A Composite Polymeric Carbon Nitride with In Situ Formed Isotype Heterojunctions for Highly Improved Photocatalysis under Visible Light

Introducing heterojunction is an effective way for improving the intrinsic photocatalytic activity of a graphitic carbon nitride (GCN) semiconductor. These heterostructures are mostly introduced by interfacing GCN with foreign materials that normally have entirely different physicochemical properties and show unfavorable compatibility, thus resulting in a limited improvement of the photocatalytic performance of the resultant materials. Herein, a composite polymeric carbon nitride (CPCN) that contains both melon‐based GCN and triazine‐based crystalline carbon nitride (CCN) is prepared by a simple thermal reaction between lithium chloride and GCN. Thanks to the intimate contact and good compatibility between GCN and CCN, an in situ formed heterojunction acts as a driving force for separating the photogenerated charge carriers in CPCN. As a result, CPCN exhibits a significantly improved photocatalytic performance under visible light irradiation, which is, respectively, 10.6 and 5.3 times as high as those of the GCN and CCN alone. This well designed isotype heterojunction by a coupling of CCN presents an effective avenue for developing efficient GCN photocatalysts.     

3D Aerogel of Graphitic Carbon Nitride Modified with Perylene Imide and Graphene Oxide for Highly Efficient Nitric Oxide Removal under Visible Light

3D materials are considered promising for photocatalytic applications in air purification because of their large surface areas, controllability, and recyclability. Here, a series of aerogels consisting of graphitic‐carbon nitride (g‐C₃N₄) modified with a perylene imide (PI) and graphene oxide (GO) are prepared for nitric oxide (NO) removal under visible‐light irradiation. All of the photocatalysts exhibit excellent activity in NO removal because of the strong light absorption and good planarity of PI–g‐C₃N₄ coupled with the favorable charge transport properties of GO, which slow the recombination of electron–hole pairs. The aerogel containing thiophene displays the most efficient NO removal of the aerogel series, with a removal ratio of up to 66%. Density functional theory calculations are conducted to explain this result and recycling experiments are carried out to verify the stability and recyclability of these photocatalysts.     

介孔石墨相氮化碳吸附材料在环境中的应用

石墨相氮化碳(Graphitic carbon nitride,g-C_3N_4)是一种由碳(C)和氮(N)元素组成的共轭聚合物材料,具有平面的三嗪聚合物(Poly(tri-s-triazine))网络结构。比起大部分其他碳材料,氮化碳是富电子体,因而赋予了其特殊的性质。然而目前对于g-C_3N_4的研究主要集中在其相关催化作用(光催化,电催化和光电催化),对于g-C_3N_4的吸附作用的研究相对很少涉及。本文探讨了g-C_3N_4材料在吸附领域中的应用,简要综述了G-C_3N_4的性质、制备方法及其作为吸附材料的应用现状,最后展望了石墨型氮化碳在吸附应用领域的未来发展方向。     

Graphitic Carbon Nitride Materials: Sensing,Imaging and Therapy

Graphitic carbon nitrides (g‐C₃N₄) are a class of 2D polymeric materials mainly composed of carbon and nitrogen atoms. g‐C₃N₄ are attracting dramatically increasing interest in the areas of sensing, imaging, and therapy, due to their unique optical and electronic properties. Here, the luminescent properties (mainly includes photoluminescence and electrochemiluminescence), and catalytic and photoelectronic properties related to sensing and therapy applications of g‐C₃N₄ materials are reviewed. Furthermore, the fabrication and advantages of sensing, imaging and therapy systems based on g‐C₃N₄ materials are summarized. Finally, the future perspectives for developing the sensing, imaging and therapy applications of the g‐C₃N₄ materials are discussed.     

Partial Sulphidation to Regulate Coordination Structure of Single Nickel Atoms on Graphitic Carbon Nitride for Efficient Solar H2 Evolution

To develop a non-precious highly efficient cocatalyst to replace Pt on graphitic carbon nitride (g-C₃N₄) for solar H₂ production is great significant, but still remains a huge challenge. The emerging single-atom catalyst presents a promising strategy for developing highly efficient non-precious cocatalyst owing to its unique adjustability of local coordination environment and electronic structure. Herein, this work presents a facile approach to achieve single Ni sites (Ni₁-N₂S) with unique local coordination structure featuring one Ni atom coordinated with two nitrogen atoms and one sulfur atom, confirmed by high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and density functional theory calculation. Thanks to the unique electron structure of Ni₁-N₂S sites, the 1095 µmol g⁻¹ h⁻¹ of high H₂ evolution rate with 4.1% of apparent quantum yield at 420 nm are achieved. This work paves a pathway for designing a highly efficient non-precious transition metal cocatalyst for photocatalytic H₂ evolution.     

