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Shape-Dependent Catalytic Activity of Nano-Fe2O3 on the Thermal Decomposition of TKX-50
Ming Zhang, Fengqi Zhao, Yanjing Yang, Hui Li, Jiankan Zhang, Wenzhe Ma, Hongxu Gao, Na Li
2020, 36(6): 1904027-0  doi: 10.3866/PKU.WHXB201904027
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摘要:
Energy components used in solid rocket propellants are beneficial for improving the energy performance, and their thermal decomposition characteristics significantly affect the combustion properties of the propellants. As a kind of energetic material with both high energy and low sensitivity (impact and friction), 5, 5'-bistetrazole-1, 1'-diolate (TKX-50) can effectively improve the energy and safety characteristics of solid propellants. Burning catalyst is another important component of solid propellants, which can significantly improve the burning rate of the propellant and reduce the pressure exponent. Among various burning catalysts, nanoscale transition metal oxides can promote the thermal decomposition of the energetic component, thus enhancing the combustion properties of the solid propellant. However, the catalytic effects of nanoscale transition metal oxides with different morphologies on the thermal decomposition of TKX-50 have rarely been studied. Based on the excellent catalytic activity of Fe2O3 for TKX-50 thermal decomposition, nano-Fe2O3 particles with spherical and tubular microstructures were used for TKX-50 thermal decomposition. The Fe2O3 nanoparticles were successfully fabricated via the solvothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. The XRD, FT-IR, and XPS results confirmed the successful fabrication of spherical and tubular Fe2O3 samples. The SEM and TEM images showed that the spherical Fe2O3 samples are composed of agglomerated Fe2O3 nanoparticles with an average particle size of 110 nm. In addition, the average diameter and length of hollow tubular Fe2O3 nanoparticles are 120 nm and 200 nm, respectively. The catalytic activities of spherical and tubular Fe2O3 for TKX-50 decomposition were studied by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) methods. The DSC and TG-DTG curves showed that both tubular and spherical Fe2O3 could effectively promote TKX-50 thermal decomposition. The first thermal decomposition peak temperature (TFDP) of TKX-50 was reduced by 36.5 K and 26.3 K in the presence of tubular and spherical Fe2O3, respectively, at 10 K·min1. The activation energy (Ea) of TKX-50, determined by the iso-conversional method, was significantly reduced in the presence of both tubular and spherical Fe2O3. The results indicated that the microstructure of the catalyst has a significant effect on its catalytic performance for TKX-50 thermal decomposition, and that tubular Fe2O3 with hollow microstructure possesses better catalytic activity than spherical Fe2O3. The excellent catalytic activity of tubular Fe2O3 can be attributed to the hollow microstructure, which has more active sites for TKX-50 thermal decomposition.
Construction of Three-Dimensional Hematite/Graphene with Effective Catalytic Activity for the Thermal Decomposition of CL-20
Ting Zhang, Cuicui Li, Wei Wang, Zhaoqi Guo, Aimin Pang, Haixia Ma
2020, 36(6): 1905048-0  doi: 10.3866/PKU.WHXB201905048
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摘要:
High-performance solid propellants are very important for the development of modern weapons. Aside from their high energy and high burning rate, safety performance is regarded as the most important factor that should be considered whenever a new solid propellant recipe is formulated. Therefore, exploring a new type of combustion catalyst that can improve both catalytic activity and reduce the sensitivity of the energetic component is significant. Traditionally, transition metals or metal oxides are used as a combustion catalyst for accelerating the thermal decomposition of energetic components. However, the existing problem of these catalysts is the aggregation of particles accompanied by poor surface area. Coupling metal oxides with graphene is a promising approach to obtain a binary composite with stable structure and large specific surface area. In this work, rod-like and granular Fe2O3 nanoparticles were synthesized using a hydrothermal method. Then, the two as-prepared Fe2O3 nanoparticles were coupled with graphene sheets using an interfacial self-assembly method, which can effectively prevent the aggregation of Fe2O3 particles and simultaneously increase the active sites that participate in the reaction. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the phase states and chemical compositions of the prepared samples. The morphology and internal structures were further demonstrated through scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption tests. Both phase analysis and structure identification indicate that the prepared Fe2O3/G has high purity and high surface area. The catalytic performance of the prepared Fe2O3 and Fe2O3/G in the thermal decomposition of hexanitrohexaazaisowurtzitane (CL-20) was evaluated based on thermal gravimetric analysis-infrared spectroscopy (TGA-IR) and differential scanning calorimetry (DSC) tests. The non-isothermal decomposition kinetics of CL-20, Fe2O3/CL-20, and Fe2O3/G/CL-20 were further studied by DSC. The results reveal the excellent catalytic activity of Fe2O3/G in the thermal decomposition of CL-20, which is attributed to the presence of abundant pore structure and large surface area. The reaction mechanisms of the exothermic decomposition process of CL-20, Fe2O3/CL-20, and Fe2O3/G/CL-20 were obtained by the logical choice method, and the composites all followed same mechanism function model as CL-20. Through comparison, the rod-like Fe2O3 coupled with graphene was found to have the best catalytic activity in the thermal decomposition of CL-20. Thus, the rod-like Fe2O3 and its Fe2O3/G composite were used to investigate their influence on the impact sensitivity of CL-20 by fall hammer apparatus. The results show that rFe2O3/G can effectively decrease the impact sensitivity of CL-20 compared with pure CL-20 and rFe2O3/CL-20. Therefore, rFe2O3 coupled with graphene not only promotes the thermal decomposition but also improves the safety performance of CL-20.
Preparation of BaO·4B2O3·5H2O Nanomaterial and Evaluation of Its Flame Retardant Performance to PP by Thermal Decomposition Kinetics Method
Jing Miao, Ruifeng Guo, Zhihong Liu
2020, 36(6): 1905052-0  doi: 10.3866/PKU.WHXB201905052
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Borate is considered one of the most important additives for improving the fire-resistance of combustible polymers because of its smoke suppression, low toxicity, and good thermal stability. However, the size of prepared borate is usually in the micrometer range, which makes it difficult to disperse in a polymer matrix, thus hindering its use as fire-retardant material. The preparation and application of borate nanomaterial as flame retardant is considered an effective method. However, the preparation of barium borate nanomaterials as flame retardant has not been reported. In this paper, nanosheets and nanoribbons with different sizes for a new barium borate BaO·4B2O3·5H2O are prepared by hydrothermal method, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermogravimetric analysis-differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The flame-retardant properties of polypropylene (PP)/BaO·4B2O3·5H2O composites are investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) thermal analysis methods and limited oxygen index (LOI) method. Considering the near TG mass losses and the near LOI values for PP with 10% prepared BaO·4B2O3·5H2O nanosheet and nanoribbon, their flame-retardant properties need to be further evaluated by non-isothermal decomposition kinetic method. The apparent activation energy for this decomposition reaction was obtained from the slope by plotting ln(β/Tp2) against 1/Tp according to Kissinger's model. With the reduction of TG mass loss, increased heat absorption in DSC under N2 atmosphere, increased apparent activation energy Ea for the thermal decomposition of PP/BaO·4B2O3·5H2O composite as well as increased LOI value, the flame-retardant performance of prepared BaO·4B2O3·5H2O samples with PP gradually improved from bulk to nanoribbon to nanosheet. This can be attributed to the decrease in the size of BaO·4B2O3·5H2O samples because the smaller sample size leads to improved dispersion and increased contact area with the polymer. The flame-retardant mechanism is discussed by analyzing the after-flame chars of the PP/BaO·4B2O3·5H2O composite in SEM images, which show that the char layer is more compact and continuous for the PP/BaO·4B2O3·5H2O nanosheet composite. The influence of loading BaO·4B2O3·5H2O nanomaterials on the mechanical properties of PP is also tested using a universal material testing machine, in which the PP/BaO·4B2O3·5H2O nanosheet composite has higher tensile strength. The PP/BaO·4B2O3·5H2O nanosheet composite has the best flame-retardant and mechanical properties, which is promising to be developed for the application as flame-retardant material.
Synthesis, Thermal Decomposition Kinetics and Detonation Performance of a Three-Dimensional Solvent-Free Energetic Ag(I)-MOF
Chengfang Qiao, Lei Lü, Wenfeng Xu, Zhengqiang Xia, Chunsheng Zhou, Sanping Chen, Shengli Gao
2020, 36(6): 1905085-0  doi: 10.3866/PKU.WHXB201905085
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Solvent molecules can significantly reduce the heat of detonation and stability of energetic metal-organic framework (EMOF) materials, and the development of solvent-free EMOFs has become an effective strategy to prepare high-energy density materials. In this study, a solvent-free EMOF, [Ag2(DTPZ)]n (1) (N% = 32.58%), was synthesized by reacting a high-energy ligand, 2, 3-di(1H-tetrazol-5-yl)pyrazine (H2DTPZ), with silver ions under hydrothermal conditions, and it was structurally characterized by elemental analysis, infrared spectroscopy, X-ray diffraction, and thermal analysis. In 1, the DTPZ2− ligands that adopted a highly torsional configuration bridged the Ag+ ions in an octadentate coordination mode to form a three-dimensional framework (ρ = 2.812 g∙cm−3). The large steric effect and strong coordination ability of DTPZ2− effectively prevented the solvent molecules from binding with the metal centers or occupying the voids of 1. Moreover, the strong π-π stacking interactions [centroid-centroid distance = 0.34461(1) nm] between the tetrazole rings in different DTPZ2− ligands provided a high thermal stability to