光伏太阳能电池生产过程中的污染问题

日益壮大的光伏产业正在为人类发展作出积极的贡献.采用光伏发电来代替传统的发电技术,将会减少89%的空气污染.然而,在这个倡导绿色环境的时代,光伏器件生产引起的环境、健康和安全（EHS）问题也日益引起社会各界的广泛关注.认清光伏产品在生产过程中污染的真相对维持光伏产业的可持续发展有着相当重要的意义.本文综述了常见太阳能电池的EHS问题,并提出了可以减少污染的有效途径;采用生命周期评估（LCA）方法进一步比较了各种太阳能电池生产过程中污染物的排放量数据.     

Nitrogen Fixation as NOx Enabled by a Three-Level Coupled Rotating Electrodes Air Plasma at Atmospheric Pressure

In this paper, a three-level coupled rotating electrodes air plasma at atmospheric pressure is developed for evaluation of nitrogen fixation. Factors influencing the NO_x production rate and energy cost, including airflow rate, the input H₂O concentration, blade numbers at each rotating electrode and rotating speed, are examined. Air flow rates prove to have no effect on the rotational temperature of N₂ 337.1 nm and the emission intensities of N₂⁺ and N₂, but specific energy input (SEI) and species’ residence time can be shorter with higher air flow rates, resulting in lower NO_x concentration and energy cost. The addition of H₂O also has a positive effect on both NO_x concentration and energy cost. Optical emission spectrum (OES) shows that air?+?H₂O plasma has stronger 336 nm (NH) and 309 nm (OH) emission lines than air plasma, suggests NH and OH are the key species in NO_x enhancement. The most energy efficient conditions are found at airflow rate of 15 l min^?1, 12% H₂O concentration, with 4 blades on each rotating speed. Under these conditions, the lowest energy cost is observed to be 165 GJ/tN.

     

光系统I（PSI）反应中心的激子耦合

运用点偶极、单极跃迁电荷和跃迁密度等经典库仑作用的方法,考察了叶绿素a分子间面心距和错位结构等因素对激子耦合的影响．结果表明,当分子间距大于分子尺寸时,上述三种方法得到的结果基本一致;但当分子间距小于分子尺寸时,点偶极方法将明显高估激子耦合,跃迁密度的方法更适合计算分子间的激子耦合．此外,还使用上述方法计算了光系统Ⅰ（PSI）反应中心叶绿素a分子间激子耦合．结果表明,用跃迁密度计算PSI晶体结构（1jb0．pdb）e700的激子耦合为75.3cm^-1,而QM．MM优化的结构P700（ecAl．ecBl）的激子耦合为23．8cm^-1,这与考虑Dexter交换项的全对角化方法的结果（20cm^-1）一致,进而说明PSI反应中心并不是传统的P700强激子耦合对,而是ecAl-ecB2和ecBl-ecA2对强耦合二聚体构成的二聚体对．     

A pneumatic micromixer facilitating fluid mixing at a wide range flow rate for the preparation of quantum dots

A novel fluid micromixer based on pneumatic perturbation and passive structures was developed. This micromixer facilitates integration and is applicable to fluid mixing over a wide range of flow rates. The microfluidic mixing device consists of an S-shaped structure with two mixing chambers and two barriers, and two pneumatic chambers designed over the S-shaped channel. The performance of the micromixer for fluids with wide variation of flow rates was significantly improved owing to the integration of the pneumatic mixing components with the passive mixing structures. The mixing mechanism of the passive mixing structures was explored by numerical simulation, and the influencing factors on the mixing efficiency were investigated. The results showed that when using a gas pressure of 0.26 MPa and a 100 m-thick polydimethylsiloxane (PDMS) pneumatic diaphragm, the mixing of fluids with flow rates ranging from 1 to 650 L/min was achieved with a pumping frequency of 50 Hz. Fast synthesis of CdS quantum dots was realized using this device. Smaller particles were obtained, and the size distribution was greatly improved compared with those obtained using conventional methods.     

Chemical oscillation in electrochemical oxidation of methanol on Pt surface

Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscilla- tion in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode potential (e), the surface coverage of carbon monoxide (x), and adsorbed water (y). The chemical reactions and electrode potential were coupled together through the rate constant ki = exp(ai(e ? ei)). The analysis to the established model discloses the following: there are different kinetics be- haviors in different ranges of current densities. The chemical oscillation in methanol electrooxidation is assigned to two aspects, one from poison mediate CO of methanol electrooxidation, which is the in- duced factor of the chemical oscillation, and the other from the oxygen-containing species, such as H2Oa. The formation and disappearance of H2Oa deeply depend on the electrode potential, and directly cause the chemical oscillation. The established model makes clear that the potential oscillation in methanol electrooxidation is the result of the feedback of electrode potential e on the reactions in- volving poison mediates CO and oxygen-containing species H2Oa. The numerical analysis of the estab- lished model successfully explains why the potential oscillation in methanol galvanostatic oxidation on a Pt electrode only happens in a certain range of current densities but not at any current density.     

Chiral Mn(III) salen complex immobilized on imidazole-modified mesoporous material via co-condensation method as an effective catalyst for olefin epoxidation

An imidazole modified mesoporous material has been prepared through a co-condensation procedure and adopted to covalently anchor chiral Mn(III) salen complex. The active centers in the as-synthesized catalyst were presented in the form of ionic species. The results of XRD, FTIR, DRUV-Vis, and N₂ sorption confirmed the successful immobilization of chiral Mn(III) salen complex inside the channels of the modified support and the maintenance of the mesoporous structure of parent support in the immobilized catalyst. This heterogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to those of the homogeneous counterpart in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, notably high turnover frequencies have been obtained over this heterogeneous catalyst for the relatively short reaction time and low catalyst amount, due in part to the ionic property as well as the uniform distribution of the active centers.     

Chiral Mn(Ⅲ) salen complex immobilized on imidazole-modified mesoporous material via co-condensation method as an effective catalyst for olefin epoxidation

An imidazole modified mesoporous material has been prepared through a co-condensation procedure and adopted to covalently anchor chiral Mn(Ⅲ) salen complex. The active centers in the as-synthesized catalyst were presented in the form of ionic species. The results of XRD, FTIR, DRUV-Vis, and N2 sorp-tion confirmed the successful immobilization of chiral Mn(Ⅲ) salen complex inside the channels of the modified support and the maintenance of the mesoporous structure of parent support in the immobi-lized catalys...