石墨相氮化碳量子点的制备及应用的研究进展

近年来,石墨相氮化碳(g-C3N4)因其稳定的物理化学性能和良好的生物相容性而受到研究者关注。与块体g-C3N4相比,石墨相氮化碳量子点(g-CNQDs)尺寸更小、荧光效率更高,且具有量子限域效应,因此拥有特殊的理化性质与更好的光催化性能。本文主要从g-CNQDs的制备策略和应用展开讨论,着重综述了微波辅助法、低温固相法、热化学腐蚀法和电化学刻蚀法制备g-CNQDs,以及g-CNQDs在催化剂、离子检测、生物传感与诊疗等领域的最新应用研究进展;指出了目前g-CNQDs在性质、制备和应用等研究方面的重点和难点;最后对g-CNQDs存在的问题和未来的发展方向作出了展望。     

介孔氮化碳的合成及其在环境卫生领域中的应用

石墨相氮化碳是一种新兴的二维蜂窝状纳米材料,其结构中C原子和N原子以sp2方式杂化,通过PZ轨道上的孤对电子相互作用形成类似于苯环的π键,构成高度离域的共轭体系。这一独特结构使其可与一些离子或分子产生疏水、π－π键、氢键和静电力等相互作用,进而成为一种颇具潜力的吸附剂。但同时石墨相氮化碳本身紧密堆叠的层状结构导致其比表面积较小（< 10 m2/g）。介孔氮化碳应运而生,其具有孔尺寸为2～50 nm的典型介孔结构,与石墨相氮化碳相比,比表面积和孔体积获得有效提高且吸附位点更加丰富。该文总结了介孔氮化碳的合成方法及其在环境卫生领域的应用,并展望了其发展方向。     

超薄石墨相氮化碳纳米片的构建及其光催化作用

通过简单调整g-C_3N_4的热聚合方式,一步构筑了超薄氮化碳纳米片,厚度在0.2~0.4 nm左右,分布均匀,比表面积可以达到99 m~2·g~(-1)。光催化性能测试结果表明,随着纳米片比表面积的增大,材料除了表现出优异的光解水性能以外,还在微生物领域表现出一定的抗菌性能,且活性随着聚合温度的升高、纳米片层的变薄而逐渐提高。     

Hollow Carbon Sphere-Modified Graphitic Carbon Nitride for Efficient Photocatalytic H2 Production

A novel hybrid photocatalyst composed of hollow carbon nanospheres (NCS) and graphitic carbon nitride (CN) curly nanosheets has been prepared by the calcination of a NCS precursor and freeze-dried urea. The optimized photocatalyst exhibits an efficient photocatalytic performance under visible light irradiation with a highest H₂ generation rate of 3612.3 μmol g⁻¹ h⁻¹, leading to an apparent quantum yield of 10.04 % at 420 nm, five times higher than the widely reported benchmark photocatalyst CN (2.01 % AQY). The materials characterization shows that NCS-modified CN curly nanosheets can promote photoelectron transfer and suppress charge recombination through their special coupling interface and NCS as an electron acceptor, which significantly improves the photocatalytic efficiency. Thus, this study provides an efficient strategy for the design of highly efficient photocatalyst, particularly suitable for a totally metal-free photocatalytic system.     

超薄石墨相氮化碳纳米片的构建及其光催化作用

通过简单调整g-C₃N₄的热聚合方式,一步构筑了超薄氮化碳纳米片,厚度在0.2~0.4 nm左右,分布均匀,比表面积可以达到99 m²·g^-1。光催化性能测试结果表明,随着纳米片比表面积的增大,材料除了表现出优异的光解水性能以外,还在微生物领域表现出一定的抗菌性能,且活性随着聚合温度的升高、纳米片层的变薄而逐渐提高。     

二维石墨相氮化碳纳米片的制备及其在光催化领域的研究进展

二维(2D)层状石墨型氮化碳纳米片(CNNS)由于具有各向异性的2D几何形态和芳香族p-π共轭骨架,高度开放的平面结构、超高的比表面积、增强的电子迁移速率和与层厚度相关可调的半导体带隙等特征,是目前2D层状材料的研究热点之一。 本文综述了近年来氮化碳纳米片的各种制备方法、功能化改性和应用,涉及环保、能源转换及生物传感等领域。 最后指出进一步探索制备高质量氮化碳纳米片的新方法以及拓展其在光催化领域的应用是未来研究的重点。     

