CF_2Cl_2十SF_6的激光裂解

本文采用CW CO_2激光器研究了SF_6+F_(12)在不同条件下的激光诱导化学反应,并与热反应进行了对照。证明SF_6在F_(12)的激光裂解中是一光敏剂,能使F_(12)的分解分数大大提高。整个反应为碰撞级联激发过程,而非多光子过程。     

激光诱导H_2S催化裂解制备H_2的研究

在室温常压静态条件下研究了以Ｖ２Ｏ５／ＴｉＯ２为催化剂，紫外脉冲激光诱导Ｈ２Ｓ催化分解为Ｈ２和Ｓ的反应及其机理。考察了产氢量与激光不同照射条件之间的关系。     

激光诱导化学反应的并行计算机模拟

激光与分子的相互作用是研究光化学反应的关键因素,是激光控制化学反应的一个重要课题.基于一种半经典分子动力学模型模拟超快飞秒激光脉冲诱导的光化学反应,该模型通过含时的派耳斯(Peierls)替代把激光脉冲辐射场的矢势与电子进行耦合,明确引入激光脉冲和分子的相互作用;基于该模型实现了激光诱导化学反应模拟程序,通过环丁烷及C60的光裂解反应的计算机模拟与实验结果进行对比,结果表明该模拟程序能够真实地重复实验结果,并能够得到许多实验上得不到的细节.为提高大分子光化学反应模拟的效率,对模拟算法进行并行设计并实现;在大型计算机系统中进行测试,该方法可高效模拟激光脉冲对光化学反应结果的影响,为激光控制化学反应的试验提供信息.     

大功率CO_2激光器非平衡态合成WO_3/Al_2O_3新型陶瓷催化剂

用大功率 CO2 激光在高温、快速、非平衡态下合成 WO3/ Al2 O3烯烃歧化反应催化剂。利用 XRD、XPS、DTA TG等技术对催化剂的性质进行了研究。表明激光合成催化剂中存在非平衡态的 Alx WO3。低于六价的钨是烯烃歧化反应的活性中心 .同时还考查了催化剂组成、激光功率及熔炼时间与丙烯歧化反应活性之间的关系。     

粘接剂对CO2激光器Pt/SnO2催化剂性能的影响

就不同的粘接剂对小型封离式CO2激光器内CO转化催化剂的物理性能和反应性能的影响进行了研究。得出用铝基型粘结剂比用硅基型粘结剂制备出的催化剂其机械强度几乎高1倍,但用硅基型粘结剂制出的催化剂其反应活性好。如以硅溶胶或硅溶胶加碳纤维作粘结剂制备出的催化剂,在室温和-20℃时,于1×104h-1空速条件下,其CO的转化率都是100%,在-35℃时也有很好的反应活性,其CO的转化率为79.3%和95%。     

CF_2Cl_2的激光裂解研究

本工作是用连续波CO_2激光对CF_2Cl_2进行辐照,考察了不同气体压力,不同激光功率时的光解产物,并与热裂解相比较。实验结果发现激光裂解的最终产物与热裂解没有明显的差别,这表明连续CO_2激光辐照CF_2Cl_2的净效应与简单加热效应相似。实验的主要结果是:①CF_2Cl_2激光裂解的主要产物是C_3F_4Cl_2、CF_3Cl和Cl_2②气体压力在30～300托范围内,光解产物中C_2F_4Cl_2含量多;300托～常压范围内,CF_3Cl含量多,且随着压力升高,主要产物由C_2F_4Cl_2向CF_3Cl转化。③用不同功率密度(1000～2000W/cm~2)的激光辐照时,发现CF_2Cl_2的分解分数f与所吸收的能量E为一线性关系。且气体压力高时,引发反应的阈值功率密度低。④气体压力在30～300托范围内,都可找到相适应的激光功率密     

