Showing papers on "Photocatalysis published in 2013"
TL;DR: The research shows that loading suitable dual cocatalysts on semiconductors can significantly increase the photocatalytic activities of hydrogen and oxygen evolution reactions, and even make the overall water splitting reaction possible.
Abstract: Since the 1970s, splitting water using solar energy has been a focus of great attention as a possible means for converting solar energy to chemical energy in the form of clean and renewable hydrogen fuel. Approaches to solar water splitting include photocatalytic water splitting with homogeneous or heterogeneous photocatalysts, photoelectrochemical or photoelectrocatalytic (PEC) water splitting with a PEC cell, and electrolysis of water with photovoltaic cells coupled to electrocatalysts. Though many materials are capable of photocatalytically producing hydrogen and/or oxygen, the overall energy conversion efficiency is still low and far from practical application. This is mainly due to the fact that the three crucial steps for the water splitting reaction: solar light harvesting, charge separation and transportation, and the catalytic reduction and oxidation reactions, are not efficient enough or simultaneously. Water splitting is a thermodynamically uphill reaction, requiring transfer of multiple electrons, making it one of the most challenging reactions in chemistry. This Account describes the important roles of cocatalysts in photocatalytic and PEC water splitting reactions. For semiconductor-based photocatalytic and PEC systems, we show that loading proper cocatalysts, especially dual cocatalysts for reduction and oxidation, on semiconductors (as light harvesters) can significantly enhance the activities of photocatalytic and PEC water splitting reactions. Loading oxidation and/or reduction cocatalysts on semiconductors can facilitate oxidation and reduction reactions by providing the active sites/reaction sites while suppressing the charge recombination and reverse reactions. In a PEC water splitting system, the water oxidation and reduction reactions occur at opposite electrodes, so cocatalysts loaded on the electrode materials mainly act as active sites/reaction sites spatially separated as natural photosynthesis does. In both cases, the nature of the loaded cocatalysts and their interaction with the semiconductor through the interface/junction are important. The cocatalyst can provide trapping sites for the photogenerated charges and promote the charge separation, thus enhancing the quantum efficiency; the cocatalysts could improve the photostability of the catalysts by timely consuming of the photogenerated charges, particularly the holes; most importantly, the cocatalysts catalyze the reactions by lowering the activation energy. Our research shows that loading suitable dual cocatalysts on semiconductors can significantly increase the photocatalytic activities of hydrogen and oxygen evolution reactions, and even make the overall water splitting reaction possible. All of these findings suggest that dual cocatalysts are necessary for developing highly efficient photocatalysts for water splitting reactions.
2,236 citations
TL;DR: The results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals, which may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.
Abstract: Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.
1,422 citations
TL;DR: For the first time, a direct g-C3N4-TiO2 Z-scheme photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks and will provide new insights into the design of high-performance Z-Scheme photoc atalysts for indoor air purification.
Abstract: Formaldehyde (HCHO) is a major indoor pollutant and long-term exposure to HCHO may cause health problems such as nasal tumors and skin irritation. Photocatalytic oxidation is considered as the most promising strategy for the decomposition of HCHO. Herein, for the first time, a direct g-C3N4–TiO2 Z-scheme photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks. Photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic oxidation decomposition of HCHO in air. It was shown that the photocatalytic activity of the prepared Z-scheme photocatalysts was highly dependent on the g-C3N4 content. At the optimal g-C3N4 content (sample U100 in this study), the apparent reaction rate constant was 7.36 × 10−2 min−1 for HCHO decomposition, which exceeded that of pure P25 (3.53 × 10−2 min−1) by a factor of 2.1. The enhanced photocatalytic activity could be ascribed to the formation of a g-C3N4–TiO2 Z-scheme photocatalyst, which results in the efficient space separation of photo-induced charge carriers. Considering the ease of the preparation method, this work will provide new insights into the design of high-performance Z-scheme photocatalysts for indoor air purification.