石墨相氮化碳的制备及其在检测重金属离子Cd（Ⅱ）中的应用

以石墨相氮化碳(g-C3N4)修饰玻碳电极在醋酸-醋酸钠缓冲液中,采用方波溶出伏安法检测重金属离子Cd(Ⅱ)。优化了玻碳电极表面负载量、缓冲溶液pH值、富集电势等因素对检测效果的影响。在溶液pH 4.5,富集电位为-1.2 V,富集时间为5 min,玻碳电极表面修饰量为10μL的实验条件下,标准曲线呈现良好的线性关系,线性范围为1.0×10-7~1.4×10-5mol/L,线性方程为I(μA)=8.03 c(μmol/L)-2.00,r=0.998 5,检出限(3σ)达3.3×10-8mol/L。常见无机盐离子对修饰电极无干扰。用于自来水样中镉离子的测定,加标回收率为98.8%~99.6%,实验结果与原子吸收光谱法一致。     

Solar Light Active Graphitic Carbon Nitride/Biochar Nanocomposite for RhB Dye Degradation

In this work, nanocomposite graphitic carbon nitride/biochar is successfully prepared by physical mixing method to achieve efficient charge separation and photodegradation of RhB dye under sunlight. The biochar is synthesized by heating biomass in muffle furnace in an inert atmosphere. The graphitic carbon nitride is prepared using melamine as a precursor and heating it in a muffle furnace in air atmosphere. The structural characterizations FTIR and X-ray diffraction are done to confirm the functional groups and crystallography of prepared samples. The photodegradation of RhB dye by nanocomposite is analyzed using a UV–visible spectrophotometer under solar irradiation. It is found that the RhB dye is completely reduced by the nanocomposite in less than 6 min in the presence of sunlight. The kinetic study confirms the photodegradation of RhB dye is first order reaction and rate constant is found to be 0.31 min⁻¹.     

Graphitic Carbon Nitride Polymers toward Sustainable Photoredox Catalysis

As a promising two‐dimensional conjugated polymer, graphitic carbon nitride (g‐C₃N₄) has been utilized as a low‐cost, robust, metal‐free, and visible‐light‐active photocatalyst in the field of solar energy conversion. This Review mainly describes the latest advances in g‐C₃N₄ photocatalysts for water splitting. Their application in CO₂ conversion, organosynthesis, and environmental purification is also briefly discussed. The methods to modify the electronic structure, nanostructure, crystal structure, and heterostructure of g‐C₃N₄, together with correlations between its structure and performance are illustrated. Perspectives on the challenges and opportunities for the future exploration of g‐C₃N₄ photocatalysts are provided. This Review will promote the utilization of g‐C₃N₄ materials in the fields of photocatalysis, energy conversion, environmental remediation, and sensors.     

Ultrafast Condensation of Carbon Nitride on Electrodes with Exceptional Boosted Photocurrent and Electrochemiluminescence

Semiconducting polymeric carbon nitride (CN) has drawn wide attention ranging from photocatalysis to more recent biosensing owing to unique defect‐tolerated optoelectronic properties and being metal‐free, cheap, and highly stable. However, at the core of electrical–optical interconversion, the preparation of the CN photoelectrode is still challenging. Now, the growth of CN on electrodes is achieved simply by microwave‐assisted condensation in seconds. The ultrafast heating not only addressed the thermodynamic contradiction of precursor volatilization during polymerization but also led to strongly adhesive CN layer on electrodes with gradient carbon‐rich texture, greatly accelerating the electron–hole separation and mobility. Consequently, the CN photoelectrode exhibited a remarkable photocurrent and a record cathodic efficiency of electrochemiluminescence up to 7 times that of benchmark Ru(bpy)₃Cl₂ in aqueous solution.     

基于Pd/g-C3N4-SWCNTs的雌二醇电化学传感器构建及应用研究

利用表面具有丰富π电子的三聚氰胺(MAM)和单壁碳纳米管(SWCNTs)作为前驱体,通过固体研磨-热聚合法使二者通过π-π静电作用堆叠得到类石墨相氮化碳(Graphitic carbon nitride,g-C_3N_4)-SWCNTs复合材料,然后利用Na_2PdCl_4为Pd纳米粒子前体,通过自组装对g-C_3N_4-SWCNTs进行功能化修饰,得到Pd/g-C_3N_4-SWCNTs复合物。采用SEM、TEM、XRD、FTIR对该复合材料的形貌和组成进行表征,并利用循环伏安等电化学方法研究了该材料对雌二醇(E2)的电催化氧化性能。结果显示,雌二醇在Pd/g-C_3N_4-SWCNTs修饰电极上的响应电流明显大于其在g-C_3N_4、g-C_3N_4-SWCNTs修饰电极和裸玻碳电极上的响应。在优化实验条件下,采用示差脉冲伏安法考察了基质样品中E2的氧化峰电流与其浓度的关系,其氧化峰电流强度与其浓度在5～150μmol/L范围内呈良好的线性关系,线性方程为:I_(pa)(μA)=0.834 7+0.007 0C_(E2)(r=0.990),检出限(LOD,S/N=3)为1.7μmol/L。该传感器具有良好的稳定性和选择性,且与HPLC在方法学上无显著性差异,可满足饲料样品中E2的检测需求。     

