Honeycomb-like g-C3N4/CeO2-x nanosheets obtained via one step hydrothermal-roasting for efficient and stable Cr(VI) photo-reduction

Graphitic carbon nitride (g-C₃N₄)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C₃N₄/CeO₂ nanosheets with abundant oxygen vacancies (g-C₃N₄/CeO_2-x). The hydrothermal-roasting and incomplete-sealed state can (i) generate an in-situ reducing atmosphere (CO, N₂, NH₃) to tune the concentration of oxygen vacancies in CeO₂; (ii) beneficial to prevent continuous growth of g-C₃N₄ and results in honeycomb-like g-C₃N₄/CeO_2-x hybrid nanosheets. What is more, the g-C₃N₄/CeO_2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C₃N₄/CeO_2-x nanosheets could achieve 98% removal efficiency for Cr(VI) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C₃N₄ and CeO₂. This work provides a new idea for more rationally designing and constructing g-C₃N₄-based catalysts for efficient extended photochemical application.     

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.     

g-C3N4/Ag/TiO2复合材料的构筑及其光催化性能（英文）

以合成的g-C3N4纳米片和Ag/TiO2空心微球为原料,采用机械搅拌的方法构筑了g-C3N4/Ag/TiO2三元复合光催化剂。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外-可见光漫反射(UV-Vis DRS)和光致发光光谱(PL)对g-C3N4/Ag/TiO2进行了表征。研究表明,g-C3N4/Ag/TiO2是由Ag/TiO2微球和g-C3N4纳米片复合而成的。与TiO2相比,其可见光响应范围延长,光生载流子的分离速率加快。在室温下,用降解罗丹明B的反应考察了g-C3N4/Ag/TiO2的可见光催化活性。研究表明,光照180 min时,g-C3N4(0.5%)/Ag/TiO2显示了最高的光催化活性(91.9%),分别是TiO2和Ag/TiO2的7.5和1.8倍。光催化活性的提高与合理的异质结构建和Ag的导电性能有关。     

Interfacial engineering of graphitic carbon nitride (g-C3N4)-based metal sulfide heterojunction photocatalysts for energy conversion: A review

As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C₃N₄) has become research hotspots in the community. However, g-C₃N₄ photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C₃N₄-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C₃N₄-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C₃N₄, (2) modification strategies of g-C₃N₄, (3) design principles of TMS-modified g-C₃N₄ heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories: (1) Type I heterojunction, (2) Type II heterojunction, (3) p-n heterojunction, (4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C₃N₄-based heterostructured photocatalysts in H₂ evolution, CO₂ reduction, N₂ fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C₃N₄-based heterostructured photocatalysts toward practical benefits for a sustainable future.     

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...     

Novel ternary g-C3N4/Ag3VO4/AgBr nanocomposites with excellent visible-light-driven photocatalytic performance for environmental applications

Novel visible-light-induced photocatalysts were fabricated by integration of Ag₃VO₄ and AgBr semiconductors with graphitic carbon nitride (g-C₃N₄) through a facile refluxing method. The fabricated photocatalysts were extensively characterized by XRD, EDX, SEM, TEM, FT-IR, UV–vis DRS, BET, TGA, and PL instruments. The photocatalytic performance of these samples was studied by degradations of three dye contaminants under visible-light exposure. Among the ternary photocatalysts, the g-C₃N₄/Ag₃VO₄/AgBr (10%) nanocomposite displayed the maximum activity for RhB degradation with rate constant of 1366.6 × 10⁻⁴ min⁻¹, which is 116, 7.23, and 38.5 times as high as those of the g-C₃N₄, g-C₃N₄/AgBr (10%), and g-C₃N₄/Ag₃VO₄ (30%) photocatalysts, respectively. The effects of synthesis time and calcination temperature were also investigated and discussed. Furthermore, according to the trapping experiments, it was found that superoxide anion radicals were the predominant reactive species in this system. Finally, the ternary photocatalyst displayed superlative activity in removal of the contaminants under visible-light exposure, displaying great potential of this ternary photocatalyst for environmental remediation, because of a facile synthesis route and outstanding photocatalytic performance.     

Water Transport with Ultralow Friction through Partially Exfoliated g-C3N4 Nanosheet Membranes with Self-Supporting Spacers

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C₃N₄ nanosheets in a stack with elaborate structures. In water purification the g-C₃N₄ membrane shows a better separation performance than commercial membranes. The g-C₃N₄ membrane has a water permeance of 29 L m⁻² h⁻¹ bar⁻¹ and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C₃N₄ nanosheets and the spacers between the partially exfoliated g-C₃N₄ nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C₃N₄ membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C₃N₄ nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.     

