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1.
Facilitating the separation of photoexcited electron-hole pairs and enhancing the migration of photogenerated carriers are essential in photocatalytic reaction. CoS/g-C3N4/NiS ternary photocatalyst was prepared by hydrothermal and physical stirring methods. The optimized ternary composite achieved a hydrogen yield of 1.93 mmol g?1 h?1, 12.8 times that of bare g-C3N4, with an AQE of 16.4% at 420 nm. The enhanced photocatalytic activity of CoS/g-C3N4/NiS was mainly ascribed to the synergistic interaction between the Z-scheme heterojunction constructed by CoS and g-C3N4 and the NiS co-catalyst featuring a large amount of hydrogen precipitation sites, which realized the efficient separation and migration of photogenerated carriers. In addition, the CoS/g-C3N4/NiS heterojunction-co-catalyst system exhibited excellent photocatalytic stability and recyclability.  相似文献   

2.
The shortage of fossil energy has become a growing global concern. It is particularly important to make full use of the infinite solar energy resources, and transform them into sustainable and clean energy. The development of hydrogen energy has become a feasible solution to solve the energy shortage problem. The preparation of photocatalysts featuring efficient charge transfer channels and high hydrogen production activity provides a pathway for the development of hydrogen energy. In this paper, we report for the first time the direct assembly of 2D ZnIn2S4 (ZIS) nanosheets on the surface of CoTiO3 (CTO). The synthesized CoTiO3/ZnIn2S4 (CTO/ZIS) photocatalyst features a direct Z-scheme charge transfer channel, which enhances the separation rate of photogenerated carriers, and accelerates the photocatalytic H2 evolution (PHE) rate. Without the assistance of any co-catalyst, the PHE rate of prepared CoTiO3/ZnIn2S4 was as high as 5.21 mmol g?1 h?1. Moreover, the H2 evolution rate of CoTiO3/ZnIn2S4 almost did not decrease significantly after four consecutive 4 h cycles. This investigation provides a valuable approach for the exploitation of novel and efficient Z-scheme photocatalysts in the application of solar energy to hydrogen energy conversion.  相似文献   

3.
In this work, we fabricate a 1D/2D heterojunction photocatalyst composed of n-type CdS nanorods and p-type CoSx nanoflake. This photocatalyst achieves a hydrogen evolution rate of 9.47 mmol g?1 h?1, which is 13.7 times higher than that of pure CdS nanorods. Scanning Kelvin Probe, Mott-Schottky plots, UV–Vis absorption spectra and surface photocarrier orienting reaction results indicate that the enhanced photocatalytic performance of CdS/CoSx is owing to the fabrication of direct Z-Scheme heterojunction system which greatly improves the utilization, migration and separation rate of photo-generated carriers. To the best of our knowledge, this work is the first time to describe a CdS/CoSx direct Z-scheme system with 1D/2D nanostructure, which can expedite the transfer process of photogenerated carriers with strong redox energy to participate in photocatalytic reactions.  相似文献   

4.
Developing low-cost, highly efficient and robust photocatalystic hydrogen evolution system is a promising solution to environmental and energy crisis. Herein, a Z-scheme Cu3P/ZnIn2S4 heterojunction photocatalyst was successfully constructed for the first time via a facile solution-phase hybridization method. The optimized Cu3P/ZIS composite exhibited the highest H2 production rate of 2561.1 μmol g−1 h−1 under visible light irradiation (>420 nm), which was 5.2 times greater than that of bare ZnIn2S4 and even exceeded the photocatalytic performance of Pt/ZIS composite. The apparent quantum yield of 10 wt% Cu3P/ZnIn2S4 can reach 22.3% at 420 nm. The huge boost of photocatalytic hydrogen evolution activity is ascribed to the formation of heterojunction with the built in electric field within Cu3P/ZnIn2S4 and Z-scheme charge carriers transfer pathway, which result in efficient separation and migration of charge carriers. In addition, both experimental and theoretical calculation confirmed that the charge-carriers transfer pathway of Cu3P/ZnIn2S4 photocatalyst follows the Z-scheme mechanism instead of conventional type-Ⅱ heterojunction mechanism. This work is considered helpful for getting a great deal of insight into constructing high-activity and cost-effective transition metal phosphides (TMPs) based photcatalytic hydrogen production system and rationally designing Z-scheme heterojunction photocatalyst.  相似文献   

