We report an effective and green precursor-based route for preparing a sheet-like ZnO assembly composed of small ZnO particles, which showed good photocatalytic performance under UV light irradiation. The process involved first preparing a zinc glycerol precursor and then calcination to transform it into a sheet-like ZnO assembly. The microstructure of the sheet-like ZnO assembly, including the crystallite size, crystallinity degree and Brunauer–Emmett–Teller (BET) specific surface area, could be easily tuned by changing the calcination temperature. With an increase in calcination temperature, the crystallinity degree could be improved along with an increase in the crystallite size. Photocatalytic tests indicated that the as-prepared ZnO sheets showed good activity for photo-degradation of organic dye under UV light irradiation. ZnO-600 (calcination at 600 °C) exhibited the best photocatalytic activity, which was superior to that of P25 TiO2, a commercial benchmark photocatalyst. Furthermore, the sheet-like ZnO assembly could be readily separated from the reaction system by filtration or low-speed centrifugation (or natural sedimentation) after photocatalytic use due to the large particle size of 10 μm, which is favorable for separation and reuse. After 5 recycles, the ZnO-600 did not exhibit an obvious loss in activity, confirming its good activity upon recycling. By combining X-ray photoelectron spectroscopy (XPS) and BET tests, we found that the synergy of the BET surface areas and crystallinity resulted in the good performance of the sheet-like ZnO photocatalyst. In particular, due to the sheet-like structure, the ZnO could effectively combine with Ag particles, resulting in a large increase in the photocatalytic activity by more than 3 time by compounding with a small amount of Ag NPs (about 1% by mass). The present route is promising for the application of ZnO-based photocatalysts due to its easy handling process, good reproducibility, high yield and the good performance of the resulting materials.
Stable porous TiO2 photocatalysts, with higher photocatalytic activity than Degussa P25, were synthesized via a hydrothermal process using cetyltrimethylammonium bromide as the template, followed by a posttreatment in the presence of ethylenediamine. The photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, N2 adsorption−desorption, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and UV−vis diffuse reflectance spectra. The posttreatment considerably increases the thermal stability of the porous framework and inhibits the undesirable grain growth and phase transformation during calcination. The prepared TiO2 photocatalysts have large surface areas of about 205 and 117 m2/g even after calcination at 700 and 800 °C, respectively. The formation mechanism of the stable porous titania was proposed. The high crystallinity, large specific surface area, and heterojunction microstructure between anatase and brookite may be responsible for the high photocatalytic activity in terms of the degradation of organic pollutants such as phenol and rhodamine B under UV irradiation.
During the photocatalytic CO2 conversion process, fast charge transport, abundant active sites, and high visible light utilization in photocatalysts are key to achieving excellent CO2 conversion efficiency. In this work, hierarchical CuS@SnS2 p-n heterostructure hollow cubes were designed and prepared for photocatalytic CO2 reduction by fabricating CuS hollow cubes via the partial sulfidation and etching using Cu2O cubes as precursor and the final growing SnS2 nanosheets on the CuS hollow cubes. The prepared CuS@SnS2 p-n heterostructure hollow cubes showed an improved efficiency of photocatalytic CO2 reduction compared with the bare CuS and SnS2 control samples. The p-n heterojunction formed between SnS2 and CuS as well as its hollow structure enhanced the charge carrier separation and the light absorption capacity of the hybrid catalyst. Furthermore, after anchoring Au nanoparticles (NPs), the Schottky junction was constructed, and Au NPs serve as photoelectron reservoirs, triggering the aggregation of photoinduced electrons on the surface for CO2 photoreduction. The strong interaction between bimetallic sulfide support and Au NPs was found to be conducive to binding and reducing CO2 molecules. The localized surface plasmon resonance effect of Au NPs also improves the light harvesting ability of photocatalysts. Thus, the cooperative effects of these positive effects greatly facilitated photocatalytic CO2 reduction, and the optimized composite photocatalyst exhibited CO and CH4 yields of 346.3 and 208.5 μmol g-1 h-1, respectively. This work presents an efficient design of high-performance catalysts for photocatalytic CO2 reduction.
Novel hierarchical bow-like Cu2O crystals were successfully synthesized via a facile room temperature solution reaction using PVP as a structure-directing agent in the presence of NaBH4. The morphology evolution of the hierarchical bow-like Cu2O crystals were observed to be tunable as a function of reaction parameters, such as the reaction time, the quality of PVP and the reaction temperature. The possible growth mechanism of hierarchical bow-like Cu2O crystals was investigated. It involves the formation process of the intermediate octahedra Cu2O crystals and subsequent oxidation–erosion process from octahedra to hierarchical bow-like Cu2O crystals. It was found that the octahedra Cu2O crystals are a necessary intermediate for the formation of the bow-like Cu2O crystals. The prepared hierarchical bow-like Cu2O crystals exhibited a higher photocatalytic activity for photodegradation of rhodamine B aqueous solution under visible light illumination than the other prepared Cu2O crystal samples with different morphologies (nanoparticles and octahedra) because of its large surface area and specific hierarchical bow-like structure.
