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1.
A novel graphene‐like MoS 2/C 3N 4 (GL‐MoS 2/C 3N 4) composite photocatalyst has been synthesized by a facile ethylene glycol (EG)‐assisted solvothermal method. The structure and morphology of this GL‐MoS 2/C 3N 4 photocatalyst have been investigated by a wide range of characterization methods. The results showed that GL‐MoS 2 was uniformly distributed on the surface of GL‐C 3N 4 forming a heterostructure. The obtained composite exhibited strong absorbing ability in the ultraviolet (UV) and visible regions. When irradiated with visible light, the composite photocatalyst showed high activity superior to those of the respective individual components GL‐MoS 2 and GL‐C 3N 4 in the degradation of methyl orange. The enhanced photocatalytic activity of the composite may be attributed to the efficient separation of electron–hole pairs as a result of the matching band potentials between GL‐MoS 2 and GL‐C 3N 4. Furthermore, a photocatalytic mechanism for the composite material has been proposed, and the photocatalytic reaction kinetics has been measured. Moreover, GL‐MoS 2/C 3N 4 could serve as a novel sensor for trace amounts of Cu 2+ since it exhibited good selectivity for Cu 2+ detection in water. 相似文献
2.
Photocatalytic Z or S scheme merits higher redox potentials and faster charge separation. However, heterostructure photocatalysts with band gaps of bulk materials often have a type I band structure leading to poor photocatalytic activity. In view of this, we report simultaneous tuning of band gaps of Cu 2O and TiO 2, where quantum dot Cu 2O nanoparticles were formed on doped TiO 2 with Ti 3+. The reduced size of Cu 2O made its conduction band more negative, whereas the introduction of Ti 3+ made the absorption edge red shift to the visible light region. The as-formed heterostructure enabled an S-Scheme mechanism with remarkable activity and stability for visible light photodegradation of 4-chlorophenol (4-CP). The as-obtained photocatalysts’ activity demonstrated ca. 510-fold increase as compared to individual ones and a mechanical blend. The as-obtained photocatalysts maintained over 80 % for 5 cycles and 2 months exposure to O 2 did not decrease the degradation rate. ESR characterization and scavenger experiments proved the S-Scheme mechanism. 相似文献
3.
Crystalline and porous covalent organic frameworks (COFs) and metal‐organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H 2 evolution due to their long‐range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two‐dimensional (2D) COF with stable MOF. By covalently anchoring NH 2‐UiO‐66 onto the surface of TpPa‐1‐COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H 2 evolution under visible light irradiation. Especially, NH 2‐UiO‐66/TpPa‐1‐COF (4:6) exhibits the maximum photocatalytic H 2 evolution rate of 23.41 mmol g ?1 h ?1 (with the TOF of 402.36 h ?1), which is approximately 20 times higher than that of the parent TpPa‐1‐COF and the best performance photocatalyst for H 2 evolution among various MOF‐ and COF‐based photocatalysts. 相似文献
4.
Graphite-like carbon nitride (g-C 3N 4) based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-C 3N 4/SnS 2 coupling effect on the electronic structures and optical absorption of the proposed g-C 3N 4/SnS 2 heterostructure through performing extensive hybrid functional calculations. The obtained geometric structure, band structures, band edge positions and optical absorptions clearly reveal that the g-C 3N 4 monolayer weakly couples to SnS 2 sheet, and forms a typical van der Waals heterojunction. The g-C 3N 4/SnS 2 heterostructure can effectively harvest visible light, and its valence band maximum and conduction band minimum locate in energetically favorable positions for both water oxidation and reduction reactions. Remarkably, the charge transfer from the g-C 3N 4 monolayer to SnS 2 sheet leads to the built-in interface polarized electric field, which is desirable for the photogenerated carrier separation. The built-in interface polarized electric field as well as the nice band edge alignment implys that the g-C 3N 4/SnS 2 heterostructure is a promising g-C 3N 4 based water splitting photocatalyst with good performance. 相似文献
5.
In this work, by first-principles calculations, we investigate the structural, photoelectric, and catalytic properties of g-ZnO/Hf 2CO 2 vdW heterostructures to explore highly efficient photocatalysts of water splitting. Results show that the AA-stacking g-ZnO/Hf 2CO 2 vdW heterostructure (AA-HS) with an indirect bandgap of 1.738 eV has a typical type-II band alignment, which is benefit to effectively separate the photogenerated carriers into different layers and prevent their recombination. The conduction band minimum (CBM) and valence band maximum (VBM) of AA-HS straddling the water redox potentials makes it satisfies the requirements of photocatalytic water splitting at pH = 7. In addition, to evaluate the photocatalytic performance of AA-HS during oxidation evolution reaction (OER) process in water splitting, we calculated the change of Gibbs free energies of the intermediates on heterostructure under different conditions. Results show the Gibbs free energy decreases continuously at pH = 7 and U = 1.93 V. What's more, the AA-HS has good sunlight-absorption ability. External biaxial strain is not conducive to improving catalytic performance of AA-HS. 相似文献
6.
The elaborate regulation of heterostructure interface to accelerate the interfacial charge separation is one of practicable approaches to improve the photocatalytic CO 2 reduction performance of halide perovskite (HP) materials. Herein, we report an in-situ growth strategy for the construction of 2D CsPbBr 3 based heterostructure with perovskite oxide (SrTiO 3) nanosheet as substrate (CsPbBr 3/SrTiO 3). Lattice matching and matchable energy band structures between CsPbBr 3 and SrTiO 3 endow CsPbBr 3/SrTiO 3 heterostructure with an efficient interfacial charge separation. Moreover, the interfacial charge transfer rate can be further accelerated by etching SrTiO 3 with NH 4F to form flat surface capped with Ti?O bonds. The resultant 2D/2D T-SrTiO 3/CsPbBr 3 heterostructure exhibits an impressive photocatalytic activity for CO 2 conversion with a CO yield of 120.2 ± 4.9 μmol g ?1 h ?1 at the light intensity of 100 mW/cm 2 and water as electron source, which is about 10 and 7 times higher than those of the pristine SrTiO 3 and CsPbBr 3 nanosheets, surpassing the reported halide perovskite-based photocatalysts under the same conditions. 相似文献
7.
Willow branch-shaped MoS 2/CdS heterojunctions are successfully synthesized for the first time by a facile one-pot hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption measurements, diffuse reflectance spectroscopy, and photoelectrochemical and photoluminescence spectroscopy tests. The photocatalytic hydrogen evolution activities of the samples were evaluated under visible light irradiation. The resulting MoS 2/CdS heterojunctions exhibit a much improved photocatalytic hydrogen evolution activity than that obtained with CdS and MoS 2. In particular, the optimized MC-5 (5 at.% MoS 2/CdS) photocatalyst achieved the highest hydrogen production rate of 250.8 μmol h -1, which is 28 times higher than that of pristine CdS. The apparent quantum efficiency (AQE) at 420 nm was 3.66%. Further detailed characterizations revealed that the enhanced photocatalytic activity of the MoS 2/CdS heterojunctions could be attributed to the efficient transfer and separation of photogenerated charge carriers resulting from the core-shell structure and the close contact between MoS 2 nanosheets and CdS single-crystal nanorods, as well as to increased visible light absorption. A tentative mechanism for photocatalytic H 2 evolution by MoS 2/CdS heterojunctions was proposed. This work will open up new opportunities for developing more efficient photocatalysts for water splitting. 相似文献
8.
Halide perovskite quantum dots (QDs) have great potential in photocatalytic applications if their low charge transportation efficiency and chemical instability can be overcome. To circumvent these obstacles, we anchored CsPbBr 3 QDs (CPB) on NH x‐rich porous g‐C 3N 4 nanosheets (PCN) to construct the composite photocatalysts via N?Br chemical bonding. The 20 CPB‐PCN (20 wt % of QDs) photocatalyst exhibits good stability and an outstanding yield of 149 μmol h ?1 g ?1 in acetonitrile/water for photocatalytic reduction of CO 2 to CO under visible light irradiation, which is around 15 times higher than that of CsPbBr 3 QDs. This study opens up new possibilities of using halide perovskite QDs for photocatalytic application. 相似文献
9.
The production of CH 3OH from the photocatalytic CO 2 reduction reaction (PCRR) presents a promising route for the clean utilization of renewable resources, but charge recombination, an unsatisfying stability and a poor selectivity limit its practical application. In this paper, we present the design and fabrication of 0D/2D materials with polymeric C 3N 4 nanosheets and CdSe quantum dots (QDs) to enhance the separation and reduce the diffusion length of charge carriers. The rapid outflow of carriers also restrains self‐corrosion and consequently enhances the stability. Furthermore, based on quantum confinement effects of the QDs, the energy of the electrons could be adjusted to a level that inhibits the hydrogen evolution reaction (HER, the main competitive reaction to PCRR) and improves the selectivity and activity for CH 3OH production from the PCRR. The band structures of photocatalysts with various CdSe particle sizes were also investigated quantitatively to establish the relationship between the band energy and the photocatalytic performance. 相似文献
10.
Harnessing solar energy and converting it into renewable fuels by chemical processes, such as water splitting and carbon dioxide (CO 2) reduction, is a highly promising yet challenging strategy to mitigate the effects arising from the global energy crisis and serious environmental concerns. In recent years, covalent organic framework (COF)-based materials have gained substantial research interest because of their diversified architecture, tunable composition, large surface area, and high thermal and chemical stability. Their tunable band structure and significant light absorption with higher charge separation efficiency of photoinduced carriers make them suitable candidates for photocatalytic applications in hydrogen (H 2) generation, CO 2 conversion, and various organic transformation reactions. In this article, we describe the recent progress in the topology design and synthesis method of COF-based nanomaterials by elucidating the structure-property correlations for photocatalytic hydrogen generation and CO 2 reduction applications. The effect of using various kinds of 2D and 3D COFs and strategies to control the morphology and enhance the photocatalytic activity is also summarized. Finally, the key challenges and perspectives in the field are highlighted for the future development of highly efficient COF-based photocatalysts. 相似文献
11.
A Bi2O3/(BiO)2CO3 (BO/BOC) composite photocatalyst was in situ prepared via calcinating (BiO)2CO3. The as-prepared Bi2O3/(BiO)2CO3 composites displayed enhanced photocatalytic activity for the degradation of RhB under visible light. The structure–activity relationship between catalyst structure and properties was investigated by SEM, XRD, XPS, FTIR, BET, DRS and photoelectrochemical tests. Apart from the increased absorption of visible light, the accelerated charge separation and transfer was achieved via the intimate contact and matched band structure between Bi2O3 and (BiO)2CO3. The formation of heterogeneous structures could promote the production of reactive oxygen species (·O2?) and eventually improve the photocatalytic performance for the removal of organic contaminants. This heating treatment strategy might be extended for improving light absorbance and charge carriers separation for other UV-based photocatalysts. 相似文献
12.
首先在N-甲基吡咯烷酮溶液中超声剥离得到少层的MoS_2,将其与石墨相氮化碳(g-C_3N_4)复合,制得MoS_2/g-C_3N_4复合材料。采用X射线衍射(XRD),扫描电镜(SEM),X射线光电子能谱(XPS),傅里叶变换红外光谱(FTIR),Raman光谱,紫外-可见漫反射吸收光谱(DRS)和光致荧光(PL)技术对复合材料进行表征。可见光下考察MoS_2/g-C_3N_4复合材料光催化降解罗丹明B(Rh B)的活性,结果表明:将少量MoS_2与g-C_3N_4复合可明显提高光催化活性,且1%(w/w)MoS_2/g-C_3N_4复合物的光催化活性最高,可能的原因是MoS_2和g-C_3N_4匹配的能带结构,增大了界面间电荷的传输,降低了光生电子-空穴的复合,进而提高了光催化活性。 相似文献
13.
This study describes the preparation of graphitic carbon nitride (g-C 3N 4), hematite (α-Fe 2O 3), and their g-C 3N 4/α-Fe 2O 3 heterostructure for the photocatalytic removal of methyl orange (MO) under visible light illumination. The facile hydrothermal approach was utilized for the preparation of the nanomaterials. Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) were carried out to study the physiochemical and optoelectronic properties of all the synthesized photocatalysts. Based on the X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance (DRS) results, an energy level diagram vs. SHE was established. The acquired results indicated that the nanocomposite exhibited a type-II heterojunction and degraded the MO dye by 97%. The degradation ability of the nanocomposite was higher than that of pristine g-C 3N 4 (41%) and α-Fe 2O 3 (30%) photocatalysts under 300 min of light irradiation. The formation of a type-II heterostructure with desirable band alignment and band edge positions for efficient interfacial charge carrier separation along with a larger specific surface area was collectively responsible for the higher photocatalytic efficiency of the g-C 3N 4/α-Fe 2O 3 nanocomposite. The mechanism of the nanocomposite was also studied through results obtained from UV-vis and XPS analyses. A reactive species trapping experiment confirmed the involvement of the superoxide radical anion (O 2•−) as the key reactive oxygen species for MO removal. The degradation kinetics were also monitored, and the reaction was observed to be pseudo-first order. Moreover, the sustainability of the photocatalyst was also investigated. 相似文献
14.
TiO 2 photocatalysts have been widely studied and applied for removing bacteria, but its antibacterial efficiency is limited to the ultraviolet (UV) range of the solar spectrum. In this work, we use the gold (Au) nanorods to enhance the visible and near-infrared (NIR) light absorption of TiO 2 NBs, a typical UV light photocatalyst, thus the enhancement of its full solar spectrum (UV, visible and NIR) photocatalytic antibacterial properties is achieved. Preliminary surface plasmon resonance (SPR) enhancement photocatalytic antibacterial mechanism is suggested. On one hand, transverse and longitudinal SPR of Au NRs is beneficial for visible and NIR light utilization. On the other hand, Au NRs combined with TiO 2 NBs to form the heterostructure, which can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally produces the high yield of radical oxygen species and exhibits a superior antibacterial efficiency. Furthermore, we design a sterilization file cabinet with Au NR/TiO 2 NB heterostructures as the photocatalytic coating plates. Our study reveals that Au NR/TiO 2 NB heterostructure is a potential candidate for sterilization of bacteria and archives protection. 相似文献
15.
Inspired by natural photosynthesis, Z‐scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal‐free Z‐scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer‐based van der Waals heterostructures as metal‐free Z‐scheme photocatalytic systems for overall water splitting is described using aza‐fused microporous polymers (CMP) and C 2N ultrathin nanosheets as O 2‐ and H 2‐evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H 2 and O 2 was observed when aza‐CMP/C 2N heterostructures were used. A solar‐to‐hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge‐transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting. 相似文献
16.
首先在N-甲基吡咯烷酮溶液中超声剥离得到少层的MoS 2,将其与石墨相氮化碳(g-C 3N 4)复合,制得MoS 2/g-C 3N 4复合材料。采用X射线衍射(XRD),扫描电镜(SEM),X射线光电子能谱(XPS),傅里叶变换红外光谱(FTIR),Raman光谱,紫外-可见漫反射吸收光谱(DRS)和光致荧光(PL)技术对复合材料进行表征。可见光下考察MoS 2/g-C 3N 4复合材料光催化降解罗丹明B(RhB)的活性,结果表明:将少量MoS 2与g-C 3N 4复合可明显提高光催化活性,且1%( w/w)MoS 2/g-C 3N 4复合物的光催化活性最高,可能的原因是MoS 2和g-C 3N 4匹配的能带结构,增大了界面间电荷的传输,降低了光生电子-空穴的复合,进而提高了光催化活性。 相似文献
17.
Atomically precise Cu clusters are highly desirable as catalysts for CO 2 reduction reaction (CO 2RR), and they provide an appropriate model platform for elaborating their structure–activity relationship. However, an efficient overall photocatalytic CO 2RR with H 2O using assembled Cu-cluster aggregates as single component photocatalyst has not been reported. Herein, we report a stable crystalline Cu−S−N cluster photocatalyst with local protonated N−H groups (denoted as Cu 6−NH ). The catalyst exhibits suitable photocatalytic redox potentials, high structural stability, active catalytic species, and a narrow band gap, which account for its outstanding photocatalytic CO 2RR performance under visible light, with ≈100 % selectivity for CO evolution. Remarkably, systematic isostructural Cu-cluster control experiments, in situ infrared spectroscopy, and density functional theory calculations revealed that the protonated pyrimidine N atoms in the Cu 6−NH cluster act as a proton relay station, providing a local proton during the photocatalytic CO 2RR. This efficiently lowers the energy barrier for the formation of the *COOH intermediate, which is the rate-limiting step, efficiently enhancing the photocatalytic performance. This work lays the foundation for the development of atomically precise metal-cluster-based photocatalysts. 相似文献
18.
Narrow-band BiOI photocatalysts usually suffer from low photocatalysis efficiency under visible light exposure because of rapid charge recombination. In this work, to overcome this deficiency of photosensitive BiOI, oxygen vacancies, Bi particles, and Bi 2O 2CO 3 were co-induced in BiOI via a facile in situ assembly method at room temperature using NaBH 4 as the reducing agent. In the synthesized ternary Bi/BiOI/(BiO) 2CO 3, the oxygen vacancies, dual heterojunctions (i.e., Bi/BiOI and BiOI/(BiO) 2CO 3), and surface plasmon resonance effect of the Bi particles contributed to efficient electron-hole separation and an increase in charge carrier concentration, thus boosting the overall visible light photocatalysis efficiency. The as-prepared catalysts were applied for the removal of NO in concentrations of parts per billion from air in continuous air flow under visible light illumination. Bi/BiOI/(BiO) 2CO 3 exhibited a highly enhanced NO removal ratio of 50.7%, much higher than that of the pristine BiOI (1.2%). Density functional theory calculations and experimental results revealed that the Bi/BiOI/(BiO) 2CO 3 composites promoted the production of reactive oxygen species for photocatalytic NO oxidation. Thus, this work provides a new strategy to modify narrow-band semiconductors and explore other bismuth-containing heterostructured visible-light-driven photocatalysts. 相似文献
19.
A strategy to covalently connect crystalline covalent organic frameworks (COFs) with semiconductors to create stable organic–inorganic Z‐scheme heterojunctions for artificial photosynthesis is presented. A series of COF–semiconductor Z‐scheme photocatalysts combining water‐oxidation semiconductors (TiO 2, Bi 2WO 6, and α‐Fe 2O 3) with CO 2 reduction COFs (COF‐316/318) was synthesized and exhibited high photocatalytic CO 2‐to‐CO conversion efficiencies (up to 69.67 μmol g ?1 h ?1), with H 2O as the electron donor in the gas–solid CO 2 reduction, without additional photosensitizers and sacrificial agents. This is the first report of covalently bonded COF/inorganic‐semiconductor systems utilizing the Z‐scheme applied for artificial photosynthesis. Experiments and calculations confirmed efficient semiconductor‐to‐COF electron transfer by covalent coupling, resulting in electron accumulation in the cyano/pyridine moieties of the COF for CO 2 reduction and holes in the semiconductor for H 2O oxidation, thus mimicking natural photosynthesis. 相似文献
20.
Composite photocatalyst films have been fabricated by depositing BiVO 4 upon TiO 2 via a sequential ionic layer adsorption reaction (SILAR) method. The photocatalytic materials were investigated by XRD, TEM, UV/Vis diffuse reflectance, inductively coupled plasma optical emission spectrometry (ICP‐OES), XPS, photoluminescence and Mott–Schottky analyses. SILAR processing was found to deposit monoclinic‐scheelite BiVO 4 nanoparticles onto the surface, giving successive improvements in the films′ visible light harvesting. Electrochemical and valence band XPS studies revealed that the prepared heterojunctions have a type II band structure, with the BiVO 4 conduction band and valence band lying cathodically shifted from those of TiO 2. The photocatalytic activity of the films was measured by the decolourisation of the dye rhodamine 6G using λ>400 nm visible light. It was found that five SILAR cycles was optimal, with a pseudo‐first‐order rate constant of 0.004 min ?1. As a reference material, the same SILAR modification has been made to an inactive wide‐band‐gap ZrO 2 film, where the mismatch of conduction and valence band energies disallows charge separation. The photocatalytic activity of the BiVO 4–ZrO 2 system was found to be significantly reduced, highlighting the importance of charge separation across the interface. The mechanism of action of the photocatalysts has also been investigated, in particular the effect of self‐sensitisation by the model organic dye and the ability of the dye to inject electrons into the photocatalyst′s conduction band. 相似文献
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