Synthesis of Functional Molybdenum or Cobalt Based Namomaterials for the Application in Electrochemistry

Author:Zhu Xiao Qing

Supervisor:wang er kang

Database:Doctor

Degree Year:2019

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Pages:136

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As an emerging field of research,namomaterials have attracted large amount of attentation,which may be due to its attractive features,such as unique optical,electrochemical,magnetic,and thermal properties.Additionally,the physicochemical properties of nanaomaterials could be perfectly regulated by morphology and composition tuning.Therefore,nanomaterials have great application potential in many fields.The rapid development of nanomaterials also provides new opportunities for the development of electrochemistry.However,rational design and synthesis of nanomaterials with specific properties remain a big challenge.This dissertation is mainly based on the application of nanomaterials in the field of electrochemistry.Starting from the design and controllable preparation of functional molybdate cobalt-based nanomaterials,the following works are earned out:(1)The ECL efficiency could be enhanced by selecting proper nanocarrers.Luminol,as a kind of ECL organic luminophore,has many advantages,such as,low cost,high efficiency,good chemical stability,and low oxidation potential.However,most of the luminol-based ECL system was performed in the solution which would make the emission efficiency discount greatly.Nanomaterials always have the advantages of large specific surface area and good electrical conductivity.Therefore,using nanomaterials to enrich and fix luminol molecules is a very effective way to solve this problem.Herein,molybdenum carbides with the two-dimensional ultrathin nanosheet structure on the surface and excellent conductivity were successfully employed as the nanocarriers for the capture of ECL reagent of luminol-capped Au nanoparticles(luminol-AuNPs).Notably,the luminol-AuNPs in the hybrid(luminol-AuNPs@Mo2C)exhibit enhanced ECL performance(~6-fold)as compared to individual luminol-AuNPs because of the facilitated electron transfer process.Ultimately,the as-prepared ECL label was used to construct a label-free ECL immunosensor for the detection of α-fetoprotein(AFP).The immunosensor shows high selectivity and high sensitivity to AFP detection with a wide linear range of 0.1 pg mL"1 to 30 ng mL-1 and an extremely low detection limit of 0.03 pg·mL-1(S/N=3).Moreover,the fabricated ECL immunosensor exhibits satisfied performance in the practical application.This novel sensing strategy not only broadens the application of molybdenum carbides but also provides a new efficient approach to detect various biomolecules.(2)Introduction of heterogeneous interface to promote HER performance.Theoretical calculation indicates that the similar d-band state to Pt makes Mo2C a promising alternative of noble-metal catalyst.However,the HER performance of Mo2C is far inferior to commercial Pt/C.Based on this,a one-dimensional Mo/Mo2C@graphene(Mo/MO2C@G)heterointerface electrocatalyst consisting of Mo/Mo2C as the core and thin graphene layers as the shell was designed via facile carbonization of the Mo-polymelamine hybrid precursor in our work.The interconnected interfaces formed between Mo and Mo2C combined with the outer carbon capping layers endowed the as-obtained electrocatalyst with outstanding HER activity with a low overpotential of 145 mV at 10 mA cm-2 and even lower than that of commercial Pt/C when the current density exceeded 46.5 mA cm-2,as well as a small Tafel slope of 78 mV dec-1.This unique nanointerface design enriches highly accessible active sites and holds promising potential for developing efficient and stable noble-metal free HER catalysts in basic media.(3)Using defect engineering as an effective way to optimize the OER performance.The introduction of defects is an effective method to improve the OER performance,because of which could regulate the electronic structure of catalysts and provide additional active sites.We have prepared an excellent OER catalyst with a simple one-step hydrothermal method by tuning the ratio of precursors.The analysis results indicate that the ratio of reactants could not only impact the morphology of CO1MoxO/NF nanostructure,but also tune the amount of oxygen vacancy effectively.Owing to the highest oxygen vacancy content and Co2+/Co3+ratio,the nano hexagonal prism of Co1Mo0.6O/NF exhibits the best OER performance with a low overpotential of 198 mV at 10 mA cm-2,even superior to commercial RuO2.Additionally,we prepared a kind of defect-rich Co(OH)2 nanosheets on nickel foam(NF)by a dissolution-reconstruction strategy.It was found that CoMoO6 nanorods prepared by hydrothermal method could easily react with alkali solution,and imperfect lattice nanostructures were formed during the regeneration of Co(OH)2,which significantly increased the conductivity and catalytic activity of Co(OH)2.This method provides an effective way to prepare defect-rich nanomaterials.