5.
In this work, a 2D/2D heterojunction composed of CoAl layered double hydroxide (LDH) and graphitic carbon nitride nanosheets (CNNS) was designed and fabricated for boosting photocatalytic hydrogen generation. The as-prepared 20 mol% CoAl-LDH/CNNS exhibited a remarkable photocatalytic hydrogen evolution rate of 680.13 μmol h−1 g−1, which was 21 times higher than that of pure CoAl-LDH (32.91 μmol h−1 g−1). The enhanced activity could be mainly attributed to its unique structure and high surface area. Distinct from ordinary heterojunction photocatalysts, two-dimensional (2D) heterojunctions with abundant 2D coupling interfaces and strong interfacial interaction could efficiently suppress the recombination of photo-induced charge carriers and shorten charge transmission distance. Particularly, compared with other concentrations, the increased surface area (138.70 m2 g−1) of 20 mol% CoAl-LDH/CNNS, which is 3.94 times of pure CNNS (35.48 m2 g−1), is more favorable for enhanced photocatalytic activity. Increasing the surface area of sheet-on-sheet heterostructure is an effective and novel strategy to facilitate the photocatalytic hydrogen evolution from water splitting.  相似文献   

6.
Development of low cost and efficient non-noble-metal cocatalyst is still a hot topic to improve the activity of g-C3N4 in photocatalytic water splitting to produce H2. As a potential cocatalyst in photocatalytic application, transition metal phosphides (TMPs) have been proved to greatly enhance the photocatalytic H2 evolution performance comparable to noble metal Pt. Modifying TMPs by incorporation of hetero-metal has also been reported as an effective strategy for their electronic structure regulation and optimizing the intermediates absorption energy, however, which is rarely reported in the field of photocatalysis. Herein, the 0D/2D heterojunction is constructed by high-dispersity Mo-doped Ni2P nanodots supported on g-C3N4 nanosheets, which exhibits the significantly improved photocatalytic H2 evolution performance compared with that of Ni2P/g-C3N4 and Pt/g-C3N4. Specifically, the optimal H2 evolution rate reaches 67.6 μmol h−1 over Mo–Ni2P/g-C3N4 sample, which is 6.0 and 2.4 times higher than those of Pt/g-C3N4 and Ni2P/g-C3N4, respectively. The fascinating result mainly stems from the improved separation efficiency of charge carriers and more effective electron donating reaction sites resulted from the electronic structure adjustment through doping Mo element into Ni2P as cocatalyst. This work provides a valid evidence for the modification of cocatalyst to realize high H2 evolution performance, opening up new opportunities and possibilities for the application of TMPs in the photocatalytic field.  相似文献   

7.
Designing the core-shell structure and controlling defect engineering are desirable for improving the performance and stability of semiconductor photocatalysts. Herein, CdS nanorods covered with ultra-thin ZnIn2S4 nanosheets, named as CdS@ZnIn2S4-SV (CdS@ZIS-SV), was synthesized through the strategy of constructing core-shell structure and regulating vacancies. The core-shell structure can confine Cd2+ and S2? locally around CdS instead of rapidly diffusing into the solution, thereby inhibiting photo-corrosion. The abundant S vacancies can capture photogenerated electrons and promote the separation of electron-hole pairs, thereby preventing the oxidation of S2? by the holes. In addition, Z-Scheme heterojunction structure helps the effective separation of electron-hole pairs. Notably, the hydrogen production rate of CdS@ZIS-SV reached 18.06 mmol g?1 h?1, which was 16.9 and 19.6 times than pristine CdS (1.16 mmol g?1 h?1) and ZIS (0.92 mmol g?1 h?1), respectively. Photoelectric Characterization (PEC), Scanning Kelvin Probe (SKP), UV–vis diffuse reflectance spectra (UV–Vis DRS), Finite-Difference Time-Domain (FDTD) explain the electron transfer mechanism and the reason for the enhanced photocatalytic activity. This work has guiding significance for the preparation of photo-catalysts with high activity and inhibiting photo-corrosion by adjusting S vacancies.  相似文献   

