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1.
Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C3N4 because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu3P nanosheet/P-doped g-C3N4 (PCN) nanosheet heterojunction photocatalyst (PCN/Cu3P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C3N4 composite for photocatalytic H2 evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C3N4 could be well reserved in the phosphorization process, while CuS and g-C3N4 in-situ transformed into Cu3P and PCN, respectively, leading to the formation of PCN/Cu3P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu3P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H2 evolution reaches 5.12 μmol·h–1, nearly 24 times and 368 times higher than that of pristine PCN and g-C3N4, respectively. This work represents an excellent example in elaborately constructing g-C3N4-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system.   相似文献   

2.
Gold (Au) plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride (g-C3N4) nanosheets via a facile oil-bath method. The photocatalytic activity of the Au/monolayer g-C3N4 composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment. All of the Au/monolayer g-C3N4 composites showed better photocatalytic performance than that of monolayer g-C3N4 and the 1% Au/monolayer g-C3N4 composite displayed the highest photocatalytic hydrogen evolution rate of the samples. The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles, which led to the surface plasmon resonance (SPR) effect. The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process. The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g-C3N4. Thus, the Au/monolayer g-C3N4 composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron-hole pairs than those of monolayer g-C3N4. A photocatalytic mechanism for the composites was also proposed.  相似文献   

3.
In response to the increasing concerns over energy and environmental sustainability, photocatalytic water‐splitting technology has attracted broad attention for its application in directly converting solar energy to valuable hydrogen (H2) energy. In this study, high‐efficiency visible‐light‐driven photocatalytic H2 production without the assistance of precious‐metal cocatalysts was achieved on graphene–ZnxCd1?xS composites with controlled compositions. The graphene‐ZnxCd1?xS composites were for the first time fabricated by a one‐step hydrothermal method with thiourea as an organic S source. It was found that thiourea facilitates heterogeneous nucleation of ZnxCd1?xS and in situ growth of ZnxCd1?xS nanoparticles on graphene nanosheets. Such a scenario results in abundant and intimate interfacial contact between graphene and ZnxCd1?xS nanoparticles, efficient transfer of the photogenerated charge carriers, and enhanced photocatalytic activity for H2 production. The highest H2‐production rate of 1.06 mmol h?1 g?1 was achieved on a graphene–Zn0.5Cd0.5S composite photocatalyst with a graphene content of 0.5 wt %, and the apparent quantum efficiency was 19.8 % at 420 nm. In comparison, the graphene–ZnxCd1?xS composite photocatalyst prepared by using an inorganic S source such as Na2S exhibited much lower activity for photocatalytic H2 production. In this case, homogeneous nucleation of ZnxCd1?xS becomes predominant and results in insufficient and loose contact with the graphene backbone through weak van der Waals forces and a large particle size. This study highlights the significance of the choice of S source in the design and fabrication of advanced graphene‐based sulfide photocatalytic materials with enhanced activity for photocatalytic H2 production.  相似文献   

4.
Photocatalytic H2 evolution reactions on pristine graphitic carbon nitrides (g-C3N4), as a promising approach for converting solar energy to fuel, are attractive for tackling global energy concerns but still suffer from low efficiencies. In this article, we report a tractable approach to modifying g-C3N4 with vanadyl phthalocyanine (VOPc/CN) for efficient visible-light-driven hydrogen production. A non-covalent VOPc/CN hybrid photocatalyst formed via π-π stacking interactions between the two components, as confirmed by analysis of UV-vis absorption spectra. The VOPc/CN hybrid photocatalyst shows excellent visible-light-driven photocatalytic performance and good stability. Under optimal conditions, the corresponding H2 evolution rate is nearly 6 times higher than that of pure g-C3N4. The role of VOPc in promoting hydrogen evolution activity was to extend the visible light absorption range and prevent the recombination of photoexcited electron-hole pairs effectively. It is expected that this facile modification method could be a new inspiration for the rational design and exploration of g-C3N4-based hybrid systems with strong light absorption and high-efficiency carrier separation.  相似文献   

5.
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.  相似文献   

6.
Photocatalytic hydrogen evolution by water splitting is highly important for the application of hydrogen energy and the replacement of fossil fuel by solar energy, which needs the development of efficient catalysts with long-term catalytic stability under light irradiation in aqueous solution. Herein, Zn0.5Cd0.5S solid solution was synthesized by a metal–organic framework-templated strategy and then loaded with MoS2 by a hydrothermal method to fabricate a MoS2/Zn0.5Cd0.5S heterojunction for photocatalytic hydrogen evolution. The composition of MoS2/Zn0.5Cd0.5S was fine-tuned to obtain the optimized 5 wt % MoS2/Zn0.5Cd0.5S heterojunction, which showed a superior hydrogen evolution rate of 23.80 mmol h−1 g−1 and steady photocatalytic stability over 25 h. The photocatalytic performance is due to the appropriate composition and the formation of an intimate interface between MoS2 and Zn0.5Cd0.5S, which endows the photocatalyst with high light-harvesting ability and effective separation of photogenerated carriers.  相似文献   