the framework (Te = 619.1 K, Tp = 658.7 K). Thermal analysis showed that a one-step rapid weight loss with intense heat release primarily occurred during the decomposition of 1, suggesting potential energetic characteristics. Non-isothermal thermokinetic analyses (based on the Kissinger and Ozawa-Doyle methods) were performed using differential scanning calorimetry to obtain the thermoanalysis kinetic parameters of the thermodecomposition of 1 (Ea = 272.1 kJ·mol−1, Eo = 268.9 kJ·mol−1; lgA =19.67 s−1). The related thermodynamic parameters [enthalpy of activation (ΔH = 266.9 kJ·mol−1), entropy of activation (ΔS = 125.4 J·mol−1·K−1), free energy of activation (ΔG = 188.3 kJ·mol−1)], critical temperature of thermal explosion (Tb = 607.1 K), and self-accelerating decomposition temperature (TSADT = 595.8 K) of the decomposition reaction were also calculated based on the decomposition peak temperature and extrapolated onset temperature when the heating rate approached zero. The results revealed that 1 featured good thermal safety, and its decomposition was a non-spontaneous entropy-driven process. The standard molar enthalpy for the formation of 1 was calculated to be (2165.99 ± 0.81) kJ·mol−1 based on its constant volume combustion energy determined using a precise rotating oxygen bomb calorimeter. Detonation and safety performance tests revealed that 1 was insensitive to impact and friction, and its heat of detonation (10.15 kJ·g−1) was higher than that of common ammonium nitrate explosives, such as octogen (HMX), hexogene (RDX), and 2, 4, 6-trinitrotoluene (TNT), indicating that 1 is a promising high-energy and insensitive material.
综述
生物热化学和热动力学研究进展
谢文, 周莲娇, 徐娟, 郭清莲, 蒋风雷, 刘义
2020, 36(6): 1905051-0  doi: 10.3866/PKU.WHXB201905051
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生命相关过程伴随着极其复杂的化学和物理过程,包含着物质变化和能量转换,其中部分能量不可避免地会以热的形式表现出来。用微量热技术和热动力学方法,研究复杂生命体系和相关反应的热动力学过程,可宏观地、本质地反映生命相关过程的内在规律。本文综述了生物量热学方法和技术在生命科学中的应用,介绍了生物量热技术在生态系统、生物组织和器官、细胞水平、亚细胞水平和分子层面等不同生物层次和结构水平上的研究现状和进展。
热分析动力学研究方法的新进展
任宁, 王昉, 张建军, 郑新芳
2020, 36(6): 1905062-0  doi: 10.3866/PKU.WHXB201905062
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“非等温动力学”作为热分析动力学研究的核心,已经被广泛应用于化学、化工、冶金、地质、药物和环保等重要领域。热分析动力学研究的主要任务是确定机理函数、活化能和指前因子等动力学参数。在众多的热分析动力学研究方法中,“等转化率法”由于其可以在不涉及动力学模式函数的前提下,获得较为可靠的活化能值,因此被国际热分析与量热学协会(ICTAC)推荐使用。本文简要介绍了近十年来提出的热分析动力学研究方法,特别是等转化率方法的研究进展情况,评述了各种方法的特点与局限。同时,展望了热分析动力学研究方法未来的发展趋势。
超快扫描量热技术表征高分子结晶动力学
何裕成, 谢科锋, 王优浩, 周东山, 胡文兵
2020, 36(6): 1905081-0  doi: 10.3866/PKU.WHXB201905081
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高分子结晶行为是高分子材料加工过程研究的热点,因为高分子组分和加工工艺控制着高分子结晶及其产物性能。差示扫描量热仪(DSC)是研究高分子结晶动力学常规手段。但是,普通DSC所能达到的最快降温速率一般无法抑制较快的样品结晶,结晶行为将在等温结晶动力学测试之前发生,因此可进行等温结晶的研究温度范围局限于较低结晶过冷度的高温区域。近年来,具有超快速升降温扫描速率和精准控温的快速扫描芯片量热仪(FSC,其商业化版本Flash DSC 1)得到了广泛应用。FSC可以抑制高分子样品在升降温过程中的结晶成核,避免对之后的结晶动力学测试产生影响。因此FSC技术将高分子结晶动力学的研究温度区间延伸至具有较大过冷度的低温区,加深了我们对高分子结晶成核机理以及高分子工业加工过程的理解。本文首先介绍了由初级成核方程描述的高分子结晶动力学原理,初级成核自由能位垒(ΔG*)和扩散活化能位垒(ΔU)分别控制了高低温区的结晶动力学。我们还总结了FSC技术的发展,包括氮化硅薄膜芯片技术、快速扫描量热仪、商业化Flash DSC 1在不同高分子结晶熔融行为研究中的应用。然后介绍表征高分子等温结晶动力学的方法,其中包括样品制备、质量估算、消除热历史、临界扫描速率的确定等,并举例介绍FSC在高分子结晶动力学研究中的应用,涵盖高分子总结晶动力学、结晶成核动力学、高分子焓松弛对结晶成核的影响、FSC联用技术等方面。应用举例中对应形貌和结晶信息,分析了通过FSC测试得到的结晶成核动力学特点。另外通过比较不同结构特点的高分子,总结了我们对结晶动力学行为的基本理解。总之,FSC技术是一种能够提供相转变动力学和热力学信息的高效工具,特别是应用于分析只能在快速扫描中得到的样品结构变化信息。同时我们希望本文能够帮助读者考虑超快扫描量热技术在其他材料研究上的应用,包括合金、药物、生物大分子等。
论文
基于光微热量-荧光光谱联用技术研究光催化热力学和动力学的温度效应
覃方红, 万婷, 邱江源, 王一惠, 肖碧源, 黄在银
2020, 36(6): 1905087-0  doi: 10.3866/PKU.WHXB201905087
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利用光微热量-荧光光谱联用技术,对光催化过程的热谱和光谱信息同步监测,获取了五个温度下,g-C3N4@Ag@Ag3PO4光催化降解罗丹明B的原位热动力学、光谱动力学信息,探究了温度对相关参数的影响。结果表明,催化降解反应分为三个阶段:(ⅰ)污染物和催化剂的光响应过程;(ⅱ)光响应吸热和污染物降解放热的竞争过程;(ⅲ)保持稳定的放热率。吸热和放热的竞争过程符合一级动力学,降解速率随着温度的升高而增大;稳定放热阶段为拟零级反应,在283.15 K、288.15 K、293.15 K、298.15 K、303.15 K下的放热速率分别为0.4668 ± 0.3875 μJ∙s−1、0.5314 ± 0.3379 μJ∙s−1、0.5064 ± 0.3234 μJ∙s−1、0.5328 ± 0.3377 μJ∙s−1、0.5762 ± 0.3452 μJ∙s−1。本研究为探究光催化过程的原位热力学、热动力学及光谱信息及机理的推测提供科学依据。
纳米白藜芦醇脂质体的制备及分配系数测定
张茹, 元琳琳, 孙凯玥, 王珊, 耿丽娜, 张建军
2020, 36(6): 1905090-0  doi: 10.3866/PKU.WHXB201905090
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采用薄膜旋转蒸发-超声法制备了纳米白藜芦醇脂质体(RES-Lip),并用透射电子显微镜(TEM)和动态光散射技术(DLS)对产物进行表征;测定了膜材比(卵磷脂与胆固醇质量比mPC : mChol = 5 : 1,8 : 1,10 : 1,12 : 1)和药脂比(药物与卵磷脂质量比mRES : mPC = 1 : 25,1 : 40,1 : 50,1 : 60)对RES-Lip脂质体-水分配系数(Plip/w)的影响,以及油-水分配系数(lgPo/w)和脂质体-水分配系数(lgPlip/w)随pH值的变化趋势,计算了RES-Lip中药物与磷脂双分子膜之间的吉布斯自由能。结果表明,实验中所制备的RES-Lip呈球形囊泡结构,粒径约为100 nm;当膜材比和药脂比分别为10 : 1和1 : 40时,lgPlip/w最大,说明此时RES与磷脂膜间的综合作用力最大;RES-Lip的分配系数(lgPo/w和lgPlip/w)随体系pH的变化趋势相同,说明RES与磷脂膜的作用力中以疏水作用为主,氢键、静电作用为辅;RES-Lip中RES与脂质体膜之间的吉布斯自由能为−17.07 kJ∙mol−1
SDS对SB3-12胶束表面电荷密度的调控作用及对药物增溶的影响
邢肇碧, 过治军, 张雨微, 刘君玲, 王玉洁, 白光月
2020, 36(6): 1906006-0  doi: 10.3866/PKU.WHXB201906006
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两性离子甜菜碱表面活性剂(SB3-12)胶束具有较好的生物相容性,由于相反电荷的极性头之间具有静电中和作用,胶束表面具有小的负电荷密度。当加入阴离子的十二烷基硫酸钠(SDS)以后,负离子SD与SB3-12胶束极性区内层季铵正电荷的静电中和作用,能连续地调节胶束表面磺酸基的负电荷密度,这有利于对药物分子的选择性增溶和调节在生理条件下的药物的输送。等温滴定量热(ITC)研究发现SB3-12和SDS有强的协同效应,混合临界胶束浓度(CMC)和胶束化焓明显降低,并得到两者协同效应的弱静电作用机理。当模型药物分子芦丁(Rutin)与SB3-12/SDS混合胶束作用时,芦丁7位羟基的氢解离后的阴离子与SDS共同作用于SB3-12形成混合胶束。UV-Vis吸收光谱和1H NMR谱研究发现,在SB3-12胶束中,芦丁分子的A环位于季铵阳离子附近,B环位于两个相反电荷之间的弱极性区域。在SDS胶束中,B环位于栅栏层,而A环和二糖暴露于水相侧。在混合胶束中,随着SDS摩尔分数增加,对A环的静电吸引变弱。离子表面活性剂对两性离子表面活性剂胶束表面电荷密度的调节作用,本质上是对胶束极性区域的物理及化学性质的微调,进而实现对药物的可控增溶。
亮点
Cr2O3/硝化棉的相容性及热分解机理研究
韩布兴
2020, 36(6): 1907020-0  doi: 10.3866/PKU.WHXB201907020