不同条件下乙炔裂解产物的电镜分析

实验发现乙炔在氢气与氨气气氛中催化裂解产物完全不同，反应温度973K，氦气气氛下，乙炔在LaFeO3纳米催化剂上裂解为碳纳米管，平均管径为30nm；在氢气气氛中乙炔主要在热电偶上裂解为碳纤维，直径平均为600nm左右。实验在没有催化剂存在时，对乙炔直接热裂解进行了研究．结果表明在没有氢气条件下，乙炔很少积碳；随氢气量的增加乙炔在热电偶上的积碳量逐渐增加，沉积的碳均成纤维状结构，平均直径随氢气量的增加逐渐增大。在1073K氢气气氛下，乙炔裂解产物中发现了大量螺旋状结构的碳纤维，其直径为80～200nm，长度一般在几um～十几um。     

煤的连续波CO_2激光裂解

早在激光技术发展的初期,煤的激光裂解研究已引起人们的兴趣.直到目前为止,在这一激光裂解研究中,主要是利用红宝石、钕玻璃等脉冲固体激光器作为裂解光源.一般结论是:在激光脉冲作用下,煤可以有效地发生裂解,其产物分布则由于激光加热的快速性以及等离子体生成,而和一般加热裂解产物分布有明显差异.但是,由于煤的组成甚为复杂,而且类似品位的煤样也会因取样不同、产地不同而有明显的差别.因而在类似的实验中不同的作者往往得到不同,甚至相互矛盾的结果.例如:N.E.Vanderborgh等的实验结果表明,在惰性气氛(He)和还原性气氛中激光裂解煤的气相低分子量产物分布并无明显不同.然而A.G.Sharkey等在用红     

光引发F_2/H_2链反应诱导期间的激光现象

Whittier在研究F_2/H_2链反应脉冲激光时发现,激光出现在未测出F_2消耗之前。他们认为这是反常现象而未能解释。称这种F_2消耗的延迟是链反应的诱导期。本文的紫外动态吸收光谱测定和脉冲F_2/H_2链反应激光简化模型的数值计算结果,确认了反应诱导期的存在,并证明在诱导期间产生了激光。计算结果表明,在诱导期间,只需很少量的F_2(例如10~(-10)mol/cm~3)与H_2反应即有足够增益而实现激光输出。而这少量的F_2消耗用紫外动态吸收光谱法是难于检测的。这就解释了上述疑题。在初始F_2解离度η≤1%范围内,诱导期随 F_2解离度提高而急剧缩短。当η>2%,解离度对诱导期影响很小,诱导期一般地均小于1微     

CO_2激光诱导NH_3的光化学

在用激光引发的反应体系中引入催化剂表面,目的在于探索实现高选择性皮应的新途径,本文简述在所建立的实验装置上观察到的一些实验现象。一、用连续 CO_2激光诱导 NH_3的光化学实验装置如图。CO_2激光功率15—50瓦连续可调,NH_3经液氮冷冻净化;白金(pt)可加热处理,反应器抽空到10~(-2)mmHg 柱。实验结果:①在一定的激光功率下,一定的 NH_3压力范围内,红外发射谱的强度随压力增加而增强。②在NH_3压力为60mmHg 柱时,测出了焦点处 NH_3     

NH_3-O_2体系单脉冲CO_2激光复相爆燃反应研究

研究了以TEA CO_2单脉冲激光辐照在Pt-Rh(10％)等金属表面上引发的NH_3 O_2复相爆燃反应。Pt-Rh等表面的存在明显地降低了引爆反应所需的激光功率密度。该反应的引爆阈值与激光的频率、不同的金属表面和处理方法、以及NH_3 O_2混合气体的总压力和分压比都有关。此外,还测定了该爆燃反应所产生的化学发光光谱,并讨论了反应机理。     

Opportunities and Challenges in Precise Synthesis of Transition Metal Single-Atom Supported by 2D Materials as Catalysts toward Oxygen Reduction Reaction

