Different non-radical oxidation processes of persulfate and peroxymonosulfate activation by nitrogen-doped mesoporous carbon

Activated persulfate oxidation is an emerging advanced oxidation process for organic pollutant degradation. Own to different molecular structures and oxidation potentials, persulfate (PDS) and peroxymonosulfate (PMS) may show different degradation performances due to various catalytic mechanisms even by the same catalysts. In this study, the nitrogen-doped mesoporous carbon (N-OMC) was applied to activate PDS and PMS for degrading a model organic pollutant phenol to reveal their activation mechanisms. Results show that both PDS and PMS could be efficiently activated by N-OMC. The degradation of phenol fitted well with pseudo-first-order kinetics, whose kinetic constants increased with the increase of pH, PDS/PMS dosage, and N-OMC dosage. Based on quenching experiments and electron spin resonance spin-trapping technique, the N-OMC was found to activate PDS and PMS via non-radical process of electron transfer and singlet oxygen formation, respectively, instead of the commonly observed radical process. This work will be useful to understand the activation processes of PDS and PMS, and benefit for the development of catalysts for pollutant degradation.     

A general strategy via photoelectrocatalytic oxygen reduction for generating singlet oxygen with carbon bridged carbon-nitride electrode

With the ever-growing demand of clean water for the healthy world, water purification has become an urgent global issue. Singlet oxygen (¹O₂) as unique non-radical derivative of oxygen, possessing unoccupied π* orbital and exhibiting high selectivity towards electron-rich organic pollutants. Nevertheless, most of the approaches suffer from low-efficiency or biotoxicity, which severely restrict their potential applications. Therefore, in this work, we propose a general strategy via photoelectrocatalytic for selectively reducing oxygen to ¹O₂ with designed carbon bridged carbon nitride (CBCN). This work highlights the important role of synergistic photo-electro-catalytic effect for selectively generating the ¹O₂ via oxygen reduction pathway, which can be a promising way especially for degrading electron-rich pollutants.     

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...     

Boosting Visible‐Light‐Driven Photocatalytic Hydrogen Evolution with an Integrated Nickel Phosphide–Carbon Nitride System

Solar light harvesting by photocatalytic H₂ evolution from water could solve the problem of greenhouse gas emission from fossil fuels with alternative clean energy. However, the development of more efficient and robust catalytic systems remains a great challenge for the technological use on a large scale. Here we report the synthesis of a sol–gel prepared mesoporous graphitic carbon nitride (sg‐CN) combined with nickel phosphide (Ni₂P) which acts as a superior co‐catalyst for efficient photocatalytic H₂ evolution by visible light. This integrated system shows a much higher catalytic activity than the physical mixture of Ni₂P and sg‐CN or metallic nickel on sg‐CN under similar conditions. Time‐resolved photoluminescence and electron paramagnetic resonance (EPR) spectroscopic studies revealed that the enhanced carrier transfer at the Ni₂P–sg‐CN heterojunction is the prime source for improved activity.     

The role of Cs dopants for improved activation of molecular oxygen and degradation of tetracycline over carbon nitride

Molecular oxygen (O₂) is activated to reactive oxygen species (ROS) by transferring energy and carriers in the photocatalytic process, which plays an important role in environmental remediation. Herein, Cs-doped carbon nitride (CN-xCs, x = 0.2, 0.8, 1) was prepared by CsCl directly inducing the structural reconstruction of carbon nitride (CN), which had obvious molecular oxygen activation ability to promote tetracycline (TC) degradation. Besides, we explored the influence of Cs doping concentration. As a consequence, the doping concentration of Cs was an important factor affecting the activation of O₂, which could cause changes in the physical and chemical structure of CN, make O enter the CN structure, form N vacancy defects and cyano groups. In addition, a proper amount of Cs doping could reduce the band gap value, increase the light absorption range, have better charge separation and transfer performance, which could remarkably promote the activation of O₂. Benefiting from these advantages, CN-0.8Cs could generate a higher concentration of superoxide radicals (^?O₂^?, 179.30 µmol/L), which was much higher than CN (6.22 µmol/L). Therefore, it exhibited excellent TC degradation photocatalytic performance, and the rate constant k of TC degradation was 0.020 min^?1, which was 6.7 times the degradation rate of CN (k = 0.0030 min^?1). Furthermore, the possible degradation pathways of TC were proposed based on the results of HPLC-MS.     

