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1.
A series of reduced graphene oxide/TiO2 (RGO/TiO2) nanowire microsphere composites were synthesized with a facile one-step hydrothermal method using TiCl3 and graphene oxide (GO) as the starting materials, during which the formation of TiO2 and the reduction of GO occur simultaneously. The obtained nanocomposites were characterized with X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, respectively. UV–vis absorption spectra showed that the absorption edges of TiO2 were extended into visible light region with the addition of RGO. The photocatalytic activities of the samples with and without Pt as cocatalysts were evaluated by hydrogen evolution from water photo-splitting under UV–vis light illumination. Enhanced photocatalytic properties were observed for the as-prepared RGO/TiO2 nanocomposites. The amount of hydrogen evolution from the optimized photocatalyst reached to 43.8 μmol h−1, which was about 1.6 times as high as that of bare TiO2. The results shown here indicate a convenient and applicable approach to further exploitation of high activity materials for photocatalytic water splitting applications.  相似文献   

2.
Overcoming the low charge transfer efficiency and poor photothermal stability of halide perovskite quantum dots (QDs) is the booster to achieve photocatalytic applications. In this paper, the Pt2+-doped CsPbBr3 QDs/two-dimensional accordion-like Ni-MOF (CPPB QDs/Ni-MOF) composite was firstly synthesized by fixing the CPPB QDs into the pores of Ni-MOF. Electron separation and transfer efficiency were analyzed by PL spectra and electrochemical data. The photocatalyst exhibited outstanding photocatalytic performance in hydrogen (H2) evolution. The optimal H2 evolution efficiency of the composite reached 153.6 μmol h?1, which was about 9 times than that of pure Ni-MOF and remained 134.8 μmol h?1 after the cycle test. The splendid efficiency could be benefited from the advantages of 2D layered structure of Ni-MOF and the high charge separation and transmission efficiency of CPPB QDs. Finally, the mechanism of electron migration and additional electron transfer channels between composite interfaces was further demonstrated by density functional theory (DFT) calculations. The present work opens up a novel perspective for photocatalytic applications of doped halide perovskite QDs/Ni-MOF nanocomposites.  相似文献   

3.
As an emerging two-dimensional (2D) nanomaterial, 2D MoSe2 nanosheets has the advantages of wide light response and rapid charge migration ability. In this work, 2D MoSe2/TiO2 nanocomposites were successfully synthesized through a simple hydrothermal method. The microstructure and photocatalytic activity of the nanocomposites were systematically investigated and determined. The corresponding Raman peaks and crystal planes of MoSe2 were analysed by Raman spectroscopy and transmission electron microscopy respectively, demonstrating the successful combination of the MoSe2 nanosheets and TiO2 nanoparticles. UV-vis diffused reflectance spectra demonstrated that the introduction of MoSe2 did increase the light absorption ability of the nanocomposites. A lower recombination of electrons and holes was demonstrated for the MoSe2/TiO2 heterojunction from photoluminescence results. The photocatalytic hydrogen evolution test showed that the hydrogen production rate was 4.9 μmol h−1 for the sample with 0.1 wt.% MoSe2, 2 times higher than that of bare TiO2. This work provides a novel strategy for improving the photocatalytic properties of semiconductor photocatalyst.  相似文献   

4.
This work presents the photocatalytic hydrogen generation of BiI3 films when they are exposed under simulated solar irradiation. Those films were fabricated by a simple bath chemical deposition method. The images of Scanning electron microscopy show that the BiI3 films are formed by polycrystalline particles with hexagonal shape and a closer inspection shows that nanoplates grown into them. The performance for the hydrogen generation of BiI3 films synthesized with different times (from 1 to 3 h), BiI3 films decorated with silver nanoparticles (BiI3-Ag) and BiI3 powders were compared. We found that the presence of Ag nanoparticles in the BiI3 films increased the hydrogen generation from 9 mmol/g·h to 14 mmol/g·h because these nanoparticles improved electron conductivity, reduced the amount of defects in the BiI3 films, raised the optical absorption, and produced higher photocurrents (with respect to the BiI3 films without nanoparticles) as confirmed by electrochemical experiments. On the contrast, the BiI3 powders had a poor hydrogen generation rate of only 0.5 mmol/g·h, this was due to the fact that they are formed by nanoplates 10 times bigger than these ones grown on the BiI3 films, consequently, they had lower surface area than the nanoplates in the BiI3 films. A possible mechanism for the hydrogen generation by the BiI3 and BiI3-Ag films is also discussed.  相似文献   