泡沫状氮化碳的制备及其可见光分解水产氢性能

以三聚氰胺为前驱体,价格低廉、来源广泛的海泡石作为硬模板,制备出具有特殊空腔结构的泡沫状氮化碳。 通过透射电子显微镜、X射线粉末衍射、傅里叶变换红外光谱、N₂吸附-脱附、紫外可见漫反射光谱及荧光光谱等手段对样品的表面形貌和结构等物理性质进行表征,以光解水产氢性能考察其光催化活性,并通过电化学测试手段考察其光生电荷传输和分离情况。 结果表明,聚多巴胺能起到粘接剂作用,改善了前驱体与模板的结合,制备出的泡沫状氮化碳具有更大的比表面积;随模板用量增加,氮化碳的比表面积增大,当聚多巴胺改性海泡石与三聚氰胺质量比为2:1时,泡沬状氮化碳比表面积可达389.2 m²/g,其可见光产氢速率约为1061.87 μmol/(g·h),较体相氮化碳和未经多巴胺改性海泡石制备的氮化碳分别提高了7和2.6倍。 这表明大比表面积的泡沫状氮化碳为光催化反应提供了更多的活性位点,改善了多相光催化反应的传质扩散过程,提高了光生电子-空穴的分离效率,其特殊的空腔结构能有效地提高光的利用率,从而提高其光催化活性。     

石墨相氮化碳/三聚氯氰复合光催化剂的制备及其光催化活性

研制了一种石墨相氮化碳/三聚氯氰(g-C₃N₄/C₃Cl₃N₃)复合型光催化剂。 由于该催化剂在g-C₃N₄的基础上有效拓展了π共轭体系,同时引入氯原子,使带隙位置上移,改善了光生电荷的还原能力,在可见光照射下,能有效降解有机污染物。 实验结果表明,20 min内对RR染料废水的降解率达94.7%,重复使用5次后,降解率仍达94%。 通过在降解体系中加入氧化性活性物种捕获剂的方法,研究了g-C₃N₄/C₃Cl₃N₃吸收可见光降解有机污染物的机理。     

石墨相碳化氮(g-C3N4)纳米材料在分析化学中的应用进展

石墨相碳化氮(g-C_3N_4)具有类似于石墨烯的片层结构,其独特的电子能带结构、热稳定性以及高化学稳定性,优异的光学、电学性质,使之在生物成像、光、电传感器方面具有广阔的应用前景。该文综述了g-C_3N_4纳米材料在电化学、光学分析等分离分析方面的应用进展,并展望了其发展前景。     

石墨相氮化碳纳米管的合成及光催化产氢性能

通过硬模板法,采用氰胺前驱物和二氧化硅纳米管(SiO₂-NTs)模板,合成石墨相氮化碳纳米管(CN-NTs)光催化剂。采用扫描电镜(SEM)、透射电镜(TEM)、X射线粉末衍射(XRD)、傅立叶变换红外光谱(FT-IR)、氮气吸附/脱附测试、紫外可见漫反射光谱(UV-Vis DRS)、荧光光谱、热重分析(TGA)等手段对CN-NTs催化剂的结构与性能进行表征。结果表明,CN-NTs的化学组成是石墨相氮化碳(g-C₃N₄),形貌为均匀的纳米管,且是介孔材料。与体相氮化碳(B-CN)和介孔石墨相氮化碳(mpg-CN)相比,CN-NTs的光吸收带边蓝移到440 nm,荧光发射谱的峰强减弱。在可见光(λ>420 nm)照射下,CN-NTs具有较高的光催化分解水活性,产氢速率为58 μmol/h,且表现出良好的光催化活性稳定性和化学结构稳定性。研究结果表明纳米管状结构能有效促进g-C₃N₄半导体激子解离,提高光生电子-空穴的分离效率,进而显著优化g-C₃N₄的光催化产氢性能。     

Highly Selective and Stable Reduction of CO2 to CO by a Graphitic Carbon Nitride/Carbon Nanotube Composite Electrocatalyst

A stable and selective electrocatalyst for CO₂ reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g‐C₃N₄/MWCNTs). The as‐prepared composite is able to reduce CO₂ exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO₂ reduction is attributed to the formation of active carbon–nitrogen bonds, high specific surface area, and improved material conductivity of the g‐C₃N₄/MWCNT composite.     