Upgraded charge transport in g-C3N4 nanosheets by boron doping and their heterojunction with 3D CdIn2S4 for efficient photodegradation of azo dye

The facilitation of charge transport toward the targeted chemical reaction is a challenging task for two-dimensional (2D) nanomaterials. We demonstrate the effectiveness of two different strategies, non-metal doping and heterojunction formation, to adjust the electronic and molecular structures of g-C₃N₄ nanosheets (CN), which could widen the visible-light response and improve the photo-induced electron–hole separation. The g-C₃N₄ nanosheets containing impurity levels (boron doping (BCN)) were prepared by a high-temperature solid-state reaction. Additionally, by anchoring the 3D dichalcogenide structures (CdIn₂S₄) elicited by a wet chemical route, hybrid BCN/CdIn₂S₄ nanostructures were obtained. The resulting BCN/CdIn₂S₄ (BCN–CIS3) nanostructures exhibited an excellent degradation efficiency (95%) for methyl orange (MO) compared to pristine g-C₃N₄ nanosheets (CN) (28%) and boron-doped g-C₃N₄ (BCN) (35%). All the optimized photocatalysts were thoroughly characterized using various techniques and investigated for comparative structural, optical, morphological, and catalytic properties. Our results reveal that introducing boron atoms into the lattice of g-C₃N₄ nanosheets leads to reduction in the band-gap energy and rapid electron transfer. The formation of heterojunctions with the 3D CdIn₂S₄ further assists in improving the degradation efficiency by minimizing the undesired electron–hole recombination, as confirmed by time-resolved photoluminescence (TRPL) analysis. This work proposes feasible strategies and their synergy to develop innovative materials for sustainable energy conversion and environmental remediation applications.     

Cascaded electron transition proved by femto-second transient absorption spectroscopy for enhanced photocatalysis hydrogen generation

Regulating flow direction of photo-excited electrons from interior to active sites in surface is critical to enhance the photocatalytic performance. Herein, photoinduced chemical reduction process was utilized to pinpoint deposit CdS and NiS nanodots sequentially onto g-C₃N₄ nanosheets. The resulted hybrid composite NiS/CdS/g-C₃N₄ was much more active under visible light, and eventually boosted the hydrogen evolution rate of 3015 μmol g^?1 h^?1, to be 2.4 folds better than that of g-C₃N₄. Because of the relative low content of CdS (around 3.0 wt%), the enhanced activity is due to the favoring band overlapping and promoting charge separation rather than increasing light absorption. Femto-second time-resolved transient absorption spectroscopy (fs-TAS) clearly reveals that the photo-excited electrons are from g-C₃N₄, and then migrate unidirectionally to CdS and finally to NiS, which is caused by the precisely regulate the position of CdS and NiS on g-C₃N₄ surface. This study elucidates the electron transfer kinetics and processes in multi-component system and affords a new avenue to construct stable photocatalysts with high activity.     

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.     

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.     

g-C3N4基复合分离膜的制备及光催化性能

利用g-C₃N₄纳米片表面的氨基与膜基底材料氯甲基化聚醚砜（CMPES）的苄氯基团发生化学交联反应,再通过相转化法制备出g-C₃N₄/CMPES复合膜。系统研究了g-C₃N₄纳米片的添加对复合膜的结构、形貌及过滤、光催化、抗污染性能的影响,并探讨其光催化降解牛血清白蛋白溶液（BSA）的机理。研究结果表明：g-C₃N₄纳米片与膜基底材料通过化学键相连接,有效提高了复合膜的光催化性能和稳定性。由于g-C₃N₄纳米片的亲水性和光催化作用,使复合膜表现出优异的过滤性能和抗污染性能。     

Novel PtPd alloy nanoparticle-decorated g-C3N4 nanosheets with enhanced photocatalytic activity for H2 evolution under visible light irradiation

PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C₃N₄) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H₂ evolution of the g-C₃N₄ nanosheets shows that it was significantly enhanced when PtPd alloy NPs were introduced as a co-catalyst. The 0.2 wt% PtPd/g-C₃N₄ composite photocatalyst gave a maximum H₂ production rate of 1600.8 μmol g^–1 h^–1. Furthermore, when K₂HPO₄ was added to the reaction system, the H₂ production rate increased to 2885.0 μmol g^–1 h^–1. The PtPd/g-C₃N₄ photocatalyst showed satisfactory photocatalytic stability and was able to maintain most of its photocatalytic activity after four experimental photocatalytic cycles. In addition, a possible mechanism for the enhanced photocatalytic activity was proposed and verified by various photoelectric techniques. These results demonstrate that the synergistic effect between PtPd and g-C₃N₄ helps to greatly improve the photocatalytic activity of the composite photocatalyst.     

