Synthesis and applications of multinary layered metal chalcogenide nanomaterials

• Main Author: Lai, Zhuangchai
• Other Authors: Zhang Hua
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Materials
• Online Access: https://hdl.handle.net/10356/89688; http://hdl.handle.net/10220/46339
• Institution: Nanyang Technological University

Preparation of novel layered transition metal chalcogenide nanomaterials is of great importance for the exploration of new properties of nanomaterials for a wide range of applications. Inspired by this, the aim of this thesis is to synthesize novel layered metal chalcogenide nanomaterials with new functionalities and then explore their potential applications in catalysis and energy storage devices. First, I prepared the large-scale and solution-processable alloyed 1T’-phase ReS2xSe2(1-x) (x=0-1) nanodots via combining the chemical vapor transport (CVT) and chemical Li-intercalation and exfoliation method. The produced ReSSe nanodots possess the ultrasmall size of around 1.7 nm and the ultrathin thickness of around 1.2 nm. As characterized by the XPS and XANES techniques, some chalcogen atoms are lost due to the vigorous exfoliation process, resulting in the asymmetric S vacancy. More importantly, as predicted by the DFT calculation, the low site S vacancy in the ReSSe nanodots is the most active sites for electrocatalytic HER. Significantly, the 1T’-phase ReSSe nanodots show the best water-splitting performance with a small Tafel slope of 50.1 mV dec-1. Moreover, a low overpotential of 84 mV can be achieved at current density of 10 mA cm-2. The optimal hydrogen absorption energy of the active site is concluded to the reason for the great hydrogen evolution performance, which is resulted from by the asymmetric S vacancy in the highly asymmetric 1T’ structure. Second, I obtained the large-scale production of single-layer Ni3Cr2P2S9 and Ni3Cr2P2Se9 nanosheets by exfoliation of the corresponding bulk crystals prepared by CVT method. The prepared Ni3Cr2P2S9 nanosheets possess the narrow distribution on thickness of around 1.4 nm, which corresponds to the single-layer thickness. The obtained Ni3Cr2P2S9 nanosheets were restacked by the vacuum filtration method to form a freestanding film. The prepared freestanding film was then supported on the conductive carbon paper for electrochemical measurements in 1.0 M H2SO4 electrolyte, delivering a high specific capacitance of 160.7 and 51.3 mF cm-2, at the scan rate of 20 mV s-1 and current density of 0.9 mA cm-2, respectively. The galvanostatic charge/discharge measurements also reveal the good rate capacity of the fabricated device based on restacked Ni3Cr2P2Se9 film.