단순 침전법으로 제조한 CdZnS/ZnO 광촉매를 이용하여 가시광선하에서 메틸렌블루의 광분해 반응에 대한 연구를 수행하였다. X선 회절분석법과 UV-vis 확산반사 분광법 등을 이용하여 제조된 촉매들의 물리화학적 특성을 분석하였다. 그리고 CdZnS/ZnO 광촉매의 활성을 조사하고 CdS 및 TiO2와 비교 검토하였다. CdZnS/ZnO 광촉매는 자외선뿐만 아니라 400nm에서 600nm 범위의 가시광선 영역에 있어서도 우수한 광흡수 특성을 나타내었다. 가시광선하에서 메틸렌 블루의 광분해 반응에 대해서 CdZnS/ZnO 광촉매는 CdS 와 TiO2 보다 우수한 광촉매 활성을 나타내는 것을 알 수 있었다. 그리고 가시광선하에서의 메틸렌블루의 광분해 반응에는 광촉매 반응뿐만 아니라 감광반응도 관여하고 있음을 확인할 수 있었다.

In this study, photocatalytic degradation of ammonia in petrochemical wastewater is investigated by solar light photocatalysis. Two-dimensional ultra-thin atomic layer structured MoS2 are synthesized via a simple hydrothermal method. We examine all prepared samples by means of physical techniques, such as SEM-EDX, HRTEM, FT-IR, BET, XRD, XPS, DRS and PL. And, we use fullerene modified MoS2 nanosheets to enhance the activity of photochemically generated oxygen (PGO) species. Surface area and pore volumes of the MoS2-fullerene samples significantly increase due to the existence of MoS2. And, PGO oxidation of MB, TBA and TMST, causing its concentration in aqueous solution to decrease, is confirmed by the results of PL. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the PGO effect increase in the case with modified fullerene. The experimental results show that this heterogeneous catalyst has a degradation of 88.43% achieved through visible light irradiation. The product for the degradation of NH3 is identified as N2, but not NO2−or NO3−.

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2- sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 oC. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 oC improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

A facile microwave assisted solvothermal process is designed for fabricating SnS nanoparticles decorated on graphene nanosheet, which used as visible light driven photocatalyst. Some typical characterization techniques such as XRD, FT-IR, SEM with EDX analysis, and TEM and BET analysis are used to analyse the physical characteristics of as-prepared samples. Spherical SnS nanoparticles are uniformly dispersed on the surface of graphene nanosheet due to ammonia, which can prevent the aggregation of graphene oxide. Meanwhile, microwave radiation provides fast energy that promotes the formation of spherical SnS nanoparticles within a short time. The visible light photocatalytic activity of as-prepared SnS-GR nanocomposites is analysed through photodegradation efficiency of methylene blue with high concentration. According to the higher photocatalytic property, the as-prepared SnS-GR nanocomposites can be expected to be an efficient visible light driven photocatalyst. After five cycles for decolorization, the rate decreases from 87 % to 78 % (about 9 %). It is obvious that the photocatalytic activity of SnS-GR nanocomposite has good repeatability.

Reducing CO2 into high value fuels and chemicals is considered a great challenge in the 21st century. Efficiently activating CO2 will lead to an important way to utilize it as a resource. This article reviews the latest progress of g-C3N4 based catalysts for CO2 reduction. The different synthetic methods of g-C3N4 are briefly discussed. Article mainly introduces methods of g-C3N4 shape control, element doping, and use of oxide compounds to modify g-C3N4. Modified g-C3N4 has more reactive sites, which can significantly reduce the probability of photogenerated electron hole recombination and improve the performance of photocatalytic CO2 reduction. Considering the literature, the hydrothermal method is widely used because of its simple equipment and process and easy control of reaction conditions. It is foreseeable that hydrothermal technology will continue to innovate and usher in a new period of development. Finally, the prospect of a future reduction of CO2 by g-C3N4-based catalysts is predicted.

In this work, a carbon-doped carbon nitride photocatalyst is successfully synthesized through a simple centrifugal spinning method after heat treatment. The morphology and properties of the prepared photo catalyst are characterized by Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectrophotometer (UV-vis), and specific surface area. The results show that the band gap of the prepared sample, g-CN-10 is 2.1 eV, is significantly lower than that of pure carbon nitride, 2.7 eV. As the amount of cotton candy increased, the absorption capacity of the prepared catalyst for visible light is significantly enhanced. In addition, the degradation efficiency of Rhodamine B (RhB) by sample g-CN-10 is 98.8 % over 2h, which is twice that value of pure carbon nitride. The enhancement of photocatalytic ability is attributed to the increase of specific surface area after the carbon doping modifies carbon nitride. A possible photocatalytic degradation mechanism of carbon-doped carbon nitride is also suggested.