7.
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.  相似文献   

8.
Bimetallic AgPd nanoparticles have been synthesized before, but the interfacial electronic effects of AgPd on the photocatalytic performance have been investigated less. In this work, the results of hydrogen evolution suggest that the bimetallic AgPd/g-C3N4 sample has superior activity to Ag/g-C3N4 and Pd/g-C3N4 photocatalysts. The UV/Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, CO adsorption diffuse reflectance FTIR spectroscopy, and FTIR results demonstrate that in the AgPd/g-C3N4, the surface electronic structures of Pd and Ag are changed, which is beneficial for faster photogenerated electron transfer and greater H2O molecule adsorption. In situ ESR spectra suggest that, under visible light irradiation, there is more H2O dissociation to radical species on the AgPd/g-C3N4 photocatalyst. Furthermore, DFT calculations confirm the interfacial electronic effects of AgPd/g-C3N4, that is, Pdδ−⋅⋅⋅Agδ+, and the activation energy of H2O molecule dissociation on AgPd/g-C3N4 is the lowest, which is the main contributor to the enhanced photocatalytic H2 evolution.  相似文献   

9.
Efficient separation of photogenerated electrons and holes is of key importance in photocatalysis. Tuning the charge separation pathway is significant but still suffering from low efficiency for the charge extraction from semiconductors. Herein, taking 2D g-C3N4 (CN) nanosheets as a model photocatalyst, it was found the decoration of homophase junction between brookite TiO2 rods and nanoparticles (BN-BR) onto CN can effectively modulate photogenerated charge extraction and transfer in BN-BR/CN composites. The BN-BR/CN exhibits a remarkably enhanced photocatalytic H2 evolution under visible light irradiation (λ>420 nm) compared with the single component. A continuous electron transfer channel constructed by an interfacial chemical bond Ti−O−N between CN and brookite rods (BR) and BN-BR homophase junction between brookite nanoparticles and rods was proposed to benefit the charge extraction and transfer. This work provides a strategy to tune the charge separation and transfer to facilitate the photocatalytic performance in heterogeneous photocatalysis.  相似文献   

10.
As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H2) energy through solar water splitting, it is regarded as the “Holy Grail” in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn0.8Cd0.2S hetero-structured photocatalyst for high-performance visible-light-induced H2 production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn0.8Cd0.2S, the high distribution of Zn0.8Cd0.2S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H2 production performance.  相似文献   

11.
Ag nanoparticles (NPs) were deposited on the surface of g-C3N4 (CN) by an in situ calcination method. NiS was successfully loaded onto the composites by a hydrothermal method. The results showed that the 10 wt%-NiS/1.0 wt%-Ag/CN composite exhibits excellent photocatalytic H2 generation performance under solar-light irradiation. An H2 production rate of 9.728 mmol·g?1·h?1 was achieved, which is 10.82-, 3.45-, and 2.77-times higher than those of pure g-C3N4, 10 wt%-NiS/CN, and 1.0 wt%-Ag/CN composites, respectively. This enhanced photocatalytic H2 generation can be ascribed to the co-decoration of Ag and NiS on the surface of g-C3N4, which efficiently improves light harvesting capacity, photogenerated charge carrier separation, and photocatalytic H2 production kinetics. Thus, this study demonstrates an effective strategy for constructing excellent g-C3N4-related composite photocatalysts for H2 production by using different co-catalysts.  相似文献   

12.
采用简单固相法成功制备了CeTiO4/g?C3N4?x(CTO/CN?x,x g为g?C3N4的添加量)复合材料,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、N2吸附-脱附测试、紫外可见吸收光谱(UV?Vis)及电化学测试对材料进行表征。研究发现:CeTiO4与g?C3N4层状纳米片紧密复合,并成功构建了界面异质结结构;形成CTO/CN?x复合相的光催化材料具有良好的可见光光响应性能,且光生空穴-电子对的分离和迁移率明显提高;通过太阳光模拟不同样品光催化降解有机污染物罗丹明B,降解140 min后复合材料CTO/CN?6表现出最高的光催化活性,反应速率常数为0.0202 min-1。其活性增强的主要原因是异质结结构的构筑降低了CTO光生载流子的复合几率,提高了光生载流子的迁移速率。  相似文献   