Efficient activation of peroxymonosulfate by hollow cobalt hydroxide for degradation of ibuprofen and theoretical study

Hollow microsphere structure cobalt hydroxide (h-Co(OH)₂) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate (PMS) for degradation of a typical pharmaceutically active compound, ibuprofen (IBP). The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)₂, and the crystalline phase was assigned to α-Co(OH)₂. h-Co(OH)₂ could efficiently activate PMS for radicals production, and 98.6% of IBP was degraded at 10 min. The activation of PMS by h-Co(OH)₂ was a pH-independent process, and pH 7 was the optimum condition for the activation-degradation system. Scavenger quenching test indicated that the sulfate radical (SO₄^{? ?}) was the primary reactive oxygen species for IBP degradation, which contributed to 75.7%. Fukui index (f ^?) based on density functional theory (DFT) calculation predicted the active sites of IBP molecule for SO₄^{? ?} attack, and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation. The developed hollow Co(OH)₂ used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.     

Graphitic Carbon Nitride Polymer as a Recyclable Photoredox Catalyst for Fluoroalkylation of Arenes

Heterogeneous catalysis for trifluoromethylations and perfluoroalkylations has been performed. Through the usage of cheap, metal‐free and recyclable mesoporous graphitic carbon nitride (mpg‐CN) it was possible to fluoroalkylate various arenes by the reductive activation of sulfonyl chlorides with visible light. Thus, we were able to demonstrate the robustness and versatility of mpg‐CN as a photoredox catalyst beyond water splitting and the activation of oxygen.     

Preparation of carbon nitride nanoparticles by nanoprecipitation method with high yield and enhanced photocatalytic activity

As an emerging 2D conjugated material,graphitic carbon nitride(CN) has attracted great research attention as important catalytic medium for transforming solar energy.Nanostructure modulation of CN is an effective way to improve catalytic activities and has been extensively investigated,but remains challenging due to complex processes,time consuming or low yield.Here,taking advantage of recent discovered good solvents for CN,a nanoprecipitation approach using poor solvents is proposed for preparation of CN nanoparticles(CN NPs).With simple processes of CN dissolution and precipitation,we can quickly synthesize CN NPs(^40 nm) with a yield of up to 50%,the highest one to the best of our knowledge.As an example of potential applications,the as-prepared CN NPs were applied to photocatalytic degradation of dyes with an evident boosted performance up to 2.5 times.This work would open a new way for batch preparation of nanostructured CN and pave its large-scale industrial applications.     

Fabrication of dual Z-scheme photocatalyst via coupling of BiOBr/Ag/AgCl heterojunction with P and S co-doped g-C3N4 for efficient phenol degradation

Advances in noble metal mediated Z-scheme photocatalytic system have ushered in a climax on environmental remediation. Herein, graphitic carbon nitride (GCN) and phosphorus sulphur co-doped graphitic carbon nitride (PSCN) were synthesized via calcination process. GCN, PSCN and Z-scheme visible light driven (VLD) ternary BiOBr/PSCN/Ag/AgCl nanophotocatalyst were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–visible diffuse reflectance spectra (UV–vis DRS). BiOBr/PSCN/Ag/AgCl nanocomposite exhibited superior visible light driven photocatalytic ability as compared to pristine PSCN, AgCl and BiOBr towards degradation of phenol. The results explicated promising photocatalytic activity along with space separation of photocarriers caused via formation of BiOBr/PSCN/Ag/AgCl Z-scheme heterojunction. The visible light absorption efficacy of BiOBr/PSCN/Ag/AgCl photocatalyst was confirmed by photoluminescence (PL) spectra. Finally, recycling experiments were explored for the mechanistic detailing of phenol photodegradation employing BiOBr/PSCN/Ag/AgCl photocatalyst. After seven successive cycles photodegradation efficacy of photocatalyst was reduced to 90% from 98%. Proposed mechanism of BiOBr/PSCN/Ag/AgCl nanophotocatalyst for degradation of phenol was discussed. OH and O₂⁻ radicals were main reactive species responsible for photocatalytic phenol degradation.     

In-situ synthesis of N,S co-doped hollow carbon microspheres for efficient catalytic oxidation of organic contaminants

Metal-free heteroatom doped nanocarbons are promising alternatives to the metal-based materials in catalytic ozonation for destruction of aqueous organic contaminants.In this study,N,S co-doped hollow carbon microspheres（NSCs） were synthesized from the polymerization products during persulfate wet air oxidation of benzothiazole.The contents of doped N and S as well as the structural stability were maneuvered by adjusting the subsequent N₂-annealing temperature.Compared with the prevai...     

A natural manganese ore as a heterogeneous catalyst to effectively activate peroxymonosulfate to oxidize organic pollutants

Heterogeneous transition metal catalysts are indispensable in improving environmental pollution. However, their fabrication is often costly and cumbersome, and they can easily pollute the environment. This study proposed using a natural Gabonese ore (GBO) containing Mn_xO_y and Fe_xO_y as catalysts to degrade orange II (OII) via peroxymonosulfate (PMS) activation. The GBO + PMS system exhibited extraordinarily high stability and catalytic activity towards OII elimination (92.2%, 0.0453 min^?1). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging tests and electron spin-resonance (ESR) analysis. Singlet oxygen (¹O₂) represented the dominant reactive species for OII degradation, while the system presented a lower reaction energy barrier and was effective in a broad pH range (2–10). This work also proposed the activation mechanism for the GBO + PMS system and OII degradation pathways. This study revealed a new approach for exploring inexpensive, eco-friendly, efficient, and stable heterogeneous transition metal catalysts.     

Sol Processing of Conjugated Carbon Nitride Powders for Thin‐Film Fabrication

The chemical protonation of graphitic carbon nitride (CN) solids with strong oxidizing acids, for example HNO₃, is demonstrated as an efficient pathway for the sol processing of a stable CN colloidal suspension, which can be translated into thin films by dip/disperse‐coating techniques. The unique features of CN colloids, such as the polymeric matrix and the reversible hydrogen bonding, result in the thin‐film electrodes derived from the sol solution exhibiting a high mechanical stability with improved conductivity for charge transport, and thus show a remarkably enhanced photo‐electrochemical performance. The polymer system can in principle be broadly tuned by hybridization with desired functionalities, thus paving the way for the application of CN for specific tasks, as exemplified here by coupling with carbon nanotubes.     

石墨相氮化碳量子点的简易水热制备和荧光性能

本文以线状石墨相氮化碳(Lg-CN)为原料,在无需强酸加入的情况下,利用简单的纯水中的水热反应成功制得了氮化碳量子点(CN QDs),并利用傅里叶变换红外光谱、X射线粉末衍射、透射电镜、X射线光电子能谱等对所得量子点的形貌和结构进行了表征,进而解释了量子点的形成机理;利用紫外-可见吸收光谱和荧光光谱对其光学性质进行了研...     

Biochar-Based Graphitic Carbon Nitride Adorned with Ionic Liquid Containing Acidic Polymer: A Versatile,Non-Metallic Catalyst for Acid Catalyzed Reaction

A novel biochar-based graphitic carbon nitride was prepared through calcination of Zinnia grandiflora petals and urea. To provide acidic and ionic-liquid functionalities on the prepared carbon, the resultant biochar-based graphitic carbon nitride was vinyl functionalized and polymerized with 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylic acid and the as-prepared 1-vinyl-3-butylimidazolium chloride. The final catalytic system that benefits from both acidic (–COOH and –SO₃H) and ionic-liquid functionalities was applied as a versatile, metal-free catalyst for promoting some model acid catalyzed reactions such as Knoevenagel condensation and Biginelli reaction in aqueous media under a very mild reaction condition. The results confirmed high activity of the catalyst. Broad substrate scope and recyclability and stability of the catalyst were other merits of the developed protocols. Comparative experiments also indicated that both acidic and ionic-liquid functionalities on the catalyst participated in the catalysis.     

Nitrogen and phosphorus co-doped carbocatalyst for efficient organic pollutant removal through persulfate-based advanced oxidation processes

Carbocatalysts doped with heteroatoms such as nitrogen or sulphur have been reported to be useful in persulfate-based advanced oxidation processes for organic pollutant removal. However, there is limited research on the effect of doping with phosphorus atoms on degradation performance. In this work, a new nitrogen and phosphorus-doped carbocatalyst (N, P-HC) was designed using hydrothermal carbonization followed by pyrolysis at 700 °C, with olive pomace as a carbon source, to degrade organic pollutants in the presence of peroxydisulfate (PDS). Experimental results showed that N, P-HC, with its large specific surface area (871.73 m².g⁻¹), high content of N-pyridinic and N-pyrrolic groups, and the presence of P-O-C and O-P-C bonds, exhibited high degradation performance (98% degradation of Rhodamine B (RhB) in 40 min, with an apparent rate constant (k_app) of 0.055 min⁻¹ and an excellent turnover frequency (TOF) of 0.275 min⁻¹). Quenching study and EPR analysis revealed that singlet oxygen generation (¹O₂) and direct electron transfer were the main reaction pathways for the non-radical pathway in the degradation of RhB. The improved catalytic efficiency in the N, P-HC/PDS/RhB system can be attributed to the synergistic effect between N and P atoms in the graphitic structure of the carbocatalyst, its high surface area, and the presence of oxygenated functional groups on the surface of the N, P-HC. The used N, P-HC carbocatalyst can also be efficiently recovered by heat treatment at 500 °C. Overall, this study presents a simple and environmentally friendly method for synthesizing a high-performance N, P co-doped olive pomace-based carbocatalyst for water decontamination through PS-AOPs processes.     