Transition metal single-atom catalysts (SACs) are currently a hot area of research in the field of electrocatalytic oxygen reduction reaction (ORR). In this review, the recent advances in transition metal single-atom supported by 2D materials as catalysts for ORR with high performance are reported. Due to their large surface area, uniformly exposed lattice plane, and adjustable electronic state, 2D materials are ideal supporting materials for exploring ORR active sites and surface reactions. The rational design principles and synthetic strategies of transition metal SACs supported by 2D materials are systematically introduced while the identification of active sites, their possible catalytic mechanisms as well as the perspectives on the future of transition metal SACs supported by 2D materials for ORR applications are discussed. Finally, according to the current development trend of ORR catalysts, the future opportunities and challenges of transition metal SACs supported by 2D materials are summarized.     

Plasmon‐Promoted Electrochemical Oxygen Evolution Catalysis from Gold Decorated MnO2 Nanosheets under Green Light

The oxygen evolution reaction (OER) is of great importance for renewable energy conversion and storage; however, the intrinsic process is sluggish and suffers from severe efficiency loss as well as large overpotentials. In this work, with the introduction of the plasmonic effects by design of the Au‐MnO₂ hybrid catalysts, it is demonstrated that this photophysical phenomenon could largely promote the confinement of the outer electrons of Mn cations by plasmonic “hot holes” generated on gold surface. These “hot holes” work as the effective electron trapper to form the active Mnⁿ⁺ species which could provide active sites to extract electrons from OH^? and eventually facilitate the electrochemical OER catalysis under low laser power. By tuning the laser intensity from 100 to 200 mW, the overpotential is decreased from 0.38 to 0.32 V, which is comparable to IrO₂ and RuO₂ catalysts. These findings may provide insights into activation of plasmon‐promoted electrocatalysis under low power laser irradiation/treatment and the design of novel composite electrocatalysts.     

封闭循环TEA CO_2激光器用催化剂的实验研究

在不同的催化剂和不同温度的条件下,用磁氧分析仪监测了封离型TEA C0_2激光器中O_2含量随时间或脉冲次数的变化。对实验现象进行了分析。对几种催化剂的特性给出了详细的比较。     

Controllable Thermochemical Generation of Active Defects in the Horizontal/Vertical MoS2 for Enhanced Hydrogen Evolution

As for 2D transition metal dichalcogenides, the creation of proper active defects concentrations is considered as the efficient strategy for improving hydrogen evolution performance. However, the synthesis methods of large-area MoS₂ catalysts with controllable active defects are limited, also for its working mechanism. Herein, thermochemical generation of active defects for MoS₂ catalysts has established by annealing sodium hypophosphite, in which the phosphine is spontaneously generated and chemically tailors the MoS₂ lattice. The defects formation is confirmed by the investigation of slightly-changed surface structure and unpaired electrons for the annealed samples. The hydrogen evolution reaction performances of horizontally/vertically grown MoS₂ films are improved by controlling reaction conditions, indicating the active defects could form in the basal plane and edges with retained crystal structure. The overpotential of MoS₂ samples converted from 10 nm Mo reduces from −520 to −265 mV with largely decreased Tafel slope. The electrochemical microreactor studies reveal the protons adsorption of active sites shows much more significant contribution, than interfacial charge transfer with the enhanced remarkable performance (−100 mV at 10 mA cm⁻²). This study presents the large-area synthesized strategy for MoS₂ based catalysts with controllable defects concentration and helps establish rational design principles for future MoS₂ family electrocatalysts.     

