石墨炔在光催化及光电催化中的应用

长久有效地利用太阳能,是可持续发展永恒的主题。石墨炔是碳同素异形体的一颗新星,仅由sp和sp²杂化的碳原子组成,具有巨大的共轭网络和延展的二维多孔结构。独特的拓扑结构使石墨炔显示出与众不同的半导体和光学特性,表现出优异的电荷迁移率和本征带隙。因此,在太阳能的转换和利用方面具有广阔的应用前景。然而,作为一个新出现的碳同素异形体家族,石墨炔类碳材料用作光催化剂的真正潜能有待进一步探索。本文简要介绍了几种石墨炔的合成、形貌及表征方法,系统阐述了近年来石墨炔基光催化剂在污水处理、裂解水、CO₂还原以及光电催化等领域的应用及机理研究。提出了目前研究中存在的一些问题,并对未来的发展及研究方向进行了展望。     

石墨炔与锡烯层状体系的形变势和电声耦合及载流子传输理论研究

我们对sp + sp²杂化的碳同素异形体—石墨炔,以及锡烯等层状体系的电子结构、形变势、电声耦合和电荷输运性质进行了回顾。有些二维石墨炔具有类似石墨烯的狄拉克锥,同时石墨炔电子结构可通过将其沿不同方向裁剪成不同宽度一维纳米带来调节。采用玻尔兹曼输运方程和形变势近似,结合第一性原理计算,我们预测石墨炔电荷载流子室温迁移率可达10⁴–10⁵ cm²·V^-1·s^-1,尤其6, 6, 12-石墨炔,因有两个狄拉克锥及比石墨烯弱的电声耦合,其室温迁移率甚至能高于石墨烯。因此具有独特电子结构和高迁移率的石墨炔能成为继石墨烯之后未来的纳米电子器件材料。此外我们着重分析了形变势方法的适用性：密度泛函微扰理论和瓦尼尔插值技术能精确计算任意波矢和模式的声子对载流子散射,该方法在石墨烯和石墨炔上的运用表明二维平面碳材料中对载流子输运起主导作用的是长波长纵声学声子散射,因而形变势方法是适用的;但通过对锡烯等二维非平面buckling结构的材料声子散射和迁移率的计算,发现此类不具备σ_h对称性的材料有较强的面外声子散射和横声学声子谷间散射,使得常用的形变势失效。     

X-射线衍射方法对几种乱层碳结构的研究

本文用X-射线衍射峰宽法对易石碳进行了研究,对其a、c轴方向原子排布的缺陷和畸变分别用两套平行的参数(L_a、σ_a和L_c、σ_c)、d₀₀₂、L_t(112)进行了表述,比较全面地对其结构作了评价。对高石墨化度碳,发现其三维结构规整性主要依赖于c轴向晶格畸变,低石墨化度碳随着热处理温度的升高,其微观结构呈现不同的变化特征,有的发生了畸变分布型式的转变。总体上,结构的变化趋于三维晶态石墨结构。     

石墨二炔及其电子转移增强特性

石墨二炔是由sp和sp²杂化的碳原子构成的新的碳同素异形体。由于石墨二炔具有独特的拓扑结构和电子结构、较高的电荷迁移率及优异的电子传输性能,使其与其他材料相互作用,可表现出独特的电子转移增强特性。本文基于石墨二炔的电子转移增强特性,概述了石墨二炔及其电子转移增强特性的最新研究进展,包括金属氧化物/石墨二炔、金属纳米颗粒/石墨二炔、聚合物/石墨二炔以及染料分子/石墨二炔等多种石墨二炔基材料。本文从理论和实验研究两个方面详细阐述了石墨二炔的电子转移增强特性、石墨二炔与不同材料的相互作用以及相关的应用。希望该综述能对石墨炔化学的发展起到一定的积极作用。     