Acetamide- or Formamide-Assisted In Situ Approach to Carbon-Rich or Nitrogen-Deficient Graphitic Carbon Nitride for Notably Enhanced Visible-Light Photocatalytic Redox Performance

Acetamide- or formamide-assisted in situ strategy is designed to synthesize carbon atom self-doped g-C₃N₄ (AHCN_x) or nitrogen vacancy-modified g-C₃N₄ (FHCN_x). Different from the direct copolymerization route that suffers from the problem of mismatched physical properties of acetamide (or formamide) with urea, the synthesis of AHCN_x (or FHCN_x) starts from a crucial preorganization step of acetamide (or formamide) with urea via freeze drying-hydrothermal treatment so that the chemical structures as well as C-doping level in AHCN_x and N-vacancy concentration in FHCN_x can be precisely regulated. By using various structural characterization methods, well-defined AHCN_x and FHCN_x structures are proposed. At the optimal C-doping level in AHCN_x or N-vacancy concentration in FHCN_x, both AHCN_x and FHCN_x exhibit remarkably improved visible-light photocatalytic performance in oxidation of emerging organic pollutants (acetaminophen and methylparaben) and reduction of proton to H₂ in comparison of unmodified g-C₃N₄. Combination of the experimental results with theoretical calculations, it is confirmed that AHCN_x and FHCN_x show different charge separation and transfer mechanisms, while the enhanced visible-light harvesting capacity and the localized charge distributions on HOMO and LUMO are responsible for this excellent photocatalytic redox performance of AHCN_x and FHCN_x.     

Sulfur‐Modified Graphitic Carbon Nitride Nanostructures as an Efficient Electrocatalyst for Water Oxidation

There is an urgent need to develop metal‐free, low cost, durable, and highly efficient catalysts for industrially important oxygen evolution reactions. Inspired by natural geodes, unique melamine nanogeodes are successfully synthesized using hydrothermal process. Sulfur‐modified graphitic carbon nitride (S‐modified g‐CN _x ) electrocatalysts are obtained by annealing these melamine nanogeodes in situ with sulfur. The sulfur modification in the g‐CN _x structure leads to excellent oxygen evolution reaction activity by lowering the overpotential. Compared with the previously reported nonmetallic systems and well‐established metallic catalysts, the S‐modified g‐CN _x nanostructures show superior performance, requiring a lower overpotential (290 mV) to achieve a current density of 10 mA cm^?2 and a Tafel slope of 120 mV dec^?1 with long‐term durability of 91.2% retention for 18 h. These inexpensive, environmentally friendly, and easy‐to‐synthesize catalysts with extraordinary performance will have a high impact in the field of oxygen evolution reaction electrocatalysis.     

Crafting Mussel‐Inspired Metal Nanoparticle‐Decorated Ultrathin Graphitic Carbon Nitride for the Degradation of Chemical Pollutants and Production of Chemical Resources

The development of efficient photocatalysts for the degradation of organic pollutants and production of hydrogen peroxide (H₂O₂) is an attractive two‐in‐one strategy to address environmental remediation concerns and chemical resource demands. Graphitic carbon nitride (g‐C₃N₄) possesses unique electronic and optical properties. However, bulk g‐C₃N₄ suffers from inefficient sunlight absorption and low carrier mobility. Once exfoliated, ultrathin nanosheets of g‐C₃N₄ attain much intriguing photocatalytic activity. Herein, a mussel‐inspired strategy is developed to yield silver‐decorated ultrathin g‐C₃N₄ nanosheets (Ag@U‐g‐C₃N₄‐NS). The optimum Ag@U‐g‐C₃N₄‐NS photocatalyst exhibits enhanced electrochemical properties and excellent performance for the degradation of organic pollutants. Due to the photoformed valence band holes and selective two‐electron reduction of O₂ by the conduction band electrons, it also renders an efficient, economic, and green route to light‐driven H₂O₂ production with an initial rate of 0.75 × 10^?6 m min^?1. The improved photocatalytic performance is primarily attributed to the large specific surface area of the U‐g‐C₃N₄‐NS layer, the surface plasmon resonance effect induced by Ag nanoparticles, and the cooperative electronic capture properties between Ag and U‐g‐C₃N₄‐NS. Consequently, this unique photocatalyst possesses the extended absorption region, which effectively suppresses the recombination of electron–hole pairs and facilitates the transfer of electrons to participate in photocatalytic reactions.     

