Preparation Of Graphene/oxide Nanocomposites Materials And Their Photoelectric Properties Research

Lithium-ion batteries(LIBs) are wide-spreadly used in portable electronic devices and electrical vehicles for their large energy density, high operation voltage and long cycle life. As the energy shortages and environmental degradation, exploring new clean alternative sources of energy has become a development trend, the research of lithium-ion batteries also draw more and more attention of the researchers. In recent years, graphene because of its large specific surface area and good electrical conductivity, could form nanocomposites with other materials as anode materials for lithium ion batteries. This kind of nanocomposites materials can not only get rid of disadvantages of traditional material itself, but also play the unique properties of graphene materials. Therefore graphene/oxide nano composites materials, in the catalyst, photoelectric, energy storage and other fields have good application prospects.Under the irradiation of ultraviolet light, Ti O2 can be decomposed hardly degradable substance, poisonous and harmful pollutants, and Ti O2 is cheap and non-toxic, does not produce secondary pollution, so Ti O2 has been widely researched and used. However, the band gap of Ti O2 without optimization process is wider. Furthermore, light carrier is easy to compound and greatly affected the photocatalytic properties of Ti O2. Based on the good electrical conductivity of graphene and hollow structure, in this work, the graphene- Ti O2 hollow nanocrystals nanocomposites were researched and syntheticed. Different hybrids were prepared by adjusting the weight ratio of graphene of mixture in the process of experiment, then their photocatalytic properties and electrical properties are studied.Sn O2 is considered as one of the most promising lithium-ion battery anode materials because of its high theoretical capability(790 m Ahg-1), no memory effect and environmental benignity. However, it has serious drawbacks of huge volume change and poor electronic conductivity during the charge and discharge process, which displays poor cycle life and rate performance. So, bulk Sn O2 isunsuitable for the practical application. In this paper, the graphene-Sn O2-Ti O2 nanocomposites were prepared by hydrothermal method. In general, introducing graphene can effectively improve the electrical conductivity and possibly mitigatethe agglomeration of nanoparticles.(1) Graphite oxide was prepared by improved Hummers method using natural flake graphite as raw material, then graphene oxide was got after the ultrasonic dispersion of graphite oxide. Morphology of graphene oxide structure was analysised by observing TEM and SEM. It is found that GO has a flake-like structure with wrinkles. Furthermore, graphene oxide is composed of several layers instead of a single one.(2) Using the two-dimensional structure and good electrical conductivity of grapheme, three-dimensional graphene-Ti O2 hollow nanocrystal composites were synthesised via a simple one-step hydrothermal method with hydrogen in titanium oxide as the precursor. Our results show that Ti O2 hollow nanocrystals are evenly dispersed nanoparticles on graphene. The diameter of Ti O2 hollow nanocrystals is smaller than 20 nm and the diameter of the hollow part is approximately from 3 to 5 nm. The specific surface area of G1-Ti O2 is calculated to be higher than 111 m2g-1.(3) The amount of grapheme was changed in the process of experiment, six kinds of different weight ratio of graphene-Ti O2 hollow nanocrystal composites, such as G0-Ti O2, G0.5-Ti O2, G1-Ti O2, G2-Ti O2 and G5-Ti O2, were synthesized. Their photocatalytic performance and electrochemical properties were studied. Experiments have shown that the G1-Ti O2 composite material display the best photocatalytic performance. Using methylene blue as degradation compounds, after degradation for 25 min, the degradation rate can reach 98.02%, while photocatalytic degradation of methyl orange for 30 min, the degradation rate can reach 99%.G1-Ti O2 composite material has the best cycle stability, a high initial reversible capacity of 217.2 m Ahg-1 for the G1-Ti O2 composite material is obtained at 0.2 C after 100 cycles, which is far higher than theoretical capacity of Ti O2(168 m Ahg-1).(4) By Sn Cl2· 2H2 O as raw materials, graphene-Sn O2 composites were synthesized through the hydrothermal method, their nanometer micro-structure and electrochemical performance were studied. The experiment results show that Sn O2 nanoparticles dispersed on the surface of graphene unevenly, there is a clear phenomenon of agglomeration, the size of Sn O2 nanoparticle is about 5 nm, graphene-Sn O2 composites exhibited good cycle stability, a high specific capacity of 1024 m Ah-1 is obtained at 0.2 C after 50 cycles.(5) By tetrabutyl titanate and Sn Cl2·2H2O as raw materials, a solvothermal method combined with a hydrothermal two-step method is developed to synthesize grapheme-Sn O2-Ti O2 ternary nanocomposite, their nanometer micro-structure and electrochemical performance were studied. The experiment results show that after joining extremely small amount of Ti O2, Sn O2 nanoparticles evenly dispersed on the surface of graphene, and there is no agglomeration, the size of Sn O2 nanoparticle is about 5 nm, graphene-Sn O2-Ti O2 ternary nanocomposite exhibited higher reversible capacity and better cycle stability, a high specific capacity of 1073 m Ah-1 is obtained at 0.2 C after 50 cycles.