Hydrothermal Synthesis Of ZnFe₂O₄@MnO₂ And Af-MWNTs And Their Applications In Supercapacitors And Solar Cells

The ever-changing modern life has made our demand for energy grow rapidly.On the other hand,the depletion of traditional fossil energy,wind energy,tidal energy,solar energy,geothermal energy,the rise of these new energy symbolizes the awakening of human environmental awareness.At this time,people are eagerly expecting a new type of energy storage and conversion equipment.This type of equipment is best suited to meet high capacity density and high power density requirements.Therefore,supercapacitors have emerged.In addition to having a high power density,supercapacitors have the advantages of long cycle life and extremely fast charge and discharge speed.At present,more and more people are investing in the research work on supercapacitors,a variety of electrode materials,electrode microstructures,and colorful electrolytes are made to improve the electrochemical performance of supercapacitors.The result of the effort is also a hot spot in the research of supercapacitors at this stage.The research in this paper is to use the transition metal oxide nanosheet array as the core structure,and load the metal oxide shell structure on the surface and adjust the specific surface area of the material by adjusting the pore size of the electrode material.The contact area between electrode and electrolyte was increased to improve the electrochemical properties of supercapacitors.In addition to supercapacitors,solar cells are an integral part of future energy systems.A solar cell is a device that converts solar energy into electrical energy.The device is often composed of inorganic materials.The process is complicated and costly,and the environment is seriously polluted.In order to improve the photoelectric conversion efficiency,organic solar cells have been studied,which are capable of mass production,low in cost,high in absorbance,and have flexibility not possessed by inorganic solar cells.The development of high-performance hole transport layers is currently the focus of research on organic solar cells.The main research of the paper is divided into the following two parts:?1?we synthesized ZnFe₂O₄@MnO₂ by hydrothermal method and investigated its morphology changes by adjusting the reaction time.A binder-free electrode was obtained using a facile hydrothermal method,which was studied for application in supercapacitors and asymmetric supercapacitors.We also synthesized ZnFe₂O₄nanosheets on nickel foam?NF?under specific temperature and reaction time,followed by loading MnO₂ onto ZnFe₂O₄ under different reaction time.The prepared ZnFe₂O₄@MnO₂ showed excellent property as the electrode for supercapacitors.The specific capacitance of the ZnFe₂O₄@MnO₂ electrodes reached 1442 F g at 2 mAg^-1.The capacitance retained 90%after 3000 cycles in the cyclic stability test.The asymmetric supercapacitor was subsequently assembled,with the ZnFe₂O₄@MnO₂electrode as the positive electrode and activated carbon as the negative electrode.These asymmetric supercapacitors exhibited an energy density of 2 mW h cm^-3 at 2 mA cM^-2.All these results demonstrated that ZnFe₂O₄@MnO₂ could be a promising electrode for asymmetric supercapacitors.?2?we demonstrated the synthesis of amino functionalized MWNTs?af-MWNTs?via a simple and facile hydrothermal process and the af-MWNTs was acted as the hole transport layers?HTLs?of polymer solar cells?PSCs?based on active layers of Poly[N-9?-hepta-decanyl-2,7-carbazolealt-5,5-?4?,7?-di-2-thienyl-2?,1?,3?-benzothiadiazole?]?PCDTBT?and fullerene derivative[6,6]-phenyl-C71-butyric acid methylester(PC₇₁BM).Comparing with the control devices,devices based on af-MWNTs HLTs achieved an optimal power conversion efficiency?PCE?of 6.970%,increasing by 17.6%.The af-MWNTs exhibited not only a high electrical conductivity,but also an excellent hole mobility,which were beneficial to the hole transport and extraction.The enhancement of PCE was mainly attributed to the superior hole transport and extraction capabilities.Meanwhile,the af-MWNTs exhibited a suitable work function?WF?which was beneficial to hole extraction from the photoactive layer to the ITO anode.The experimental results indicated that the af-MWNTs HTLs not only presented excellent optical and electrical properties,but also played an important role for improving the efficiency of PSCs.