封闭循环TEA CO2激光器用催化剂的实验研究

在不同的催化剂和不同温度的条件下,用磁氧分析仪监测了封离型TEA C0₂激光器中O₂含量随时间或脉冲次数的变化。对实验现象进行了分析。对几种催化剂的特性给出了详细的比较。     

Comprehensive Understanding of the Spatial Configurations of CeO2 in NiO for the Electrocatalytic Oxygen Evolution Reaction: Embedded or Surface‐Loaded

Introducing cerium (Ce) species into electrocatalysts has been recently developed as an effective approach to improve their oxygen evolution reaction (OER) performance. Importantly, the spatial distribution of Ce species in the hosts can determine the availability of Ce species either as additives or as co‐catalysts, which would dictate their different contributions to the enhanced electrocatalytic performance. Herein, the comprehensive investigations on two different catalyst configurations, namely CeO₂‐embedded NiO (Ce‐NiO‐E) and CeO₂‐surface‐loaded NiO (Ce‐NiO‐L), are performed to understand the effect of their specific spatial arrangements on OER characteristics. The Ce‐NiO‐E catalysts exhibit a smaller overpotential of 382 mV for 10 mA cm^?2 and a lower Tafel slope of 118.7 mV dec^?1, demonstrating the benefits of the embedded configuration for OER, as compared with those of Ce‐NiO‐L (426 mV and 131.6 mV dec^?1) and pure NiO (467 mV and 140.7 mV dec^?1), respectively. The improved OER property of Ce‐NiO‐E originates from embedding small‐sized CeO₂ clusters into the host for the larger specific surface area, richer surface defects, higher oxygen adsorption capacity, and better optimized electronic structures of the surface active sites, as compared with Ce‐NiO‐L. Above findings provide a valuable guideline for and insight in designing catalysts with different spatial configurations for enhanced catalytic properties.     

Design of 2D Layered Catalyst by Coherent Heteroepitaxial Conversion for Robust Hydrogen Generation

The structural engineering of 2D layered materials is emerging as a powerful strategy to design catalysts for high-performance hydrogen evolution reaction (HER). However, the ultimate test of this technology under typical operating settings lies in the reduced performance and the shortened lifespan of these catalysts. Here, a novel approach is proposed to design efficient and robust HER catalysts through out-of-plane deformation of 2D heterojunction using metal-organic chemical vapor deposition. High-yield, single-crystalline WTe₂ nanobelts are used as an epitaxial template for their coherent conversion to WS₂. During the conversion process, the WTe₂/WS₂ heterostructure containing both lateral and vertical junctions are achieved by coherent heteroepitaxial stacking despite differences in symmetry. The lattice coherency drives out-of-plane deformation of heteroepitaxially grown WS₂. The increase in the effective surface area and decrease in the electron-transfer resistance across the 2D heterojunctions in turn enhances the HER performance as well as the long-term durability of these electrocatalysts.     

Controllably Engineering Mesoporous Surface and Dimensionality of SnO2 toward High‐Performance CO2 Electroreduction

Currently, the precise control of the architecture and surface of functional materials for high‐performance still remains a great challenge. Here, a feasible approach is presented to synchronously manipulate mesoporous surface and dimensionality of SnO₂ catalysts into hierarchically mesoporous nanosheets and nanospheres within one simple reaction system. By adjustment of the hydrophobic chain length of different fluorinated surfactants, 0D SnO₂ nanospheres with average size of 165 nm, and 2D SnO₂ ulthrathin nanosheets with thickness of 22.5 nm with the distinct dimensionalities are separately obtained (one stone, two birds), both of which are well decorated with ordered mesopore arrays on their surfaces (pore size of 16 nm). The following calcination gave rise to the formation of hierarchically mesopores (5 and 16 nm, respectively) with high crystallization and improved surface area (96.8 m² g^?1). The resultant mesoporous SnO₂ nanosheets as catalyst for CO₂ electroreduction reaction (CO₂ RR) exhibit excellent selectivity, with a high Faraday efficiency (FE) of HCOOH reaching up to 90.0% at ?1.3 V and C₁ FE of 97.4% at ?1.2 V versus reversible hydrogen electrode, as well as long‐term stability, which is among the best performance compared to reported SnO₂ materials, thanks to the collective contributions of the unique architecture and mesoporous structure.