Preparation Of Metal Chalcogenide Nanomaterials And Study Of Their Photocatalytic And Electrochemical Performance

Photocatalysis and supercapacitor have important significance in solving the global energy shortage and environmental pollution. This paper explored the preparation of several kinds bismuth oxyhalides, transition metal oxides and transition metal dichalcogenides of nanomaterials and the research of their photocatalytic properties and supercapacitor electrochemical performance. In this paper, in situ formed Bi/Bi OBrx I1-x heterojunction of hierarchical microspheres with efficient visible light photocatalytic activity were synthesized by facile one-step solvothermal method. Photocatalytic activity was evaluated by the degradation of Rh B under visible-light irradiation. The photocatalytic mechanism of Bi/Bi OBrx I1-x under visible light irradiation has been analysised. The supercapacitor electrode materials of the Co O nanoparticles and the Ni Co2O4 hollow nanocubes have been synthesized, and studied their electrochemical capacitor performance. Preparation of the metallic 1T-Mo S2 ultra-thin single layer nanosheets, and studied its electrochemical capacitor performance. The main contents are as follows:(1) In this work, in situ formed Bi/Bi OBrx I1-x heterojunction of hierarchical microspheres with efficient visible light photocatalytic activity were synthesized by facile one-step solvothermal method. During the process of synthesis, the Bi nanoparticles were deposited on the surface of Bi OBrx I1-x microspheres through the in situ reduction of Bi3+ by ethylene glycol. The tremendously enhanced visible light photocatalytic activity of Bi/Bi OBrx I1-x samples can be ascribed to the contribution of efficient separation of electron-hole pairs and prolonged lifetime of charge carriers by Bi nanoparticles. Among the as-synthesized samples, the Bi/Bi OBr0.266I0.734 sample exhibited the highest photocatalytic activity and the high photochemical stability under repeated visible-light irradiation, which is especially promising for its practical applications. The hydroxyl radicals were confirmed to be the main active species for Rh B photo-oxidation. Bi/Bi OBrx I1-x could generate more hydroxyl radicals, which is responsible for the enhanced oxidation ability. The metallic Bi nanoparticles with noble metal like behavior exerted multiple positive effects on Bi OBrx I1-x, including increased visible light absorption and enhanced charge separation and transfer. The present work demonstrated the possibility for the utilization of low-cost Bi nanoparticles as a substitute for noble metals to improve the performance of other photocatalysts, meanwhile, provided new insights into the in situ preparation of Bi/semiconductor nanocomposites.(2) We have successfully synthesized the Co O nanoparticles by ball milling. The prepared nanoparticles exhibit high specific surface area and good crystallinity. The specific capacitances of Co O nanoparticles which have been milled for 96 h electrode are 600, 594, 584, 544, 520,488, 456 and 416 F g-1 at current densities of 0.5, 1, 2, 3, 4, 8, 12 and 16 A g-1, respectively. Co O nanoparticles electrode has the specific capacitance retention of 96.6% over 2000 charge-discharge cycles at a current density of 2 A g-1 and 95.3% at a current density of 4 A g-1. The high capacitance and the excellent cyclic stability of the Co O nanoparticles electrode attributed to the high surface area and good crystalline nature. The excellent cyclic stability of the Co O nanoparticles enables its excellent performance as a superior electrode material for supercapacitor as energy storage applications.(3) We have successfully synthesized the Ni Co2O4 hollow nanocubes by “coordinating etching & precipitating”(CEP) route. The prepared Ni Co2O4 hollow nanocubes exhibit high specific surface area of 134.52 m2 g-1 and mesoporous structure of 2.4-6 nm. The specific capacitances of Ni Co2O4 hollow nanocubes electrode are 795.6, 680, 622.2, 568.9 and 497.8 F g-1 at current densities of 1, 2, 4, 8 and 16 A g-1, respectively. Ni Co2O4 hollow nanocubes due to the high surface area and mesoporous hollow nanostructure, which provide effective diffusion channels for the electrolyte ions and result in the high capacitance. The high surface area and mesoporous hollow nanostructure also cause the high stability, Ni Co2O4 hollow nanocubes electrode has the specific capacitance retention of 97.5% over 2000 charge-discharge cycles at a current density of 1 A g-1 and 96.1% at a current density of 2 A g-1. The high capacitance and the excellent cyclic stability of the Ni Co2O4 hollow nanocubes electrode attributed to the high surface area and mesoporous hollow nanostructure.(4) We have successfully synthesized the Mo S2 ultra-thin single layer nanosheets by the two-steps solvothermal methods. The main components of the nanosheet sample is the metallic 1T-Mo S2, and that the 1T phase concentration of the nanosheets is ～60%. The as-prepared Mo S2 nanosheets showed high crystallitity and good conductivity. The specific capacitances of Mo S2 nanosheets electrode are 388.8, 305, 271.3 and 230 F g-1 at current densities of 1, 2, 4 and 8 A g-1, respectively. Good crystallitity and conductivity are helpful to the of the electrolyte ion better diffusion and transmission, leading to the high specific capacitance. Good conductivity of the metallic 1T-Mo S2 also cause high stability, Mo S2 nanosheets electrode has the specific capacitance retention of 97.1% over 2000 charge-discharge cycles at a current density of 1 A g-1. The high specific capacitance and the excellent cyclic stability of the Mo S2 nanosheets electrode attributed to good crystallitity and conductivity of the metallic 1T-Mo S2, and enables its excellent performance as a superior electrode material for supercapacitor as energy storage applications.