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Flash DSC跨界表征材料的热导率
张建军
2020, 36(6): 1907048-0  doi: 10.3866/PKU.WHXB201907048
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前言
热分析动力学与热动力学
王键吉, 张建军
2020, 36(6): 1909020-0  doi: 10.3866/PKU.WHXB201909020
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论文
硫化镉反蛋白石光子晶体制备及光解水制氢
张若兰, 王超, 陈浩, 赵恒, 刘婧, 李昱, 苏宝连
2020, 36(3): 1803014-0  doi: 10.3866/PKU.WHXB201803014
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对硫化镉反蛋白石结构光子晶体薄膜进行了可控合成,用巯基乙酸修饰的纳米晶和P(St-MMA-SPMAP)高分子小球共组装,成功地构筑了反蛋白石结构并用于可见光光解水产氢。结果表明,在可见光(λ ≥ 420 nm)照射下,CdS-310反蛋白石结构薄膜的光解水产氢性能比硫化镉纳米颗粒提高了一倍。这主要是因为等级孔结构反蛋白石光子晶体特性对催化剂的光催化性能的提升:首先,反蛋白石的周期性结构增加了光子在材料中的传播,提高了催化剂对太阳光的利用率;同时,大孔孔壁是由纳米颗粒堆积而成的,在反应中提供了更多的反应活性位点;此外,孔结构有利于物质的传输和分子的吸附。
Article
Fabrication of Z-Scheme Heterojunction of SiC/Pt/Cds Nanorod for Efficient Photocatalytic H2 Evolution
Dan Cao, Hua An, Xiaoqing Yan, Yuxin Zhao, Guidong Yang, Hui Mei
2020, 36(3): 1901051-0  doi: 10.3866/PKU.WHXB201901051
[摘要]  (41) [HTML全文] (41) [PDF 2562KB] (41)
摘要:
In this study, a novel silicon carbide/platinum/cadmium sulfide (SiC/Pt/CdS) Z-scheme heterojunction nanorod is constructed using a simple chemical reduction-assisted hydrothermal method, in which Pt nanoparticles are anchored at the interface of SiC nanorods and CdS nanoparticles to induce an electron-hole pair transfer along the Z-scheme transport path. Multiple characterization techniques are used to analyze the structure, morphology, and properties of these materials. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the SiC/Pt/CdS materials with good crystal structure are successfully synthesized. Transmission electron microscopy reveals that Pt nanoparticles grow between the interfaces of SiC nanorods and CdS nanoparticles. UV-Vis diffuse reflectance spectroscopy shows that the as-prepared Z-scheme heterojunction samples have a wider light absorption range in comparison with pristine CdS materials. Photoluminescence spectroscopy and the transient photocurrent response further demonstrate that the SiC/Pt/CdS nanorod sample with an optimal molar ratio possesses the highest electron-hole pair separation efficiency. The loading amount of CdS on the surface of SiC/Pt nanorods is effectively adjusted by controlling the molar ratio of SiC and CdS to achieve the optimal performance of the SiC/Pt/CdS nanorod photocatalysts. The optimal H2 evolution capacity is achieved at SiC : CdS = 5 : 1 (molar ratio) and the maximum H2 evolution rate reaches a high value of 122.3 µmol·h−1. In addition, scanning electron microscopy, XRD, and XPS analyses show that the morphology and crystal structure of the SiC/Pt/CdS photocatalyst remain unchanged after three cycles of activity testing, indicating that the SiC/Pt/CdS nanocomposite has a stable structure for H2 evolution under visible light. To prove the Z-scheme transfer mechanism of electron-hole pairs, selective photo-deposition technology is used to simultaneously carry out the photo-reduction deposition of Au nanoparticles and photo-oxidation deposition of Mn3O4 nanoparticles in the photoreaction. The experimental results indicate that during photocatalysis, the electrons in the conduction band of CdS participate mainly in the reduction reaction, and the holes in the valence band of SiC are more likely to undergo the oxidation reaction. The electrons in the conduction band of SiC combine with the holes in the valence band of CdS to form a Z-scheme transport path. Therefore, a possible Z-scheme charge migration path in SiC/Pt/CdS nanorods during photocatalytic H2 production is proposed to explain the enhancement in the activity. This study provides a new strategy for synthesizing a Z-scheme photocatalytic system based on SiC nanorods. Based on the characterization results, it is determined that SiC/Pt/CdS nanocomposites are highly efficient, inexpensive, easy to prepare, and are stable structures for H2 evolution under visible light with outstanding commercial application prospects.
Cu2+ Modified g-C3N4 Photocatalysts for Visible Light Photocatalytic Properties
Xiaowei Li, Bin Wang, Wenxuan Yin, Jun Di, Jiexiang Xia, Wenshuai Zhu, Huaming Li
2020, 36(3): 1902001-0  doi: 10.3866/PKU.WHXB201902001
[摘要]  (41) [HTML全文] (41) [PDF 1870KB] (41)
摘要:
Photocatalytic technology can effectively solve the problem of increasingly serious water pollution, the core of which is the design and synthesis of highly efficient photocatalytic materials. Semiconductor photocatalysts are currently the most widely used photocatalysts. Among these is graphitic carbon nitride (g-C3N4), which has great potential in environment management and the development of new energy owing to its low cost, easy availability, unique band structure, and good thermal stability. However, the photocatalytic activity of g-C3N4 remains low because of problems such as wide bandgap, weakly absorb visible light, and the high recombination rate of photogenerated carriers. Among various modification strategies, doping modification is an effective and simple method used to improve the photocatalytic performance of materials. In this work, Cu/g-C3N4 photocatalysts were successfully prepared by incorporating Cu2+ into g-C3N4 to further optimize photocatalytic performance. At the same time, the structure, morphology, and optical and photoelectric properties