Increasing Solar Absorption of Atomically Thin 2D Carbon Nitride Sheets for Enhanced Visible‐Light Photocatalysis

Atomically thin 2D carbon nitride sheets (CNS) are promising materials for photocatalytic applications due to their large surface area and very short charge‐carrier diffusion distance from the bulk to the surface. However, compared to their bulk counterpart, CNS' applications always suffer from an enlarged bandgap and thus narrowed solar absorption range. Here, an approach to significantly increase solar absorption of the atomically thin CNS via fluorination followed by thermal defluorination is reported. This approach can greatly increase the visible‐light absorption of CNS by extending the absorption edge up to 578 nm. The modulated CNS loaded with Pt cocatalyst as a photocatalyst shows a superior photocatalytic hydrogen production activity under visible‐light irradiation to Pt‐CNS. Combining experimental characterization with theoretical calculations shows that this approach can introduce cyano groups into the framework of CNS as well as the accompanied nitrogen vacancies at the edges, which leads to both narrowing the bandgap and changing the charge distribution. This study will provide an effective strategy to increase solar absorption of carbon‐nitride‐based photocatalysts for solar energy conversion applications.     

Impact of Interfacial Electron Transfer on Electrochemical CO2 Reduction on Graphitic Carbon Nitride/Doped Graphene

Effective electrocatalysts are required for the CO₂ reduction reaction (CRR), while the factors that can impact their catalytic activity are yet to be discovered. In this article, graphitic carbon nitride (g‐C₃N₄) is used to investigate the feasibility of regulating its CRR catalytic performance by interfacial electron transfer. A series of g‐C₃N₄/graphene with and without heteroatom doping (C₃N₄/XG, XG = BG, NG, OG, PG, G) is comprehensively evaluated for CRR through computational methods. Variable adsorption energetics and electronic structures are observed among different doping cases, demonstrating that a higher catalytic activity originates from more interfacial electron transfer. An activity trend is obtained to show the best catalytic performance of CRR to methane on C₃N₄/XG with an overpotential of 0.45 V (i.e., ?0.28 V vs reverse hydrogen electrode [RHE]). Such a low overpotential has never been achieved on any previously reported metallic CRR electrocatalysts, therefore indicating the availability of C₃N₄/XG for CO₂ reduction and the applicability of electron transfer modulation to improve CRR catalytic performance.     

类石墨相氮化碳二维纳米片的制备及可见光催化性能研究

以三聚氰胺为原料制备类石墨相氮化碳(g-C3N4),采用球磨与超声联用技术制备g-C3N4二维纳米片. 利用X 射线衍射光谱(XRD)、紫外-可见漫反射(UV-Vis)光谱、扫描电镜(SEM)、透射电镜(TEM)、原子力显微镜(AFM)、荧光(PL)光谱等分析手段对制备的催化剂进行了表征. 结果表明: g-C3N4二维纳米片具有与体相g-C3N4相同的晶体结构,片层结构仅有5个原子层厚.g-C3N4二维纳米片增加了对可见光的吸收,提高了光生电子-空穴对的分离效率.以染料罗丹明B的降解反应研究了g-C3N4二维纳米片在可见光下的催化性能. 结果表明,球磨超声1 h后制备的g-C3N4二维纳米片表现出最佳的光催化性能, 150 min 内对罗丹明B的降解率高达94%,是体相g-C3N4的2 倍.     

类石墨相氮化碳二维纳米片的制备及可见光催化性能研究

以三聚氰胺为原料制备类石墨相氮化碳(g-C_3N_4),采用球磨与超声联用技术制备g-C_3N_4二维纳米片。利用X射线衍射光谱(XRD)、紫外-可见漫反射(UV-Vis)光谱、扫描电镜(SEM)、透射电镜(TEM)、原子力显微镜(AFM)、荧光(PL)光谱等分析手段对制备的催化剂进行了表征。结果表明:g-C_3N_4二维纳米片具有与体相g-C_3N_4相同的晶体结构,片层结构仅有5个原子层厚。g-C_3N_4二维纳米片增加了对可见光的吸收,提高了光生电子-空穴对的分离效率。以染料罗丹明B的降解反应研究了g-C_3N_4二维纳米片在可见光下的催化性能。结果表明,球磨超声1h后制备的g-C_3N_4二维纳米片表现出最佳的光催化性能,150min内对罗丹明B的降解率高达94%,是体相g-C_3N_4的2倍。     

Co@CNT复合电磁波吸收剂的制备及其吸波性能

以石墨相氮化碳(g-C₃N₄)和六水合硝酸钴为原料制备Co@CNT复合电磁波吸收剂,调节Co元素含量以提高其电磁波吸收性能。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱、扫描电镜(SEM)、能谱分析(EDS)和透射电镜(TEM)等手段表征其微结构和物相组成,使用矢量网络分析仪测量复合物电磁参数并进行Matlab模拟得到反射损耗图。结果表明,Co@CNT-1与石蜡质量比为1：3的材料,其吸波性能最优,厚度为4.1 mm时对电磁波的吸收最强,最小反射损耗(RL_min)为-45.5 dB;厚度仅为1.5 mm的材料,有效吸收带宽(RL<-10 dB)最大为4.42 GHz。