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。     

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。     

The facile synthesis of graphitic carbon nitride from amino acid and urea for photocatalytic H<Subscript>2</Subscript> production

We report on the facile synthesis of g-C₃N₄ based polymers by co-condensing urea with glycine for photocatalytic hydrogen evolution. The as-prepared photocatalysts were then characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence emission spectrometry, electron paramagnetic resonance spectrometry and transmission electron microscopy. Compared with pristine g-C₃N₄, obtained from direct pyrolysis of urea, the CNU-G₅ photocatalyst showed largely enhanced photocatalytic H₂ activities about 75 μmol h^?1, which is 5 times higher than of the pristine CNU. The enhanced activities are ascribed to the larger specific area surface, strengthened optical absorption and improved electron transport ability. Our work opens up a new pathway for the synthesis graphitic carbon nitride photocatalysts with glycine modification to enhance photocatalytic activities.     

Photocatalytic activity under visible light illumination of organic dyes over g-C3N4/MgAl2O4 nanocomposite

Using a grinding method, nanocomposites of graphitic carbon nitride (g-C₃N₄) and magnesium aluminate (MgAl₂O₄) spinel were successfully synthesized for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Variously formulated g-C₃N₄/MgAl₂O₄ nanocomposites were characterized by thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and surface area and micropore analysis (BET surface area). The g-C₃N₄ powder exhibited a nanosheet structure whereas the MgAl₂O₄ spinel comprised agglomerated nanoparticles. The optical properties of the g-C₃N₄/MgAl₂O₄ nanocomposites were investigated by diffuse reflectance spectroscopy (DRS). As the g-C₃N₄ loading content increased from 0 to 30%, the optical band gap energy of the nanocomposite decreased from 3.84 to 2.86 eV, the specific surface area decreased from 153.78 to 114.45 m²/g, and the porosity decreased from 0.447 to 0.347 cm³/g. A 20%g-C₃N₄/MgAl₂O₄ nanocomposite proved to be the most effective photocatalyst and degraded MB faster and more completely than MO. The degradation rates of both MO (0.0107 min^?1) and MB (0.0386 min^?1) in a mixed MO-MB system were greater than the degradation rates in their single systems. The key factor that improved the photocatalytic degradation of MO was the synergistic effect whereas the synergistic effect and photosensitization were the key factors that enhanced the photocatalytic degradation of MB. The g-C₃N₄/MgAl₂O₄ nanocomposite is suitable for the photocatalytic degradation of mixed dyes because its point of zero charge is neutral and it is stable and recyclable.     

Constructing a coplanar heterojunction through enhanced π-π conjugation in g-C3N4 for efficient solar-driven water splitting

Adjusting the electronic structure of graphitic carbon nitride（g-C₃N₄） photocatalyst through π-π conjugation is an effective method to achieve efficient photogenerated carrier separation. One key challenge ofπ-π conjugation control is to tune the degree of such conjugation without destroying the g-C₃N₄structure. Herein we report a conceptual design that achieves a coplanar heterojunction by enhancing theπ-π conjugation via the doping of crystalline g-C...     

In-situ polymerization for PPy/g-C3N4 composites with enhanced visible light photocatalytic performance

Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C₃N₄) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C₃N₄. The PPy/g-C₃N₄ is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C₃N₄ composites increases upon assembly of the amorphous PPy nanoparticles on the g-C₃N₄ surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C₃N₄ surface, thus inhibiting the recombination of photogenerated carriers of g-C₃N₄ and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C₃N₄ composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C₃N₄ in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O₂^? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C₃N₄ composites for environmental applications.     

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.     

A novel P-doped and NCDs loaded g-C3N4 with enhanced charges separation for photocatalytic hydrogen evolution

Graphite carbon nitride(g-C₃N₄) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light.In this work, P-doped and N-doped carbon dots(NCDs) supported g-C₃N₄were successfully prepared via hydrothermal and polymerization reactions. The sub-bandgap formed by P-doping enhances the utilization of visible light, and the high electron de...     

Fast electron transfer and enhanced visible light photocatalytic activity by using poly-o-phenylenediamine modified AgCl/g-C3N4 nanosheets

Exfoliation of bulk graphitic carbon nitride (g-C₃N₄) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g-C₃N₄ nanosheets (CN) have larger specific surface areas and more reaction sites. In addition, poly-o-phenylenediamine (PoPD) can improve the electrical conductivity and photocatalytic activity of semiconductor materials. Here, the novel efficient composite PoPD/AgCl/g-C₃N₄ nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach. The obtained photocatalysts have larger specific surface areas and could achieve better visible-light response. However, silver chloride (AgCl) is susceptible to agglomeration and photocorrosion. The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density, which is three times that of CN. Obviously enhanced photocatalytic activities of PoPD/AgCl/g-C₃N₄ are revealed through the photodegradation of tetracycline. The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly. Furthermore, ?O₂^? and h⁺ are the main active species, which are confirmed through a trapping experiment and ESR spin-trap technique. Therefore, the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst, in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles. This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.     

