Constructing CdSe QDs modified porous g-C3N4 heterostructures for visible light photocatalytic hydrogen production

Constructing heterostructures with narrow-band-gap semiconductors is a promising strategy to extend light absorption range of graphitic carbon nitride (g-C3N4) and simultaneously promote charge separa-tion for its photocatalytic activity improvement.However,its highly localized electronic states of g-C3N4 hinder photo-carrier migration through bulk towards heterostructure interfaces,resulting in low charge carrier separation effidency of solid bulk g-C3N4-based heterostructures.Herein,porous g-C3N4 (PCN)material with greatly shortened migration distance of photo-carriers from bulk to surface was used as an effective substrate to host CdSe quantum dots to construct type Ⅱ heterostructure of CdSe/PCN for pho-tocatalytic hydrogen production.The homogeneous modification of the CdSe quantum dots throughout the whole bulk of PCN together with proper band alignments between CdSe and PCN enables the ef-fective separation of photo-generated charge carriers in the heterostructure.Consequently,the CdSe/PCN heterostructure photocatalyst gives the greatly enhanced photocatalytic hydrogen production activity of 192.3 μmol h-1,which is 4.4 and 8.1 times that of CdSe andPCN,respectively.This work provides a fea-sible strategy to construct carbon nitride-based heterostructure photocatalysts for boosting visible light driven water splitting performance.     

可见光驱动Z-scheme g-C3N4/α-Fe2O3催化剂高效产H2

作为一种新型的具有可见光响应的半导体光催化剂,g-C3N4在光催化产氢领域得到了广泛的研究。然而,纯g-C3N4存在可见光响应范围较窄、光生电子-空穴复合率高、量子效率低等问题。针对纯g-C3N4的缺陷,采用简单的水热合成法制备出一种高效纳米晶胶体g-C3N4/α-Fe2O3复合材料。为了检测g-C3N4/α-Fe2O3的光催化产氢性能,将其引入以NaBH4为底液的体系中。结果表明,当Fe质量分数为1%,体系温度为30℃、NaBH4浓度为50 mmol/L时,产氢量为30 mL。利用PL、EIS以及PC等手段对g-C3N4/α-Fe2O3的光电响应能力进行了分析。结果表明,g-C3N4/α-Fe2O3复合材料具有较低的光致发光强度、较高的光电流密度和较小的电荷转移电阻,说明了光生电荷载流子的有效分离和快速转移。另外,Z-scheme电荷转移途径赋予了g-C3N4/α-Fe2O3较强的氧化能力,为光催化裂解NaBH4提供了较大的驱动力。主要意义在于对光催化产氢有一个新认识,为合理设计和构建Z型光催化剂提供参考。     

Significantly enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS with carbon nanotubes as the electron mediators

The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts.However,it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system.In the present paper,the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators,and its photocatalytic hydrogen production performance was studied.Compared with single-phase g-C3N4,CdZnS and biphasic g-C3 N4/CdZnS photocatalysts,the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced.Meanwhile,g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability.The enhanced photocatalytic hydrogen production performance of g-C3 N4/CNTs/CdZnS is attributed to the fact that CNTs,as an electron mediator,can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS,which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons,increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers.This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.     

A novel Z-scheme CeO2/g-C3N4 heterojunction photocatalyst for degradation of Bisphenol A and hydrogen evolution and insight of the photocatalysis mechanism

CeO2/g-C3N4 heterojunction photocatalyst had been successfully fabricated through a one-step in-situ pyrolysis formation of 3D hollow CeO2 mesoporous nanospheres and 2D g-C3N4 nanosheets together with simultaneous removal of carbon sphere templates after heat treatment.The sample shows high catalytic performances for photocatalytic hydrogen generation and photocatalytic oxidation of Bisphe-nol A(BPA)under visible light irradiation,and the catalytic degradation route of BPA was suggested by the degradation products determined by GC-MS.The enhancing catalytic activity was attributed to the effective interfacial charge migration and separation.Finally,it was proposed that the CeO2/g-C3N4 het-erojunction photocatalyst could follow a more appropriate Z-scheme charge transfer mechanism,which was confirmed by the analysis of experiment and theoretical calculation results.     

