RESUMEN
The multiwavelength laser array (MLA) with fine wavelength tunability is demonstrated experimentally. The studied MLA has good single-longitudinal-mode performance, and the side-mode suppression ratio (SMSR) even reaches 62.1 dB. Meanwhile, the wavelength range of the MLA can be tuned to 25.003 nm with 63 channels of 50 GHz spacing. All lasers are within a wavelength deviation of ±0.02nm. The output power is almost constant with standard deviation 0.63 dBm. The SMSRs are all above 50 dB.
RESUMEN
We report a facile atmospheric plasma reaction synthesis of Pt x Fe1-x alloys with the different Pt/Fe stoichiometric ratio in Pt x Fe1-x alloys on graphene (G) as efficient counter electrode (CE) materials and atmospheric plasma reaction synthesised TiO2 nanoparticles/G as photoanode in dye-sensitized solar cells (DSSCs). Well-distributed Pt x Fe1-x nanoparticles or TiO2 nanoparticles on the G surface were obtained. Remarkably, DSSCs prepared by the Pt0.7Fe0.3/G CE have much higher catalytic activity and stable durability than Pt1Fe0/G CE. The as-synthesized Pt0.7Fe0.3/G CE exhibits the largest value of |J red| = 1.479 mA and the lowest value of R ct = 2.86 Ω. With the Pt0.7Fe0.3/G as CE and TiO2/G as the photoanode, the DSSC can deliver an overall power conversion efficiency (PCE) of 10.13%, which is significantly higher than the 9.72% of the expensive Pt1Fe0/G counterpart. The obtained results indicate that the Pt x Fe1-x /G nanohybrids fabricated using atmospheric plasma reaction exhibited potential as a reference for next generation CE materials in highly efficient DSSCs. We believe that this work provides an effective strategy for optimizing Pt utilization for the low-cost and efficient application of DSSCs.
RESUMEN
CoS has been emerging as a promising Pt-free counter electrode (CE) material for dye-sensitized solar cells (DSSCs) due to its satisfactory electrocatalytic properties for redox reactions. However, its low electronic and ionic conductivities have limited its use in DSSCs. The doping of Ag with appropriate amount significantly improved the properties of CoS for application as a CE. Ag-doped CoS samples with various doping amounts were prepared by a facile one-step hydrothermal approach. There were very sharp changes of morphologies and particle sizes after doping different amounts of Ag. It is found that the DSSC fabricated with the 5% Ag-doped CoS CE achieved an impressive power-conversion efficiency (PCE) of 8.35% which was higher than that of the DSSC with a Pt CE (8.17%) by 2.2%, while the DSSC consisting of undoped CoS only exhibited a PCE of 6.93%. Such an enhanced PCE could be attributed to the significantly improved electrochemical activity and mixed conductivity resulting from the Ag dopant. Therefore, the excellent electrocatalytic activity, facile preparation and low material cost of the Ag-doped CoS electrode provide it with promising potential for large-scale production of new-generation DSSCs.
RESUMEN
NiCoSe2 microspheres have been successfully synthesized by a facile one-step hydrothermal method at different hydrothermal temperatures. The prepared samples are divided according to their reaction temperatures (90, 120, 150 and 180 °C) and named NiCoSe2-90, NiCoSe2-120, NiCoSe2-150 and NiCoSe2-180, respectively. The diameters of the NiCoSe2 microspheres strongly depend on the different hydrothermal temperatures. When the temperature is increased to 150 °C, the size of the resultant NiCoSe2 microspheres changes from 200 to 800 nm, and the interior of NiCoSe2-150 possesses a flocculent structure. However, NiCoSe2-180 displays a cauliflower-like aggregated structure. The prepared NiCoSe2 alloys are used as high-performance Pt-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). Cyclic voltammogram measurement indicates that NiCoSe2-150 CE has larger current density than Pt CE. Electrochemical impedance spectroscopy shows that NiCoSe2-150 CE has a low charge-transfer resistance of 1.8 Ω cm2. Due to their unique morphologies and well-defined interior and exterior structures, DSSCs based on NiCoSe2-120 and NiCoSe2-150 CEs achieve high power conversion efficiencies of 8.48% and 8.76%, respectively, which are higher than that of the solar cell based on Pt CE (8.31%).
RESUMEN
MoS2 and MoS2/carbon allotrope (MoS2/C) composites for use as anodes in supercapacitors were prepared via a facile hydrothermal method. In this study, we report the effects of various carbon-based materials (2D graphene nanosheet (GNS), 1D carbon nanotube (CNT), and 0D nano carbon (NC)) on the electrochemical performances. Among all nanocomposites studied, MoS2/CNT exhibited the best electrochemical performance. Specifically, the MoS2/CNT composite exhibits remarkable performances with a high specific capacitance of 402 F g-1 at a current density of 1 A g-1 and an outstanding cycling stability with 81.9% capacitance retention after 10 000 continuous charge-discharge cycles at a high current density of 1 A g-1, making it adaptive for high-performance supercapacitors. The superiority of MoS2/CNT was investigated by field emission scanning electron microscopy and transmission electron microscopy, which showed that MoS2 nanosheets were uniformly loaded into the three-dimensional interconnected network of nanotubes, providing an excellent three dimensional charge transfer network and electrolyte diffusion channels while effectively buffering the collapse and aggregation of active materials during charge-discharge processes. Overall, the MoS2/CNT nanocomposite synthesized by a simple hydrothermal process presents a new and promising candidate for high-performance anodes for supercapacitors.
RESUMEN
Three-dimensional (3D) hierarchical CoMn2O4@Co3O4 core/shell nanoneedle/nanosheet arrays for high-performance supercapacitors were designed and synthesized on Ni foam by a two-step hydrothermal route. The hybrid nanostructure exhibits much more excellent capacitive behavior compared with either the pristine CoMn2O4 nanoneedle arrays alone or Co3O4 nanosheets alone. The formation of an interconnected pore hybrid system is quite beneficial for the facile electrolyte penetration and fast electron transport. The CoMn2O4@Co3O4 electrode can achieve a high specific capacitance of 1627 F g-1 at 1 A g-1 and 1376 F g-1 at 10 A g-1. In addition, an asymmetric supercapacitor (ASC) was assembled by using the CoMn2O4@Co3O4 core/shell hybrid nanostructure arrays on Ni foam as a positive electrode and activated carbon as a negative electrode in an aqueous 3 M KOH electrolyte. A specific capacitance of 125.8 F g-1 at 1 A g-1 (89.2% retention after 5000 charge/discharge cycles at a current density of 2 A g-1) and a high energy density of 44.8 W h kg-1 was obtained. The results indicate that the obtained unique integrated CoMn2O4@Co3O4 nanoarchitecture may show great promise as ASC electrodes for potential applications in energy storage.
RESUMEN
Due to a diffusive nearest-neighbor coupling, phase-synchronized states can emerge in two-dimensional chaotic coupled map lattices. By defining a direction phase (like a spin with up or down direction) as the direction of two sequential iterations of the logistic map, we find several novel kinds of phase synchronization which correspond to four different regions in a phase diagram. For the phase with partial phase synchronization, as the coupling strength epsilon increases to a critical threshold epsilon(c), a percolationlike transition is found in the cluster feature of the direction phases relating to the pattern formation. In addition, a scaling of the percolation probability rho approximately (epsilon-epsilon(c))(beta) with beta=2.1 is obtained. The spatial and time correlation functions of the phase clusters are also discussed.