Realizing high-efficiency carrier separation in 3D hierarchical carbon nitride nanosheets via intramolecular donor-acceptor motifs strategy

The insufficient visible light responsive region and fast charge recombination probability are still the key obstacles for designing high-performance photocatalytic system. Herein, a “One Stone, Two Birds” strategy was reported in three-dimensional (3D) hierarchical graphitic carbon nitride (g-C₃N₄) nanosheet with intramolecular donor-acceptor (D-A) motifs (3D CN) photocatalyst, which solved two urgent problems simultaneously. The 3D hierarchical nanosheets structure endowed 3D CN with abundantly exposed reaction active sites and cross-plane diffusion channels. The formation of internal D-A system facilitated the light absorption and accelerated the transfer and separation of charge carriers. Furthermore, the introducing of D-A motifs optimized the bandgap of g-C₃N₄ and negative-shifted conduction band position. The as-prepared 3D CN showed excellent visible-light photocatalytic H₂ performance, with H₂ evolution rate of 2521.2 μmol h^?1/g, which was six times higher than the pristine CN. This outstanding performance was ascribed to the synergistic effect of 3D hierarchical nanosheets structure and intramolecular D-A motifs. This current work provides a novel insight to design and construct of 3D hierarchical CN nanostructures with D-A motifs simultaneously, which can be further promising applications for clean and sustainable energy conversion.     

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%。     

The photocatalytic •OH production activity of g-C3N4 improved by the introduction of NO

The efficiency of photocatalytic pollutant removal largely depends on the ability of the photocatalytic system to produce hydroxyl radicals (^?OH). However, the capability of photocatalyst to produce ^?OH is not strong at present. Advancing the capacity of photocatalytic system to produce ^?OH has always been a tough problem and challenge in the field of environmental science. In this research, it was found that introducing nitric oxide (NO) into the graphitic carbon nitride (g-C₃N₄) photocatalytic system could memorably enhance the ability of producing ^?OH group. This study provides a new idea for improving the capacity of photocatalytic ^?OH production.     

Gold/monolayer graphitic carbon nitride plasmonic photocatalyst for ultrafast electron transfer in solar-to-hydrogen energy conversion

Gold (Au) plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride (g-C₃N₄) nanosheets via a facile oil-bath method. The photocatalytic activity of the Au/monolayer g-C₃N₄ composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment. All of the Au/monolayer g-C₃N₄ composites showed better photocatalytic performance than that of monolayer g-C₃N₄ and the 1% Au/monolayer g-C₃N₄ composite displayed the highest photocatalytic hydrogen evolution rate of the samples. The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles, which led to the surface plasmon resonance (SPR) effect. The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process. The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g-C₃N₄. Thus, the Au/monolayer g-C₃N₄ composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron-hole pairs than those of monolayer g-C₃N₄. A photocatalytic mechanism for the composites was also proposed.     

Exploring recent advances in silver halides and graphitic carbon nitride-based photocatalyst for energy and environmental applications

Engineering visible light active photocatalytic systems for renewable energy production and environmental remediation has always been a promising technology to counter overall energy demands and pollution challenges. As a fascinating conjugated polymer graphitic carbon nitride (g-C₃N₄) has been developed as a hotspot in the research field as a metal-free semiconducting material with the appealing band gap of 2.7 eV. Recently, g-C₃N₄ has gained tremendous interest in photocatalytic wastewater abatement as well as for hydrogen (H₂) generation, carbon dioxide (CO₂) reduction, and pollutant degradation, under exposure to visible light. Plasmonic silver halides (AgX) such as AgCl, AgBr, and AgI as plasmonic photocatalyst have received immense research interest owing to their escalating photocatalytic efficacy and strong surface plasmon resonance effect (SPR). AgX is the photosensitive, broad bandgap semiconducting materials with effectual antimicrobial properties. This review summarizes the heterostructure of carbonaceous g-C₃N₄ with plasmonic AgX, to reduce the recombination of photo-generated charge carriers, thus enhancing the natural light absorption. g-C₃N₄ grafted AgX nanoarchitectures can be utilized for several potential applications, for instance, overall water splitting (OWS), CO₂ conversion to hydrocarbon fuels, pollutant exclusion, and antibacterial disinfection. This review focuses on the evolution of g-C₃N₄ as well as AgX, facile, and synthetic routes for fabrication of g-C₃N₄ tailored AgX, construction of nano-junctions (AgX/g-C₃N₄) with various photocatalytic applications. Finally, we provided a viewpoint of current hassles and some perceptions of novel trends in this exciting as well as developing research arena.     