Metal-free π-conjugated hybrid g-C3N4 with tunable band structure for enhanced visible-light photocatalytic H2 production

Development of low-cost and efficient photocatalytic materials with visible-light response is of urgent need for solving energy and environmental problems.Here,a metal-free two-dimensional (2D) π-conjugated hybrid g-C3N4 photocatalyst with tunable band structure was prepared by a novel one-pot bottom-up method based on a supersaturated precipitation process of urea and triethanolamine (TEOA)solution.The microstructure of the hybrid g-C3N4 is revealed to be a compound of periodic tri-s-triazine units grafted with N-doped graphene (GR) fragments.From experimental evidence and theoretical calcu-lations,the two different π-conjugated fragments in the hybrid g-C3N4 material are proved to construct a 2D in-plane junction structure,thereby expanding the light absorption range and accelerating the inter-face charge transfer.The π-conjugated electron coupling in the 2D photocatalyst eliminates the grain boundary effect,and the coupled highest occupied molecular orbital (HOMO) effectively promotes the separation of photo-induced charge carriers.Compared with the g-C3N4 prepared by the conventional method,the visible-light H2 production activity of the optimized sample is enhanced by 253 ％.This work provides a new strategy of constructing metal-free g-C3N4 hybrids for efficient photocatalytic water splitting.     

Increasingπ-electron availability in benzene ring incorporated graphitic carbon nitride for increased photocatalytic hydrogen generation

Increasing the availability ofπ-electron in graphitic carbon nitride(g-C₃N₄)can reduce the band gap and thus enhance the photocatalytic hydrogen(H₂)generation activity upon exposure to visible light,However,such strategy has not yet been largely applied to increase the H₂generation of g-C₃N₄.Herein,we succes s fully increased the amount ofπ-electron in g-C₃N₄by incorporatingπ-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air.The incorporation of benzene rings not only extends the light absorption of g-C₃N₄to 650 nm,but also improves the electrical conductivity due to delocalization ofπelectrons in benzene rings.As a result,a 3.4 times enhancement of photocatalytic H₂generation was achieved from the g-C₃N₄with benzene ring incorporation in comparing with that of pristine g-C₃N₄.More interestingly,H₂generation still occurs under irradiation of the light ofλ≥490 nm,above the absorption edge of pristine g-C₃N₄(~460 nm),illustrating the positive effectiveness of incorporated benzene rings on enhancing the H₂generation capacity of g-C₃N₄.The present work manifests the advantages of increasingπ-conjugated electrons on designing highly active g-C₃N₄photocatalysts.     

可见光驱动RGO/g-C3N4活化过硫酸盐降解水中双酚A

光催化氧化法能够高效去除水体中的持久性有机污染物, 在污水净化领域展现出广阔的应用前景。本研究分别以尿素和双氰胺为原料, 采用冷干辅助热聚合法制备了还原性氧化物石墨烯/氮化碳(RGO/g-C₃N₄)二元可见光催化剂, 并对样品的形貌结构和光学性能进行了分析表征。结果表明, 二维层状g-C₃N₄与RGO在异质结界面上紧密的结合在一起。同时以内分泌干扰物双酚A (BPA)为降解污染物, 研究了不同催化剂在可见光下活化过硫酸盐去除BPA的活性。光催化实验结果显示, 在可见光(λ>420 nm)照射下, 加入氧化剂过硫酸盐(PS)作为电子受体, 有效地增强了光催化剂可见光降解BPA的活性。以尿素为原料制备的RGO/g-C₃N₄催化剂在40 min内几乎完全去除溶液中的BPA。经过5次循环反应后, 可见光照射40 min, 该催化剂对BPA的去除率仍能达到80%以上, 表现出良好的稳定性。     

基于g–C3N4光催化型抗菌包装纸的制备及其抗菌性研究

目的 解决g–C3N4存在的比表面积小，电子–空穴复合速率快从而导致光催化性能不佳等问题。方法 以尿素和硫脲为前驱体材料，通过热解聚辅助水蒸气活化合成S掺杂石墨相氮化碳(g–C3N4)，并用界面聚合制备出光催化型抗菌包装纸。利用扫描电镜(SEM)、红外光谱(FTIR)、水接触角(WCA)、热重分析(TGA)、光催化抗菌实验等对抗菌包装纸的形态结构、表面官能团、纸张性质、光催化抗菌性进行详细研究。结果 致密的g–C3N4层有效提高了抗菌包装纸的疏水性和热稳定性。可见光照射下，光催化型抗菌包装纸对大肠杆菌和金黄色葡萄球菌的杀灭率达100%。未经可见光照射的原纸比光催化型包装纸的抗菌性差。结论 g–C3N4光催化型抗菌包装纸具有良好的广谱抗菌性，为绿色抗菌包装材料的制备提供了新思路。     

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.     