含异原子石墨炔基电极材料的研究进展

碳材料具有价格低廉、 易制备、 环境友好、 导电性高、 比表面积大以及适合离子存储和迁移等优点, 已成为目前应用于电化学储能器件电极的重要材料之一. 石墨炔(GDY)是一种新型的二维碳同素异形体, 由sp²碳杂化形式的苯环和sp碳杂化形式的炔键构成. 这种独特的化学结构一方面保持了碳材料良好的导电特性, 另一方面形成了新颖的离子传输通道, 为碳材料带来了不同的离子传输和存储特性. 与此同时, 由于石墨炔的空间结构可调性, 可以通过引入异原子微调石墨炔电子结构, 拓展石墨炔在电极材料领域的应用. 本文重点对近几年异原子杂化石墨炔基电极材料在锂离子电池、 钠离子电池、 金属硫电池、 电容器、 金属空气电池和电极保护等储能领域的研究工作进行总结, 并对未来石墨炔类材料在储能领域的发展进行了展望.     

催化裂解CH4或CO制碳纳米管结构性能的谱学表征

利用TEM、HRTEM、XRD、XPS和TPO等方法对CH₄或CO催化分解生成的碳纳米管结构和性能进行了表征.结果表明,所得产物是管径15～20nm的均匀碳纳米管.其XRD谱图与石墨的相近,但特征衍射峰稍宽化,表明其长程有序度较石墨的低.由CH₄制备的碳纳米管系由多层具有类石墨片状结构的同心、等径及中空圆锥形面叠合而成,类石墨层面取向与管轴倾斜;而由CO制备的碳纳米管系由多层具有类石墨片状结构的圆柱形面围叠而成,类石墨层面取向与管轴平行.碳纳米管中C_1s的电子结合能比石墨的下降约0.5eV.TPO试验结果显示所制备的两种产物中无定形碳含量都很低,其整体结构石墨化程度较高;由CH₄制得的碳纳米管与O₂反应的起燃温度比由CO制得的约高100K.     

纳米Fe(OH)3为模板的三维石墨烯类多孔碳的制备及其催化氧还原性能研究

以煤焦油沥青为碳源,纳米Fe(OH)₃为模板制备了一种三维石墨烯类多孔碳材料,通过测试氧还原性能,确定了最佳制备工艺为：反应物煤沥青,纳米Fe(OH)₃,KOH的质量配比为6:8:4,热解温度为800 ℃. 扫描电镜（SEM）测试结果表明,制得的产品具有明显的孔结构且分布均匀. 透射电镜（TEM）测试结果进一步表明,产品具有泡沫状的多孔结构,高分辨透射电子显微镜图像表明该产品具有多层的三维石墨烯结构. X射线衍射（XRD）数据表明,在29^o位置出现的衍射峰是多层石墨烯结构,42^o位置的衍射峰表明,产品具有一定程度的石墨化. 由拉曼光谱结果计算I_G与I_2D的比值表明产品为多层石墨烯结构. X射线光电子能谱分析（XPS）检测到的C元素含量约为88.7%,主要包含C-C键,图谱中未发现铁元素的存在,证明纳米Fe(OH)₃模板已被洗净. 根据比表面积测定（BET）可知,多孔碳的比表面积为2040 m²•g^-1,孔径集中分布在10~400 nm,这与TEM测试得到的结果一致. 在0.1 mol•L^-1 KOH中进行催化氧还原性能测试,起始还原电位为0 V (vs. Hg/HgO),电子转移数为3.58。测试结果表明,制得的三维石墨烯类多孔碳具有良好的催化氧还原性能.     

还原氧化石墨烯封装核壳多孔Fe3O4锂离子电池阳极材料

首先,将葡萄糖和尿素按1∶1的质量比进行混合,作为多孔造孔剂,以水热法和煅烧法制备多孔结构的前驱体Fe₂O₃。随后,通过碳热还原的方法在制备碳包覆核壳结构的同时将Fe₂O₃还原成Fe₃O₄。最后,通过溶剂热法使用还原氧化石墨烯(rGO)对核壳多孔Fe₃O₄(CP-Fe₃O₄@C)进行封装,形成三维层状复合材料,记为rGO-CP-Fe₃O₄@C。具有三维网络传输结构的rGO-CP-Fe₃O₄@C在0.3 A·g^-1的电流密度下循环200圈之后的比容量为839 mAh·g^-1。值得关注的是,rGO-CP-Fe₃O₄@C在6 A·g^-1的大电流密度下充放电的比容量能够达到165 m...     

