高比表面积石墨相氮化碳的制备及其光催化应用研究

石墨相氮化碳(g-C_3N_4)具有较好的物理化学稳定性、合适的能带结构和良好的可见光吸收性能,因而在光催化领域得到了广泛关注.作为异相催化剂,高比表面积可以提供较多的反应位点,增加反应物的接触,改善传质,从而促进催化性能的提升.本文综述了高比表面积g-C_3N_4的合成方法,介绍了两种增加g-C_3N_4比表面积的途径:(1)模板法制备多孔g-C_3N_4;(2)剥离法制备薄层g-C_3N_4纳米片.本文对高比面积g-C_3N_4的光催化应用也做了相应的介绍,并对g-C_3N_4的发展前景做了展望.     

Ag/α-Fe_2O_3/g-C_3N_4光催化降解罗丹明B

为了使g-C_3N_4光生电子和空穴容易复合,改善可见光响应低等缺点,该实验中采用溶胶-凝胶法将g-C_3N_4和α-Fe_2O_3进行复合形成g-C_3N_4异质结光催化剂,再采用光沉积法将Ag沉积在α-Fe_2O_3/g-C_3N_4上,构建Z型机制Ag/α-Fe_2O_3/g-C_3N_4催化剂材料,改善光生电荷的分离和传输能力及可见光响应,进一步增强其光催化降解污染物活性.最后通过XRD、FT-IR、XPS、SEM、TEM、紫外-可见漫反射光谱表征光催化剂结构和性能,并以染料罗丹明B溶液模拟废水,研究催化剂的降解动力学特性,通过活性基团捕获实验探究光催化机制.实验结果表明:(1)α-Fe_2O_3和g-C_3N_4复合形成异质结,当α-Fe_2O_3负载量为3%时,α-Fe_2O_3/g-C_3N_4光催化性能比纯的g-C_3N_4有了明显的提高,光催化性能降解罗丹明B达到79%.(2)Ag负载在α-Fe_2O_3/g-C_3N_4,当Ag的负载量为3%时,在可见光下3.5 h能够对罗丹明B达到95%以上的降解.(3)Ag/α-Fe_2O_3/g-C_3N_4增强的光催化剂性归因于α-Fe_2O_3和g-C_3N_4形成异质结以及Ag加入后形成Z型异质结结构.     

g-C_3N_4/RGO/AgI复合光催化剂的制备及性能研究

采用热聚合法制备石墨相氮化碳(g-C_3N_4),超声法制备还原氧化石墨烯/石墨相氮化碳(RGO/g-C_3N_4)二元复合光催化剂,再利用共沉淀法在二元复合光催化剂RGO/g-C_3N_4表面负载AgI,制得g-C_3N_4/RGO/AgI复合光催化剂。运用XRD、SEM、FT-IR、UV-Vis和FTIR等手段对材料进行表征,以罗丹明B(Rh B)作为目标物,用g-C_3N_4/RGO/AgI进行光催化降解实验。结果表明:光照210min后,g-C_3N_4/RGO/AgI光催化剂对Rh B的降解率为96. 52%。相同条件下,RGO/g-C_3N_4和gC_3N_4/AgI对RhB的降解率分别为58. 28%和73. 80%。g-C_3N_4/RGO/AgI复合光催化剂具有优异的光催化性能。     

环境光催化剂改性及应用研究进展

碳酸氧铋和石墨型碳化氮(g-C_3N_4)作为近年报道的新型光催化材料受到研究者的广泛关注,介绍了碳酸氧铋和g-C_3N_4两种光催化剂的制备及改性方法;归纳了非金属元素掺杂碳酸氧铋、碳酸氧铋复合光催化剂、金属表面沉积碳酸氧铋材料的研究;总结了近年g-C_3N_4形貌调控,g-C_3N_4复合光催化剂,g-C_3N_4掺杂改性的研究;阐述了碳酸氧铋和g-C_3N_4光催化材料的发展趋势。     

Yb_2O_3/g-C_3N_4复合光催化剂的制备及光催化性能研究

为了验证可见光下Yb_2O_3/g-C_3N_4光催化剂分别降解水体中的苯酚和盐酸四环素(TTCH)的光催化效果.本研究采用热解和超声混合方法制备Yb_2O_3/g-C_3N_4光催化剂,并用多种仪器进行性能表征.Yb_2O_3/g-C_3N_4在可见光下对20 mg/L苯酚和TTCH的降解率分别为80.83%和85.01%;Yb_2O_3/g-C_3N_4复合光催化剂的光催化性能明显提高,其降解苯酚的速率是g-C_3N_4的3.80倍,降解TTCH的速率g-C_3N_4的6.57倍.结果表明,Yb_2O_3/g-C_3N_4具有更加高效的可见光响应能力,且具备更好的光催化性能.     

