Self-Assembled Perovskite Nanoislands on CH3NH3PbI3 Cuboid Single Crystals by Energetic Surface Engineering

Organometal perovskite single crystals have been recognized as a promising platform for high-performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal-based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet-controlled cuboid MAPbI₃ (MA = CH₃NH₃⁺) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs-Pb-rich nanoislands is constructed on the surface of the MAPbI₃ single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm² V⁻¹ s⁻¹. As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high-quality perovskite single-crystal surface for optoelectronic applications.     

Activation,Deactivation and Reversibility in a Series of Homogeneous Iridium Dehydrogenation Catalysts

Dehydrogenation is a sustainable form of oxidation catalysis, as it avoids any primary oxidant and the waste that would accompany it. Homogeneous catalyst design for this reaction is delicate: the catalyst must have a sufficient H₂ affinity to abstract two hydrogen atoms from the substrate but not so much affinity as to fail to release them as free H₂. N-Heterocyclic carbene (NHC) ligands achieve this balancing act in a series of iridium catalysts based on the Ir(IMe)₂ motif (IMe=N,N′-dimethylimidazol-2-ylidene). Catalyst design also needs to account for mechanistic points outside of the catalytic cycle itself. To enter the cycle, there is often an initial precatalyst activation process, and elucidating this can lead to optimization of both precatalyst and reaction conditions. To leave the cycle, we can have reversible formation of off-cycle species as well as an irreversible catalyst deactivation step. In our Cp*Ir(IMe)₂Cl precatalyst for dehydrogenative oxidation, Cp* is lost in the activation step. This suggested moving to a catalyst precursor lacking the Cp*, [Ir(IMe)₂(CO)₂]⁺. Catalyst deactivation produces a series of unusual cluster cations such as [Ir₆(IMe)₈(CO)₂H₁₄]²⁺. Among applications, dehydrogenative oxidation can be useful in upgrading of biomass glycerol by conversion to lactate, as a part of hydrogen borrowing chemistry and in reversible hydrogenation/dehydrogenation for H₂ storage.      

真空变压吸附分离CH4/N2/O2实验、模拟与安评

针对CH₄/N₂/O₂混合物脱氧效果差以及安全性低等问题,采用实验室自制活性炭为吸附剂,通过数值模拟和实验进行了双塔真空变压吸附（VPSA）分离25% CH₄/59% N₂/16% O₂混合物的工艺研究。通过考察进料流量和置换流量对甲烷产品纯度和回收率的影响,实验验证了数值模型的准确性。在模拟和实验的基础上,对VPSA工艺全流程进行了系统的安全性分析,并针对存在安全隐患的过程,提出一种更为安全的VPSA工艺流程。研究结果表明,通过双塔VPSA可以获得甲烷纯度为51.36%的产品气,甲烷回收率可达85.65%,存在安全隐患的过程主要集中在吸附、均压和终升压步骤,通过原料气的惰化过程,可以实现VPSA工艺的安全操作。     

全量程甲烷测量仪

介绍了设计矿用全量程甲烷测量仪的原理及硬件，软件组成，该仪器测量甲烷浓度范围为０－１００％。由于采用了新型单片机ＰＩＣ１６Ｃ５７和使用Ｉ＾２ＣＢＵＳ等串行Ｉ／Ｏ技术，使整机硬件结构得到简化。软件对热导元件非线性进行校正，提高了测量精度。     

石墨烯吸附甲醛分子理论研究

基于密度泛函理论的第一性原理计算研究石墨烯与甲醛分子的吸附现象。结果表明,甲醛单分子与石墨烯的结合能约为-0.064 eV,结合强度较小;可通过掺杂原子提高石墨烯与甲醛分子的结合强度,这为甲醛分子的储存材料研究提供了参考。     

天然气大气式灶具的CO排放特性预测

CO是城市燃气燃烧过程中生成的主要污染物之一,必须对其排放量进行严格的控制。随着我国气源多样化格局的形成,不同组分的天然气在同一管网中运输,可能会引发末端设备的互换性问题,造成CO排放量的不稳定。为此,通过实验分析了天然气组分与大气式灶具CO排放特性之间的关系,并提出CO排放特性的预测公式。实验分为3个阶段:(1)在设计的大气式基准燃烧器上,测试了2 kPa条件下CH_4掺混单一组分时CO的排放特性,确定了C_2H_6、C_3H_8、C_4H_(10)、N_2和H_2各自对CO排放量的影响;(2)进行以CH_4为主要成分的多组分随机掺混配气CO的排放实验测试,并对实验结果进行多元线性回归分析,确定CO排放量与天然气各组分含量之间的数学关系;(3)选取3台结构型式具有代表性的实际天然气灶具,进行不同组分天然气的CO排放特性测试,验证提出的数学关系式的通用性。实验验证结果表明:实验回归得到的计算公式具有一定的通用性,可以很好地预测天然气组分变化时燃烧器的CO排放性能。     

Circumventing fuel-NOx formation in catalytic combustion of gasified biomass

It has been shown that it is possible to decrease fuel-NO_x produced from NH₃ using catalytic combustion of a synthetic gasified biomass at fuel-lean conditions. In a certain temperature regime where the conversion of fuel components, such as CO, H₂ and CH₄, is low and conversion of NH₃ is high, it is suggested that the formed NO_x is reduced by the remaining fuel components, mainly hydrocarbons. With oxide catalysts only ca. 10% of the NH₃ was converted to NO_x, the rest to N₂. It has also been shown that the ignition sequence of CO, H₂ and CH₄ varied for different catalysts and different experimental conditions, and that methane coupling and methanation reactions occurred before ignition of CH₄.     

Development of thin‐film composite membranes for carbon dioxide and methane separation using sulfonated poly(phenylene oxide)

Novel membranes based on sulfonated poly (phenylene oxide) (SPPO) was developed. SPPO membranes in the hydrogen form were converted to metal ion forms. The effect of exchange with metal ions including monovalent (Li⁺, Na⁺, K⁺), divalent (Mg²⁺, Ba²⁺, Ca²⁺) and trivalent (Al³⁺) ions was investigated in terms of permeation rate and permeation rate ratios for CO₂ and CH₄ gases. Both dense homogeneous membranes and thin‐film composite (TFC) membranes were studied for their gas separation characteristics. The effect of membrane preparation conditions and operating parameters on the membrane performance were also investigated. The selectivity of the TFC membrane increased as the cationic charge density increased as a result of electrostatic cross‐linking. TFC membrane of very high selectivity was achieved by coating a thin layer of SPPO‐Mg on a PES substrate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 735–742, 2000     

德国污泥处置技术的分析与研究

分析德国的污泥处置技术,旨在对我国的污泥处置方式进行改进．德国采用的污泥处理技术为：污泥消化发酵产甲烷气用于发电;消化后的污泥,利用垃圾焚烧厂烟气废热干燥,干燥的污泥颗粒作为燃料用于发电厂或水泥厂,或直接作为燃料应用于发电厂．但是,在甲烷气进入发电机前,首先必须对其采用活性炭吸附技术净化,净化后可保证含Si有机物质量分数小于0．6mg／L;不然,该物质将对发电机正常运行造成危害．研究表明,德国技术在我国的应用是可行的、实用的．