of Cu/g-C3N4 photocatalysts were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy (DRS), and photoelectric tests. XRD and XPS were used to ensure that the prepared photocatalysts were Cu/g-C3N4 and the valence state of Cu was in the form of Cu2+. Under visible light irradiation, the photocatalytic activity of Cu/g-C3N4 and pure g-C3N4 photocatalysts were investigated in terms of the degradation of RhB and CIP by comparing the amount of introduced copper ions. The experimental results showed that the degradation ability of Cu/g-C3N4 photocatalysts was stronger than that of pure g-C3N4. The N2 adsorption-desorption isotherms of g-C3N4 and Cu/g-C3N4 demonstrated that the introduction of copper had little effect on the microstructure of g-C3N4. The small difference in specific surface area indicates that the enhanced photocatalytic activity may be attributed to the effective separation of photogenerated carriers. Therefore, the enhanced photocatalytic degradation of RhB and CIP over Cu/g-C3N4 may be due to the reduction of carrier recombination rate by copper. The photoelectric test showed that the incorporation of Cu2+ into g-C3N4 could reduce the electron-hole recombination rate of g-C3N4 and accelerate the separation of electron-hole pairs, thus enhancing the photocatalytic activity of Cu/g-C3N4. Free radical trapping experiments and electron spin resonance indicated that the synergistic effect of superoxide radicals (O2•−), hydroxyl radicals (•OH) and holes could increase the photocatalytic activity of Cu/g-C3N4 materials.
Controlling Self-Assembly of 3D In2O3 Nanostructures for Boosting Photocatalytic Hydrogen Production
Ruijie Chen, Di Li, Zhenyuan Fang, Yuanyong Huang, Bifu Luo, Weidong Shi
2020, 36(3): 1903047-0  doi: 10.3866/PKU.WHXB201903047
[摘要]  (39) [HTML全文] (39) [PDF 953KB] (39)
摘要:
Exploring economical and efficient photocatalysts for hydrogen production is of great significance for alleviating the energy and environmental crisis. In this study, 3D In2O3 nanostructures with appropriate self-assembly degrees were obtained using a facile hydrothermal strategy. To study the significance of 3D In2O3 nanostructures with appropriate self-assembly degrees in photocatalytic hydrogen production, the photocatalytic performances of samples were evaluated based on the amount of hydrogen gas release under visible-light irradiation (λ > 400 nm) and simulated solar light illumination. Interestingly, the 3D In2O3-150 nanostructured photocatalyst (hydrothermal temperature was 150 ℃, denoted as In2O3-150) exhibited extremely superior photocatalytic hydrogen evolution activity, which may have been caused by their unique structure to improve light reflection and gas evolution. The special structure can enhance light harvesting and induce more carriers to participate in photocatalytic hydrogen production. Despite possessing similar 3D nanostructures, the In2O3-180 photocatalyst exhibited poor photocatalytic activity. This may have been caused by the high self-assembly degree, which can hinder light irradiation and isolate a portion of the water. In addition, the 3D nanostructures could effectively make uniform the carrier migration direction, which is from the interior to the rod end. However, the direction of carrier migration of the In2O3-110 photocatalyst could transfer in various directions, whereas the In2O3-130 photocatalyst could transfer to both ends of the rod. This might cause partial migration to counteract each other. The compact cluster rod-like structure of In2O3-180 might prevent the light from exciting the carrier effectively. Through a photocatalytic recycling test, the 3D In2O3-150 nanostructured photocatalyst exhibited outstanding photochemical stability. This work highlights the importance of controlling the self-assembly degree of 3D In2O3 nanostructures and explores the performances of 3D In2O3 nanostructured photocatalysts in hydrogen production under visible light and simulated solar light.
Rod-Shaped Metal Organic Framework Structured PCN-222(Cu)/TiO2 Composites for Efficient Photocatalytic CO2 Reduction
Shuhua Duan, Shufeng Wu, Lei Wang, Houde She, Jingwei Huang, Qizhao Wang
2020, 36(3): 1905086-0  doi: 10.3866/PKU.WHXB201905086
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摘要:
The photocatalytic reduction of CO2 has attracted considerable attention owing to the dual suppression of environmental pollution and energy shortage. The technology uses solar energy to convert carbon dioxide into hydrocarbon fuel, which is of great significance for achieving the carbon cycle. The development of low-cost photocatalytic materials is critical to achieving efficient solar energy to fuels conversion. One of the most commonly employed photocatalysts is TiO2. However, it suffers from broad band gap as well as the recombination of photo-excited holes and electron. Hence, in this work, we report the photochemical reduction of CO2 using rod-like PCN-222(Cu)/TiO2 composites as photocatalyst through a simple hydrothermal method, in which TiO2 nanoparticles are anchored at the interface of the SiC rod PCN-222(Cu). Multiple characterization techniques were used to analyze the structure, morphology, and properties of the PCN-222(Cu)/TiO2 composite. A series of characterizations including X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy, photo-electrochemical, and