Electrochemical Investigations On Graphene-like Molybdenum Disulfide

Since 2010, few-layer molybdenum disuflde(Mo S2) has attracted a great deal of attention for applications in optics, electrics and chemistry etc, due to versatile properties involved with large specific surface area, controllable band gap, high carrier mobility and electrochemical stability. Mo S2 monolayer belongs to hexagonal crystal system which is composed of S-Mo-S units through weak van der Waals forces. However, less catalytic sites and low intrinsic conductivity of Mo S2 material limits their potential performances. Heteroatom doping Mo S2 nanosheets could change its electronic structure, which has been an effective approach to increase electrochemical catalytic performances. Recently, theoritcal studies indicate that transitionmetal elements could be introduced into the hexagonal lattice and bring more defects. In this work, a one-step high-temperature pyrolytical method was developed to prepare 2D Mo S2 and heteroatom-doped Mo S2 nanosheets. The electrochemical performances of these Mo S2-based nanosheets were systematically explored.In chapter one, synthesis of 2D Mo S2 and its application of biomolecules detection were introduced. The ultrathin Mo S2 sheets were successfully achieved via one-step thermal pyrolysis of ammonium molybdate, thiourea and melamine, during which ammonium molybdate acts as molybdenum source, thiourea acts as sulphur source and layered products by pyrolytic melamine acts as sacrifice template. In the buffered solution containing ascorbic acid, dopamine and uric acid(AA, DA, and UA), large oxidation potential separation and improve electrocatalytic performances were achieved. The peak potential separation of AA–DA, DA–UA was 165 m V and 128 m V, respectively. The linear response was 5.0 to 1200 μM, 1.0 to 900 μM, and 1.0 to 60 μM for each biomolecule. The detection limit for AA, DA, and UA was 1.89, 0.20, and 0.56 μM. The 2D Mo S2 material was successfully applied for simultaneous electrochemical determination of biomolecules in a wide concentration range and low detection limit with high selectivity, good reproducibility and stability.In chapter two, synthesis of heteroatom-doped Mo S2 nanosheets and their electrocatalytic properties were studied. Under a N2 atmosphere, via sacrificial template and adsorption of metal atoms, a one-step high-temperature pyrolysis approach was developed to synthesize heteroatom-doped 2D Mo S2. By using manganese chloride as manganese source, chromium trichloride as chromium source, manganese and chromium atoms were successfully doped into 2D Mo S2, improved electrochemical activities for both hydrogen evolution and oxygen reduction were achieved. The effect of doping concentration on electrocatalytic activity was systematically investigated.