Preparation Of Novel Transition Metal Nanomaterial Arrays And Their Electrocatalysis And Sensing Applications

Nanomaterial science is an important foundation for the development of modern science and technology.Due to the rapid development of social productivity and science and technology,people put forward new and higher requirements for materials in the fields of information,energy,environment and biotechnology.Nanomaterials have attracted more and more attention and research because of their unique properties.They are widely used in energy storage and conversion,catalysis,analytical sensing,biomedicine and other fields.With the rapid increase of energy demand and the deterioration of global environment caused by excessive consumption of fossil fuels,people have speeded up the search for clean energy.As a clean and efficient two energy source,hydrogen has attracted the attention of scientific workers.At present,the production of hydrogen is mainly caused by the combustion of coal,oil and natural gas.The products after combustion contain a large number of carbon monoxide and carbon dioxide,resulting in the greenhouse effect.Hydrogen production by electrolysis is widely concerned because of its advantages of simple operation and high purity of products.The electrolysis of water is generally divided into two reactions:the anodic oxygen evolution reaction?OER?and the cathodic hydrogen evolution reaction?HER?.There is a high overpotential in the reaction of hydrogen evolution,which makes the electrolysis water consume a large amount of electric energy.Noble metals RuO₂,IrO₂ and Pt are the most effective anodic oxygen evolution catalysts and cathode hydrogen evolution catalysts at present.However,because of their high price and low storage capacity,their applications are limited.Therefore,the design and development of the earth's abundant reserves of alternative materials is very attractive.Transition metal is one of the most abundant materials in the earth,which has been paid more and more attention.Through the synthesis of low price,with a large surface of transition metal nanomaterials nanostructure area and volume ratio,can effectively improve the activity of specific sites,thereby reducing the load of catalyst;in addition,nanoarray structure by exposing more active sites to promote diffusion into the electrolyte and gas to improve the electrocatalytic performance,achieve the cost is low,can be applied to large-scale application of the high efficiency catalyst.Based on the above advantages,transition metal nanomaterials array can also be used to synthesize composite nanomaterials arrays by simple methods,which can be used to detect biological macromolecules,small molecules,metal ions,antibiotics and other sensing fields.The main pionts of this thesis are summarized as follow:?1?Developing highly efficient electrocatalysts for water splitting is critical for various renewable-energy technologies.In this communication,we demonstrate the development of MnCo₂S₄ nanowire array grown on Ti mesh?MnCo₂S₄ NA/TM?behaving as a electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH.This MnCo₂S₄ NA/TM electrode drives 50 mA cm^-2 at an overpotential of 325 mV for oxygen evolution.And at overpotential of 500 mV,this catalyst electrode achieves a high turnover frequency of 0.81 mol O₂ s^-1.This has found a feasible way to find new energy and solve environmental problems.?2?We demonstrate the hydrothermal growth of a Co-MOF nanosheet array on Ni foam?Co-MOF/NF?as a high-performance catalyst for the OER.As a 3D electrode,the resulting Co-MOF/NF is superior in catalytic activity with the demand for an overpotential of only 311 mV to afford a geometrical catalytic current density of 50 mA cm^-2 in 1.0 M KOH.Such Co-MOF/NF also shows excellent long-term electrochemical durability for at least 105 h.Besides,this catalyst achieves a high turnover frequency?TOF?of 0.18 mol O₂ s^-1 at an overpotential of 400 mV.?3?We report the preparation of amorphous Ni?OH?₂ decorated Fe₂P nanoarray on Ti mesh?Ni?OH?₂–Fe₂P/TM?via electrodeposition.As a 3D electrode for the hydrogen evolution reaction,such Ni?OH?₂–Fe₂P/TM demonstrates superior catalytic activity.The characteristic of the catalysts were characterized by X-ray powder diffraction?XRD?,scanning electron microscope?SEM?,fourier transform infrared spectroscopy?FT-IR?,X-ray photoelectron spectroscopy?XPS?and transmission electron microscopy?TEM?.The as-prepares electrocatalyst requires an overpotential of only 76 mV to drive a current density of 10 mA cm^-2,which is 94 mV less than that for Fe₂P/TM.?4?The development of a sustainable route to ammonia production is one of the most attractive targets in chemistry.The primary method of ammonia production,haber-bosch process,can bring about excessive consumption of fossil fuels and large CO₂ emission.Hence,we develop the VN nanowire array on carbon cloth?VN/CC?as a high-performance catalyst for nitrogen reduction reaction?NRR?under ambient conditions.This work not only provides us an attractive catalyst material for NRR in acidic media,but would open up an exciting new avenue to the rational design and fabrication of transition metal nitrides for NRR.?5?A new photoelectrochemical composite ZnO-CdS@Au was synthesized in this experiment,which promoted the electron transfer through effective absorption of light and used for hypersensitive detection of tetracycline.Au nanoparticles and CdS nanoparticles were successfully modified on the spindle like ZnO nanorods with larger specific surface area.Due to the large specific surface area,the body is fixed on the surface of the ZnO-CdS@Au.Compared with ZnO and ZnO-CdS nanomaterials,the ZnO-CdS@Au nanocomposite can greatly improve the photocurrent due to the enhanced light absorption and charge separation.The PEC detection strategy was successfully applied to TET detection in environmental water samples with desirable precision and accuracy,demonstrating the potential applications of ZnO-CdS@Au nanocomposite in PEC devices.This method is fast and sensitive,which paves the way for a new approach in developing high-performance PEC based on nanocomposite materials.