photoluminescence (PL) confirm the successful preparation of PCN-222(Cu)/TiO2 composites. SEM reveals that the TiO2 nanoparticles are uniformly distributed on the surface of the rod-shaped PCN-222(Cu)/TiO2. XRD results show that PCN-222(Cu) and PCN-222(Cu)/TiO2 composite photocatalysts with good crystal structure were successfully synthesized. According to the DRS results, the prepared PCN-222(Cu)/TiO2 composite samples exhibit characteristic absorption peaks of metalloporphyrins in the visible region. PL spectroscopy, transient photocurrent response, and electrochemical impedance spectroscopy further confirm that the rod-like PCN-222(Cu)/TiO2 samples have high electron-hole pair separation efficiency. By controlling the mass ratio of PCN-222(Cu) and TiO2, the photocatalytic CO2 reduction performance test shows that the 10% PCN-222(Cu)/TiO2 composite achieves optimal catalytic performance, yielding 13.24 μmol·g−1·h−1 CO and 1.73 μmol·g−1·h−1 CH4, respectively. All the rod-like PCN-222(Cu)/TiO2 composites exhibit better photocatalytic CO2 activity than that of TiO2 nanoparticles or PCN-222(Cu) under the illumination of xenon lamps, which is attributed to charge transport and electron-hole separation capabilities. After three test cycles, the catalytic activity of PCN-222(Cu)/TiO2 photocatalyst was virtually unchanged. The reduction yield of the catalyst increased for 8 h under continuous illumination, indicating that PCN-222(Cu)/TiO2 composites have acceptable stability. The estimation of the band gap curve and the Mote-Schottky curve test show that the lowest unoccupied molecular orbital position of PCN-222(Cu) is more negative than the TiO2 of the conduction band; hence, a possible photocatalytic reaction mechanism of the PCN-222(Cu)/TiO2 composite is proposed. This study provides a new strategy for the integration of metal-organic frameworks and oxide semiconductors to construct efficient photocatalytic systems.
综述
光催化全解水助催化剂的设计与构建
孙尚聪, 张旭雅, 刘显龙, 潘伦, 张香文, 邹吉军
2020, 36(3): 1905007-0  doi: 10.3866/PKU.WHXB201905007
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摘要:
能源和环境危机是当今社会面临的两大关键课题,利用太阳光驱动化学反应、将太阳能转化为化学能是解决上述问题的重要措施。通过光催化分解水是直接利用太阳能生产氢燃料的有效策略。光催化水分解过程可以分为三个基元步骤:光吸收、电荷分离与迁移、以及表面氧化还原反应。助催化剂可有效提高电荷分离效率、提供反应活性位点并抑制催化剂光腐蚀的发生,进而提高水分解效率。助催化剂也可以通过活化水分子以提高表面氧化还原动力学,进而提升整体光催化反应的太阳能转换效率。本文综述了助催化剂在光催化反应中的重要作用以及目前常用的助催化剂类型,详细说明了在光催化全解水过程中双助催化剂体系的构建及作用机理,并根据限制全解水的关键因素提出了新型助催化剂的设计策略。
基于立方烷结构的分子催化剂在光催化水氧化中的研究进展
孙万军, 林军奇, 梁向明, 杨峻懿, 马宝春, 丁勇
2020, 36(3): 1905025-0  doi: 10.3866/PKU.WHXB201905025
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摘要:
随着化石燃料大量使用带来的气候变化和环境污染问题日趋严重,寻找清洁高效的可再生能源用做传统化石燃料的替代品,已经成为当前的研究热点。光驱动的水分解反应被认为是太阳能制氢的可行途径。水的全分解包括两个半反应-水的氧化和质子还原。其中水的氧化反应是一个涉及四个电子和四个质子转移的复杂过程,需要很高的活化能,被认为是全分解水反应的瓶颈步骤。因此,开发高效、稳定、廉价丰产的水氧化催化剂是人工光合作用突破的关键因素。立方烷具有类似自然界光合作用酶光系统Ⅱ(PSⅡ)活性中心Mn4CaO5簇的结构,世界各国的科学家受自然界光合作用的启发,开发出了许多基于过渡金属的立方烷结构的催化剂,常见的有锰、钴和铜等立方烷催化剂。本文简要地综述了近年来立方烷分子催化剂在光催化水氧化中的研究进展。首先介绍了立方烷基光催化水氧化反应历程,继而详细介绍了基于有机配体的立方烷配合物和全无机的多金属氧酸盐立方烷水氧化催化剂,其次是半导体(BiVO4或聚合的氮化碳(PCN))为捕光材料复合立方烷分子催化剂的水氧化体系最新研究进展。最后总结并展望了该领域所面临的挑战及其前景。
光电催化二氧化碳还原研究进展
周威, 郭君康, 申升, 潘金波, 唐杰, 陈浪, 区泽堂, 尹双凤
2020, 36(3): 1906048-0  doi: 10.3866/PKU.WHXB201906048
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摘要:
CO2是最常见的化合物,作为潜在的碳一资源,可用于制备多种高附加值的化学品,如一氧化碳、甲烷、甲醇、甲酸等。传统的热催化转化CO2方法能耗高,反应条件苛刻。因此,如何在温和条件下高效地将CO2转化成高附加值的化学品,一直以来是催化领域的研究热点和难点之一。光催化技术反应条件温和、绿色环保。然而,纯光催化反应普遍存在太阳能利用效率有限,光生载流子分离效率低等问题。针对上述问题,在光催化的基础上引入电催化,可以提高载流子的分离效率,在较低的过电位下,实现多电子、质子向CO2转移,从而提高催化反应效率。总之,光电催化技术可以结合光催化和电催化的优势,提高CO2催化还原反应效率,为清洁、绿色利用CO2提供了一种新方法。本文依据光电催化CO2还原反应基本过程,从光吸收、载流子分离和界面反应等三个角度综述了光电催化反应的基本强化策略,并对未来可能的研究方向进行了展望。
光催化甲烷转化研究进展
许振民, 卞振锋
2020, 36(3): 1907013-0  doi: 10.3866/PKU.WHXB201907013
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摘要:
甲烷催化转化为高附加值产物、实现甲烷高效利用,具有重要的研究意义及工业应用价值。长期以来,如何在较温和的条件下将甲烷转化为其它更有价值的有机衍生物,如醇、芳烃、长链烷烃和烯烃等,是催化、化学及化工领域的热点和难点课题之一。光催化反应由光能激发产生光生电子和空穴,参与到甲烷C―H键活化和自由基形成,这为低温甲烷转化提供新的途径,本文主要围绕甲烷氧化和偶联反应,总结了近年来光催化研究进展,并对如何进一步提高光催化性能提出展望。
Review
Recent Progress in Photocatalytic Hydrogen Evolution
Jinbo Pan, Sheng Shen, Wei Zhou, Jie Tang, Hongzhi Ding, Jinbo Wang, Lang Chen, Chak-Tong Au, Shuang-Feng Yin
2020, 36(3): 1905068-0  doi: 10.3866/PKU.WHXB201905068
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摘要:
The photocatalytic hydrogen evolution reaction (PHER) has gained much attention as a promising strategy for the generation of clean energy. As opposed to conventional hydrogen evolution strategies (steam methane reforming, electrocatalytic hydrogen evolution, etc.), the PHER is an environmentally friendly and sustainable method for converting solar energy into H2 energy. However, the PHER remains unsuitable for industrial applications because of efficiency losses in three critical steps: light absorption, carrier separation, and surface reaction. In the past four decades, the processes responsible for these efficiency losses have been extensively studied. First, light absorption is the principal factor deciding the performance of most photocatalysts, and it is closely related to band-gap structure of photocatalysts. However, most of the existing photocatalysts have a wide bandgap, indicating a narrow light absorption range, which restricts the photocatalytic efficiency. Therefore, searching for novel semiconductors with a narrow bandgap and broadening the light absorption range