8.
An oxygen-vacancy rich, bismuth oxide (Bi2O3) based MoS2/Bi2O3 Z-scheme heterojunction catalyst (2-BO-MS) was prepared in an autoclave hydrothermal method using ethanol and water. The performance of MoS2/Bi2O3 catalyst was examined for photocatalytic hydrogen evolution, photoelectrochemical activity, and crystal violet (CV) dye degradation by comparing with pristine Bi2O3 and MoS2. The hydrogen evolution performances of 2-BO-MS catalyst exhibited 3075.21 μmol g−1 h−1, which is 7.18 times higher than that of MoS2 (428.14 μmol g−1 h−1). The XPS, XRD and HRTEM analyses covered that the superior photocatalytic performance of 2-BO-MS catalyst might have stemmed out due to the existence of oxygen vacancies, enhanced strong interfacial interaction between MoS2 and Bi2O3 and specific surface area. The in-depth investigation has been performed for MoS2/Bi2O3 Z-scheme heterojunction using several characterization techniques. Moreover, the photocatalytic mechanism for hydrogen evolution and photodegradation were proposed based on trapping experiment results. This results acquired using MoS2/Bi2O3 Z-scheme heterojunction would be stepping stone for developing heterojunction catalyst towards attaining outstanding photocatalytic activity.  相似文献   

9.
Constructing heterojunction structure is a feasible way to realize an efficient and durable photocatalysts. Herein, a novel Z-scheme zero/three dimensional (0D/3D) ZnIn2S4/Ag6Si2O7 (ZIS/ASO) composite was rationally designed, synthesized and analyzed. ZIS/ASO composite possesses a layer structure for increasing light response, a special 0D/3D structure for reducing the photo-induce carriers migration path, and numerous active sites for absorbing H2O and producing H2. This composite retains the high oxidation and reduction ability by facilitating separation and migration as well as limiting recombination of photo-induced carriers via the intimate interface between ZIS and ASO. Undoubtedly, the synthesized ZIS/ASO photocatalyst achieved a high photocatalytic H2 activity, and the optimum sample shows a satisfactory H2 evolution rate of 590.56 μmol g−1 h−1, distinctly better than that of pure ZIS. More importantly, this composite exhibits high stability and recyclability and is expected to be applied in practical application. Based on the H2 evolution experimental results and electrochemical tests, the Z-scheme heterostructure construction of the composite was confirmed. This work expects to inspire a unique protocol for synthesizing Z-scheme photocatalysts for water splitting under visible light irradiation.  相似文献   

10.
Structure and interface control of heterojunction is usually a challenging issue to improve the photocatalytic performance. Herein, a new 3D/2D CoCO3/g-C3N4 heterojunction is assembled by embedding hexahedral CoCO3 on g-C3N4 nanosheets. The unique step-like hierarchical structure of CoCO3, the formed built-in electric field and Z-scheme charge transfer behavior at the interface jointly drive the high-efficient separation of photogenerated carriers to boost the photocatalytic H2 production. It achieves the optimal H2 production rate that is almost 2.6 times than g-C3N4, apparent quantum efficiency (AQE) of 10.1% at 400 nm and continuous running of 60 h over the 3D/2D CoCO3/g-C3N4 heterojunction. This work endows a fresh structural control strategy for the fabrication of 3D/2D Z-scheme heterojunction to improve the photocatalytic H2 production performance.  相似文献   

11.
A designed type-II heterojunction photocatalyst, NiSe2/Cd0.5Zn0.5S (NiSe2/CZS), was successfully synthesized and it exhibits outstanding photocatalytic hydrogen evolution performance. The optimal loading amount of NiSe2 on Cd0.5Zn0.5S is 13 wt %, and the corresponding hydrogen production rate is approximately 121.01 mmol g?1 h?1 under visible light. The heterojunction structure between Cd0.5Zn0.5S and NiSe2 promoted the separation of photogenerated electron-hole pairs, effectively suppressed the photogenerated carrier recombination and endowed the material with excellent interfacial charge transfer properties, thus improving the photocatalytic performance.  相似文献   

12.
Excellent light harvest, efficient charge separation and sufficiently exposed surface active sites are crucial for a given photocatalyst to obtain excellent photocatalytic performances. The construction of two-dimensional/two-dimensional (2D/2D) or zero-dimensional/2D (0D/2D) binary heterojunctions is one of the effective ways to address these crucial issues. Herein, a ternary CdSe/WS2/g-C3N4 composite photocatalyst through decorating WS2/g-C3N4 2D/2D nanosheets (NSs) with CdSe quantum dots (QDs) was developed to further increase the light harvest and accelerate the separation and migration of photogenerated electron-hole pairs and thus enhance the solar to hydrogen conversion efficiency. As expected, a remarkably enhanced photocatalytic hydrogen evolution rate of 1.29 mmol g−1 h−1 was obtained for such a specially designed CdSe/WS2/g-C3N4 composite photocatalyst, which was about 3.0, 1.7 and 1.3 times greater than those of the pristine g-C3N4 NSs (0.43 mmol g−1 h−1), WS2/g-C3N4 2D/2D NSs (0.74 mmol g−1 h−1) and CdSe/g-C3N4 0D/2D composites (0.96 mmol g−1 h−1), respectively. The superior photocatalytic performance of the prepared ternary CdSe/WS2/g-C3N4 composite could be mainly attributed to the effective charge separation and migration as well as the suppressed photogenerated charge recombination induced by the constructed type-II/type-II heterojunction at the interfaces between g-C3N4 NSs, CdSe QDs and WS2 NSs. Thus, the developed 0D/2D/2D ternary type-II/type-II heterojunction in this work opens up a new insight in designing novel heterogeneous photocatalysts for highly efficient photocatalytic hydrogen evolution.  相似文献   

