钾离子掺杂对石墨型氮化碳光催化剂能带结构及光催化性能的影响

以双氰胺和氢氧化钾为原料制备了能带可控的钾离子掺杂石墨型氮化碳(g-C3N4)光催化剂,并与碱处理的g-C3N4及g-C3N4/KOH复合催化剂进行了对比。采用X射线衍射(XRD)光谱、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FTIR)光谱、N2吸附、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X 光电子能谱(XPS)等分析手段对制备的催化剂进行了表征。结果表明,钾离子含量对氮化碳催化剂的价带及导带位置有显著影响。此外,钾离子的引入抑制了氮化碳晶粒的生长,提高了氮化碳的比表面积以及对可见光的吸收,降低了光生电子-空穴对的复合几率。以染料罗丹明B的降解为探针反应系统研究了钾离子掺杂对g-C3N4在可见光下催化性能的影响,研究了光催化反应机理。结果表明,钾离子掺杂后氮化碳的光催化性能显著提高。制备的钾离子掺杂氮化碳催化剂表现出良好的结构及催化稳定性。     

Quaternary ammonium hydroxide-functionalized g-C3N4 catalyst for aerobic hydroxylation of arylboronic acids to phenols

A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C₃N₄ catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C₃N₄-OH) has been prepared from graphitic carbon nitride (g-C₃N₄) scaffold by converting the residual –NH₂ and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C₃N₄-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N₂ adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C₃N₄-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C₃N₄-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5%).     

Synthesis g-C3N4 of high specific surface area by precursor pretreatment strategy with SBA-15 as a template and their photocatalytic activity toward degradation of rhodamine B

Using SBA-15 as a template, high surface area porous graphitic carbon nitrides (g-C₃N₄) were successfully synthesized by pretreating melamine using hydrochloric acid, and fully characterized by Fourier-Transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron micrographs (SEM), N₂ adsorption-desorption, ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence (PL) spectrum. The results of these analyses indicated that the g-C₃N₄ synthesized from HCl-pretreated melamine with SBA-15 as a template has enhanced specific surface area and increased the separation rate of the photogenerated electrons and holes compared with bulk g-C₃N₄, but didn’t change the structure of bulk g-C₃N₄. The photocatalytic activity of samples was evaluated by the degradation of rhodamine B (RhB) under xenon lamp. The results indicated that the activity was improved significantly with the increase of specific surface area. The rate constant for CN-3（HCl pretreatment melamine precursor and SBA-15 as a template） was 13 times as high as g-C₃N₄. Furthermore, the CN-3 catalyst exhibited outstanding structural and catalytic stability.     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能

通过在三聚氰胺热分解过程中加入NaHCO₃制备出具有氮缺陷的石墨相氮化碳（g-C₃N₄）,利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N₂吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征,并在可见光（λ> 420nm）照射下,以水相中罗丹明B（RhB）的降解为模型反应,研究了该氮缺陷g-C₃N₄对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C₃N₄对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C₃N₄的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C₃N₄对RhB的降解率仅为59.8%。     

多孔纳米片状石墨相氮化碳的制备及其可见光催化

以三聚氰胺和硫脲为前驱体,通过简易的氧气刻蚀制备了多孔纳米片状氮化碳。相比于三聚氰胺制备的薄片状氮化碳（MCNS）,以硫脲制备的多孔纳米片状的g-C₃N₄（TCNS）片层更薄,其单片厚度约为30 nm,且TCNS的层状结构明显,能带隙约为3.03 eV,高于石墨相氮化碳（2.77 eV）,更宽的禁带赋予载流子更强的氧化还原能力。较大的比表面积（114 m²·g^-1）可以提供更多的活性位点,同时纳米片状结构可以促进电子与空穴的有效分离和转移,且能有效地降低光生载流子的复合率,因而TCNS具有更高的光催化活性。     