可见光驱动改性氮化碳无牺牲剂光催化析氢（英文）

载铂石墨氮化碳(g-C₃N₄)是一种较好的可见光下催化析氢光催化剂.但催化水裂解需要牺牲电子供体,如三乙醇胺等.目前,无牺牲剂条件下g-C₃N₄的催化析氢仍是一个挑战.本文通过尿素热处理制备了氮化碳纳米片(NS-C₃N₄),并研究了其在可见光(λ>400 nm)下利用可逆电子给体无牺牲剂条件下析氢的光催化活性.在含有I^-, Fe²⁺或[Fe(CN)₆]^4-的水溶液中,负载铂的NS-C₃N₄上无H₂产生,用CrO_x改性Pt/NS-C₃N₄的光催化剂上可观察到H₂的析出.透射电镜和能量色散X射线光谱结果表明,在NS-C₃N₄上形成了Pt/CrO_x核壳结...     

一锅法制备磁性石墨相氮化碳复合材料及其去除亚甲基蓝研究

为促使石墨相氮化碳循环使用、提高去除有机污染物能力,以高温煅烧制备的石墨相氮化碳和六水合三氯化铁作为原材料,利用一锅水热法合成磁性石墨相氮化碳。进一步利用正交试验L₁₆(4⁵)确定最适宜去除亚甲基蓝工艺条件：光照时间为20.0 h、pH为7.00、Fe₃O₄和g-C₃N₄之比为5:2、Fe₃O₄/g-C₃N₄复合材料投加量为0.20 g时,亚甲基蓝的去除效果可达95.73%。与对照实验相比,单一g-C₃N₄对亚甲基蓝的去除率为58.07%,远低于Fe₃O₄/g-C₃N₄复合材料的去除效果。Fe₃O₄/g-C₃N₄复合材料循环处理亚甲基蓝五次后,其去除率仍...     

Polymorphic phases of sp3-hybridized carbon under cold compression

It is well established that graphite can be transformed into superhard carbons under cold compression (Mao et al. Science 2003, 302, 425). However, structure of the superhard carbon is yet to be determined experimentally. We have performed an extensive structural search for the high-pressure crystalline phases of carbon using the evolutionary algorithm. Nine low-energy polymorphic structures of sp(3)-hybridized carbon result from the unbiased search. These new polymorphic carbon structures together with previously reported low-energy sp(3)-hybridized carbon structures (e.g., M-carbon, W-carbon, and Cco-C(8) or Z-carbon) can be classified into three groups on the basis of different ways of stacking two (or more) out of five (A-E) types of buckled graphene layers. Such a classification scheme points out a simple way to construct a variety of sp(3)-hybridized carbon allotropes via stacking buckled graphene layers in different combinations of the A-E types by design. Density-functional theory calculations indicate that, among the nine low-energy crystalline structures, seven are energetically more favorable than the previously reported most stable crystalline structure (i.e., Cco-C(8) or Z-carbon) in the pressure range 0-25 GPa. Moreover, several newly predicted polymorphic sp(3)-hybridized carbon structures possess elastic moduli and hardness close to those of the cubic diamond. In particular, Z-carbon-4 possesses the highest hardness (93.4) among all the low-energy sp(3)-hybridized carbon structures predicted today. The calculated electronic structures suggest that most polymorphic carbon structures are optically transparent. The simulated X-ray diffraction (XRD) spectra of a few polymorphic structures are in good agreement with the experimental spectrum, suggesting that samples from the cold-compressed graphite experiments may consist of multiple polymorphic phases of sp(3)-hybridized carbon.     

