Synthesis And Performance Study Of Bi-based Nanocomposites For Automotive Ultracapacitors And Exhaust Treatment

Global car number increases year by year, which exacerbates the traditional oil consumption. The overuse of fossil energy fuel more vehicle exhaust emissions, which will cause serious environmental pollution. Therefore the development of new energy and effectively handling automobile exhaust are important for sustainable development. Electric vehicle not only won't produce pollution but also cause little noise which is benefit for both environment and human. One of the key to produce electric vehicle or hybrid vehicle is the energy storage. As a new generation of energy storage components, supercapacitors have great potential application in many fields for their high power density, high charge and discharge performance and long cyclic life. In the treatment of vehicle exhaust, photocatalysis can make full use of solar energy to degrade NO, in this way, some major environmental pollution like photochemical smog, acid rain, etc., can be avoid. In numerous materials, bismuth-based material have been widely concerned due to their high electrochemical stability, high oxidation-reduction reversibility, good photocatalytic activity and unique electronic/band structure for electrochemical and photocatalytic.In this work, we fabricated different composites based on bismuth. The purposes of these designs are to enhance the electrochemical and photocatalytic performance, respectively. The crystal structure, chemical valence, morphologies and sample composition were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, focused ion beam scanning electron microscopy, transmission electron microscope and thermogravimetric analysis. Electrochemical properties were characterized by galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Photocatalytic performances were evaluated by UV-vis diffuse reflection spectra, Photoluminescence spectra and the removal of NO at ppb-level under visible light irradiation. The research content and the main conclusion are summarized as below:Uniform bismuth oxide carbonate nanoflowers have been prepared by properly adjusting the amount of bismuth citrate and sodium carbonate. After hydrothermal with potassium permanganate,?BiO?₂CO₃@MnO₂ nanocomposite has been synthesized. Ultrathin MnO₂ nanoplates load on the surface of?BiO?₂CO₃, forming a core-shell structure. When tested as electrode materials, the core-shell structure obtained the highest capacitance of 196.0 F g-1 with favorable cycling abilities?125% remain after 1000 cycles?.Bismuth oxide was obtained by calcining bismuth oxide carbonate nanoflowers, and then reacted with potassium permanganate to fabricate Bi₂O₃@MnO₂. The load mass of MnO₂ decreases significantly. When tested as electrode materials, the Bi₂O₃@MnO₂ obtained the highest capacitance of 139.4 F g-1 with excellent cycling abilities?112% remain after 1000 cycles?. But its electrochemical performance is a little worse than?BiO?₂CO₃@MnO₂.Ni-doped ?-Bi₂O₃ microspheres were prepared by a facile solvothermal route. By adjusting the addition of nickel powder, we can obtain different composite with nickel content, marked as undoped Bi₂O₃, Ni-Bi₂O₃-2, and Ni-Bi₂O₃-5 respectively. Time-dependent experiment reveals that the Ni-doped ?-Bi₂O₃ microspheres are developed from a layered platelet precursor to subsequent growth of microspheres and consumption of precursor simultaneously. The composite not only has mesoporous structure, a larger specific surface but also has a better electrical conductivity because of the addition of nickel. These characteristics are beneficial to photocatalytic properties. Ni-Bi₂O₃-5 exhibited the highest absorption in visible light region, the lowest recombination rate of electron–hole pairs and the highest removal rate of NO?52.2%?.This work provides a new avenue for preparation, composite of bismuth-based materials and its electrochemical and photocatalytic performance study while establishes technological base for the further development and practical application.