多孔纳米片状石墨相氮化碳的制备及其可见光催化

以三聚氰胺和硫脲为前驱体,通过简易的氧气刻蚀制备了多孔纳米片状氮化碳。相比于三聚氰胺制备的薄片状氮化碳(MCNS),以硫脲制备的多孔纳米片状的g-C_3N_4(TCNS)片层更薄,其单片厚度约为30 nm,且TCNS的层状结构明显,能带隙约为3.03 eV,高于石墨相氮化碳(2.77 eV),更宽的禁带赋予载流子更强的氧化还原能力。较大的比表面积(114 m~2·g~(-1))可以提供更多的活性位点,同时纳米片状结构可以促进电子与空穴的有效分离和转移,且能有效地降低光生载流子的复合率,因而TCNS具有更高的光催化活性。     

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。     

A facile single-step approach to achieve in situ expanded g-C3N4 for improved photodegradation performance

Improved graphitic carbon nitride (g-C₃N₄) was synthesized through a unique one-step cost-effective technique involving a dynamic gas bubbling phenomenon using ammonium chloride (NH₄Cl) as a bubbling agent. An extensive investigation was carried out to optimize the weight ratio of NH₄Cl and melamine during the thermal pyrolysis process. Here, we report an improved form of g-C₃N₄ namely “expanded g-C₃N₄” with increased interlayer distance and remarkable volume expansion. The surface area of this improved version has notably increased leading to higher photocatalytic efficiency as compared with its counterpart, an synthesized without adding NH₄Cl. Synthesized photocatalyst materials were further used to study the Rhodamine B photodegradation under visible light. It was observed that the expanded g-C₃N₄ showed a 2.4 times higher photodegradation rate than its counterpart and degraded 94% of the dye in just 30 min.     

Photocatalytic debromination of decabromodiphenyl ether by graphitic carbon nitride

The graphitic carbon nitride(g-C3N4) is found to be an efficient photocatalyst for the reductive degradation of decabromodiphenyl ether(BDE209) under UV irradiation(>360 nm).g-C3N4 was prepared by heating dicyandiamide.X-ray diffraction,X-ray photoelectron spectroscopy,and UV-vis spectra were used to characterize the properties of as-prepared catalysts.The photoreductive degradation kinetics of BDE209 was further investigated under different reaction conditions.The degradation of BDE209 is a stepwise process,and the bromines at meta positions are much more susceptible to remove than those at the ortho and para positions.A possible photoreductive mechanism was also proposed.     

Fe掺杂g-C3N4的制备及其可见光催化性能

以硝酸铁和三聚氰胺为原料制备不同含铁量的Fe 掺杂石墨氮化碳（g-C₃N₄）. 采用X 射线衍射光谱（XRD）、紫外-可见（UV-Vis）光谱、傅里叶变换红外（FT-IR）光谱、电感耦合等离子体-原子发射光谱（ICP-AES）、荧光（PL）光谱、X光电子能谱（XPS）等分析手段对制备的催化剂进行了表征. 结果表明,铁以离子形式镶嵌在g-C₃N₄的结构单元中,影响了g-C₃N₄的能带结构,增加了g-C₃N₄对可见光的吸收,降低了光生电子-空穴对的复合几率. 以染料罗丹明B的降解为探针反应系统研究了不同含铁量对g-C₃N₄在可见光下催化性能的影响. 结果表明,m（Fe）/m（g-C₃N₄）=0.14%时,制备的Fe 掺杂g-C₃N₄表现出最佳的光催化性能,120 min 内罗丹明B的降解率高达99.7%,速率常数达到0.026 min^-1,是纯g-C₃N₄的3.2 倍. 以叔丁醇、对苯醌、乙二胺四乙酸二钠为自由基（·OH）、自由基（O₂^-·）和空穴（h_VB⁺）的捕获剂,研究了光催化反应机理.     