A series of perovskite-like complex oxides La_(2-x)Sr_xCuO_(4+δ)(0≤x≤1)were prepared.The air electrode with different mass ratio Sr as catalyst layer material have been prepared,in alkaline solution,The electrocatalytic performances for oxygen reduction were evaluated by means of polarization curve、cyclic voltammetry.by using Hg/HgO as a reference electrode,the results disclosed that La_(2-x)Sr_xCuO_(4+δ)(0≤x≤1)have excellent and different activity withThe different ratio of Sr.and also study the kinetics characteristic of air electrode.
Abstract Core/shell heterostructure composite has great potential applications in photocatalytic field because the introduction of core can remarkably improve charge transport and enhance the electron-hole separation. Herein, hierarchical Bi 2 S 3 /In 2 S 3 core/shell structured microspheres were prepared via a simple one-pot hydrothermal process based on different growth rate of the two kinds of sulphides. The results showed that, the as-prepared hierarchical Bi 2 S 3 /In 2 S 3 core/shell heterostructure exhibits significant visible light photocatalytic activity for degradation of 2, 4-dichlorophenol. The introduction of Bi 2 S 3 core can not only improve charge transport and enhance the electron-hole separation, but also broaden the visible light response. The hierarchical porous folwer-like shell of In 2 S 3 could increase the specific surface area and remarkably enhanced the chemical stability of Bi 2 S 3 against oxidation.
Abstract Thermally‐stable, ordered mesoporous anatase TiO 2 with large pore size and high crystallinity has been successfully synthesized through an evaporation‐induced self‐assembly technique, combined with encircling ethylenediamine (EN) protectors to maintain the liquid crystal mesophase structure of TiO 2 primary particles, followed by calcination at higher temperature. The structures of the prepared mesoporous TiO 2 are characterized in detail by small‐angle and wide‐angle X‐ray diffraction, Raman spectra, N 2 adsorption/desorption isotherms, and transmission electron microscopy. Experimental results indicate that the well‐ordered mesoporous structure could be maintained up to 700 °C (M700) and also possesses large pore size (10 nm), high specific BET surface area (122 m 2 g −1 ), and high total pore volumes (0.20 cm 3 g −1 ), which is attributed to encircling EN protectors for maintaining the mesoporous framework against collapsing, inhibiting undesirable grain growth and phase transformation during the calcination process. A possible formation mechanism for the highly stable large‐pore mesoporous anatase TiO 2 is also proposed here, which could be further confirmed by TG/FT‐IR in site analysis and X‐ray photoelectron spectroscopy. The obtained mesoporous TiO 2 of M700 exhibit better photocatalytic activity than that of Degussa P25 TiO 2 for degradation of highly toxic 2,4‐dichlorophenol under UV irradiation. This enhancement is attributed to the well‐ordered large‐pore mesoporous structure, which facilitates mass transport, the large surface area offering more active sites, and high crystallinity that favors the separation of photogenerated electron‐hole pairs, confirmed by surface photovoltage spectra.
Fabricating photocatalysts with customizable structure and composition using different metal-organic framework (MOF) building blocks has intriguing implications in chemistry and materials science, but it is challenging to do so. This work developed hierarchical MIL-125(Ti)@TiO2\Co3S4 ternary hybrid photocatalysts with hollow nanodisk structure for photocatalytic CO2 reduction. The creation of MIL-125(Ti) nanodiscs was the first step in the synthesis. Next, Co-based zeolite imidazolium ester backbone (ZIF-67) nanolayer was encapsulated on the MIL-125(Ti) nanodisks to form core@shell MIL-125(Ti)@ZIF-67 nanodisks. The following sulfidation process under solvothermal condition leads to the production of hierarchical MIL-125(Ti)@TiO2\Co3S4 hollow nanodisks. Along with offering a huge number of active sites, this hollow nanodisk structure ternary hybrid significantly enhances charge mobility and visible light absorption. Considering the advantages listed above, the CO2 photoreduction activity of the optimized hierarchical MIL-125(Ti)@TiO2\Co3S4 hollow nanodisk catalyst was significantly increased when compared to single-component catalysts (MIL-125(Ti), TiO2, and Co3S4) and binary hybrid catalysts (MIL-125(Ti)@TiO2 and TiO2\Co3S4) under simulated sunlight irradiation. CO is the main product with a productivity of 587.50 μmolg-1h-1, which is almost seven times higher than that of pure MIL-125(Ti). The potential photocatalytic mechanism of the ternary hybrid photocatalyst has also been demonstrated. This study presents a simple and effective technique for fabricating MOF-based hybrid catalysts for photocatalytic applications.
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