5.
Solar-driven photocatalytic hydrogen generation by splitting water molecules requires an efficient visible light active photocatalyst. This work reports an improved hydrogen evolution activity of visible light active TiO2-x photocatalyst by introducing reduced graphene oxide via an eco-friendly and cost-effective hydrothermal method. This process facilitates graphene oxide reduction and incorporates intrinsic defects in TiO2 lattice at a one-pot reaction process. The characteristic studies reveal that RGO/TiO2-x nanocomposites were sufficiently durable and efficient for photocatalytic hydrogen generation under the visible light spectrum. The altered band gap of TiO2-x rationally promotes the visible light absorption, and the RGO sheets present in the composites suppresses the electron-hole recombination, which accelerates the charge transfer. Hence, the noble metal-free RGO/TiO2-x photocatalyst exhibited hydrogen production with a rate of 13.6 mmol h?1g?1cat. under solar illumination. The appreciable photocatalytic hydrogen generation activity of 947.2 μmol h?1g?1cat with 117 μAcm?2 photocurrent density was observed under visible light (>450 nm).  相似文献   

6.
An effective improvement of hydrogen evolution from water splitting under solar light irradiation was investigated using quantum dots (QDs) compounds loaded onto a Au/TiO2 photocatalyst. First, Au/TiO2 was prepared by the deposition-precipitation method, and then sulfide QDs were loaded onto the as-prepared Au/TiO2 by a hydrothermal method. QDs were loaded onto Au/TiO2 to enhance the energy capture of visible light and near-infrared light of the solar spectrum. The results indicated that the as-prepared heterojunction photocatalysts absorbed the energy from the range of ultraviolet light to the near-infrared light region and effectively reduced the electron-hole pair recombination during the photocatalytic reaction. Using a hydrothermal temperature of 120 °C, the as-prepared (ZnS–PbS)/Au/TiO2 photocatalyst had a PbS QDs particle size of 5 nm, exhibited an energy gap of 0.92 eV, and demonstrated the best hydrogen production rate. Additionally, after adding 20 wt % methanol as a sacrificial reagent to photocatalyze for 5 h, the hydrogen production rate reached 5011 μmol g−1 h−1.  相似文献   

7.
In this study, TiO2 coated carbon fiber (TiO2@CF) was synthesized and used for the improvement of hydrogen (H2) evolution. Obtained results from scanning electron microscopy (SEM), X-ray diffraction (XRD), gas adsorption analysis (BET), UV–vis diffuse (UV–vis), and X-ray photoelectron spectroscopy (XPS) confirmed that the surface area and light absorption of the material was significantly improved. The synthesized TiO2@CF photocatalyst exhibited improved photocatalytic performance toward hydrogen generation. The enhancement of photocatalytic H2 evolution capacity by TiO2@CF was ascribed to its narrowed bandgap energy (2.76eV) and minimized recombination of photogenerated electron-hole pairs The hydrogen production rate by the TiO2@CF reached 3.238 mmolg?1h?1, which was 4.8 times higher than unmodified TiO2 (0.674 mmolg?1h?1). The synthesized TiO2@CF was relatively stable with no distinct reduction in photocatalytic activity after five recycling runs. The photoluminescence and photocurrent were employed to support the photocatalytic H2 production mechanism proposed mechanism.Based on these results, TiO2@CF with unique properties, easy handle, and high reusability could be suggested as an efficient strategy to develop a high-performance photocatalyst for H2 production.  相似文献   

8.
A TiO2 nanotube-based nanoreactor was designed and fabricated by facile two steps synthesis: firstly, hydrothermal synthesized SrTiO3 was deposited on TiO2 nanotubes (TiO2NTs). Secondly, the Au nanoparticles (NPs) were encapsulated inside the TiO2NTs followed by vacuum-assisted impregnation. The as-synthesized composites were characterized using Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectra (PL) and Ultraviolet–visible absorption spectroscopy (UV–vis). The photocatalytic performance was evaluated by the hydrogen evolution reaction. The results revealed that the SrTiO3 modified TiO2NTs confined Au NPs (STO-TiO2NTs@Au) achieved an enhanced hydrogen evolution rate at 7200 μmol h−1 g−1, which was 2.2 times higher than that of bald TiO2NTs@Au at 3300 μmol h−1 g−1. The improved photocatalytic activity could be attributed to the synergistic effect of the electron-donating of SrTiO3 and TiO2NTs confinement. The as-designed nanoreactor structure provides an example of efficient carriers' separation photocatalyst.  相似文献   