Highly sensitive fluorescence detection of chloride ion in aqueous solution with Ag-modified porous g-C3N4 nanosheets

The porous g-C₃N₄ (PCN) nanosheets are successfully synthesized and further modified with nano-sized Ag by a simple wet-chemical process. Interestingly, the Ag-modified porous g-C₃N₄ (Ag-PCN) nanosheets exhibit competitive fluorescence detection performance of chloride ion (Cl⁻) in aqueous solution. Under the optimized conditions, the concentration of Cl⁻ could be quantitative analyzed with the Ag-PCN in a wide detection range from 0.5 mmol/L to 0.1 mol/L, with a low detection limitation of 0.06 mmol/L. It is confirmed that the fluorescence of PCN could be effectively decayed by the photoinduced charge transfer via the adsorbed Cl⁻ for trapping holes, mainly by means of the time-resolved fluorescence and surface photovoltage spectra. The porous structure and modified Ag promote the adsorption of Cl⁻ on resulting Ag-PCN, leading to excellent fluorescence detection for Cl⁻. This work provides a feasible route to develop a fluorescence detection of Cl⁻ with g-C₃N₄ nanosheets in environment water.     

Direct electrospinning method for the construction of Z-scheme TiO2/g-C3N4/RGO ternary heterojunction photocatalysts with remarkably ameliorated photocatalytic performance

A series of Z-scheme TiO₂/g-C₃N₄/RGO ternary heterojunction photocatalysts are successfully constructed via a direct electrospinning technique coupled with an annealing process for the first time. They are investigated comprehensively in terms of crystal structure, morphology, composition, specific surface area, photoelectrochemical properties, photodegradation performance, etc. Compared with binary TiO₂/g-C₃N₄ and single-component photocatalysts, ternary heterojunction photocatalysts show the best photodegradation performance for RhB under stimulated sunlight. This can be attributed to the enlarged specific surface area (111.41 m²/g), the formation of Z-scheme heterojunction, and the high separation migration efficiency of photoexcited charge carriers. A potential Z-scheme mechanism for ternary heterojunction photocatalysts is proposed to elucidate the remarkably ameliorated photocatalytic performance based on active species trapping experiments, PL detection test of hydroxyl radicals, and photoelectrochemical properties.     

Pt/g-C_3N_4/KB纳米复合催化剂的制备及其甲醇氧化性能

采用溶液中等离子放电法制备出了Pt纳米颗粒,用热氧化刻蚀和水热法成功的对石墨相氮化碳(g-C_3N_4)进行处理进而均匀吸附在科琴黑(KB)表面,最终制备出了Pt/g-C_3N_4/KB纳米复合催化剂。通过XRD分析,扫描电镜,透射电镜和电化学工作站探究了催化剂的组成、结构、颗粒大小以及电化学性能。Pt/g-C_3N_4/KB纳米复合催化剂展现出了良好的甲醇电氧化性能,性能的提升可能是由于g-C_3N_4良好的化学稳定性,N元素的存在改变Pt外层电子结构从而提高催化活性,这些因素提高了Pt的催化效率。     

溶液法剥离的氮化碳在各种衬底上分散的AFM研究

石墨相氮化碳(g-C_3N_4)因为其特殊的层状结构及电子性质在催化和光催化领域里受到广泛关注和研究。本文以异丙醇及异丙醇-水混合溶液为介质对g-C_3N_4粉末进行超声液相剥离,并利用原子力显微镜详细表征了剥离后的溶液分散至云母、高定向热解石墨(HOPG)、Au(111)等不同衬底表面的结果。发现溶液经10h超声后,g-C_3N_4被剥离成尺寸约100nm左右的扁平颗粒,但无法形成完美的超薄层结构。这可能是由于经热聚合法合成的g-C_3N_4本身晶化程度较低所致。     

Facile synthesis of GO as middle carrier modified flower-like BiOBr and C3N4 nanosheets for simultaneous treatment of chromium(VI) and tetracycline

A novel GO modified g-C₃N₄ nanosheets/flower-like BiOBr hybrid photocatalyst is fabricated by a facile method. The characterization results reveal that wrinkled GO is deposited between g-C₃N₄ nanosheets and flower-like BiOBr forming a Z-scheme heterojunction. As a mediator, plicate GO plays a positive role in prompting photogenerated electrons transferring through its sizeable 2D/2D contact surface area. The g-C₃N₄/GO/BiOBr hybrid displays a superior photocatalytic ability to g-C₃N₄ and BiOBr in photodegrading tetracycline (TC), whose removal efficiency could reach 96% within 2 h. Besides, g-C₃N₄/GO/BiOBr composite can reduce Cr(VI), and simultaneously treat TC and Cr(VI) combination contaminant under the visible light. The g-C₃N₄/GO/BiOBr ternary composite also exhibits satisfactory stability and reusability after four cycling experiments. Further, a feasible mechanism related to the photocatalytic process of g-C₃N₄/GO/BiOBr is put forward. This study offers a ternary hybrid photocatalyst with eco-friendliness and hopeful application in water pollution.     