Graphitic Carbon Nitride/Nitrogen‐Rich Carbon Nanofibers: Highly Efficient Photocatalytic Hydrogen Evolution without Cocatalysts

An interconnected framework of mesoporous graphitic‐C₃N₄ nanofibers merged with in situ incorporated nitrogen‐rich carbon has been prepared. The unique composition and structure of the nanofibers as well as strong coupling between the components endow them with efficient light‐harvesting properties, improved charged separation, and a multidimensional electron transport path that enhance the performance of hydrogen production. The as‐obtained catalyst exhibits an extremely high hydrogen‐evolution rate of 16885 μmol h^?1 g^?1, and a remarkable apparent quantum efficiency of 14.3 % at 420 nm without any cocatalysts, which is much higher than most reported g‐C₃N₄‐based photocatalysts even in the presence of Pt‐based cocatalysts.     

Synchrotron X-ray Electron Density Analysis of Chemical Bonding in the Graphitic Carbon Nitride Precursor Melamine

Melamine is a precursor and building block for graphitic carbon nitride (g-CN) materials, a group of layered materials showing great promise for catalytic applications. The synthetic pathway to g-CN includes a polycondensation reaction of melamine by evaporation of ammonia. Melamine molecules in the crystal organize into wave-like planes with an interlayer distance of 3.3 Å similar to that of g-CN. Here we present an extensive investigation of the experimental electron density of melamine obtained from modelling of synchrotron radiation X-ray single-crystal diffraction data measured at 25 K with special focus on the molecular geometry and intermolecular interactions. Both intra- and interlayer structures are dominated by hydrogen bonding and π-interactions. Theoretical gas-phase optimizations of the experimental molecular geometry show that bond lengths and angles for atoms in the same chemical environment (C−N bonds in the ring, amine groups) differ significantly more for the experimental geometry than for the gas-phase-optimized geometries, indicating that intermolecular interactions in the crystal affects the molecular geometry. In the experimental crystal geometry, one amine group has significantly more sp³-like character than the others, hinting at a possible formation mechanism of g-CN. Topological analysis and energy frameworks show that the nitrogen atom in this amine group participates in weak intralayer hydrogen bonding. We hypothesize that melamine condenses to g-CN within the layers and that the unique amine group plays a key role in the condensation process.     

缺陷工程调控石墨相氮化碳及其光催化空气净化应用进展

Since the pioneering work on polychlorinated biphenyl photodegradation by Carey in 1976, photocatalytic technology has emerged as a promising and sustainable strategy to overcome the significant challenges posed by energy crisis and environmental pollution. In photocatalysis, sunlight, which is an inexhaustible source of energy, is utilized to generate strongly active species on the surface of the photocatalyst for triggering photo-redox reactions toward the successful removal of environmental pollutants, or for water splitting. The photocatalytic performance is related to the photoabsorption, photoinduced carrier separation, and redox ability of the semiconductor employed as the photocatalyst. Apart from traditional and noble metal oxide semiconductors such as P25, bismuth-based compounds, and Pt-based compounds, 2D g-C₃N₄ is now identified to have enormous potential in photocatalysis owing to the special π-π conjugated bond in its structure. However, some inherent drawbacks of the conventional g-C₃N₄, including the insufficient visible-light absorption ability, fast recombination of photogenerated electron-hole pairs, and low quantum efficiency, decrease its photocatalytic activity and limit its application. To date, various strategies such as heterojunction fabrication, special morphology design, and element doping have been adopted to tune the physicochemical properties of g-C₃N₄. Recent studies have highlighted the potential of defect engineering for boosting the light harvesting, charge separation, and adsorption efficiency of g-C₃N₄ by tailoring the local surface microstructure, electronic structure, and carrier concentration. In this review, we summarize cutting-edge achievements related to g-C₃N₄ modified with classified non-external-caused defects (carbon vacancies, nitrogen vacancies, etc.) and external-caused defects (doping and functionalization) for optimizing the photocatalytic performance in water splitting, removal of contaminants in the gas phase and wastewater, nitrogen fixation, etc. The distinctive roles of various defects in the g-C₃N₄ skeleton in the photocatalytic process are also summarized. Moreover, the practical application of 2D g-C₃N₄ in air pollution control is highlighted. Finally, the ongoing challenges and perspectives of defective g-C₃N₄ are presented. The overarching aim of this article is to provide a useful scaffold for future research and application studies on defect-modulated g-C₃N₄.      

Palladium Nanoparticles Supported on Titanium‐Doped Graphitic Carbon Nitride for Formic Acid Dehydrogenation

Pd nanoparticles (NPs) supported on Ti‐doped graphitic carbon nitride (g‐C₃N₄) were synthesized by a deposition–precipitation route and a subsequent reduction with NaBH₄. The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N₂‐physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti‐doped g‐C₃N₄. Compared to Pd loaded on pristine g‐C₃N₄, the Pd NPs supported on Ti‐doped g‐C₃N₄ exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti‐doped g‐C₃N₄.