Micro-Raman and Tip-Enhanced Raman Spectroscopy of Carbon Allotropes

Summary: Raman spectroscopic data are obtained on various carbon allotropes like diamond, amorphous carbon, graphite, graphene and single wall carbon nanotubes by micro-Raman spectroscopy, tip-enhanced Raman spectroscopy and tip-enhanced Raman spectroscopy imaging, and the potentials of these techniques for advanced analysis of carbon structures are discussed. Depending on the local organisation of carbon the characteristic Raman bands can be found at different wavenumber positions, and e.g. quality or dimensions of structures of the samples quantitatively can be calculated. In particular tip-enhanced Raman spectroscopy allows the investigation of individual single wall carbon nanotubes and graphene sheets and imaging of e.g. local defects with nanometer lateral resolution. Raman spectra of all carbon allotropes are presented and discussed.     

2020 Roadmap on Carbon Materials for Energy Storage and Conversion

Carbon is a simple, stable and popular element with many allotropes. The carbon family members include carbon dots, carbon nanotubes, carbon fibers, graphene, graphite, graphdiyne and hard carbon, etc. They can be divided into different dimensions, and their structures can be open and porous. Moreover, it is very interesting to dope them with other elements (metal or non‐metal) or hybridize them with other materials to form composites. The elemental and structural characteristics offer us to explore their applications in energy, environment, bioscience, medicine, electronics and others. Among them, energy storage and conversion are extremely attractive, as advances in this area may improve our life quality and environment. Some energy devices will be included herein, such as lithium‐ion batteries, lithium sulfur batteries, sodium‐ion batteries, potassium‐ion batteries, dual ion batteries, electrochemical capacitors, and others. Additionally, carbon‐based electrocatalysts are also studied in hydrogen evolution reaction and carbon dioxide reduction reaction. However, there are still many challenges in the design and preparation of electrode and electrocatalytic materials. The research related to carbon materials for energy storage and conversion is extremely active, and this has motivated us to contribute with a roadmap on ‘Carbon Materials in Energy Storage and Conversion’.     

An experimental and theoretical study of the formation of nanostructures of self-assembled cyanuric acid through hydrogen bond networks on graphite

The self-assembly of cyanuric acid into ordered nanostructures on a crystalline substrate, highly ordered pyrolytic graphite (HOPG), has been investigated at low temperature under ultrahigh vacuum (UHV) conditions by means of scanning tunneling microscopy in conjunction with theoretical simulations. Many domains with different self-assembly patterns were observed. One such domain represents the formation of an open 2D rosette (cyclic) structure from the self-assembly process, the first observation of this type of structure for pure cyanuric acid on a graphite substrate. Each self-assembled domain exhibits characteristic superstructures formed through different hydrogen bond networks at low coverage and low deposition rate. Experimental observation of coexistent, two-dimensional crystalline structures with distinct hydrogen bond patterns is supported by energy minimizations and molecular dynamics calculations, which show multiple stable structures for this molecule when self-assembled on graphite.     

An analytical bond‐order potential for carbon

Carbon is the most widely studied material today because it exhibits special properties not seen in any other materials when in nano dimensions such as nanotube and graphene. Reduction of material defects created during synthesis has become critical to realize the full potential of carbon structures. Molecular dynamics (MD) simulations, in principle, allow defect formation mechanisms to be studied with high fidelity, and can, therefore, help guide experiments for defect reduction. Such MD simulations must satisfy a set of stringent requirements. First, they must employ an interatomic potential formalism that is transferable to a variety of carbon structures. Second, the potential needs to be appropriately parameterized to capture the property trends of important carbon structures, in particular, diamond, graphite, graphene, and nanotubes. Most importantly, the potential must predict the crystalline growth of the correct phases during direct MD simulations of synthesis to achieve a predictive simulation of defect formation. Because an unlimited number of structures not included in the potential parameterization are encountered, the literature carbon potentials are often not sufficient for growth simulations. We have developed an analytical bond order potential for carbon, and have made it available through the public MD simulation package LAMMPS. We demonstrate that our potential reasonably captures the property trends of important carbon phases. Stringent MD simulations convincingly show that our potential accounts not only for the crystalline growth of graphene, graphite, and carbon nanotubes but also for the transformation of graphite to diamond at high pressure. © 2015 Wiley Periodicals, Inc.     