Review of Acetic Acid Synthesis from Various Feedstocks Through Different Catalytic Processes

Acetic acid (AA) has been largely used with a wide range of applications such as a raw material for a synthesis of vinyl acetate monomer, cellulose acetate or acetate anhydrate, acetate ester and a solvent for a synthesis of terephthalic acid and so on. The present paper briefly summarizes the commercialized chemical processes with their Rh or Ir-based catalytic systems in a liquid-phase carbonylation reaction such as Monsanto, Cativa and Acetica processes. In addition, some alternative catalytic systems such as heterogeneous catalysts to produce AA by direct oxidation or indirect carbonylation of dimethyl ether through BP-SaaBre process in a gas-phase reaction to solve some problems such as a difficult separation of homogeneous catalysts in a corrosive reaction medium. Some home-made heterogeneous catalysts such as a rhodium incorporated graphitic carbon nitride (Rh-g-C₃N₄) and some heterogenized homogeneous catalysts using the supports of tungsten carbide, iron oxide or graphitic carbon nitride containing rhodium complexes were also introduced for the synthesis of AA through a liquid-phase methanol carbonylation reaction to effectively solve the leaching problem of active rhodium metal as well as to mitigate the separation problem of homogeneous catalysts.     

Mg-induced g-C3N4 synthesis of nitrogen-doped graphitic carbon for effective activation of peroxymonosulfate to degrade organic contaminants

The nitrogen-doped carbon derived from graphitic carbon nitride （g-C₃N₄） has been widely deployed in activating peroxymonosulfate （PMS） to remove organic pollutants.However,the instability of g-C₃N₄at high temperature brings challenges to the preparation of materials.The nitrogen-doped graphitic carbon nanosheets （N-GC750） were synthesized by magnesium thermal denitrification.Magnesium undergoes the displacement reaction with small molecules produced b...     

石墨相氮化碳的化学合成及应用

石墨相氮化碳(g-C₃N₄)具有独特的电子结构和优异的化学稳定性, 近年来不仅被作为不含金属组分的催化剂和催化剂载体, 广泛地应用于有机官能团的选择性转换、光催化分解水、氧还原和Au、Pd、Ag、Pt等贵金属的负载, 还被作为绿色储能材料和硬模板剂用于H₂、CO₂的存储和纳米金属氮(氧)化物的制备等, 在能源和材料相关领域逐渐引起人们的关注. 本文将从材料的制备和应用角度,综述国内外同行近年来在g-C₃N₄研究中所取得的一些重要进展, 并对其未来发展趋势,特别是在能源和环境领域中的应用进行了展望.     

Tuning band structure of graphitic carbon nitride for efficient degradation of sulfamethazine: Atmospheric condition and theoretical calculation

Numerous approaches have been used to modify graphitic carbon nitride（g-C₃N₄） for improving its photocatalytic activity. In this study, we demonstrated a facial post-calcination method for modified graphitic carbon nitride（g-C₃N₄-Ar/Air） to direct tuning band structure, i.e., bandgap and positions of conduction band（CB）/valence band（VB）, through the control of atmospheric condition without involving any additional elements or metals or semiconductors. ...     

Supported Palladium-Catalyzed Carbonylative Synthesis of Diaryl Ketones from Aryl Bromides and Arylboronic Acids

A palladium supported on graphitic carbon nitride (Pd/g-C₃N₄) catalyzed carbonylative reaction of aryl bromides and arylboronic acids by has been developed for the construction of diaryl ketones. Using benzene-1,3,5-triyl triformate (TFBen) as the CO source, the reaction proceeded well to give various diaryl ketones in moderate to good yields.     

Graphitic carbon nitride embedded hydrogels for enhanced gel electrophoresis

Here, we show, for the first time, the use of graphitic carbon nitride (g-C₃N₄) nanosheets to improve the resolution and efficiency of protein separation in gel electrophoresis. By loading 0.04% (m/v) g-C₃N₄ nanosheets into the polyacrylamide gel at 25 °C, the thermal conductivity increased approximately 80% which resulted in 20% reduction in Joule heating and overall increase of separation efficiency. Also, polymerization of acrylamide occurred in the absence of tetramethylethylenediamine (TEMED) when the polyacrylamide gel contained g-C₃N₄ nanosheets. Hence, the g-C₃N₄ act simultaneously as a polymerization catalyst as well as heat sinks to lower Joule heating effect on band broadening.     

