1. Introduction Because of the fast development of the modern industry in the last century, the reserves of fossil en-ergy resources, such as oil, natural gas, and coal, were reduced rapidly. In addition, the contamination of global environment aggravated because of the industrial growth. To overcome these problems and to find a source of renewable energy, scientists have extensively studied the utilization of hydrogen en-ergy for several decades, which is harmless to the environment [1]. Fuji… 相似文献
Microlasers are narrow-band and coherent light from small cavities, which have been widely applied in biomedicine, optical interconnection, integration devices, etc. Lanthanide doped upconversion materials are potential gain media for microlasers from near infrared (NIR) to visible and UV regimes due to their multi ladder-like metastable energy levels and superior optical frequency conversion capability. The optical feedback from photon scattering of the porous upconversion nanoparticles clusters has been reported to produce upconversion random lasers. The light bouncing back and forth between two reflective surfaces or internal surface has been utilized to achieve modulated upconversion lasing emission. In addition, photon lattices and plasmonic cavities with enhanced electromagnetic fields can amplify the upconversion process within the sub-diffraction volumes and produce highly efficient upconverting lasers. In this review, the recent advances on using lanthanide doped upconversion materials for random, whispering gallery mode (WGM)/Fabry-Perot (FP) cavity and photon lattice/plasmonic cavity modulated upconversion microlasers are overviewed. Current challenges and future directions of the upconverting lasers are also discussed. 相似文献
Direct methanol fuel cell (DMFC) systems are mostly composed of massive water recycling devices such as coolers, condensers or mixers even for small and light portable applications. Integrated systems, where system components serve more than one function, can be equipped with fewer components and have a lighter weight than conventional ones. However, the process integration can also bring about significant methanol evaporation in separators, resulting in low fuel efficiency. The here presented highly integrated system can minimize methanol loss with optimized concentration control to improve efficiency. Two system variants are compared with regard to concentration, temperature, water recovery controllability and efficiency. The simulation results are compared with the previously published mingled-outlet system and validated with experiments. 相似文献
Direct peroxide-peroxide fuel cell (DPPFC) employing with H2O2 both as the fuel and oxidant is an attractive fuel cell due to its no intermediates, easy handling, low toxicity and expense. However, the major gap of DPPFC is the cathode performance as a result of the slow reaction kinetics of H2O2 electro-reduction and thus the target issue is to design cathode catalysts with high performance and low cost. Herein, different with using noble metal of state-of-the-art, we have successfully synthesized ultra-fine NiFe ferrocyanide (NiFeHCF) nanoparticles (the mean particles size is 2.5 nm) through a co-precipitation method, which is used as the cathode catalyst towards H2O2 reduction in acidic medium. The current density of H2O2 reduction on the resultant NiFeHCF electrode after the 1800 s test period at ?0.1, 0 and 0.1 V are 121, 93 and 76 mA cm2, respectively. Meanwhile, a single two-compartment DPPFC cell with NiFeHCF nanoparticles as the cathode and Ni/Ni foam as the anode is assembled and displayed a stable OCP of 1.09 V and a peak power density of 36 mW cm?2 at 20 °C, which is much higher than that of a DPPFC employed with Pd nano-catalyst as cathode. 相似文献
In this paper, a novel direct current glow discharge plasma chemical vapor deposition (DC-PCVD) process, i.e., hot cathode DC-PCVD, is employed to deposit diamond films on molybdenum substrate. Compared with the conventional DC-PCVD method, the hot cathode DC-PCVD process is distinctive for its hot cathode with the temperature ranging from 700 to 1600 °C. Detailed experiments and analyses showed that the cathode temperature plays a key role in the stabilization of gas discharge and growth of diamond films. 相似文献
The catalytic activity of materials is highly dependent on their composition and surface structure, especially the density of low-coordinated surface atoms. In this work, we have prepared two-dimensional hexagonal FeS with high-energy (001) facets (FeS-HE-001) via a solution-phase chemical method. Nanosheets (NSs) with exposed high-energy planes usually possess better reaction activity, so FeS-HE-001 was used as a counter electrode (CE) material for dye-sensitized solar cells (DSSCs). FeS-HE-001 achieved an average power conversion efficiency (PCE) of 8.88% (with the PCE of champion cells being 9.10%), which was almost 1.15 times higher than that of the Pt-based DSSCs (7.73%) measured in parallel. Cyclic voltammetry and Tafel polarization measurements revealed the excellent electrocatalytic activities of FeS-HE-001 towards the I3–/I– redox reaction. This can be attributed to the promotion of photoelectron transfer, which was measured by electrochemical impedance spectroscopy and scanning Kelvin probe, and the strong I3– adsorption and reduction activities, which were investigated using first-principles calculations. The presence of high-energy (001) facets in the NSs was an important factor for improving the catalytic reduction of I3–. We believe that our method is a promising way for the design and synthesis of advanced CE materials for energy harvesting.
Black thin films deposited on metallic substrates are selective in nature and are promising for photothermal conversion of solar energy. In this paper, we have discussed the methods of deposition of three such coatings (i) magnesium sulphide, (ii) zinc oxide and (iii) Ni black on A1 substrates. From the experimentally observed spectra, the figures-of-merit, i.e. a/e ratios, are calculated and found to be 6.4, 5.0 and 10.0, respectively. 相似文献