is increased by 215 times, while the catalytic performance of CB and SNS 2 can be ignored At the same time, the author found that the opening potential of Sn 0.3w 0.7s 2 + CB is much lower than that of other products at - 0.158 v It shows that the high intrinsic conductivity of 1t '- Sn 0.3w 0.7s 2 provides a faster electronic supply