13.
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.  相似文献   

14.
The activity and stability of Me/Cd0.3Zn0.7S (Me = Au, Pt, Pd) photocatalysts in the course of hydrogen production from water under the action of visible radiation have been investigated. The mechanism of activation and deactivation of the catalysts have been elucidated for the first time using X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. An increase in the hydrogen evolution rate is observed for all of the catalysts at the early stages of testing. The highest hydrogen evolution rate, 5.4 μmol/min, is afforded by the 1%Pt/Cd0.3Zn0.7S catalyst. The activity of the Au/Cd0.3Zn0.7S and Pt/Cd0.3Zn0.7S catalysts becomes constant 7.5–9 h after the beginning of the photocatalytic test, while in the case of Pd/Cd0.3Zn0.7S the hydrogen evolution rate increases over the initial 6 h and then decreases. These specific features of the catalysts likely correlate with the initial state of the metals on the support surface. In particular, supported palladium is in the form of PdO, while gold and platinum are in the metallic state. The Au/Cd0.3Zn0.7S and Pt/Cd0.3Zn0.7S photocatalysts are activated due to metal encapsulation; the 1%Pd/Cd0.3Zn0.7S catalyst, due to the partial reduction of PdO to PdO x . The 1%Pd/Cd0.3Zn0.7S catalyst is deactivated because of the aggregation of nanoparticles of the cadmium sulfide–zinc sulfide solid solution.  相似文献   

15.
The insufficient visible light responsive region and fast charge recombination probability are still the key obstacles for designing high-performance photocatalytic system. Herein, a “One Stone, Two Birds” strategy was reported in three-dimensional (3D) hierarchical graphitic carbon nitride (g-C3N4) nanosheet with intramolecular donor-acceptor (D-A) motifs (3D CN) photocatalyst, which solved two urgent problems simultaneously. The 3D hierarchical nanosheets structure endowed 3D CN with abundantly exposed reaction active sites and cross-plane diffusion channels. The formation of internal D-A system facilitated the light absorption and accelerated the transfer and separation of charge carriers. Furthermore, the introducing of D-A motifs optimized the bandgap of g-C3N4 and negative-shifted conduction band position. The as-prepared 3D CN showed excellent visible-light photocatalytic H2 performance, with H2 evolution rate of 2521.2 μmol h?1/g, which was six times higher than the pristine CN. This outstanding performance was ascribed to the synergistic effect of 3D hierarchical nanosheets structure and intramolecular D-A motifs. This current work provides a novel insight to design and construct of 3D hierarchical CN nanostructures with D-A motifs simultaneously, which can be further promising applications for clean and sustainable energy conversion.  相似文献   

16.
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。  相似文献   

17.
利用原位沉积法将Bi OBr纳米片生长到g-C_3N_4表面,制得g-C_3N_4-Bi OBr 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Bi OBr和g-C_3N_4两相组成,Bi OBr纳米片在片状g-C_3N_4表面快速形核生长形成面-面复合结构。相比于纯相g-C_3N_4和Bi OBr,g-C_3N_4-Bi OBr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 gC_3N_4-Bi OBr复合光催化剂光催化活性分别是纯相g-C_3N_4和Bi OBr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。  相似文献   

18.
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...  相似文献   

19.
Graphene oxide modified porous g-C3N4 (porous g-C3N4/GO) had been synthesized by means of one-step calcination of cyanamide for efficient photocatalysis under visible light irradiation (λ > 400 nm). We expect that the photocatalytic activity of this hybrid photocatalyst could be enhanced by the efficient visible light absorption due to the porous structure and efficient photo generated charge separation at the heterojunction formed between porous g-C3N4 and GO. Scanning electron microscopy (SEM) images demonstrated that the as prepared photocatalyst is composed of GO and porous g-C3N4. The UV-vis diffuse reflectance spectrum shows that optical absorption of porous g-C3N4/GO is more intensive than for pristine g-C3N4. The enhanced generation of photocurrent under visible light irradiation (λ > 400 nm) is observed for the porous g-C3N4/GO. The results of photocatalytic experiments reveal that the pseudofirst-order kinetic constant of photocatalytic degradation of methylene blue (MB) using the porous g-C3N4/GO is 6 times higher than that of pristine g-C3N4.  相似文献   

20.
Atomic Layer Deposition (ALD) precise controlling ultra-thin platinum (Pt) modified Graphite carbon nitride (g-C3N4) photocatalysts, which had been doped with gold nanoparticles (Au NPs) by photodeposition, were successfully synthesized. The experimental results showed that precise regulation of platinum decorated C3N4-Au(C3N4-Au/nPt (n is the number of Pt ALD cycles, 1 Å per cycle)) exhibited excellent photocatalytic degradation ability for Rhodamine B (RhB). Under simulated sunlight irradiation, the degradation rate of 10 mg/L RhB(100 mL) by 1.5 mg C3N4-Au/10Pt catalysts was 95.8% within 60 min that is much better than other photocatalysts for the degradation of RhB. The efficient degradation mechanism of RhB by C3N4-Au/10Pt photocatalysts was studied and the experiments demonstrated the ·O2 as main active species played an important role in the photocatalytic process. Local surface plasmon resonance (LSPR) of Au NPs and Schottky barrier between Pt clusters and g-C3N4 may be the reasons for enhanced C3N4-Au/10Pt photocatalytic performances. Furthermore, the successive catalytic cycles revealed the excellent stability of C3N4-Au/10Pt photocatalyst.  相似文献   

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