9.
TiO2-x/g-C3N4/CdS ternary heterojunctions are fabricated through thermal polymerization-chemical bath deposition combined with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions are formed successfully and CdS quantum dots (QDs) and TiO2 are anchored on surface of g-C3N4 nanosheets simultaneously. The visible-light-driven photocatalytic degradation ratio of Bisphenol A and hydrogen production rate are up to 95% and ∼254.8 μmol h−1, respectively, which are several times higher than that of pristine TiO2. The excellent visible-light-driven photocatalytic activity can be ascribed to the synergistic effect of TiO2−x, g-C3N4 and CdS QDs which extend the photoresponse to visible light region and favor the spatial separation of photogenerated charge carriers.  相似文献   

10.
In addition to the extended light absorption, the effective spatial charge separation is a crucial factor for highly efficient metal-oxide semiconductor-based photocatalysts. Herein, a rational design of metal-semiconductor-metal nano heterostructure for enhancing photocatalytic performance is proposed. The semiconductor nanoparticles are integrated with two metals in one single nano heterostructure. The disordered layers are induced on the surface of TiO2 to promote the light absorption capacity. More importantly, the n-n+ junction is fabricated at the contact region between crystalline TiO2 (n-TiO2) and disordered layers (n+-TiO2). Besides, the Schottky diode and Ohmic contact are formed on n-TiO2 and n+-TiO2, respectively. As a result, the existence of multi-junctions leads to the formation of multiple continuous built-in electric fields, thus remarkably accelerating the spatial separation of charge carriers. The resulting nano heterostructure with multi-junctions (Pt–TiO2–H–Ag) exhibits remarkably promoted photocatalytic performance. The maximum hydrogen generation rate of Pt–TiO2–H–Ag under solar illumination (18001.0 μmol/h/g) is 8.3, 9.3, and 1.5 times superior to that of Pt-loaded P25 (Pt–P25), Pt loaded TiO2 (Pt–TiO2), and hydrogenated Pt–TiO2 (Pt–TiO2–H), respectively. Moreover, the photocatalytic performance under visible illumination is significantly enhanced by Pt–TiO2–H–Ag. Specifically, the H2 generation rate of Pt–TiO2–H–Ag (2382.7 μmol/h/g) is about 15.1, 17.2, and 1.4 times higher than that of Pt–P25, Pt–TiO2, and Pt–TiO2–H, respectively. The corresponding apparent quantum efficiency of Pt–TiO2–H–Ag is 15.8% (420 nm). The nano heterostructure with multi-junctions also exhibits excellent stability after five cycles, remaining hydrogen evolution rates of 15581.5 and 2211.4 μmol/h/g under solar and visible illumination, respectively. This effective and controllable manufacturing strategy could provide new opportunities to simultaneously extend optical absorption and facilitate the spatial charge separation and transport of wide-bandgap metal-oxide semiconductors.  相似文献   

11.
The hybrid 1D branched TiO2 loaded with g-C3N4 QDs was successfully fabricated that plays a significant role in photocatalysis. The 1D branched TiO2 prepared by electrospinning followed by alkali-hydrothermal process, and g-C3N4 QDs were grafted over it by a chemical vapor deposition method. The composite display enhancement in photocatalytic hydrogen evolution is about 10.57 mmol. g−1.h−1 in comparison to the g-C3N4 sample that only produces 0.32 mmol. g−1.h−1 while the HBTiO2 sample evolved a negligible amount of hydrogen under visible light. The composite sample shows quantum efficiency for HER at 420 nm light is 18.6% that is much higher than the other two samples. The specific surface area of the composite sample is 92.39 m2g-1 that is about 13 times more than bulk g-C3N4. The bandgap of HBTiO2/g-C3N4 QDs, g-C3N4, and HBTiO2 samples calculated as 2.71 eV, 2.67eV, and 3.24eV, respectively. The TRPL spectra imply that the duration of the lifetime of composite becomes longer which effectually overwhelm the electron-hole recombination. The 1D branched TiO2 fiber reduces the charge recombination by fast transfer of electron while g-C3N4 QDs facilitate the visible light absorption by improving the optical properties. The formation of the type II heterostructure system remarkably promotes the separation and transfer of electron holes and facilitates the photo-reduction reaction.  相似文献   