Platinum-coordinated graphitic carbon nitride nanosheet used for targeted inhibition of amyloid β-peptide aggregation

Amyloid β-peptide (Aβ) aggregation is a critical step in the pathogenesis of Alzheimer's disease (AD).Inhibition of Aβ production,dissolution of existing aggregates and clearance of Aβ represent valid therapeutic strategies against AD.Herein,a novel platinum(Ⅱ)-coordinated graphitic carbon nitride (g-C3N4)nanosheet (g-C3N4@Pt) has been designed to covalently bind to Aβ and modulate the peptide's aggregation and toxicity.Furthermore,g-C3N4@Pt nanosheets possess high photocatalytic activity and can oxygenate Aβ upon visible light irradiation,remarkably attenuating both the aggregation potency and neurotoxidty of Aβ.Due to its ability to cross the blood-brain barrier (BBB) and its good biocompatibility,g-C3N4@Pt nanosheet is a promising inhibitor of Aβ aggregation.This study may serve as a model for the engineering of novel multifunctional nanomaterials used for the treatment of AD.     

g-C_3N_4-CdS异质结的合成及其光催化性能研究

以尿素为前驱体,550℃热聚合反应5 h,制备了块状g-C_3N_4。然后将块状g-C_3N_4超声剥离得到片状g-C_3N_4,在g-C_3N_4纳米片上原位生长Cd S(直径约130 nm),从而制备了g-C_3N_4-Cd S异质结。g-C_3N_4-Cd S异质结的吸收边约505 nm处,与g-C_3N_4(约460 nm)相比具有明显的红移,可吸收更多的可见光。此外,g-C_3N_4-Cd S异质结可降解99%的罗丹明B,具有较高的光催化活性。     

In-situ synthesized and photocatalytic performance evaluation of MoS2-C-g-C3N4 heterostructure photocatalyts

The heterostructure between two semiconductor materials that had suitable band edge positions can contribute to the separation of photoelectrons and holes. In this paper, the heterostructure MoS₂-C-g-C₃N₄ photocatalysts were in-situ synthesized at one-pot high temperature processing. The obtained 0.4 MoS₂-C-g-C₃N₄ composites displayed the highest photocatalytic hydrogen evolution activity with a corresponding H₂ evolution rate of 238 μmol g⁻¹h⁻¹, which was about 4.5 times higher than that of 3% C-g-C₃N₄, and the photocatalyts exhibited excellent stability which was used for photocatalytic hydrogen evolution reaction for 12 h. The 0.4 MoS₂-C-g-C₃N₄ sample displayed well degradation activities for MO, MB, RhB, MR and Ar18, and the scavenging studies indicated the major involvement of ·O₂^– radicals in the degradation process. The enhanced photocatalytic activity of MoS₂-C-g-C₃N₄ composite was predominantly attributed to the synergistic effects of type II heterostructure between g-C₃N₄ and MoS₂, which effectively accelerated the transfer and separation of photogenerated charge carriers. Besides, the introduction of noble metal-free MoS₂ co-catalyst further improved visible light absorption and provided more active sites for H₂ evolution reaction. Such work is promising for designing a novel heterostructure photocatalysts for solar-to-fuel conversion and environmental modification.     

