Design And Construction Of The Noble Metal And Transition Metal Sulfide Nanocrystals/Nanofibers Hybrid And Their Electrochemical Properties

New materials and energy are considered as the mainstream of future social hightech industry, and under this new context condition, functional fiber materials are developing to the multi-functionality, integrated and low cost, focusing on the development of unique optical, electrical, magnetic and other properties of functional fiber materials. Because of their excellent physical and chemical properties, nanomaterials has been worldwidely studied, and however, due to the high surface free energy, long-term utilization on nanomaterials can cause agglomeration and active inactivation. Meanwhile, fibrous material exhibits good flexibility, large amounts of surface groups and high mechanical strength, and it is very suitable as support to carry nanostructures, leading to design and development of new functional fiber material.In recent years, based on the electrospinning technology to produce onedimensional long continuous nanofiber material is subjected to researchers’ attention. Because of the high surface area, porosity and good adsorption properties of nanofibrous membrane, this study use nanofibers to load, arrangement and grow precious metals and transition metal sulfide nanocrystals. The fabricated nanostructure/nanofiber hybrid macroscopic materials are used as electrochemical sensors and hydrogen evolution electrode materials. To investigate the relationship between morphology and microstructure of hybrid material and its catalytic behavior of precious metal and transition metal sulfides. Exploring the mechanism of transition metal based hydrogen evolution catalyst, revealing a series of hybrid materials science and theoretical issues in catalysis and the hydrogen evolution.A facile and green approach has been demonstrated for the fabrication of highly uniform and monodisperse noble metal(Ag, Au, Pt) nanoparticles in polymer nanofibers by combining an in situ reduction and electrospinning technique, which are used as efficient biosensor for the detection of H2O2. Through the electrospinning technique, uniform and smooth nanofibers can be obtained and the noble metal nanoparticles with narrow size distributions are well dispersed in PVA nanofibers. The investigation indicates that the viscosity of the PVA solution play an important role in controlling the size of noble metal nanoparticles. The fabricated AgNPs/PVA nanofibers functionalized electrodes exhibits remarkable increased electrochemical catalysis toward H2O2 and excellent stability and reusability. The biosensor allows the highly sensitive detection of H2O2 with a broad linear range span of the concentration of H2O2. The rapid electrode response to the change of the H2O2 concentration is attributed to the fast diffusion of the H2O2 onto the surface of small AgNPs through the porous nanofibers structures.We have demonstrated a novel, facile and green approach for the fabrication of H2O2 detection biosensor using water-stable polymer nanofibers decorated with noble metal(Ag, Au, Pt, Rh) nanoparticles by combining an in situ reduction approach and electrospinning technique. Two methods were used to synthesize small, uniform and well-dispersed noble metal nanoparticles embedded in the polymer nanofibers and immobilized on the surfaces of nanofibers. The fabricated HRP/AgNPs/(PVA/PEI) biosensor allowed the highly sensitive detection of H2O2, GSH and glucose and exhibited a fast response, broad linear range, low detection limit and excellent stability and reusability. The response and redox peak currents increase with the increase of the ratio of exposed AgNPs. The feasible process and high detection sensitivity of the biosensor based on AgNPs decorated PVA/PEI nanofibers may pave the way in developing a new film support-enzyme hybrid substrate material for biosensors or bioelectrocatalysts.A novel strategy for the design of novel nanostructure-based electrochemical biosensors originating from an unexpected behavior of Au nanoparticles embedded in the interior of PAN nanofibers, which can migrate to the external surfaces of the carbon nanofibers during the graphitization process. Small and uniform AuNPs embedded in PANFs were synthesizedviaa combination of electrospinning and in situ reduction. With the conversion from the amorphous structures of PANFs to graphene layered structures of CNFs, the AuNPs can migrate from the interior of PANFs to the external surfaces of CNFs. The migration of AuNPs through the nanofiber matrix is strongly dependent on the graphitization temperature and heating rates. These novel nanomaterials were constructed as a nonenzymatic H2O2 electrochemical sensor and the sensors based on Au-CNFs with increased density of exposed AuNPs exhibit significantly promoted electrochemical activity. The Au-CNFs(1000 ℃, 2 ℃/min) with high exposed density and small sizes of AuNPs possess higher specific surface area and active sites, leading to higher electrocatalytic activity.Two-dimensional MoS2 nanoplates within carbon nanofibers with monolayer thickness, nanometer-scale dimensions and abundant edges are fabricated. CNFs play an important role in confining the growth of MoS2 nanoplates, leading to increases in the amount of exposed edge sites while hindering the stacking and aggregation of MoS2 layers, and accelerating electron transfer. The controlled growth of MoS2 nanoplates embedded in CNFs is leveraged to demonstrate structure-dependent catalytic activity in the hydrogen evolution reaction(HER). The results suggest that increases in the number of layers and the lateral dimension result in a decrease in HER activity as a general rule. Single-layer MoS2 nanoplates demonstrated the lowest overpotential of 93 mV(J= 10 mA/cm2), the highest current density of 80.3 mA/cm2 at η=300 mV and the smallest Tafel slope of 42 mV dec-1. The S-rich MoS2-NCNFs hybrid nanomaterial exhibited extraordinary HER activity, with a very low onset potential of 30 mV and a small Tafel slope of 38 mV per decade, due to synergistic effects. Graphitic carbon layers acted as a channel for transferring electrons to MoS2 in the MoS2-NCNFs hybrid, this together with the abundant catalytic activity of the MoS2 nanoplates and pyridinic N and graphitic N, lead to excellent HER activity.Large-scale continuous hierarchical MoS2-CNF nanomaterials with highly exposed edge site architecture of MoS2, with tunable structures from 1D scrolls to 2D nanosheets that exhibit structure-sensitive properties for the HER. By controlling the MoS2 morphology at the nanoscale, we have produced evolutions in the structure and preferentially exposed more catalytically active edge sites, enabling improved performance for electrochemical catalytic activity. Because of the highly exposed edges and excellent chemical and electrical coupling to the underlying CNFs, the MoS2-CNFs nanofiber mats exhibited excellent HER activity with a small overpotential of-0.12 V and small Tafel slope of 45 mV dec-1. The construction of structure-sensitive nanomaterials with enhanced HER activity provide a feasible way to design and engineer advanced nanostructures for catalysis, electronic devices and other potential applications.We describe a new class of Co9S8@MoS2 core-shell structures formed on CNFs with cubic Co9S8 as the core and layered MoS2 as the shell. The investigations of HER and OER electrocatalytic performances suggest that the unique Co9S8@MoS2/CNFs hybrid demonstrates significant enhancement in both HER and OER performance and superior durability and thus can serve as cocatalyst for HER and OER in electrocatalytic water splitting. The high hydrogen and oxygen evolution activities of the Co9S8@MoS2 are due to the electrocatalytic synergetic effects of the nanointerfaces generated by the directly contacting regions between the Co9S8 core and the MoS2 shell. These advantages generate strong electron transfer between Co and Mo through the intermediate sulfur atoms bonded to both metals, leading to promising promoted electrocatalytic activity.