Preparation And Electrochemical Performances Of The Templated Carbon And Its Metal Oxides Composites

Recently, templated carbon materials (TC) were widely employed as electrode materials and used in an electrochemical capacitor for their charming characteristics, for instance, adjustable pore size and structure and high specific surface area. In general, the technological process of preparation of TC, which is relative complicated, consists of template synthesis, impregnate, polymerization of carbon sources, carbonization and etch the template. The commercial template can be applied to omit the first step and simply the technological process of the preparation of TC, but it will increase the costs of TC obviously. We used natural zeolite, which is very abundant on the earth, as hard template, maltose as carbon sources to prepare large specific surface area TC. For the purpose of improving the electrochemical properties of TC, a series of composites were synthesized and their physical and electrochemical features were investigated.Mesoporous carbons (NZMC-18(6)-700-3) were synthesized by using single-step nanocasting in which maltose was used as carbon precursors and natural zeolite as template. Physical property characterization methods such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2absorption/desorption, and X-ray diffraction (XRD) were employed to determine the structure and crystallinity of NZMC-18(6)-700-3. The results show that the materials possess a disordered lamellar structure and numerous nanopores. The specific surface area (SSA) and pore volume reach up to1076.9m2·g-1and1.46cm3·g-1, respectively. Typical electrochemical measurements revealed that NZMC-18(6)-700-3has excellent charge storage capability. Specific capacitance is175.6F·g-1in the alkaline media when the current density is600mA·g-1. After750cycles, the specific capacitance retention value is94.5%, which proves that NZMC-18(6)-700-3is a promising electrode material for electrochemical capacitors because of its long-term cycle stability.NZMC-18(6)-700-3/Co3O4composite materials with different cobalt contents were synthesized at low reaction temperature using a facile chemical precipitation method. The electrochemical measurements show that the composite materials, which possess incompact layer-by-layer structure with some irregular agglomerated Co3O4particles adhering, have outstanding charge storage ability and the specific capacitance can reach up to462.34F·g-1when the calcination temperature and calculative Co3O4content are250℃and95wt.%.A promising coral-like porous electrode materials, NZMC-18(6)-700-3/NiO, were prepared by using NiSO4·6H2O and NH3·H2O as nickel source and precipitant, respectively, and the reaction temperature was set as20℃, the sequentially calcination was conducted in air atmosphere at a high temperature. The N2absorption/adsorption tests describe that the composites have a high specific surface aera of193.6m2·g-1. The constant currnt charge/discharge (CCD) tests were operated to calculate the specific capacitance of the as-prepared composites and2M KOH was used as electrolyte. The maximum specific capacitance of1294.2F·g-1was achieved at the current density of10mA·cm-2when the composites prepared at350℃with the nickel oxides contents of80wt.%.The MnOx and NZMC-18(6)-700-3/MnOx were synthesized through chemical precipitation method and the sequentially calcination was conducted at different high temperatures in the air atmosphere. The influence of reaction temperature to the microstructure of MnOx was studied, furthermore, the contents of manganese and calcination temperature were investigated to learn the electrochemical performances of the composite electrode materials. The FESEM results describe that NZMC-18(6)-700-3/MnOx and MnOx prepared at low reaction temperature exhibits good sphericity, which was self-assembled with conical nano-rod under the force of electrostatic, and a higher reaction temperature will destroy the sphere structure. The electrochemical tests were conducted and the CCD, which operated at the current density=10mA·cm-2, tests results approve that the as-synthesized composites have outstanding electrochemical properties, and the specific capacitance can reach up to492.4F·g-1when NZMC-18(6)-700-3/MnOx prepared at the optimum conditions: calcination temperature is400℃, the calculated percentage of Mn is80wt.%and a low reaction temperature of20℃. Moreover, the specific capacitance retention value reaches up to70.7%after1500continuously CCD tests when the current density is25mA·cm-2.A novel carbon source, maltose, was used in the technology of the preparation of mesoporous TC, which enriched the choice range of carbon source. Meanwhile, the natural zeolite employeded as template could radical cut the costs of NZMC-18(6)-700-3. Series of NZMC-18(6)-700-3/metal oxides (Co3O4, NiO, MnOx), which possess the merit of both metal oxides (large specific capacitance) and carbon (good cycle life), were synthesized at a low temperature (the reaction temperature is20℃).