Study On Preparation And Properties Of Molybdenum Sulfide Nanotube-based Composites

Electrochemical water decomposition is an efficient and environmental friendly method of hydrogen production.Platinum group metals with relatively low overpotential and large exchange current density are the most effective catalyst for hydrogen evolution reaction（HER）,while problems like low reserves and high cost limit their large-scale applications.Molybdenum-based compounds have been attracting more and more researchers’attention and in-depth researches due to their similar electronic structures to platinum group metals.However,traditional molybdenum-based materials still have problems such as low electrical conductivity and insufficient active sites,which restricts their catalytic performance of such materials in hydrogen evolution reactions.In order to enhance their performance,methods like the introduction of a conductive matrix and the design of nanostructures with abundant active sites have become effective means.In this thesis,MoS₂nanotubes with rich edge structure were prepared,and the active material was doped on the surface of the nanotubes by in-situ substitution,which enhanced the electronic synergy between the elements,improved the number of active sites and conductivity of the material,and effectively strengthened the HER performance of the material.At the same time,a variety of characterization analysis methods were used to explore the relationship between the structural composition and performance of the material.The specific research content was as follows:（1）MoS₂ nanotubes were synthesized under hydrothermal conditions using MoO₃-EDA hybrid nanowires as precursors and C₃H₇NO₂S as sulfur source.Then the Mo N/MoS₂ nanocomposite materials were synthesized by chemically vapor-deposition（CVD）method of nitriding the MoS₂ surface at750℃using NH₃ as nitrogen source.Mo N/MoS₂ exhibited good catalytic activity because that N-doped into the lattice of MoS₂ formed catalytically active Mo N,and N-doping improved the conductivity of MoS₂ nanotubes.It was tested for hydrogen evolution performance when using 0.5 M H₂SO₄ as the electrolyte,an overpotential of 148 m V was required to reach a current density of 10 m A·cm^-2,and the Tafel slope is 91 m V·dec^-1.（2）Using MoO₃-EDA hybrid nanowires as precursors and CH₄N₂S as sulfur sources,MoS₂ nanotubes were synthesized in the same way.Then using（NH₄）₂HPO₄ as phosphorus sources,Mo P/MoS₂ nanocomposite materials were synthesized by chemical vapor deposition method at 850℃.Due to the Interface effect of Mo P and MoS₂,the obtained Mo P/MoS₂nanotubes showed excellent HER catalytic activity in 0.5 M H₂SO₄ aqueous solution.It only needed an overpotential of 68 m V to reach the current density of 10 m A·cm^-2,with its Tafel slope of 69 m V·dec^-1.It was worth noting that after 1000 cycles,the overpotential was reduced to only 49 m V due to the positive effect of electrochemical activation,which exhibited better cycle stability compared to other molybdenum-based materials.