Novel CaCO3/g-C3N4 composites with enhanced charge separation and photocatalytic activity

A novel CaCO₃/graphitic carbon nitride (g-C₃N₄) photocatalyst was synthesized for the first time via a facile calcination method using CaCO₃ and melamine as precursors. The as-prepared samples were characterized using various techniques, such as scanning and transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, as well as Fourier-transform infrared, X-ray photoelectron, photoluminescence, and UV–vis diffuse reflectance spectroscopy. The results of the experiments confirm the successful coupling of CaCO₃ to g-C₃N₄. The photocatalytic activity of the synthesized CaCO₃/g-C₃N₄ composites was evaluated by assessing their performance in the photocatalytic degradation of crystal violet (CV) in water under visible light irradiation. The analysis shows that CaCO₃/g-C₃N₄ exhibits higher photocatalytic activity towards CV degradation (76.0%) than pristine g-C₃N₄ (21.6%) and CaCO₃ (23.2%). Radical trapping and electron spin resonance experiments show that hydroxyl radicals (OH) and holes (h⁺) are the key reactive species in the photocatalytic process. The enhanced photocatalytic activity of the composite is mainly attributed to the efficient separation rate of electron-hole pairs achieved through the incorporation of CaCO₃.     

Electrochemiluminescence biosensor for carcinoembryonic antigen detection based on Au-Ag/g-C3N4 nanocomposites

Herein, an electrochemiluminescence (ECL) aptasensor for carcinoembryonic antigen (CEA) detection was developed based on Au-Ag/g-C₃N₄ nanocomposites (NCs), which were synthesized by decorating graphitic carbon nitride (g-C₃N₄) nanosheets with alloy-structured Au-Ag bimetallic nanoparticles (NPs) via one-step in situ chemical reduction. As ECL sensing platform, Au-Ag/g-C₃N₄ NCs could significantly improve the ECL intensity of luminol due to the good conductivity of Au-Ag NPs, electrocatalytic activity for oxygen evolution reaction (OER) and the ability to adsorb luminol via π stacking interaction. In addition, it could load the thiol terminated aptamers of CEA via Au-S or Ag-S bonds. In the presence of CEA, the ECL response of the proposed biosensor decreased significantly due to the fact that the assembled protein layers hindered the electron transfer and the diffusion of ECL reactants toward the electrode surface. The proposed ECL sensor exhibited a good linear relationship with CEA in the range of 1.0–1.0 × 10^?6 ng/mL with a detection limit of 8.9 × 10^?7 ng/mL. The satisfactory results were obtained in the detection of CEA in human serum samples.     

Enhanced oxidase-like activity of g-C3N4 nanosheets supported Pd nanosheets for ratiometric fluorescence detection of acetylcholinesterase activity and its inhibitor

The undesirable enzymatic activity of nanozymes under near neutral p H condition and the traditional single signal output always restrict the analytical application of nanozyme-based biosensors.Herein,graphitic carbon nitride nanosheets supported palladium nanosheets composite （Pd/g-C₃N₄） with both oxidase-like activity and fluorescent property is synthesized.Notably,Pd/g-C₃N₄exhibits enhanced oxidase-like activity compared to Pd NSs under p H 7.4.By c...     

Quantum-chemical calculations on graphitic carbon nitride (g-C3N4) single-layer nanostructures: polymeric slab vs. quantum dot

Graphitic carbon nitride (g-C₃N₄) has been the focus of enormous attention in recent years for its fantastic in-plane and surface properties. Several periodic and cluster models of g-C₃N₄ including a quantum dot have been investigated using density functional theory (DFT) at the HSE06/Def2-TZVP level. The quantum dot with side triazine rings in nearly perpendicular alignment to the central ring was (by 98.40 kcal/mol) more stable than any other cluster, including its planar analogue—a metastable phase of carbon nitride. The g-C₃N₄ quantum dot showed the largest deviation (3.27 eV, 7.9%) from the bandgap of the polymeric material. On the other hand, the unrelaxed symmetrical cluster had the smallest deviation (+?0.03 eV, 1.0%) from the reference bandgap (and also in terms of global hardness), indicating that it could be taken as a replacement cluster for modeling of a polymeric surface in such explorations. The plots of the density of states (DOS) revealed the inherent instabilities of the planar models compared to the quantum dot. Furthermore, the g-C₃N₄ quantum dot showed the highest chemical hardness among the models investigated. The electronic band structures of the g-C₃N₄ quantum dot implied its relatively better photoabsorption ability referenced to the polymeric surface. However, the structural changes had significant effects on the orbital and charge distributions in the C₃N₄ models.

     

MoS2/g-C3N4复合材料的制备及可见光催化性能

首先在N-甲基吡咯烷酮溶液中超声剥离得到少层的MoS₂,将其与石墨相氮化碳（g-C₃N₄）复合,制得MoS₂/g-C₃N₄复合材料。采用X射线衍射（XRD）,扫描电镜（SEM）,X射线光电子能谱（XPS）,傅里叶变换红外光谱（FTIR）,Raman光谱,紫外-可见漫反射吸收光谱（DRS）和光致荧光（PL）技术对复合材料进行表征。可见光下考察MoS₂/g-C₃N₄复合材料光催化降解罗丹明B（RhB）的活性,结果表明：将少量MoS₂与g-C₃N₄复合可明显提高光催化活性,且1%（w/w）MoS₂/g-C₃N₄复合物的光催化活性最高,可能的原因是MoS₂和g-C₃N₄匹配的能带结构,增大了界面间电荷的传输,降低了光生电子-空穴的复合,进而提高了光催化活性。