ZnO/g-C_3N_4复合材料的制备及其光催化性能研究

采用一步法成功制备了氧化锌/石墨相氮化碳(ZnO/g-C_3N_4)复合光催化材料,通过XRD,SEM,TEM,FT-IR和UV-vis DRS对所得样品的微观形貌和吸光特性进行了表征.结果表明,ZnO颗粒均匀分布在片状g-C_3N_4表面上,ZnO/g-C_3N_4最大光吸收边的位置相对于纯相ZnO发生了明显的红移.利用光催化降解甲基橙溶液评估了所得样品的光催化活性,发现ZnO/g-C_3N_4复合材料的光催化效率远高于纯相ZnO和纯相g-C_3N_4,分别达到ZnO的14倍和g-C_3N_4的9倍.复合材料光催化性能得以提升的主要原因有两点:复合样品材料具有比纯相ZnO更大的光吸收范围,提高了太阳光的利用率;ZnO纳米颗粒与g-C_3N_4紧密耦合形成的异质结构有效促进了光生电子-空穴对的分离.     

TNTAs／g-C3 N4的制备及光催化降解罗丹明B

采用水热法制备了二氧化钛纳米管(TNTAs),以尿素为前驱体采用煅烧法制备了g-C_3N_4,然后通过超声制备了TNTAs/g-C_3N_4复合物,并研究了复合物对罗丹明B(RhB)的光催化降解活性.结果表明:TNTAs与g-C_3N_4的复合,增强了对可见光的利用率,复合物中异质结的形成,有效抑制了催化剂中光生电子和空穴对的复合,TNTAs/g-C_3N_4复合物光催化降解RhB的性能得到了明显提高,其中TNTAs/g-C_3N_4-1∶2具有最高的光催化降解活性.     

ZnIn2S4/g-C3N4异质结光催化剂的制备及可见光降解甲硝唑的研究

本研究以甲硝唑为污染底物,分析ZnIn_2S_4/g-C_3N_4光催化剂的光催化降解性能、降解动力学和反应催化机理.采用水热和超声相结合的方法将ZnIn_2S_4负载到g-C_3N_4上,通过改变ZnIn_2S_4负载量得到不同ZnIn_2S_4含量的ZnIn_2S_4/g-C_3N_4异质结光催化剂.利用多种表征手段分析样品的结构、组成、形貌和光吸收等.实验结果表明ZnIn_2S_4/g-C_3N_4的结构是分层异质结构,当ZnIn_2S_4负载量为30%时,ZnIn_2S_4/g-C_3N_4催化剂的催化活性最佳,氙灯下2 h对甲硝唑的光催化降解率达到了90%.     

表面负载型g-C_3N_4/TiO_2复合催化剂的制备及可见光催化还原Cr(Ⅵ)的性能研究

采用热聚合-溶剂热法得到表面负载型g-C_3N_4/TiO_2复合材料,其结构组成、形貌和光电性质通过XRD、TEM、HRTEM、FT-IR、BET和UV-vis测试分析.结果表明TiO_2纳米小颗粒负载于微米级片状g-C_3N_4表面,形成稳定的g-C_3N_4/TiO_2固-固异质结构,扩大了光响应范围、显著提高光生载流子的分离效率.在可见光催化还原水中Cr(Ⅵ)的过程中,g-C_3N_4的质量百分含量是影响光催化活性的重要因素,g-C_3N_4/TiO_2-C具有最高的光催化活性和良好的稳定性.依据实验结果和光电流响应实验给出光催化反应机理.     

复合催化剂NiS/g-C_3N_4的制备及光催化产氢性能

利用原位离子交换法制得复合催化剂Ni S/g-C_3N_4(g-C_3N_4为石墨相氮化碳),采用X射线衍射、透射电镜、紫外-可见漫反射光谱和红外光谱对该催化剂的组成、形貌和光物理性能进行了表征.以廉价的有机染料如曙红Y(EY)、中性红(NR)为敏化剂,三乙醇胺(TEOA)为牺牲剂,构建了完全不含贵金属的光催化产氢体系,考察了NiS的量、敏化剂种类与浓度、牺牲剂的体积分数及体系pH值对产氢性能的影响.结果表明,Ni S的复合和敏化剂EY的引入可使得g-C_3N_4的产氢性能显著提高.结合g-C_3N_4和Ni S/g-C_3N_4的荧光光谱性能,初步推测了该体系的产氢机理.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the