Exploration of Carbon Allotropes with Four-membered Ring Structures on Quantum Chemical Potential Energy Surfaces

The existence of a new carbon allotrope family with four-membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism-, polymerized prism-, sheet-, tube-, and wavy-forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp³, sp², and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS-ADDF (s caled-h ypersphere-s earch combined with the a nharmonic d ownward d istortion f ollowing) method within the GRRM software program package. The height of the barriers indicates that the well is deep enough for the carbon structures to exist. This class of carbon allotropes is expected to be energy-reservoirs with extra energy of 100–350 kJ mol⁻¹ per one carbon atom. This article presents the structures, energies and reactivity of the carbon allotropes with four-membered ring structures as well as the background of the findings in the context of the global exploration of potential energy surfaces. © 2018 Wiley Periodicals, Inc.     

Carbon as a hard template for nano material catalysts

As one of the naturally abundant elements,carbon can present in different molecular structures(allotropes) and thus lead to various physical/chemical properties of carbon-based materials which have found wide applications in a variety of fields including electrochemistry,optical,adsorption and catalysis,etc.On the other hand,its different allotropes also endow carbon-based materials with various morphostructures,which have been recently explored to prepare oxides and zeolites/zeotypes with tailored structures.In this review,we mainly summarize the recent advances in using carbon materials as hard templates to synthesize structural materials.Specifically,we focus on the development in the synthetic strategies,such as endotemplating,exotemplating approaches and using carbon materials as chemical reagents for the synthesis of metal carbides or nitrides,with an emphasis laid on the control of morphostructure.Meanwhile,the applications of the obtained materials will be highlighted,especially,in the field of heterogeneous catalysis where enhanced performances have been achieved with the materials derived from carbon-templated methods.     

Aromaticity of carbon nanotubes

Carbon nanotubes are composed of cylindrical graphite sheets. Both nanotubes and graphite sheets are benzenoid derivatives composed of sp2 carbon atoms arranged in a hexagonal pattern. Therefore both systems are aromatic. The extent of the aromatic character of a molecule G (here benzenoids) can be explained in terms of the number of possible Kekulé structures in G. In this work the Kekulé structures in carbon nanotubes and the corresponding, rectangular, graphite-sheets the tubes might originate from, were enumerated. It was shown that (2,2), (3,3), and (4,4) carbon nanotubes are more aromatic than the corresponding, rectangular, planar structures. This explains why it might be more difficult to saturate nanotubes by addition reactions than the respective, "narrow", graphite sheets.     

A review of linear carbon chains

Linear carbon chains (LCCs) are a one-dimensional sp¹-hybridized allotrope of carbon. LCCs are extremely unstable: The longer the LCCs, the less stable the materials. Thus, it is a big challenge to synthesize long LCCs. Although the research on the short LCCs, e.g., polyynes, can be traced back to the 18^th, LCCs are still not well-known compared to other allotropes of carbon, e.g., fullerenes, carbon nanotubes and graphene. Therefore, introducing recent progress on LCCs is of great significance to draw more attention in the community of nanocarbons as well as nanomaterials in general. Theoretically, various excellent properties have been predicted. Experimentally, LCCs with different length in many kinds of forms have been successfully synthesized. In this review, we summarized recent studies of polyynic LCCs from both theoretical and experimental aspects. Also, perspectives are highlighted to point out the further investigations of the materials.     

Growth and characterization of ultrathin carbon films on electrodeposited Cu and Ni

Ultrathin carbon films were grown on different types of metallic substrates. Free‐standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH₄‐H₂ atmosphere. Obtained films were characterized by Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X‐rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer.