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.     

Construction of direct Z-scheme g-C3N4/TiO2 nanorod composites for promoting photocatalytic activity

Direct Z-scheme g-C₃N₄/TiO₂ nanorod composites were prepared for enhancing photocatalytic activity for pollutant removal. The characterization revealed that the g-C₃N₄/TiO₂ nanorod composite formed a close interface contact between g-C₃N₄ and TiO₂ nanorods, which was of benefit for the charge transfer and resulted in its high photocatalytic activity. The g-C₃N₄/TiO₂ nanorod composites exhibited higher photocatalytic activity for degradation of Rhodamine B (RHB) than bare g-C₃N₄ and TiO₂ nanorods. The high photocatalytic activity of g-C₃N₄/TiO₂ nanorod composites is attributed to the formation of the direct Z-scheme system, in which the electrons from the conduction band (CB) of TiO₂ combine with the holes from the valence band (VB) of C₃N₄ while the electrons from the CB of C₃N₄ and holes from the VB of TiO₂ with stronger redox ability are used to reduce and oxidize pollutants. Based on the radical-trapping experiments, the main reactive species for RHB degradation are O₂⁻ and · OH, which are produced by photoinduced electrons and holes with high redox ability. This work provides insights into the photocatalytic mechanism of composite materials for the photocatalytic removal of organic pollutants.     

Flower-like shaped Bi12TiO20/g-C3N4 heterojunction for effective elimination of organic pollutants: Preparation,characterization, and mechanism study

Flower-like shaped Bi₁₂TiO₂₀ (Bismuth Titanate)/g-C₃N₄ (graphite-like carbon nitride) heterojunction was prepared through hydrothermal and sonification methods for the degradation of organic pollutants by visible-light irradiation. The preparation process, chemical structures, and the mechanism of photocatalytic enhancement of the heterostructures were studied systematically. Under visible-light irradiation, the novel flower-like shaped Bi₁₂TiO₂₀/g-C₃N₄ heterojunction demonstrates prominent activities for the degradation of rhodamine B and p-nitrophenol, with the introduction of flower-like shaped Bi₁₂TiO₂₀ into g-C₃N₄ composites greatly increasing the activity of pure g-C₃N₄. This activity enhancement for the heterojunction could be mainly attributed to its low recombination speed of electron–hole pairs, high adsorption ability of organic pollutants, and better optical absorption ability. Moreover, in the visible-light system of Bi₁₂TiO₂₀/g-C₃N₄, ^•OH also contributed to the degradation of pollutants, which may explain the enhanced photocatalytic activity after the introduction of Bi₁₂TiO_20, as ^•OH is inactive in pure g-C₃N₄. Furthermore, 10 wt.% Bi₁₂TiO₂₀/g-C₃N₄ showed not only high activity but also good stability for degradation of aqueous organic pollutants, implying potential applications prospect.     

Degradation of tetracycline hydrochloride by ultrafine TiO2 nanoparticles modified g-C3N4 heterojunction photocatalyst: Influencing factors,products and mechanism insight

The unique heterojunction photocatalyst of graphite carbon nitride（g-C₃N₄） modified ultrafine TiO₂（gC₃N₄/Ti O₂） was successfully fabricated by electrochemical etching and co-annealing method. However,the effects of various environmental factors on the degradation of TC by g-C₃N₄/Ti O2and the internal reaction mechanism are still unclear. In this study, the effects of initial p H, anions, and cations on the ph...     

碳化MoS2/掺硫g-C3N4异质结的合成及其在可见光下催化降解罗丹明B机理

为了进一步提高聚合物半导体类石墨相氮化碳（g-C₃N₄）降解有机物的活性,通过简单的水热法复合得到碳化MoS₂/掺硫g-C₃N₄异质结（MoSC/S-CN）,并在可见光下研究其罗丹明B （RhB）的降解性能。结果表明,相较于纯g-C₃N₄,最优化的MoSC/S-CN样品对可见光的吸收范围得到明显拓宽,并且在100 min内对RhB的降解效率为92.5%,比纯g-C₃N₄性能提高68.83%。一系列的结构和光学性质表明,掺硫后再进一步与碳化MoS₂耦合可以协同作用于g-C₃N₄,改善g-C₃N₄的能带结构,加速光生电子空穴对的分离,有效提高光催化活性。     

Photocatalytic removal of tetracycline by a Z-scheme heterojunction of bismuth oxyiodide/exfoliated g-C3N4: performance,mechanism, and degradation pathway

Antibiotics, once being released into the environment, become recalcitrant organic pollutants, which pose a potential risk to ecological balance and human health. In this study, a Z-scheme heterojunction of bismuth oxyiodide (BiOI)/exfoliated g-C₃N₄ (BiOI/ECN hereafter) was synthesized by the combination of thermal exfoliation of g-C₃N₄ and chemical precipitation of BiOI for efficient photocatalytic degradation of tetracycline in aqueous solutions under visible light irradiation. The optimized BiOI/ECN delivered an outstanding degradation rate at circa 0.0705 min^?1, which was 10 times higher than that of the bulk g-C₃N₄. The photocatalytic degradation efficiency of tetracycline remained almost unchanged in a pH range of 3–11, and the BiOI/ECN displayed an excellent photostability upon recycled usage. The photocatalytic mechanism of tetracycline was ascribed to the main reactive oxidation species of photogenerated holes and superoxide radicals. In addition, the possible degradation pathways of tetracycline were investigated by HPLC-MS to identify intermediates. The toxicity of photocatalytic-generated intermediates of tetracycline was found significantly alleviated according to the calculation of quantitative structure–activity relationship prediction. This work not only provides an attractive photocatalyst for the removal of tetracycline but also opens a new avenue for rational design of Z-scheme heterojunction composites for tetracycline degradation.     

BiOBr/g-C3N4 S型异质结无H2O2光-自芬顿高效催化降解RhB

通过焙烧-超声混合法成功地制备了BiOBr/g-C₃N₄S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)。研究了所制备样品有/无Fe³⁺的光-自芬顿催化/光催化降解罗丹明B(RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C₃N₄S型异质结能原位生成H₂O₂,添加Fe³⁺后,H₂O₂被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min^-1,约为无Fe³⁺光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe...     

BiOBr/g-C3N4 S型异质结无H2O2光-自芬顿高效催化降解RhB

通过焙烧-超声混合法成功地制备了BiOBr/g-C₃N₄ S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe³⁺的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C₃N₄ S型异质结能原位生成H₂O₂,添加Fe³⁺后,H₂O₂被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min^-1,约为无Fe³⁺光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe³⁺的加入促进了光生电荷的分离和H₂O₂的活化,超氧阴离子自由基(·O₂^-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O₂^-作用更大。     

Defect-assisted surface modification enhances the visible light photocatalytic performance of g-C3N4@C-TiO2 direct Z-scheme heterojunctions

To increase the number of active sites and defects in TiO₂ and promote rapid and efficient transfer of photogenerated charges, a g-C₃N₄@C-TiO₂ composite photocatalyst was prepared via in situ deposition of g-C₃N₄ on a carbon-doped anatase TiO₂ surface. The effects of carbon doping state and surface modification of g-C₃N₄ on the performance of g-C₃N₄@C-TiO₂ composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO₂ gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C₃N₄@C-TiO₂ for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C₃N₄@10C-TiO₂ sample exhibited the highest apparent reaction rate constant of 0.036 min^?1 (0.039 min^?1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO₂, 10C-TiO₂, g-C₃N₄, and g-C₃N₄@TiO₂, respectively. g-C₃N₄ was grown in situ on the surface of C-TiO₂ by surface carbon hybridization and bonding. The resultant novel g-C₃N₄@C-TiO₂ photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.     

Bi2Fe4O9/g-C3N4/UiO-66三元复合材料的协同光催化作用

通过水热法合成具有协同机制的三元复合材料Bi₂Fe₄O₉/g-C₃N₄/UiO-66,研究表明三元复合光催化剂的催化活性要高于二元材料和纯材料。这主要是由于Bi₂Fe₄O₉更易于和g-C₃N₄结合形成稳定的Z-scheme异质结结构,使三元复合材料增强了可见光响应能力,提高了电子-空穴分离能力,增强了空穴和电子的氧化还原能力。     

Bi2Fe4O9/g-C3N4/UiO-66三元复合材料的协同光催化作用

通过水热法合成具有协同机制的三元复合材料Bi₂Fe₄O₉/g-C₃N₄/UiO-66,研究表明三元复合光催化剂的催化活性要高于二元材料和纯材料。这主要是由于Bi₂Fe₄O₉更易于和g-C₃N₄结合形成稳定的Z-scheme异质结结构,使三元复合材料增强了可见光响应能力,提高了电子-空穴分离能力,增强了空穴和电子的氧化还原能力。     

石墨相氮化碳/二氧化锡复合材料的制备及光催化性能

采用热聚合法和水热法相结合的方法制备了g-C_3N_4/SnO_2复合光催化剂。利用XRD、SEM、TEM、FT-IR和UV-Vis DRS等多种测试手段对所得样品的物相结构、微观形貌和吸光特性等进行了表征。结果表明,异质结构复合光催化剂的最大光吸收边位置相对纯相SnO_2发生了明显的红移,并且SnO_2颗粒均匀分布于g-C_3N_4表面,其中最优组分(50%-g-C_3N_4/SnO_2)光催化降解染料罗丹明B(RhB)的效率达到了纯相g-C_3N_4的3.78倍。     

Synergistic improvement of Cr(VI) reduction and RhB degradation using RP/g-C3N4 photocatalyst under visible light irradiation

The RP/g-C₃N₄ heterojunction photocatalyst was fabricated by a facile heat treatment strategy. The obtained composite has excellent light harvesting ability and charge separation performance. Compared to single RP and g-C₃N₄, the 50%-RP/g-C₃N₄ exhibited enhanced photocatalytic activity for simultaneously removing Cr(VI) and RhB, and the removal rates can reach 92% and 99% in 25 min, respectively. The enhanced mechanism was revealed by active species capturing experiments, showing that electrons can reduce Cr(VI) and produce O₂^– in air and that holes can directly oxidize the dyes. The coexistence of Cr(VI) and RhB will lead to a synergistic improvement of Cr(VI) reduction and RhB degradation due to rapid surface reactions. This further improves the charge separation except for the heterojunction effect. In addition, the COD analysis demonstrates that organic dyes are mainly degraded into CO₂, H₂O and some intermediates.     

Two-step calcination synthesis of Z-scheme α-Fe2O3/few-layer g-C3N4 composite with enhanced hydrogen production and photodegradation under visible light

Solar photocatalytic technology is of great significance for adjusting energy structure and environmental improvement. Developing an efficient and low-cost photocatalyst is key to realizing the conversion of solar to chemical energy. In this study, α-Fe₂O₃-modified few-layer g-C₃N₄ hybrids (α-Fe₂O₃/FL g-C₃N₄) were successfully prepared by a two-step calcination route with a mixture of α-Fe₂O₃ and melamine. The samples were characterized by Thermogravimetric analysis, X-ray diffraction, Fourier transform infrared, scanning electron microscope, transmission electron microscope, High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, UV–Vis absorption spectrum, photoluminescence, and Time-resolved photoluminescence spectroscopy; furthermore, their photoelectrochemical measurements and their photocatalytic performances were evaluated by visible light-driven hydrogen evolution and degradation of RhB. The results showed that the hydrogen production activity and degradation ability of α-Fe₂O₃/FL g-C₃N₄ were significantly enhanced compared with those of α-Fe₂O₃ / multilayer g-C₃N₄ (α-Fe₂O₃/ML g-C₃N₄) and FL g-C₃N₄. The enhanced photoactivities were mainly attributed to the synergistic effect between the increased visible-light absorption, enhanced surface area, and highly efficient electron transfer and separation on the Z-type heterojunction interface. This work not only provides evidence for the formation of FL g-C₃N₄ nanosheets using a thermal exfoliation method but also provides new insights into the interfacial charge carrier dynamics of Z-scheme α-Fe₂O₃/FL g-C₃N₄ heterostructures for photocatalytic H₂ generation and pollutant degradation.     

单分散g-C3N4量子点修饰一维棒状BiPO4微晶的合成及其对光催化活性增强机理

利用水热法合成了一维棒状BiPO₄微晶,在此基础上采用浸渍-被烧法进行g-C₃N₄量子点表面修饰获得新颖的g-C₃N₄/BiPO₄异质结。借助X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(HRTEM)、能谱(EDS)、紫外-可见漫反射(UV-Vis-DRS)等测试手段对所得样品的相组成、形貌和谱学特征进行了表征。选择罗丹明B(RhB)和苯酚作为模型污染物研究了所得在可见光下的催化活性。结果表明,样品16%(w/w) g-C₃N₄/BiPO₄对RhB降解的速率常数分别是纯和的g-C₃N₄和BiPO₄的16倍和4.6倍。g-C₃N₄量子点与BiPO₄之间形成异质结,抑制了光生电子-空穴对的复合,从而提高了催化剂的活性。自由基捕获实验进一步表明,超氧负离子自由基(·O₂-)是催化降解RhB和苯酚的主要活性物种。     

Enhancement in the photocatalytic activity of TiO2 nanofibers hybridized with g-C3N4 via electrospinning

TiO₂/g-C₃N₄ nanofibers with diameter of 100–200 nm were prepared by electrospinning method after calcination at high temperature, using polyvinylpyrrolidone (PVP), Melamine (C₃H₆N₆), Ti(OC₄H₉)₄ as raw materials. The composite nanofibers were characterized by XRD, FT-IR, SEM, UV–vis and PL respectively. The effects of different g-C₃N₄ contents on structure and photocatalytic degradation of the composite nanofibers were investigated. The results indicated that with increasing g-C₃N₄ content, the diameter of the composite fibers increased and the morphology changed from uniform structure to a nonuniform one, containing beads. The composite nanofibers displayed the best photocatalytic degradation on RhB, when the g-C₃N₄ content was 0.8 wt%. The degree of degradation was up to 99% at the optimal conditions of 40 min. The degradation activity of the composite nanofibers on RhB, MB and MO was found to be higher than that of the TiO₂ nanofibers.     

单分散g-C3N4量子点修饰一维棒状BiPO4微晶的合成及其对光催化活性增强机理

利用水热法合成了一维棒状BiPO₄微晶,在此基础上采用浸渍-焙烧法进行g-C₃N₄量子点表面修饰获得新颖的g-C₃N₄/BiPO₄异质结。借助X射线衍射（XRD）、场发射扫描电镜（FE-SEM）、透射电镜（HRTEM）、能谱（EDS）、紫外-可见漫反射（UV-Vis-DRS）等测试手段对所得样品的相组成、形貌和谱学特征进行了表征。选择罗丹明B（RhB）和苯酚作为模型污染物研究了所得在可见光下的催化活性。结果表明,样品16%（w/w） g-C₃N₄/BiPO₄对RhB降解的速率常数分别是纯g-C₃N₄和BiPO₄的4.6倍和15倍。g-C₃N₄量子点与BiPO₄之间形成异质结,抑制了光生电子-空穴对的复合,从而提高了催化剂的活性。自由基捕获实验进一步表明,超氧负离子自由基（·O₂^-）是催化降解RhB和苯酚的主要活性物种。     

Synthesis of eco-friendly porous g-C3N4/SiO2/SnO2 composite with excellent visible-light responsive photocatalysis

Forming eco-friendly heterojunction photocatalysts is excellent method to accelerate the separation rate of photogenerated charge carriers, which is attracting more and more attention. In this study, a novel and stable disordered porous g-C₃N₄/SiO₂/SnO₂ (DOP-CSiSn) heterojunction composites was fabricated by a sol-gel hard template method, and the optimal g-C₃N₄ doped ratio was adjusted in DOP-CSiSn. The DOP-CSiSn photocatalyst had the much larger specific surface area and disordered porous structure, which exhibited strong photocatalytic effect to degrade Rhodamine B (RhB), Methylene blue (MB) and Methyl orange (MO) under visible light. When the g-C₃N₄ doping content was 30 wt%, the highest photocatalytic activities were obtained, and the degradation rate of MB and MO were 99.73% and 95.58% after 50 min, respectively. Degradation rate of RhB was 95.10% after 90 min. Photocatalytic degradation rate of organic pollutants were still more than 90% after six time consecutive cycles, the composite had wonderful stability and potential value in environmental purification.     

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.     

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。