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Metal Sulfide Photocatalysis: Visible-Light-Induced Organic Transformations
摘要： Transition-metal sulfides belong to an important subgroup of semiconductor photocatalysts that could promote a variety of valuable redox reactions under mild conditions. One notable merit of metal sulfides is their relatively smaller bandgaps than metal oxides, which in turn make sure that many of them can directly utilize visible light. Historically, the deployment of metal sulfides for visible-light-induced organic transformations took place shortly after the genesis of the research field of heterogeneous photocatalysis. In this review, we primarily focus on recent state-of-the-art advancements of metal sulfide photocatalysis aimed at visible-light-induced selective organic transformations. Interests in this specific branch of photocatalysis have been rekindled due to the new methods for materials synthesis; the pursuit of new mechanisms; or the integration of metal sulfides with metal oxides, metal nanoparticles or other emerging materials. Thus we categorize them into four sections according to the different strategies in developing novel or more efficient organic processes. Binary and ternary metal sulfides, usually associated with new materials synthesis and mechanistic insights, can be used directly for visible-light-induced organic transformations. This is the basis of other further developments and will be introduced firstly. Next, the cooperation between metal sulfides and metal oxides or metal nanoparticles can be conducive to many photocatalytic systems. These developments will be discussed in the next two ensuing sections. Furthermore, the integration of metal sulfides with recent developed emerging materials such as metal-organic frameworks (MOFs), graphene and graphitic carbon nitride (g-C3N4) would be discussed in another section to highlight the importance of merging metal sulfides with these materials. We attempt to keep an impartial panorama of these four distinctive sections even though the phases of development are quite different among sections, leaving plenty of room for the future expansion of this burgeoning area.
关键词： Metal Sulfide,Selective Oxidation,Photocatalysis,Visible Light,Selective Reduction
更新于2025-09-23 15:23:52
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Solar Heterogeneous Photocatalytic Oxidation for Water and Wastewater Treatment: Problems and Challenges
摘要： Solar operation of heterogeneous photocatalytic oxidation reactors is looked at as a sustainable process for water and wastewater treatment, because it does not consume electric power and chemicals. However, there are still problems for technical-scale application. The problems addressed in this article are large area demand, water evaporation from open reactors and lack of simple photocatalyst recovery. An optimum solar reactor type is the parabolic compound collector reactor with borosilicate glass tubes. Challenges for further research are improvement in mass transfer as well as identification of novel photocatalysts which make use also of visible light, are efficient and stable, and are easy to be produced in an economically feasible way. Also the combination of photocatalysts with adsorbents is promising. Although membrane filtration processes have been successfully combined with solar photocatalytic oxidation and represent a safe barrier against spreading photocatalyst nanoparticles into the aquatic environment, more simple and less energy-consuming methods for photocatalyst recovery would be desirable.
关键词： Photocatalyst recovery,Novel photocatalysts,Solar photocatalytic oxidation,Photocatalysis adsorption hybrid process,Mass transfer
更新于2025-09-23 15:23:52
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Hybrid composite of CuO with $$\hbox {g}\hbox {-C}_{3}\hbox {N}_{4}$$g-C3N4 as a photoactive catalyst: an efficient approach for the oxidation of alcohols
摘要： An eco-friendly method for the oxidative transformation of alcohols to their corresponding carbonyl compounds by using g-C3N4@CuO as a photoactive heterogeneous catalyst has been developed. The catalyst was characterized by SEM-EDX, TEM, BET surface area measurements, powder XRD, FTIR, photoluminescence and UV-Vis spectroscopy. It was found to be very effective for the conversion of both primary and secondary alcohols into aldehydes and ketones with excellent yields using tert-butyl hydrogen peroxide (TBHP) as oxidant at room temperature in the presence of visible light in aqueous medium. The catalyst can be separated from the reaction mixture by simple centrifugation and reused up to five cycles without significant loss in activity.
关键词： Nanocomposite,alcohol oxidation,copper oxide,photocatalyst,graphitic carbon nitride
更新于2025-09-23 15:23:52
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Optical Properties of Nanohole Arrays with Various Depths
摘要： Studies to imitate structural colors have been conducted with various methods, most of which are disadvantageous for mechanical stability and economic feasibility because of complexity or lack of reproducibility. Numerous alternatives to overcome these shortcomings have been proposed. One such method is the anodic oxidation of aluminum, which requires relatively simple equipment and techniques. The present study used the aluminum anodic oxidation process to fabricate nanohole arrays of various sizes. Furthermore, using the finding that the structure color is the most strongly influenced by the nanohole depth based on the Bragg's Law, this study fabricated nanoholes of various depths to identify the structural colors arising from varied depths. This study further identified the colors from the same color series occurring periodically at each interval of 250 nm using the CIE 1931 color coordinate system. Moreover, nanohole arrays with two different depths were fabricated on a single substrate to confirm the coexistence of different colors and their capacity for deformation into various shapes.
关键词： Nanohole array,Structural color,Bragg's law,Anodic aluminum oxidation,Thin film effect
更新于2025-09-23 15:23:52
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[Mo3S13]2? modified TiO2 coating on non-woven fabric for efficient photocatalytic mineralization of acetone
摘要： Improving the photocatalytic efficiency of commercial TiO2 has important significance for practical application of TiO2 based photocatalysts. A novel photocatalyst [Mo3S13]2?/TiO2 was fabricated by combining [Mo3S13]2? with commercial TiO2 by an impregnation method. This composite photocatalyst presented a remarkable enhancement on photocatalytic mineralization of acetone in comparison with commercial TiO2. The optimum loading amount of [Mo3S13]2? was 1.7wt%, which is more efficient than the Pt/TiO2 (1.5wt%). Electrochemical impedance spectroscopy (EIS) showed the smooth electron transfer pathway in [Mo3S13]2?/TiO2 composite, facilitating the photo-charges separation during the photocatalysis process. Reactive oxygen species scavenging test illustrated that superoxide radical (?O2?), hydroxyl radical (?OH) and photo-induced hole (h+) were all contributing to the acetone degradation. The [Mo3S13]2?/TiO2 photocatalyst was deposited on non-woven fabrics which showed obvious promotion on the photocatalytic degradation of acetone in comparison with pristine commercial TiO2.
关键词： TiO2,[Mo3S13]2?,Photocatalytic oxidation,VOCs degradation,Non-woven fabrics
更新于2025-09-23 15:23:52
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A novel Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst: Study on the excellent photocatalytic performance and photocatalytic mechanism
摘要： A novel three-dimensional microspheres mediator-free Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag3VO4/BiVO4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8 %, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag3VO4 and BiVO4, and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag3VO4/BiVO4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag3VO4 to BiVO4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.
关键词： Bismuth Vanadate,Z-scheme heterojunction photocatalyst,photocatalytic reduction and oxidation.
更新于2025-09-23 15:23:52
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Photocatalytic degradation of organic pollutants from wastewater using aluminium doped titanium dioxide
摘要： The objective of this research was to study the performance of batch and continuous recirculating reactor to photo-degrade dye and synthetic wastewater. Here, Aluminium (Al) was used as the doped metal. The commercially available TiO2 P-25 and Al (NO3)3 was used as a Ti-precursor and doping agent, respectively, via the impregnation method. Various parameters such as the concentration of the doping agent, and calcination temperature were studied. The TiO2 nanocrystal doped with Al was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analyzer (TGA). The photocatalytic performance of Al-doped nanoparticle was quantified by the degradation of methylene blue (MB) solution under a visible light irradiation condition. Its performance was compared against undoped-nano-TiO2. The results showed that Al (NO3)3 solution with a concentration of 0.25% and volume of 100 cm/ml, and calcined at 300 C for 4 h, was the optimum condition of Al-doped nano-TiO2. Furthermore, the highest pseudo-first-order kinetic rate was 0.096 where the doped Al(NO3)3 of 0.75 w/v was used in the batch reactor. The Al-doped nano-TiO2 that was obtained has the potential for use as a photocatalyst for degradation organics pollutant from wastewater under the visible light irradiation. The highest removal of organic pollutants from synthetic wastewater was 75% using TiO2 P-25 alone at 2 g/L dosage. In addition, the removal of organic pollutant by TiO2/doped with Al was 80% at a dosage of 0.5 g/L and was 85% at a dosage of 1 g/L.
关键词： Batch reactor,Photo-catalyst,Titanium dioxide,Advanced oxidation process
更新于2025-09-23 15:23:52
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Enhanced sensor life using UV treatment of sulphur poisoned Pt-PtOx
摘要： In this work, we report a novel method for recovery of sulphur poisoned platinum/platinum oxide (Pt-PtOx) core-shell nanowire sensor using UV irradiation. The optimum core to shell thickness ratio and the operating conditions are the key factors to achieve a high-performance H2S sensor, described in this report. The fabricated core-shell nanowire sensor demonstrated response of 6.4% at 1 ppm H2S with detection limit of 10 ppb at 150°C operating temperature. The sensor undergoes prominent time-dependent poisoning at H2S exposure of 3 ppm when operated at 150°C due to sensor surface contamination by sulphur, later confirmed by XPS analysis. Ultraviolet light at two wavelengths, 365 nm, and 248 nm is investigated to recover the poisoned Pt-PtOx surface. UV irradiation at 248 nm for 5 minutes results in sensor recovery, confirmed by further H2S sensing characterization and XPS studies on the recovered sensor. To the best of our knowledge, this is one of the first reports on UV irradiation for recovery of sulphur poisoned metal-oxide surfaces.
关键词： sulphidation,recovery,plasma oxidation,UV irradiation,core-shell nanowire
更新于2025-09-23 15:23:52
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Enhanced optoelectronic performance of plasma electrolytic oxidized monocrystalline silicon using rGO incorporation
摘要： rGO/SiO2 composite coating was successfully prepared by plasma electrolyte oxidation (PEO) process on monocrystalline silicon (mc-Si) substrate. Investigating the effect of rGO incorporation into the SiO2 coating revealed that the addition of rGO leads to a significant increase in the photo-trapping ability due to the high specific surface area and excellent electron transfer efficiency. The PL intensity of the composite sample was found to decrease, which signified the suspension of the electron-hole pairs’ recombination. As a result, the photocurrent gain of the composite coating enhanced about 5.5 times. Likewise, the time-response switching featured an over two-fold increase for the rGO/SiO2 coating, impressively.
关键词： Semiconductors,Plasma electrolyte oxidation,Optoelectrical properties,Composite materials,rGO/SiO2 composite
更新于2025-09-23 15:23:52
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Operando XAS and NAP-XPS investigation of CO oxidation on meso- and nanoscale CoO catalysts
摘要： In contrast to Co3O4, CoO has been much less studied for CO oxidation. Herein, the phase changes of commercial mesoscopic CoO (particle size ?1 μm) and nanosized CoO (20–50 nm particle size), the latter prepared by vacuum reduction of commercial Co3O4, were examined by operando X-ray absorption (XAS) and near-ambient pressure X-ray photoemission (NAP-XPS) spectroscopy during CO oxidation, as well as ex situ by transmission electron microscopy and di?raction (TEM/SAED). Commercial mesoscopic CoO exhibited CO oxidation activity at ?200 °C, but even up to 530 °C in pure O2 no substantial (bulk) oxidation was observed by operando XAS, likely due to the large grains and bulk nature of CoO. After pre-oxidation at 400 C, electron di?raction detected thin surface layers of Co3O4. This increased activity but the activity of nanosized Co3O4 of equal surface area was still not reached. For nanosized CoO (surface layers on vacuum-reduced Co3O4), operando NAP-XPS/XAS, acquired during CO oxidation, revealed oxidation of CoO to Co3O4 above 150 °C, yielding the activity of nanosized Co3O4. Evidently, the nanoscale CoO shell on a Co3O4 core with small grains more easily and more completely transformed to Co3O4 than mesoscopic (bulk) CoO with large grains. Our study demonstrates how ?exible and dynamic surfaces of cobalt oxide materials adjust to various reaction environments, which also depends on grain size and morphology (bulk vs. thin layers), illustrating the importance of operando techniques to determine active catalyst phases under reaction conditions.
关键词： CO oxidation,CoO,Co3O4,NAP-XPS,XAS,TEM,Operando
更新于2025-09-23 15:23:52