12.
This study focused on the large band gap of TiO2 for its use as a photocatalyst under light emitting diode (LED) light irradiation. The photocatalytic activities of core–shell structured Au@TiO2 nanoparticles (NPs), nitrogen doped Au@TiO2 NPs, and Au@TiO2/rGO nanocomposites (NCs) were investigated under various light intensities and sacrificial reagents. All the materials showed better photocatalytic activity under white LED light irradiation than under blue LED light. The N-doped core–shell structured Au@TiO2 NPs (Au@N–TiO2) and Au@TiO2/rGO NCs showed enhanced photocatalytic activity with an average H2 evolution rate of 9205 μmol h?1g?1 and 9815 μmol h?1g?1, respectively. All these materials showed an increasing rate of hydrogen evolution with increasing light intensity and catalyst loading. In addition, methanol was more suitable as a sacrificial reagent than lactic acid. The rate of hydrogen evolution increased with increasing methanol concentration up to 25% in DI water and decreased at higher concentrations. Overall, Au@TiO2 core–shell-based nanocomposites can be used as an improved photocatalyst in photocatalytic hydrogen production.  相似文献   

13.
In terms of improving photocatalytic hydrogen production performance, inexpensive and earth-rich cocatalysts have become promising alternatives to precious metals. Herein, a novel CoNi–TiO2 photocatalyst composed of TiO2 nanoflowers and CoNi alloy was prepared by hydrothermal and chemical reduction methods. Various characterizations and test results have confirmed that the further improvement of the photocatalytic performance of the CoNi–TiO2 photocatalyst is mainly due to the fact that the bimetallic CoNi alloy can accelerate charge transfer and inhibit the recombination of photo-induced carriers. The hydrogen production rate of the prepared CoNi–TiO2 is about 24 times higher than that of the pristine TiO2, and its hydrogen production rate value can reach 6580.9 μmol g?1 h?1, and showing comparable photocatalytic performance to 0.5 wt% Pt–TiO2. In addition, combined with the characterization results, a probable mechanism for enhanced photocatalytic performance was proposed. This study provides favorable enlightenment for the design of a series of highly efficient non-precious metal TiO2-based photocatalysts.  相似文献   

14.
Establishing efficient co-catalytic loaded semiconductors for efficient charge separation is a hopeful way for enhance photocatalytic water splitting hydrogen evolution. Herein, we successfully constructed the Cd0.5Zn0.5S/Ni2P (CZS/Ni2P) nanocomposites via two-step hydrothermal method. The CZS/Ni2P composites show much improved activity than the origin CZS for photocatalytic H2 generation. When the content of Ni2P loaded on the Cd0.5Zn0.5S (CZS) is 0.3 mol%, the photocatalyst achieves the highest photocatalytic hydrogen generation rate of 41.26 mmol g−1 h−1 under visible light. The Ni–S bonds on the close contact interface between CZS and Ni2P can be act as electron-bridge to provide a channel for electron transfer. During the photocatalysis processing, Ni2P can be used as electron traps to attract electrons from CZS, resulting in the improvement of the photocatalytic performance.  相似文献   

15.
Hollow mesoporous TiO2 photocatalysts with dual co-catalysts, located at specific positions, were prepared using Polystyrene (PS) as sacrificial templates. Au nanoparticles (NPs) were in situ loaded on the surface of PS spheres and the resulting nanocomposites were coated with TiO2 shell using sol-gel reaction. The outer surface of core-shell spheres was impregnated with Ru and the subsequent calcination produced hollow anatase spheres with Au and RuO2 dual co-catalysts. The hollow mesoporous spheres of Au@TiO2@RuO2 were proved by various techniques such as TEM, EDX, and SEM images. Photocatalysts were applied for hydrogen generation from water splitting and that with dual co-catalysts showed efficient catalytic activity under simulated solar light. The catalytic activity of photocatalysts with both oxidation and reduction co-catalysts (Au@TiO2@RuO2) showed hydrogen evolution (3165 μmol g−1) almost two times more than that Au@TiO2 and TiO2@RuO2 with single co-catalysts. And the hydrogen evolved is more than three times as compared to TiO2 (935 μmol g−1) without any co-catalyst. Hollow mesoporous morphology with different co-catalysts on inner and outer surfaces is believed to enhance photocatalytic activity which is due to better separation of photo-generated charges.  相似文献   