of known photocatalysts is an important research direction. Second, only the photogenerated electrons and holes that migrate to the photocatalyst surface can participate in the reaction with H2O, whereas most of the photogenerated electrons and holes readily recombine with one another in the bulk phase of the photocatalysts. Hence, tremendous effort has been undertaken to shorten the charge transfer distance and enhance the electric conductivity of photocatalysts for improving the separation and transfer efficiency of photogenerated carriers. Third, the surface redox reaction is also an important process. Because water oxidation is a four-electron process, sluggish O2 evolution is the bottleneck in photocatalytic water splitting. The unreacted holes can easily recombine with electrons. Sacrificial agents are widely used in most catalytic systems to suppress charge carrier recombination by scavenging the photogenerated holes. Moreover, the low H2 evolution efficiency of most photocatalysts has encouraged researchers to introduce highly active sites on the photocatalyst surface. Based on the abovementioned three steps, multifarious strategies have been applied to modulate the physicochemical properties of semiconductor photocatalysts with the aim of improving the light absorption efficiency, suppressing carrier recombination, and accelerating the kinetics of surface reactions. The strategies include defect generation, localized surface plasmon resonance (LSPR), element doping, heterojunction fabrication, and cocatalyst loading. An in-depth study of these strategies provides guidance for the design of efficient photocatalysts. In this review, we focus on the mechanism and application of these strategies for optimizing light absorption, carrier separation and transport, and surface reactions. Furthermore, we provide a critical view on the promising trends toward the construction of advanced catalysts for H2 evolution.
Progress and Prospects of Non-Metal Doped Graphitic Carbon Nitride for Improved Photocatalytic Performances
Yiqing Wang, Shaohua Shen
2020, 36(3): 1905080-0  doi: 10.3866/PKU.WHXB201905080
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摘要:
Since Fujishima and Honda demonstrated the photoelectrochemical water splitting on TiO2 photoanode and Pt counter electrode, photocatalysis has been considered as one of the most promising technologies for solving both the problems of environmental pollution and energy shortage. This process can effectively use solar energy, the most abundant energy resource on the earth, to drive various catalytic reactions, such as water splitting, CO2 reduction, organic pollutant degradation, and organic synthesis, for energy generation and environmental purification. Except for the various metal-based semiconductors, such as metal oxides, metal sulfides, and metal oxynitrides, developed for photocatalysis, graphitic carbon nitride (g-C3N4) has attracted significant attention in the recent years because of its earth abundancy, non-toxicity, good stability, and relatively narrow band gap (2.7 eV) for visible light response. However, g-C3N4 suffers from insufficient absorption of visible light in the solar spectrum and rapid recombination of photogenerated electrons and holes, thus resulting in low photocatalytic activity. Until now, various strategies have been developed to enhance the photocatalytic activity of g-C3N4, including element doping, nanostructure and heterostructure design, and co-catalyst decoration. Among these methods, element doping has been found to be very effective for adjusting the unique electronic and molecular structures of g-C3N4, which could significantly expand the range of photoresponse under visible light and improve the charge separation. Especially, non-metal doping has been well investigated frequently to improve the photocatalytic activity of g-C3N4. The non-metal dopants commonly used for the doping of g-C3N4 include oxygen (O), phosphorus (P), sulfur (S), boron (B), and halogen (F, Cl, Br, I) and also carbon (C) and nitrogen (N) (for self-doping), as they are easily accessible and can be introduced into the g-C3N4 framework through different physical and chemical synthetic methods. In this review article, the structural and optical properties of g-C3N4 is introduced first, followed by a brief introduction to the modification of g-C3N4 as photocatalysts. Then, the progress in the non-metal doped g-C3N4 with improved photocatalytic activity is reviewed in detail, with the photocatalytic mechanisms presented for easy understanding of the fundamentals of photocatalysis and for guiding in the design of novel g-C3N4 photocatalysts. Finally, the prospects of the modification of g-C3N4 for further advances in photocatalysis is presented.
亮点
硼掺杂与氮缺陷协同增强石墨相氮化碳光催化产氧性能
杨金龙
2020, 36(3): 1909054-0  doi: 10.3866/PKU.WHXB201909054
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摘要:
合理设计与组装制备高性能杂化钒酸铋基光阳极
尹双凤
2020, 36(3): 1910034-0  doi: 10.3866/PKU.WHXB201910034
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摘要:
具有可调谐自旋态的Mn-N-C结构助力太阳能驱动全解水
韩布兴
2020, 36(3): 1911007-0  doi: 10.3866/PKU.WHXB201911007
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摘要:
前言
魅力光催化剂
尹双凤, 区泽堂, 李华明
2020, 36(3): 1910023-0  doi: 10.3866/PKU.WHXB201910023
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摘要:

编委会

发布时间:


《物理化学学报》第4届编委会

(按拼音排序)

名誉主编

唐有祺

北京大学

顾问编委

包信和

中国科学院大连化学物理研究所

段雪

北京化工大学

付贤智

福州大学

侯建国

中国科学技术大学

黄维

南京工业大学

LIEBER Charles M.

Harvard University

田中群

厦门大学

万立骏

中国科学院化学研究所

吴云东

北京大学

谢晓亮

Harvard University, 北京大学

杨伟涛

 Duke University

姚建年

中国科学院化学研究所

赵新生

北京大学

主编

刘忠范

北京大学

副主编

韩布兴

中国科学院化学研究所

刘鸣华

国家纳米科学中心

申文杰

中国科学院大连化学物理研究所

吴凯

北京大学

杨金龙

中国科学技术大学

庄林

武汉大学

迟力峰

苏州大学

编委

曹勇

复旦大学

陈经广

University of Delaware

陈军

南开大学

崔屹

Stanford University

邓风

中国科学院武汉物理与数学研究所

邓友全

中国科学院兰州化学物理研究所

樊卫斌

中国科学院山西煤炭化学研究所

房喻

陕西师范大学

付红兵

中国科学院化学研究所

傅强

中国科学院大连化学物理研究所

高毅勤

北京大学

郭林

北京航空航天大学

郝京诚

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南京大学

金荣超

Carnegie Mellon University

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北京大学

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McGill University

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厦门大学

刘海超

北京大学

刘洪来

华东理工大学

刘述斌

University of North Carolina

刘义

武汉大学

刘志敏

中国科学院化学研究所

罗小民

中国科学院上海药物研究所

马晶

南京大学

孟庆波

中国科学院物理研究所

邵翔

中国科学技术大学

孙俊奇

吉林大学

谭蔚泓

湖南大学

唐智勇

国家纳米科学中心

王键吉

河南师范大学

王鹏

中国科学院长春应用化学研究所

王心晨

福州大学

王永锋

北京大学

魏子栋

重庆大学

翁羽翔

中国科学院物理研究所

吴鹏

华东师范大学

夏永姚

复旦大学

许国勤

National University of Singapore

杨俊林

国家自然科学基金委员会

余家国

武汉理工大学

尉志武

清华大学

占肖卫

北京大学

张东辉

中国科学院大连化学物理研究所

张浩力

兰州大学

张锦

北京大学

章俊良

上海交通大学

周永贵

中国科学院大连化学物理研究所

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发布时间: 2018-05-02


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发布日期:2009-06-24 浏览: