Lithium-sulfur (Li-S) batteries have attracted extensive attention along with the urgent increasing demand for energy storage owing to the high theoretical specific capacity and energy density, abundant reserves and low cost of sulfur. However, the practical application of Li-S batteries is still impeded due to the low utilization of sulfur and serious shuttle-effect of lithium polysulfides (LiPSs). Here, we fabricated the porous honeycomb-like C 3 N 4 (PHCN) through a hard template method. As a polar material, graphitic C 3 N 4 has abundant nitrogen content (~58%), which can provide enough active sites to mitigate shuttle-effect, and then conductive reduced graphene oxide (rGO) was introduced to combine with PHCN to form PHCN/rGO composite in order to improve the utilization efficiency of sulfur. After sulfur loading, the PHCN/rGO/S cathode exhibited an initial discharge capacity of 1,061.1 mA h g −1 at 0.2 C and outstanding rate performance at high current density of 5 C (495.1 mA h g −1 ), and also retained 519 mA h g −1 after 400 cycles at 1 C. Even at high sulfur loading (4.3 mg cm −2 ), the capacity fade rate was only 0.16% per cycle at 0.5 C for 200 cycles. The above results demonstrate that the special design of PHCN/rGO composite as sulfur host has high potential application for Li-S rechargeable batteries.
Dendritic Pd-Ag alloy nanowires (Pd-Ag DNWs) with different bimetallic composition have been directly self-assembled on the microelectrodes from mixed solutions of palladium and silver ions by applying an alternating current (AC) field. The size and morphology of the final product were controlled via adjusting the electrodeposition parameters and the metal ion concentration ratio. The influence of three factors on the bimetallic composition in alloy nanowires was examined. Structural characterizations suggest that there was a preferential growth along (200) and (111) directions, leading to the formation of Pd-Ag nanodendritic wires with 150-200 nm in stem and branch diameter. The mechanism of forming the DNWs is discussed. The DNWs were studied as sensing materials for the detection of hydrogen, and they were found to exhibit good sensitivity and reproducibility. The Pd-Ag sensing materials with 22.2 wt% Ag content possessed were also found to display a rapid response time of less than 1 min for 4% (V/V) hydrogen concentration.
In order to fabricate effective Pd-Ni alloy nanowire arrays with given compositions and size, the process of nucleation and growth and the dependence of alloy composition on deposition potential were investigated. The results reveal that the compositions and sizes of Pd-Ni alloy nanowires can be controlled within a desired range through adjusting suitable nucleation and growth potentials as well as the time. The Ni content in the alloy nanowires was found to vary from 6 to 28% when the deposition potential was changed from -0.3 to -1.9 V. A growth potential of -0.35 to -0.50 V was applied to fabricate Pd-Ni alloy nanowires with 8-15% Ni content. Continuous and parallel nanowire arrays can be successfully fabricated when nucleation is performed at a potential of -1.2 V for 50 ms with further growth at -0.45 V for 800 s. Pd-Ni crystal phases exist in the alloy structure forms of h111i, h200i, h220i, h311i. The nanowires have an average diameter of 150 nm and a length of 100-450 lm.
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