16.
Sustainable energy innovation is spearheading the way to achieve decarbonisation through commercially viable and highly competitive renewable technologies for green hydrogen. Photocatalytic water splitting has received global attention, as it promotes the direct conversion of solar energy to chemical energy and hydrogen production. Lanthanum orthoferrite (LaFeO3) has been selected due to its narrow bandgap perovskite-oxides (ABO3) type nature, low cost and high chemical stability but it is limited with fast charge recombination. To circumvent its constraint of fast charge recombination, an efficient graphene-based nanocomposite has been prepared by employing reduced graphene oxide (RGO) nanosheets as charge separators for visible light driven photocatalytic water splitting. Here, we present a thorough physical and spectroscopic characterization of the Lanthanum orthoferrite/Reduced Graphene oxide (LaFeO3/RGO) nanocomposites, and investigate its photocatalytic and photoelectrochemical performance. The photocurrent density of the nanocomposites demonstrated ∼21 times higher in comparison to pure LaFeO3. The as-prepared nanocomposites have been successfully used as photocatalysts for H2 generation through water reduction under visible light. A significant enhancement in H2 generation has been recorded for nanocomposites (∼82 mmol g−1 h−1) as compared to that of bare LaFeO3 (∼9 mmol g−1 h−1) which is among the highest values obtained using noble-metal-free graphene-based photocatalytic nanocomposites. This work offers a facile approach for fabricating highly efficient 1D-2D heterostructure for photocatalysis application.  相似文献   

17.
One key challenge in photocatalytic hydrogen production is how to construct high-performance photocatalyst. Covalent triazine framework (CTF) based polymers as photocatalysts show great application potential because of their good photocatalytic activity, high chemical stability, tunable electronic and optical properties, and easy synthesis process. In this paper, we designed the ternary Z-scheme heterojunction Au@TiO2-X%TrTh based on CTF polymer TrTh, TiO2 and Au nanoparticle, which exhibit higher photocatalytic hydrogen production rate compared with the corresponding binary heterojunction Au@TiO2 and TiO2-12%TrTh. The results of photocatalytic hydrogen production show that the optimized Au@TiO2-12%TrTh has a remarkable hydrogen production rate of 4288.54 μmol g?1 h?1, which is about 312.3 times of Au@TiO2 and 9.1 times of the TiO2-12%TrTh. The enhanced hydrogen production activity of the ternary heterojunction comes from the local surface plasmonic resonance effect of Au nanoparticle, lower recombination efficiency of photogenerated electron-holes pairs and Z-scheme electron transfer pathway of Au@TiO2-12%TrTh. The work provides a new strategy for designing efficient and practical photocatalyst.  相似文献   

18.
The photocatalytic hydrogen production from aqueous methanol solution was investigated with ZnO/TiO2, SnO/TiO2, CuO/TiO2, Al2O3/TiO2 and CuO/Al2O3/TiO2 nanocomposites. A mechanical mixing method, followed by the solid-state reaction at elevated temperature, was used for the preparation of nanocomposite photocatalyst. Among these nanocomposite photocatalysts, the maximal photocatalytic hydrogen production was observed with CuO/Al2O3/TiO2 nanocomposites. A variety of components of CuO/Al2O3/TiO2 photocatalysts were tested for the enhancement of H2 formation. The optimal component was 0.2 wt% CuO/0.3 wt% Al2O3/TiO2. The activity exhibited approximately tenfold enhancement at the optimum loading, compared with that with pure P-25 TiO2. Nano-sized TiO2 photocatalytic hydrogen technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy.  相似文献   

19.
This work reports a green and facile approach to synthesize chemically bonded TiO2/graphene sheets (GS) nanocomposites using a one-step hydrothermal method. The as-prepared composites were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and ultraviolet visible (UV-Vis) diffuse reflectance spectra. The photocatalytic activity was evaluated by hydrogen evolution from water splitting under UV-Vis light illumination. An enhancement of photocatalytic hydrogen evolution was observed over the TiO2/GS composite photocatalysts, as 1.6 times larger for TiO2/2.0 wt%GS than that of Degussa P25. This fabrication process features the reduction of graphene oxide and formation of TiO2 simultaneously leading to the well dispersion of generated TiO2 nanoparticles on the surface of GS.  相似文献   

20.
In this work, B–N co-doped TiO2 has been synthesized by a facile fast sol-gel method, and then, a controlled magnesiothermic reduction has been developed to synthesize B–N co-doped black TiO2 under a N2 atmosphere and at 580 °C followed by acid treatment. The prepared black TiO2 samples were characterized by X-ray diffraction, high resolution transmission electron microscopy, Raman spectrameter, photoluminescence emission spectra, X-ray photoelectron spectroscopy, and ultraviolet–visible diffuse reflectance spectra. It shows that the prepared samples possess a unique crystalline core-amorphous shell structure composed of disordered surface and oxygen vacancies, and exhibit enhanced photocatalytic activity in hydrogen production in the methanol-water system in the presence of Pt as a co-catalyst. Under the full solar wavelength range of light, the maximum hydrogen production rate of the B–N co-doped black TiO2 is 18.8 mmol h−1 g−1, which is almost 4 times higher than that of pure TiO2.  相似文献   

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