The Application Of Bismuth Based Composites And Inverse Pickering Emulsions In Energy Storage And Environment

In recent years,due to the rapid development of the economy of our country,energy shortages and environmental pollution have become increasingly severe.With the depletion of petroleum resources,the search for clean new energy has become an urgent problem to be solved.Lithium-ion batteries and electrochemical capacitors are currently hot topics in electrochemical energy storage research.Lithium-ion batteries have the advantages of high energy density,long service life,high rated voltage,and environmental protection.As a new type of energy storage device,electrochemical capacitor has the advantages of long service life,energy saving,environmental protection,short charging time,and high power density.Therefore,both of them have high commercial value.In addition,water pollutants such as 4-nitrophenol are highly toxic and difficult to degrade.Methods commonly used for treating these pollutants including catalytic hydrogenation and photodegradation,etc.But these reactions require the participation of catalysts.Therefore,it is necessary to explore novel methods for preparing nanocomposites with smaller size and higher catalytic activity.In this work,reduced graphene oxide supported bismuth molybdate composites（Bi₂MoO₆/rGO）were prepared by one-step hydrothermal approach and were used as anode materials for lithium ion batteries.The composition and morphology of the composites were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,thermogravimetric analysis（TGA）,X-ray photoelectron spectroscopy（XPS）,specific surface area（BET）,Raman,and other test methods.The galvanostatic charge and discharge tests shown that when the current density was 100 mA g^-1,the initial discharge specific capacity was 1049.6 mAh g^-1.Rate performance tests were performed at different current densities.The cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）tests were also performed.In this work,ammonium bismuth citrate was used as a novel bismuth source and thioacetamide was used as a sulfur source.“rock-candy”shape Bi₂S₃ nanocrystals were synthesized by hydrothermal method.In addition,under the same conditions,3D interconnected Bi₂S₃ nanosheet network supported by a nickel film was hydrothermally synthesized.The composition and morphology of“rock-candy”shape Bi₂S₃ nanocrystals and 3D interconnected Bi₂S₃ nanosheet were characterized by XRD,SEM,TEM and XPS,etc.In the tests of the electrode materials,the electrochemicalperformanceswereinvestigatedbyCV,galvanostatic charge/discharge（GCD）and EIS measurements in a three-electrode setup and asymmetrical two-electrode setup.In this work,inverse Pickering emulsions were prepared by using carbon quantum dots as solid particle emulsifiers,the stability and average droplet size and stability depended on several factors including oil phase type,ultrasonic time,carbon quantum dots concentration,oil/water ratio,pH,and salt concentration.In addition,the Ag/CQDs microspheres were prepared using the Pickering emulsion templates.Furthermore,the best conditions for obtaining optimal emulsion were confirmed.In addition,Ag/CQDs microspheres with average size of less than 1μm were achieved using inverse Pickering emulsions as templates.These microspheres exhibited high catalytic activity and cycle stability in the reduction of 4-nitrophenol in the presence of NaBH₄.