Nitrogen-doped Carbon Nanospheres-Modified Graphitic Carbon Nitride with Outstanding Photocatalytic Activity

Metals and metal oxides are widely used as photo/electro-catalysts for environmental remediation.However,there are many issues related to these metal-based catalysts for practical applications,such as high cost and detrimental environmental impact due to metal leaching.Carbon-based catalysts have the potential to overcome these limitations.In this study,monodisperse nitrogen-doped carbon nanospheres(NCs)were synthesized and loaded onto graphitic carbon nitride(g-C3N4,GCN)via a facile hydrothermal method for photocatalytic removal of sulfachloropyridazine(SCP).The prepared metal-free GCN-NC exhibited remarkably enhanced efficiency in SCP degradation.The nitrogen content in NC critically influences the physicochemical properties and performances of the resultant hybrids.The optimum nitrogen doping concentration was identified at 6.0 wt%.The SCP removal rates can be improved by a factor of 4.7 and 3.2,under UV and visible lights,by the GCN-NC composite due to the enhanced charge mobility and visible light harvesting.The mechanism of the improved photocatalytic performance and band structure alternation were further investigated by density functional theory(DFT)calculations.The DFT results confirm the high capability of the GCN-NC hybrids to activate the electron–hole pairs by reducing the band gap energy and efficiently separating electron/hole pairs.Superoxide and hydroxyl radicals are subsequently produced,leading to the efficient SCP removal.     

三维大孔g-C3N4吸附和光催化还原U(VI)性能研究

将易溶的U(VI)还原为微溶的U(IV)是治理放射性铀污染的有效方法。本研究以SiO₂纳米球作为硬模板, 通过热聚合-刻蚀制备具有连续贯通的三维大孔g-C₃N₄光催化剂, 用于吸附-光催化还原U(VI)。材料表征结果显示: 三维大孔g-C₃N₄比表面积显著增加, 对可见光的吸收明显增强; 同时具有三维有序大孔结构, 并呈规则的紧密堆积结构, 孔壁完整多孔, 整个结构具有良好的三维连通性。吸附实验表明: 三维大孔g-C₃N₄对U(VI)最大吸附容量可达~30.5 mg/g, 该过程更符合Langmuir吸附模型, 与块体g-C₃N₄相比吸附容量提高了~1.83倍。光催化还原实验表明: 三维大孔g-C₃N₄具有高的光催化活性和良好的稳定性, 其还原反应速率常数为~0.0142 min ^-1, 是块体g-C₃N₄ (~0.0024 min ^-1)的~5.9倍。鉴于三维大孔g-C₃N₄具有较优异的吸附-催化还原性能, 该材料有望应用于放射性废水中U(VI)的快速高效清除。     

具有三维网状结构的石墨相氮化碳/还原氧化石墨烯/钯复合材料的合成及可见光催化性能

石墨相氮化碳(g-C_3N_4)已经被认为是一种高效的非金属半导体光催化剂。为进一步优化其光催化性能,通过热解-水热两步法制备了三维网状结构的g-C_3N_4/还原氧化石墨烯(rGO)/钯纳米颗粒(Pd NPs)复合材料。该复合材料由大量超薄片组成,而且薄片上有大量直径约为10nm的Pd NPs。g-C_3N_4/rGO/Pd NPs复合材料展现了一个宽的可见光吸收(边~460nm),其在460~800nm波长范围内还有一个随波长增加的光吸收。经可见光(λ400nm)照射140 min后,g-C_3N_4/rGO/Pd NPs复合材料可降解90%罗丹明B(RhB)。此外,循环实验表明g-C_3N_4/rGO/Pd NPs复合材料具有良好的稳定性。因此,g-C_3N_4/rGO/Pd NPs复合材料有望成为一种高效稳定的光催化剂,在水污染处理领域具有潜在的应用价值。     

Creating Graphitic Carbon Nitride Based Donor‐π–Acceptor‐π–Donor Structured Catalysts for Highly Photocatalytic Hydrogen Evolution