Palladium/graphitic carbon nitride catalyst for selective oxygen transfer in Wacker oxidation

Nanoscaled palladium particles supported on graphitic carbon nitride (Pd⁰/g-C₃N₄) is prepared to improve the oxygen transfer in Wacker oxidation via chemical reduction method. From the analysis of FT-IR, XRD, SEM, TEM, XPS and ICP, Pd⁰ particles are firmly combined with g-C₃N₄ layers, and sub-surface ones occupy most of the components. It is worth mentioning that graphene oxide (GO), which is completely recyclable without further pollution, can be used as a ‘solid weak acid’ taking the place of H₂SO₄ and CF₃COOH. Under the optimization conditions, as many as 46 kinds of olefins are transferred into corresponding products with satisfactory yields, and o-methyl styrene gets the highest yield of 94%. After five times of recycling experiment, the yield of acetophenone only decreases by about 7.0% in the uniform reaction process. In virtue of former research results and molecular electrostatic potential, a possible mechanism is put forward to explain the catalytic process.     

Ag nanoparticles loaded on porous graphitic carbon nitride with enhanced photocatalytic activity for degradation of phenol

Highly efficient photocatalyst of visible-light-driven Ag nanoparticles loaded on porous graphitic carbon nitride (g-C₃N₄) was prepared by the reduction of Ag ions on porous g-C₃N₄. The obtained Ag/porous g-C₃N₄ composite products were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectra (DRS), thermal gravimetric analysis (TGA). The results demonstrated that a homogeneous distribution of Ag NPs of 10 nm was attached onto the surface of the porous g-C₃N₄. The prepared Ag/porous g-C₃N₄ samples were applied for catalyzing the degradation of phenol in water under visible light irradiation. Porous g-C₃N₄ demonstrated an excellent support for the formation and dispersion of small uniform Ag NPs. When the weight percentage of Ag reaches 5%, the nanohybrid exhibits superior photocatalytic activities compared to bulk g-C₃N₄, porous g-C₃N₄, and 2% Ag/porous g-C₃N₄ hybrids. The enhanced photocatalytic performance is due to the synergic effect between Ag and porous g-C₃N₄, which suppressed the recombination of photogenerated electron-hole pairs.     

Defects Promote Ultrafast Charge Separation in Graphitic Carbon Nitride for Enhanced Visible-Light-Driven CO2 Reduction Activity

Fundamental photocatalytic limitations of solar CO₂ reduction remain due to low efficiency, serious charge recombination, and short lifetime of catalysts. Herein, two-dimensional graphitic carbon nitride nanosheets with nitrogen vacancies (g-C₃N_x) located at both three-coordinate N atoms and uncondensed terminal NH_x species were prepared by one-step tartaric acid-assistant thermal polymerization of dicyandiamide. Transient absorption spectra revealed that the defects in g-C₃N₄ act as trapped states of charges to result in prolonged lifetimes of photoexcited charge carriers. Time-resolved photoluminescence spectroscopy revealed that the faster decay of charges is due to the decreased interlayer stacking distance in g-C₃N_x in favor of hopping transition and mobility of charge carriers to the surface of the material. Owing to the synergic virtues of strong visible-light absorption, large surface area, and efficient charge separation, the g-C₃N_x nanosheets with negligible loss after 15 h of photocatalysis exhibited a CO evolution rate of 56.9 μmol g⁻¹ h⁻¹ under visible-light irradiation, which is roughly eight times higher than that of pristine g-C₃N₄. This work presents the role of defects in modulating light absorption and charge separation, which opens an avenue to robust solar-energy conversion performance.     

Direct Synthesis of Porous Nanorod‐Type Graphitic Carbon Nitride/CuO Composite from Cu–Melamine Supramolecular Framework towards Enhanced Photocatalytic Performance

Facile and direct synthesis of porous nanorod‐type graphitic carbon nitride/CuO composite ( CuO‐g‐C₃N₄ ) has been achieved by using a Cu–melamine supramolecular framework as a precursor. The CuO‐g‐C₃N₄ nanocomposite demonstrated improved visible‐light‐driven photocatalytic activities. The results indicate that metal–melamine supramolecular frameworks can be promising precursors for the preparation of efficient g ‐C₃N₄ nanocomposite photocatalysts.