Molybdenum-Based One-Dimensional Organic-Inorganic Hybrid Functional Nanomaterials:Synthesis, Mechanism, Transformation And Applications

With the development of nano-science and technology, one-dimensional (1D) nanomaterials have attracted explosive interest in the fields of material science, physics, chemistry, and etc., from the viewpoints of their 1D structure and growth characteristics. The superior properties of 1D nanomaterials than their bulky counterparts has been revealed in many fields. Among this 1D system, organic-inorganic hybrid 1D nanomaterials have become a new highlight due to their combination of the characteristics of organic, inorganic and nanomaterials. They have potential applications in many fields, including catalysis, sensing, biology, electrochemistry and optics because of their uniform 1D structure, tunable components and functional properties. Moreover, they are good templates and building blocks for designing other functional 1D nanomaterials.However, the system of organic-inorganic hybrid 1D nanomaterials still has many challenges. Firstly, the kind of organic-inorganic 1D nanomaterials is limited and their growth mechanism is obscure, mainly in that limited synthesis method and complex system; secondly, the study on fabricating other functional nanostructures with the employment of organic-inorganic 1D nanomaterials is still lacking, especially for the transformation method, process and mechanism. These problems limit seriously their development and applicaiton. Therefore, it is necessary to study their synthesis and transformation method, growth and transformation mechanism, and also building other functional nanomaterials. These are believed to open up opportunities for the development and application of such 1D hybrid nanomaterials.Based on the above research background and a series of problems, this thesis focus on molybdenum-based 1D hybrid nanomaterials, and includes two aspects, "synthesis and growth mechanism", "fabricating 1D functional nanomaterials and transformation process". To build more 1D hybrids, MoOx/amine nanowires were developed and their growth mechanism was proposed. These 1D hybrids provided abundant precursor materials for subsequent transformation and several 1D polymer-hybrids (e.g. MoOx/PANI、Fe-MoOx/PANI MoS2/PANI) and carbide catalysts (e.g. Mo2C. Mo2C/RGO) were successfully obtained. And new transformation mechanism have been proposed with the study on the conversion process in detail. They exhibit high performance in catalysis and electrochemistry. The synthetic strategies and routes provide opportunities and new ideas for the design of functional 1D nanomaterials, which are suitable catalysts for the relevant reactions. The details are listed below.In chapter 3, the synthesis and growth of Mo3O10(C6H8N)2·2H2O nanowires were discussed in detail. Through co-precipitation method, Mo3O10(C6H8N)2·2H2O、 Mo3O10(C2H10N2) and Mo3O10(C5H6N)2·H2O nanowires have been synthesized. The synthesis parameters, including reaction time, pH conditions, feeding ratio are carefully studied, and thus the growth mechanism of ’1D growth originating from anisotropic molybdate anions’ was proposed. Significantly, MoOx/amine nanohybrids exhibit abundant photochromic properties, in which 1D morphology improves the photosensitivity. Their tailored component and structure endow them with tunable properties.In chapter 4, we proposed a novel strategy to fabricate 1D polymer-hybrid nanostructures based on 1D hybrid precursors. Through a novel chemical oxidative polymerization approach, MoOx/PANI nanocomposites have been controllable prepared based on the Mo3010(C6H8N)2·2H2O nanowire precursor. The nanotubes, nanowires, and rambutan-like nanoparticles of MoOx/PANI were successfully obtained through simply modulating the region of pH values. The nanowire morphology of the precursor is the key to achieve the 1D structures of final 1D polymer-hybrid. A new polymerization-dissolution mechanism is proposed to explain the formation of such products with different morphologies, in which the match between polymerization and dissolution processes of the precursor plays the important role. Remarkably, the polymerization significantly increases the conductivity of such nanomaterials, indicating this approach will find a new way to controllably prepare various 1D functional nanohybrids especially for polymer-hybrid.In chapter 5, the route of designing 1D polymer-hybrid nanostructures from 1D hybrid precursors was further developed, and abundant 1D functional polymer-hybrids were achieved. Novel Fe-MoOx/PANI and MoS2/PANI 1D polymer-hybrid nanostructures were successfully fabricated via the chemical polymerization and hydrothermal transformation of Mo3010(C6H8N)2·2H2O nanowire precursors, which showed high performance in cyclooctene epoxidation and remarkably improved electrochemical performances as anode materials for Li ion battery.Molybdenum carbide (Mo2C) is a rising efficient catalyst in hydrocarbon conversions because of its platinum-like catalytic properties. In chapter 6, several nanoporous Mo2C nanomaterials were synthesized via calcining MoOx/amine precursor with different morphologies under Ar flow, which are composed of Mo2C nanoparticles and possesses large surface. Among this, nanoporous Mo2C nanowire exhibits superior electrocatalytic activity towards hydrogen production due to its enriched nanoporosity, composed of nanosized crystallite structure. Furthermore, the surface area, porosity and crystallite size are crucial structural parameters dominating the HER.In chapter 7, Mo2C/RGO were successfully synthesized via a safe and facile strategy from the Mo3010(C6HgN)2·2H2O precursors. The amine pre-intercalated in the 1D hybrid precursors leads to the synchronous reduction of precursor to Mo2C and GO to RGO. The intimate contact between high dispersed 3-5 nm Mo2C nanoparticles and RGO support as well as their synergy endow Mo2C/RGO with high active surface. The material presents high current densities, low onset overpotential and high stability in HER system. The necessity and superiority of synthetic strategy for fabricating Mo2C/RGO from 1D hybrid precursors is well demonstrated. And such earth-abundant materials with high electrocatalytic performance hold great promise for a variety of applications in the fields of energy conversion and storage.In summary, the abundant Mo-based 1D nanohybrids have been realized through facile co-precipitation and second transformation process, such as hydrothermal and chemical polymerization methods. The’1D growth originating from anisotropic molybdate anions’ and ’polymerization-dissolution’mechanism were proposed to explain the formation of such 1D Mo-hybrid nanomaterials. Their performance in alkene epoxidation, Li ion battery and hydrogen evolution reaction are discussed. The research will open up opportunities for the design and development of new organic-inorganic 1D functional nanomaterials.