Conjugated polymers with tailored donor–acceptor units have recently attracted considerable attention in organic photovoltaic devices due to the controlled optical bandgap and retained favorable separation of charge carriers. Inspired by these advantages, an effective strategy is presented to solve the main obstructions of graphitic carbon nitride (g‐C₃N₄) photocatalyst for solar energy conversion, that is, inefficient visible light response and insufficient separation of photogenerated electrons and holes. Donor‐π–acceptor‐π–donor polymers are prepared by incorporating 4,4′‐(benzoc 1,2,5 thiadiazole‐4,7‐diyl) dianiline (BD) into the g‐C₃N₄ framework (UCN‐BD). Benefiting from the visible light band tail caused by the extended π conjugation, UCN‐BD possesses expanded visible light absorption range. More importantly, the BD monomer also acts as an electron acceptor, which endows UCN‐BD with a high degree of intramolecular charge transfer. With this unique molecular structure, the optimized UCN‐BD sample exhibits a superior performance for photocatalytic hydrogen evolution upon visible light illumination (3428 µmol h^?1 g^?1), which is nearly six times of that of the pristine g‐C₃N₄. In addition, the photocatalytic property remains stable for six cycles in 3 d. This work provides an insight into the synthesis of g‐C₃N₄‐based D‐π–A‐π–D systems with highly visible light response and long lifetime of intramolecular charge carriers for solar fuel production.     

All-solid-state Z-scheme BiVO4-Bi6O6(OH)3(NO3)3 heterostructure with prolonging electron-hole lifetime for enhanced photocatalytic hydrogen and oxygen evolution

As a visible-light response photocatalyst,BiVO4 is widely used in photocatalytic oxygen evolution.In this study,a novel BiVO4-Bi6O6(OH)3(NO3)3(BBN)heterostructure fabricates via a simple one-pot hydrothermal approach is certified to effectively restrain the recombination of carriers by efficient spa-tial charge separation.By employing BBN as a reductive-function photocatalyst,a solid-state Z-scheme is constructed to improve the photo-redox capacity of BiVO4 and hydrogen production is realized in the BiVO4-BBN heterostructure for the first time.The solid-state Z-scheme introduced in the BiVO4-BBN ensures the photoexcited carriers with the powerful redox capacity to participate in the photocatalytic reaction.     

Construction of hierarchical TiO<Subscript>2</Subscript> nanorod array/graphene/ZnO nanocomposites for high-performance photocatalysis

The photocatalytic performance of heterostructure photocatalysts is limited in practical use due to the charge accumulation at the interface and its low efficiency in utilizing solar energy during photocatalytic process. In this work, a ternary hierarchical TiO₂ nanorod arrays/graphene/ZnO nanocomposite is prepared by using graphene sheets as bridge between TiO₂ nanorod arrays (NRAs) and ZnO nanoparticles (NPs) via a facile combination of spin-coating and chemical vapor deposition techniques. The experimental study reveals that the graphene sheets provide a barrier-free access to transport photo-excited electrons from rutile TiO₂ NRAs and ZnO NPs. In addition, there generates an interface scattering effect of visible light as the graphene sheets provide appreciable nucleation sites for ZnO NPs. This synergistic effect in the ternary nanocomposite gives rise to a largely enhanced photocurrent density and visible light-driven photocatalytic activity, which is 2.6 times higher than that of regular TiO₂ NRAs/ZnO NPs heterostructure. It is expected that this hierarchical nanocomposite will be a promising candidate for applications in environmental remediation and energy fields.     

Co-BiVO4光催化剂的制备及其用于光催化氧化噻吩

采用水热法制备了掺杂型可见光催化剂Co-BiVO4,用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射(DRS)和低温氮吸附等表征手段对其结构性质进行了表征.结果显示,Co的掺杂没有改变BiVO4的晶相,在pH=7时制备的Co-BiVO4是单斜晶系白钨矿,晶型较完整.同时Co的掺杂延伸了BiVO4的可见光吸收范围,吸收边带明显红移,能隙禁带宽窄于纯BiVO4.低温氮吸附表明Co-BiVO4催化剂(pH=7)的孔半径主要分布在2.67 nm附近.在空气–有机溶剂体系中,研究了Co-BiVO4氧化脱除FCC汽油中特征硫化物噻吩的效果.实验结果表明,催化剂加入量为1.0 mg/L,空气通气量为150 mL/min,氙灯光照3.0 h,Co-BiVO4(pH=7.0)对模拟汽油的脱硫率可达到86%.     

Optimized design of visible light-driven g-C3N4 nanorod/Ag3PO4 Z-scheme heterojunction with enhanced interfacial charge separation and photocatalytic activity

Journal of Materials Science: Materials in Electronics - A g-C3N4 nanorod/Ag3PO4 (CN-A) Z-Scheme heterojunction, which can response to visible light, was prepared through a convenient and green...