ZnO/reduced graphite oxide composites were synthesized using a two-step method in which KOH reacts with Zn(NO3)2 in the aqueous dispersions of graphite oxide (GO) to form a Zn(OH)2/graphite oxide precursor, followed by thermal treatment in air. It was found that the dispersion of reduced graphene oxide (rGO) sheets within composites was key for achieving an excellent capacitive performance of the samples. However, the mass ratio of ZnO to rGO determined whether rGO sheets within composites were dispersed or agglomerated. The composite achieved homogeneous incorporation of rGO sheets within the ZnO matrix when the mass ratio of ZnO to rGO was equal to 93.3:6.7. This composite, in which the weight percent of rGO was only 6.7%, appeared in the SEM images to be almost entirely filled with rGO sheets coated by ZnO and exhibited high specific capacitance and excellent cycling ability. Furthermore, the sheets overlapped to form a three-dimensional network structure, through which electrolyte ions easily access the surface of the rGO or electrochemical active sites. The homogeneously incorporated rGO sheets were shown to provide 128% enhancement in specific capacitance compared with 135 F g−1 for pure zinc oxide samples. Also, the unexpected phenomena involved in the experimental processes are discussed in detail.

In the present work, we used charge-bearing nanosheets as building blocks to construct a binary composite composed of NiCo 2 O 4 and reduced graphene oxide (RGO). Co-Ni hydroxides intercalated by p-aminobenzoate (PABA) ion and graphite oxide (GO) were exfoliated into positively charged hydroxide nanosheets and negatively charged graphene oxide nanosheets in water, respectively, and then these oppositely charged nanosheets were assembled to form heterostructured nanohybrids through electrostatic interactions. The subsequent thermal treatment led to the transformation of the hydroxide nanosheets into spinel NiCo 2 O 4 and also to the reduction of graphene oxide. The asobtained NiCo 2 O 4 -RGO composite exhibits an initial specific capacitance of 835 F g À1 at a specific current of 1 A g À1 and 615 F g À1 at 20 A g À1 . More interestingly, the specific capacitance of the composite increases with cycling numbers, reaches 1050 F g À1 at 450 cycles and remains at 908 F g À1 (higher than the initial value) after 4000 cycles. The high specific capacitance, remarkable rate capability and excellent cycling ability of the composites mean that they show promise for application in supercapacitors. Comparison with the capacitive behavior of pure NiCo 2 O 4 and NiCo 2 O 4 mechanically mixed with RGO displays the importance of the self-assembly of the nanosheets in making a wide range of graphene-based composite materials for applications in electrochemical energy storage.

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In the present work, tert-butylhydroquinone (TBHQ) was used to decorate graphene nanosheets to obtain a novel and environmentally friendly electrode material for supercapacitors. The fast redox reactions between hydroquinone and quinone generate pseudocapacitance. Graphene layers which have adsorbed TBHQ interact with each other to construct a three-dimensional network. Through this network, electrolyte ions can easily access the surface of graphene to generate electric double-layer capacitance. Electrochemical measurements have shown that using TBHQ as a redox modifier of graphene can obtain a maximum value of 302 F g -1 and provide a 51% enhancement in specific capacitance. Furthermore, excellent rate capability and cycling ability are achieved using the TBHQ-decorated graphene nanosheet electrode. To improve the capacitive behavior of graphene-based materials further, only a few studies have investigated the use of graphene coupled with conducting polymers [8][9][10][11]. Also, some researchers are trying to introduce the transition metal oxides/hydroxides with high theoretical specific capacitances into graphene systems [12][13][14][15][16]. In particular, Ni(OH) 2 hexagonal nanoplates grown on graphene sheets have shown both high-power and energy capabilities [17]. However, inorganic materials are non-renewable. Their excessive consumption usually causes a series of environmental problems. There are some organic molecules with reversible electrochemical redox couples that could generate pseudocapacitance under a set of given conditions. For instance, 2-nitro-1-naphthol and anthraquinone have been introduced into carbon black [18] and carbon fabric [19], respectively. In the former case, voltammetric and impedance data obtained in a conventional three-electrode cell were reported, but the modified carbon black was not evaluated as a supercapacitor. In the latter case, the use of anthraquinone as a Graphene

First, a frequency doubling model with 4-dimensional temperature-beam coupling was proposed in this paper on the assumption of an infinite transverse crystal section. The frequency doubling process, by using analytical formula and iterative method, was simulated in the BBO crystal pumped by a laser with watt-level power. The amplitudes and conversion efficiencies of the fundamental, and harmonic beams and temperature distributions were obtained, together with the time evolution of temperature field and beam intensities. The influence of the pumping power and crystal length on the conversion efficiency and temperature field was analyzed secondly. The results finally showed that the temperature distribution has great influence on the conversion efficiency and beam quality. A compensation for the phase mismatch induced by temperature can well improve the reduction of conversion efficiency induced by the thermal effect, which thus should be considered in practice.

In this work, Al-substituted α-Co(OH) 2 /GO composites with supercapacitive properties were prepared by chemical co-precipitated method in which cobalt nitrate and aluminum nitrate were used as the raw material, and graphite oxide was employed as carrier. The as-prepared materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and fourier transform infrared spectroscopy (FT-IR). Cyclic voltammetry (CV) and galvanostatic charge/discharge measurements showed that the Al-substituted α-Co(OH) 2 /GO electrode material had excellent electrochemical capacitance. The specific capacitance of 1137 F•g -1 was achieved in 6 mol/L KOH solution at a current density of 1 A•g -1 within a potential range of 0-0.5 V. Moreover, only 12% losses of the initial specific capacitance were found after 500 cycles at a current density of 1 A•g -1 .

摘要: 用溶胶-凝胶方法合成了 Mn3O4 和 Ce 掺杂 Mn3O4. 采用 X 射线衍射(XRD)、 傅里叶变换红外(FT-IR)光 谱、 场发射扫描电镜(FESEM)和透射电子显微镜(TEM)对其结构和形貌进行了表征. 采用循环伏安、 电化学交 流阻抗和恒流充放电技术对其电化学性能进行了测试. 研究结果表明, Ce 掺杂对 Mn3O4的形貌和电化学性能 均有显著影响. 当 Ce 离子占金属离子总量的 3%时, 掺杂 Mn3O4的单电极比电容高达 477 F•g-1 , 比未掺杂的提 高了 43.7%, 并且表现出更好的循环稳定性.