13.
In this work, the 2D SnS/g-C3N4 nanosheets have been successfully prepared by a facile ultrasonic and microwave heating approach, which formed intimate interfacial contact and suitable energy band structure. The optimized sample displayed enhanced photocatalytic hydrogen evolution from water assisted with Pt co-catalyst, which is much higher than that of pure g-C3N4. After loaded with MoO3 particles, the stability of photocatalysts displayed significate improvement due to the formed Z-scheme heterojunction. With the characterization, the enhanced hydrogen evolution reaction (HER) performance might be ascribed to the improved light-harvesting capability of the composite, lowered charge-transfer resistance, increased electrical conductivity and the co-catalyst effect of SnS. This study provides insights about SnS assisted HER photocatalysts and a new strategy to improve the stability of metal sulfides photocatalysts.  相似文献   

14.
Fabricating 0D/2D heterojunctions is considered to be an efficient mean to improve the photocatalytic activity of g-C3N4, whereas their applications are usually restricted by complex preparation process. Here, the 0D/2D SnO2/g-C3N4 heterojunction photocatalyst is prepared by a simple one-step polymerization strategy, in which SnO2 nanodots in-situ grow on the surface of g-C3N4 nanosheets. It shows the outstanding photocatalytic H2 production activity relative to g-C3N4 under the visible light, which is due to the formation of 0D/2D heterojunction significantly contributing to the separation of photogenerated charge carriers. In particular, the H2 production rate over the optimal SnO2/g–C3N4–1 sample is 1389.2 μmol h−1 g−1, which is 6.06 times higher than that of g-C3N4 (230.8 μmol h−1 g−1). Meanwhile, the AQE value of H2 production over the SnO2/g–C3N4–1 sample reaches up to a maximum of 4.5% at 420 nm. This work develops a simple approach to design and fabricate g–C3N4–based 0D/2D heterojunctions for the high-efficiency H2 production from water splitting.  相似文献   

15.
Introducing nickel foam as assistant, a novel nonmetal intercalated high crystalline graphitic carbon nitride (g-C3N4) catalyst was successfully fabricated by β-cyclodextrin (β-CD) pretreated melamine with one step thermal polymerization process. The final results show that 0.3-NCCN presented a remarkably visible-light (λ > 400 nm) photocatalytic H2 evolution reaching 9297  μmol g?1 h?1, and the reaction process follows the zero-order kinetic model. The increase in crystallization of 0.3-NCCN implies a higher-ordered arrangement of tris-s-triazine. The nonmetal interlayer formed by oxygen-contained graphitized carbon can extend the π-conjugated system. Both above significantly benefit the rapid migration and separation of charge-carrier. Moreover, the narrowed band gap provides a stronger thermodynamic driving force for improving the photocatalytic water splitting efficiency. Our work paved a new method to construct high performance photocatalyst for water splitting.  相似文献   

16.
g-C3N4 (CN) has attracted extensive attention in photocatalysis field, but its weak visible light absorption and rapid charge recombination limit its application. In this, MoS2 and CoSx (ZIF67 derivatives) as cocatalyst grew on the surface of semiconductor CN in situ to construct CoSx/MoS2/CN double heterojunction. Then the activities of photocatalytic hydrogen evolution and degradation MB were researched. The hydrogen production rate of 5%CoSx/MoS2/CN-2 photocatalyst is 9800 μmol h?1 g?1 and is about 6.5 times as great as CN, 46 times than MoS2 and 98 times than CoSx, respectively. Under natural sunlight and simulated sunlight, the degradation efficiency of MB is 99.95% and 99.50% after 4 h, respectively. Catalyst characterizations have pointed out that CoSx/MoS2/CN catalyst has abundant active sites and larger specific surface area, which increase absorption of water and oxygen. At the same time, internal electric field and S vacancy enhance electrons transfer rate, which effectively inhibit the recombination of e?-h+. This work provides a new idea into the creation of steady, high-efficiency and continuable photocatalytic catalyst for visible light.  相似文献   