高压放电-光催化剂体系中低温等离子对g-C_3N_4的影响（英文）

高压放电能产生物理和化学效应,如高能电子(e*)、电场、紫外光、可见光和活性物质(·OH,H·,O·,·O_2~-,O_3,N·,NO_x)等,这些放电效应直接或间接应用于污染物的去除和材料的表面改性.在环境领域中,很多研究都关注于高压放电体系中活性物质的产生和利用,而忽视了物理作用,致使处理污染物的能量利用效率不高.近年来,为了提升能量效率,在放电系统中添加光催化剂的研究越来越多.放电产生的物理和化学效应提升了活性物质的产量,从而增强污染物的去除效率.然而,关于高压放电产生的活性物质和物理效应对光催化剂的影响缺乏研究.g-C_3N_4光催化剂是无毒、耐高温、低成本的非金属半导体,在环境与能源方面应用较广,但至今研究g-C_3N_4与低温等离子体协同处理污染物较少.为了使等离子体-g-C_3N_4系统能在环境中得到应用,首要解决的是高压放电对光催化剂影响的问题,从而为后期的研究奠定基础.本研究选用放电均匀、稳定、能产生高电子密度的介质阻挡放电(DBD)对g-C_3N_4进行处理.在不同电气参数(放电电压和放电时间)对g-C_3N_4进行处理,用处理前后的g-C_3N_4光催化降解10mg/L的亚甲基蓝检测其光催化活性,并对其表面的物理结构和化学特征进行表征.结果发现在低放电电压的长时间放电会降低g-C_3N_4的催化活性,而在高放电电压的较短时间内会增强光催化剂的催化性能,随着放电时间的延长,催化活性会先降低再上升.根据XPS表征结果,放电处理后的g-C_3N_4表面有化学键的破坏和新键的形成.在放电处理过程中,加入光催化剂会增强放电强度,而且亲水官能团(-OH,-COOH,-NO_2)的增加也会使放电强度增强,这与光催化剂对放电间隙的空间电荷吸附量有关.结合g-C_3N_4表面表征结果,发现g-C_3N_4的表面物理结构随着放电时间的延长层层破坏,其表面化学官能团也发生周期性变化,这些变化都会影响g-C_3N_4的光催化剂活性.如果等离子体-g-C_3N_4系统要应用于环境治理,光催化剂需避免与放电间隙接触,使光催化剂既能利用高压放电产生的光和其他物理效应,也能不受到低温等离子体的影响.     

g-C3N4-BiOBr复合材料制备及可见光催化性能

利用原位沉积法将BiOBr纳米片生长到g-C₃N₄表面,制得g-C₃N₄-BiOBr p-n型异质结复合光催化剂。采用X射线衍射(XRD)、红外光谱(FTIR)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、紫外可见漫反射(UV-Vis-DRS)和荧光光谱(PL)等测试对光催化剂结构和性能进行表征。通过可见光辐照降解甲基橙水溶液检测评估复合光催化剂光催化活性。研究结果表明:复合光催化剂由BiOBr和g-C₃N₄两相组成,BiOBr纳米片在片状g-C₃N₄表面快速形核生长形成面-面复合结构。相比于纯相g-C₃N₄和BiOBr,g-C₃N₄-BiOBr复合材料具有更强可见光吸收能力,吸收带边红移。在可见光辐照100 min后,性能最佳的2:8 g-C₃N₄-BiOBr复合光催化剂光催化活性分别是纯相g-C₃N₄和BiOBr的1.8和1.2倍,经过4次循环实验后,其降解率仍达84%,说明复合结构光催化剂催化性能和稳定性增强。复合光催化剂的荧光强度显著降低,说明光生载流子复合得到了有效抑制。复合光催化剂催化性能的提高归因于p-n型异质结促进电荷有效分离、抑制电子-空穴复合和吸收光波长范围的扩展,相比单一成分材料具有更好的催化活性和稳定性。自由基捕获实验证明,可见光降解甲基橙光催化过程中的主要活性成分为空穴,并据此提出了可能的光催化机理。