A rapid and quantitative synthesis of xanthene derivatives using sulfonated graphitic carbon nitride under ball-milling

A truly green, solventless, and fast protocol for the quantitative preparation of biologically active xanthene derivatives with 10 mol% sulfonated graphitic carbon nitride (Sg─CN) as a heterogeneous acidic catalyst was developed. Excellent yields, low cost, solvent-free conditions, high catalytic activity, reusability of the catalyst, simple workup, and heterogeneous carbon-based catalyst make the present method particularly attractive from a green chemistry perspective.     

Photoelectrochemical Reduction of Carbon Dioxide with a Copper Graphitic Carbon Nitride Photocathode

Research on the photoreduction of CO₂ often has been dominated by the use of sacrificial reducing agents. A pathway that avoids this problem would be the development of photocathodes for CO₂ reduction that could then be coupled to a photoanodic oxygen evolution reaction. Here, we present the use of copper-substituted graphitic carbon nitride (Cu−CN) on a fluorinated tin oxide (FTO) electrode for the photoelectrochemical two-electron reduction of CO₂ to CO as a major product (>95 %) and formic acid (<5 %). The results show that at a potential of −2.5 V versus Fc\Fc⁺ the CO₂ reduction activity of Cu−CN on FTO electrode improves by 25 % upon illumination by visible light with a faradaic efficiency of nearly 100 %. Independently, X-ray photoelectron spectroscopy conclusively shows a pronounced increase in the electrical conductivity of the Cu−CN upon white light illumination under vacuum and a contactless measuring configuration. This photo-assisted charge mobility is shown to play a key role in the increased reactivity and faradaic efficiency for the reduction of CO₂.     

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.     

Cobalt‐Embedded Nitrogen‐Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values

Despite being technically possible, splitting water to generate hydrogen is still practically unfeasible due mainly to the lack of sustainable and efficient catalysts for the half reactions involved. Herein we report the synthesis of cobalt‐embedded nitrogen‐rich carbon nanotubes (NRCNTs) that 1) can efficiently electrocatalyze the hydrogen evolution reaction (HER) with activities close to that of Pt and 2) function well under acidic, neutral or basic media alike, allowing them to be coupled with the best available oxygen‐evolving catalysts—which also play crucial roles in the overall water‐splitting reaction. The materials are synthesized by a simple, easily scalable synthetic route involving thermal treatment of Co²⁺‐embedded graphitic carbon nitride derived from inexpensive starting materials (dicyandiamide and CoCl₂). The materials’ efficient catalytic activity is mainly attributed to their nitrogen dopants and concomitant structural defects.     

石墨相氮化碳可见光下活化过一硫酸盐氧化降解光惰性邻苯二甲酸二甲酯的机理研究（英文）

近几年过一硫酸盐(PMS)活化技术备受关注,其中利用太阳能活化PMS具有可持续和环保的优势,但PMS本身不吸收可见光.因此,本文提出利用具有可见光响应的石墨相氮化碳(g-C3N4)激发产生光电子进而活化PMS.首先利用三聚氰胺前驱体通过热缩聚法制备g-C3N4,通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、紫外-可见光漫反射(UV-Vis)、荧光光谱(PL)、透射电镜(TEM)、N2吸附脱附测试(BET)、电化学等一系列方法对g-C3N4进行表征,研究其表面性质及光学性能.结果显示, g-C3N4具有典型的片层结构和可见光活性,禁带宽度为2.7 e V.本文选取光惰性的内分泌干扰物邻苯二甲酸二甲酯(DMP)为目标污染物,系统地研究了其降解动力学和降解机理.研究发现,在短波紫外光(254和300nm)照射下,直接光解和·OH参与的反应机理能实现DMP的光降解,而在可见光照射下g-C3N4介导的光催化过程不能使DMP分解;但当添加PMS时,体系主导自由基由·O2–转化为SO4·–和·OH,从而实现DMP的有效降解和矿化.研究还发现,高浓度的PMS和高剂量的g-C3N4均可以提高PMS的活化量和相应的DMP降解效率,但提高催化剂剂量的方式能更充分的利用PMS.尽管高浓度的DMP阻碍了PMS和光催化剂g-C3N4的有效接触,但可以提高PMS的利用率.当p H低于零电荷点(5.4)时, DMP的降解效率较高.此外,使用两种淬灭剂(乙醇和叔丁醇)与DMP进行竞争性实验,结合电子自旋共振检测,表明SO4·–和·OH都是体系主要的自由基.此外,还对g-C3N4的可持续性能进行考察,四次循环实验结果显示,该催化剂具有良好的可重复利用性.对DMP降解进行总有机碳测定,发现降低了19%.最后,利用液相色谱质谱联用对DMP降解产物进行定性定量分析,发现DMP主要通过SO4·–和·OH对苯环的攻击以及脂肪族链的氧化断键这两种途径进行降解.综上可见,利用可见光激发g-C3N4产生的光电子能有效活化PMS降解顽固型有机污染物,可为实现太阳能活化PMS技术提供有力的技术参考.