17.
Constructing type II heterojunction is an efficient strategy to enhance the light absorption and promote the charge transport. However, the improvement effect is limited by the decreased redox ability of charge carriers. The rational design of heterojunction from type II to Z-scheme is expected to overcome this obstacle. Herein, we demonstrate that the introduction of interfacial oxygen vacancies (OVs) can switch charge transfer of g-C3N4/BVO heterojunction from type II to Z-scheme. The interfacial OVs acted as the reactive center of charge carriers to quench the electrons of BVO and holes of g-C3N4, thereby promoting charge separation and migration. As a result, the interfacial OVs mediated Z-scheme g-C3N4/BVO heterojunction kept the strong oxidation/reduction potential of two single-component photocatalysts thereby significantly enhancing the photodegradation of tetracycline and CO2 photoreduction. The kinetic constant of tetracycline degradation on the optimal g-C3N4/BVO-20 sample was 2.04-fold and 2.29-fold higher than those on g-C3N4 nanosheets and pure BVO, respectively. This work provides a feasible strategy by the interfacial vacancy engineering of heterojunction for enhanced photocatalysis.  相似文献   

18.
It is still challenging to design effective g-C3N4 photocatalysts with high separation efficiency of photo-generated charges and strong visible light absorption. Herein, a simple, template-free and “bottom-up” strategy has been developed to prepare 1D/2D g-C3N4 isotype heterojunction composed of carbon-doped nanowires and ultra-thin nanosheets. The ethanediamine (EE) grafted on melamine ensures the growth of 1D g-C3N4 nanowires with high carbon doping, and the ultra-thin g-C3N4 nanosheets were produced through HCl-assisted hydrothermal strategy. The apparent grain boundary between 2D nanosheets and 1D carbon-doped nanowires manifested the formation of the isotype heterojunction. The built-in electric field provide strong driving force for photogenerated carriers separation. Meanwhile, the doping carbon in g-C3N4 nanowires promotes visible light absorption. As a result, the photocatalytic H2 evolution activity of 1D/2D g-C3N4 isotype heterojunction is 8.2 time that of the pristine g-C3N4, and an excellent stability is also obtained. This work provides a promising strategy to construct isotype heterojunction with different morphologies for effective photocatalytic H2 evolution.  相似文献   

19.
The performance and reaction mechanism of a silver (Ag)-assisted one-dimensional NiTiO3 nanorod/CN heterostructure nanocomposite (NTACN) photocatalyst for hydrogen (H2) production were explored with simulated sunlight. The physicochemical properties of the synthesized catalysts were examined using various spectrophotometers. The newly developed NTACN samples displayed an enhanced photocatalytic activity in producing hydrogen. Specifically, the H2 production rate of NTACN-5 (with a NT-to-ACN weight ratio of 5) was 3351 μmol/g-h, which was 1.42 times higher than that of ACN-4 with a Ag-to-CN ratio of 4 (2325 μmol/g-h). The effects of the Ag-to-CN and NiTiO3-to-ACN ratios on the photocatalytic activity of NTACN photocatalysts were determined. The NTACN photocatalysts exhibited a high long-term photostability under simulated sunlight irradiation. The increased photocatalyst performance and photostability were primarily ascribed to an improved charge separation efficiency due to a Z-scheme reaction mechanism as well as the assistance provided by Ag as a charge transfer shuttle and in the surface plasmon resonance effect. A photocatalytic mechanism for hydrogen generation over the NTACN photocatalysts under simulated sunlight irradiation is suggested.  相似文献   

20.
In this work, photocatalysts with a novel S-scheme heterojunction were fabricated by coupling MOF-derived TiO2 with porous g-C3N4 (MTO/PCN). The S-scheme heterojunction with matching band gap possesses different advantageous properties, which can not only inhibit photo-generated charge recombination, but also reserve outstanding redox ability. As expected, superior hydrogen evolution efficiency of 40-MTO/PCN was obtained in a TEOA-containing aqueous solution and pure water, which were 5252.9 and 974.6 μmol h−1 g−1, respectively. Meanwhile, the hybrid can also serve as a bifunctional catalyst for H2 generation (2137.3 μmol h−1 g−1) and organic contaminant removal (the RhB purification efficiency: 35.24%). This work furnishes a feasible method for devising bifunctional photocatalysts that can simultaneously produce hydrogen and purify wastewater to provide both energy-saving and environmental restoration functions.  相似文献   

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