Bismuth vanadate (BiVO4) is considered a potentially attractive candidate for the visible-light-driven photodegradation of organic pollutants. In an effort to enhance their photocatalytic activities, BiVO4 nanofibers with controlled microstructures, grain sizes, and crystallinities are successfully prepared by electrospinning followed by a precisely controlled heat treatment. The structural features, morphologies, and photo-absorption performances of the asprepared samples are systematically investigated and can be readily controlled by varying the calcination temperature. From the physicochemical analysis results of the synthesized nanofiber, it is found that the nanofiber calcines at a lower temperature, shows a smaller crystallite size, and lower crystallinity. The photocatalytic degradation of rhodamine-B (RhB) reveals that the photocatalytic activity of the BiVO4 nanofibers can be improved by a thermal treatment at a relatively low temperature because of the optimization of the conflicting characteristics, crystallinity, crystallite size, and microstructure. The photocatalytic activity of the nanofiber calcined at 350oC for the degradation of RhB under visible-light irradiation exhibits a greater photocatalytic activity than the nanofibers synthesized at 400oC and 450oC.

The emergence of green methods for the synthesis of graphene-based composites became the gateway for the solution of pollution and economic synthetic methods. Herein, we reported a single step in situ synthesis of reduced graphene oxide sheets decorated with silver nanoparticles (CRG–Ag nanocomposite) using custard apple leaf extract as an effective reducing and stabilizing agent. The ultraviolet–visible, Fourier transform infrared and Raman techniques revealed a primary confirmation about the formation of the said nanocomposite. The X-ray diffraction studies confirmed the face-centred cubic crystal structure of silver nanoparticles (Ag NPs) of 30 nm in size. The high-resolution scanning electron microscope spectra revealed the uniform distribution of Ag NPs on the graphene sheets. This simple, novel and rapid approach enabled a facile production of homogeneously deposited Ag NPs on graphene sheets. Thus synthesized CRG–Ag nanocomposite showed excellent photocatalytic efficiency of 96% in 2 h under sunlight using methylene blue as a model pollutant.

A facile one-pot wet chemical process to prepare pure anatase TiO2 hollow structures using ammonium hexafluorotitanate as a precursor is developed. By defining the formic acid ratio, we fabricate TiO2 hollow structures containing fluorine on the surface. The TiO2 hollow sphere is composed of an anatase phase containing fluorine by various analytical techniques. A possible formation mechanism for the obtained hollow samples by self-transformation and Ostwald ripening is proposed. The TiO2 hollow structures containing fluorine exhibits 1.2 - 2.7 times higher performance than their counterparts in photocatalytic activity. The enhanced photocatalytic activity of the TiO2 hollow structures is attributed to the combined effects of high crystallinity, specific surface area (62 m2g-1), and the advantage of surface fluorine ions (at 8%) having strong electron-withdrawing ability of the surface ≡ Ti-F groups reduces the recombination of photogenerated electrons and holes.

To improve photocatalytic performance, CdS nanoparticle deposited TiO2 nanotubular photocatalysts are synthesized. The TiO2 nanotube is fabricated by electrochemical anodization at a constant voltage of 60 V, and annealed at 500 for crystallization. The CdS nanoparticles on TiO2 nanotubes are synthesized by successive ionic layer adsorption and reaction method. The surface characteristics and photocurrent responses of TNT/CdS photocatalysts are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectrometer and LED light source installed potentiostat. The bandgaps of the CdS deposited TiO2 photocatalysts are gradually narrowed with increasing of amounts of deposited CdS nanoparticles, which enhances visible light absorption ability of composite photocatalysts. Enhanced photoelectrochemical performance is observed in the nanocomposite TiO2 photocatalyst. However, the maximum photocurrent response and dye degradation efficiency are observed for TNT/CdS30 photocatalyst. The excellent photocatalytic performance of TNT/CdS30 catalyst can be ascribed to the synergistic effects of its better absorption ability of visible light region and efficient charge transport process.

광촉매는 물에서 유기 염료를 분해하는 친환경적 기술이다. 산화 텅스텐은 이산화 티타늄에 비해 더 작은 밴드갭을 지니고 있어 광촉매 나노물질로서 활발히 연구되고 있다. 계층적 구조의 합성, 백금 도핑, 나노 복합물 또는 다른 반도체 와의 결합 등이 광촉매 분해 효율을 향상시키는 방법들로 연구되고 있다. 이들 방법들은 광 파장의 적색편이를 유도하여 전자 이동, 전자-정공 쌍의 형성과 재결합에 영향을 미친다. 산화 텅스텐의 형태 개질을 통해 앞서 언급한 광촉매 분해 효율을 향상시키는 방법들과 합성에 대해 분석하였으며 금속 산화물과 탄소 복합재를 결합하는 방법이 새로운 물질의 합성이 필요 없으며 가장 효율적인 방법으로 조사되었다. 이러한 광촉매 기술은 수처리 분리막기술과 모듈화하여 정수처리 목적으로 사용 될 수 있다.

A heterogeneous photocatalytic system is attracting much interest for water and air purification because of its reusability and economical advantage. Electrospun nanofibers are also receiving immense attention for efficient photocatalysts due to their ultra-high specific surface areas and aspect ratios. In this study, ZnO nanofibers with average diameters of 71, 151 and 168 nm are successfully synthesized by facile electrospinning and a subsequent calcination process at 500 ℃ for 3 h. Their crystal structures, morphology features and optical properties are systematically characterized by X-ray diffraction, scanning electron microscopy, UV-Vis and photoluminescence spectroscopies. The photocatalytic activities of the ZnO nanofibers are evaluated by the photodegradation of a rhodamine B aqueous solution. The results reveal that the diameter of the nanofiber, controlled by changing the polymer content in the precursor solution, plays an important role in the photocatalytic activities of the synthesized ZnO nanofibers.

Tungsten trioxide (WO3) is a promising candidate as a photocatalyst because of its outstanding electrical and optical properties. In this study, we prepare WO3 thin films by electrodeposition and characterize the photocatalytic degradation of methylene blue using these films. Depending on the voltage conditions (static and pulse), compact and porous WO3 films are fabricated on a transparent ITO/glass substrate. The morphology and crystal structure of electrodeposited WO3 thin films are investigated by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. An application of static voltage during electrodeposition yields a compact layer of WO3, whereas a highly porous morphology with nanoflakes is produced by a pulse voltage process. Compared to the compact film, the porous WO3 thin film shows better photocatalytic activities. Furthermore, a much higher reaction rate of degradation of methylene blue can be achieved after post-annealing of WO3 thin films.

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of TiO2, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile TiO2 because these coupled TiO2 powders can retain the benefits of TiO2, one of the best photocatalysts. In this study, anatase TiO2 nanoparticles are synthesized and coupled on the surface of rutile TiO2 powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase TiO2 nanoparticles and disperse anatase TiO2 nanoparticles uniformly on the surface of rutile TiO2 powders. Rutile TiO2 powders coupled with anatase TiO2 nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled TiO2 powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

F-containing TiO2 nanopowders are synthesized using simple wet processes (precipitation-based and hydrothermal) from ammonium hexafluorotitanate (AHFT, (NH4)2TiF6) as a precursor to apply as a photocatalyst for the degradation of rhodamine B (RhB). The surface properties of the prepared samples are evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results confirm that the synthesized anatase TiO2 has sphere-like shapes, with numerous small nanoparticles containing fluorine on the surface. The photocatalytic activity of F-containing TiO2 compared with F-free TiO2 is characterized by measuring the degradation of RhB using a xenon lamp. The photocatalytic degradation of F-containing TiO2 exhibits improved photocatalytic activity, based on the positive effects of adsorbed F ions on the surface.

Transition-metal oxide semiconductors have various band gaps. Therefore, many studies have been conducted in various application fields. Among these, methods for the adsorption of organic dyes and utilization of photocatalytic properties have been developed using various metal oxides. In this study, the adsorption and photocatalytic effects of WO3 nanomaterials prepared by hydrothermal synthesis are investigated, with citric acid added in the hydrothermal process as a structure-directing agent. The nanostructures of WO3 are studied using transmission electron microscopy and scanning electron microscopy images. The crystal structure is investigated using X-ray diffraction patterns, and the changes in the dye concentrations adsorbed on WO3 nanorods are measured with a UV-visible absorption spectrophotometer based on Beer-Lambert’s law. The methylene blue (MB) dye solution is subjected to acid or base conditions to monitor the change in the maximum adsorption amount in relation to the pH. The maximum adsorption capacity is observed at pH 3. In addition to the dye adsorption, UV irradiation is carried out to investigate the decomposition of the MB dye as a result of photocatalytic effects. Significant photocatalytic properties are observed and compared with the adsorption effects for dye removal.

Self-cleaning and photocatalytic TiO2 thin films were prepared by a facile sol-gel method followed by spin coating using peroxo titanic acid as a precursor. The as-prepared thin films were heated at low temperature(110 °C) and high temperature (400 °C). Thin films were characterized by X-ray diffraction(XRD), Field-emission scanning electron microscopy(FESEM), UVVisible spectroscopy and water contact angle measurement. XRD analysis confirms the low crystallinity of thin films prepared at low temperature, while crystalline anatase phase was found the for high temperature thin film. The photocatalytic activity of thin films was studied by the photocatalytic degradation of methylene blue dye solution. Self-cleaning and photocatalytic performance of both low and high temperature thin films were compared.