1,112 citations
TL;DR: High solar photocatalytic activity in ultrathin BiOCl nanosheets with almost fully exposed active {001} facets is achieved and some new and deep-seated insights are provided into how the defects in the exposed active facets affect the solar-driven photoc atalytic property are provided.
Abstract: Crystal facet engineering of semiconductors is of growing interest and an important strategy for fine-tuning solar-driven photocatalytic activity. However, the primary factor in the exposed active facets that determines the photocatalytic property is still elusive. Herein, we have experimentally achieved high solar photocatalytic activity in ultrathin BiOCl nanosheets with almost fully exposed active {001} facets and provide some new and deep-seated insights into how the defects in the exposed active facets affect the solar-driven photocatalytic property. As the thickness of the nanosheets reduces to atomic scale, the predominant defects change from isolated defects VBi‴ to triple vacancy associates VBi‴VO••VBi‴, which is unambiguously confirmed by the positron annihilation spectra. By virtue of the synergic advantages of enhanced adsorption capability, effective separation of electron–hole pairs and more reductive photoexcited electrons benefited from the VBi‴VO••VBi‴ vacancy associates, the ultrathin Bi...
1,037 citations
TL;DR: It is demonstrated that rational design and construction of isotype heterojunction could open up a new avenue for the development of new efficient visible-light photocatalysts and the removal of NO in air.
Abstract: The photocatalytic performance of the star photocatalyst g-C3N4 was restricted by the low efficiency because of the fast charge recombination. The present work developed a facile in situ method to construct g-C3N4/g-C3N4 metal-free isotype heterojunction with molecular composite precursors with the aim to greatly promote the charge separation. Considering the fact that g-C3N4 samples prepared from urea and thiourea separately have different band structure, the molecular composite precursors of urea and thiourea were treated simultaneously under the same thermal conditions, in situ creating a novel layered g-C3N4/g-C3N4 metal-free heterojunction (g-g CN heterojunction). This synthesis method is facile, economic, and environmentally benign using easily available earth-abundant green precursors. The confirmation of isotype g-g CN heterojunction was based on XRD, HRTEM, valence band XPS, ns-level PL, photocurrent, and EIS measurement. Upon visible-light irradiation, the photogenerated electrons transfer from ...
1,024 citations
TL;DR: In this article, a simple chemical exfoliation method was used to obtain single atomic layer nanosheets with a single thickness of 0.4 nm and a lateral size of micrometers.
Abstract: Single atomic layer nanosheet materials show great application potential in many fields due to their enhanced intrinsic properties compared to their counterparts and newly born properties. Herein, g-C3N4 nanosheets with a single atomic layer structure are prepared by a simple chemical exfoliation method. The as-prepared nanosheets show a single atomic thickness of 0.4 nm and a lateral size of micrometers. The structure and photocatalytic properties of the as-prepared single layer g-C3N4 are then studied. Compared with the bulk g-C3N4, single layer g-C3N4 nanosheets show great superiority in photogenerated charge carrier transfer and separation. Accordingly, the photocatalytic H2 production and pollutant decomposition activities and photocurrent generation of single layer g-C3N4 nanosheets are much higher than those of the bulk g-C3N4, indicating the great application potential of single layer g-C3N4 nanosheets in photocatalysis and photosynthesis.
1,023 citations
TL;DR: In this paper, a review of the research and application of heterogeneous semiconductor photocatalysis for the treatment of low-level concentrations of pollutants in water and air using titanium dioxide as a “model” semiconductor.
Abstract: Semiconductor heterogeneous photocatalysis, the subject of this review, is a versatile, low-cost and environmentally benign treatment technology for a host of pollutants. These may be of biological, organic and inorganic in origin within water and air. The efficient and successful application of photocatalysis demands that the pollutant, the catalyst and source of illumination are in close proximity or contact with each other. The ability of advanced oxidation technology to remove low levels of persistent organic pollutants as well as microorganisms in water has been widely demonstrated and, progressively, the technology is now being commercialized in many areas of the world including developing nations. This review considers recent developments in the research and application of heterogeneous semiconductor photocatalysis for the treatment of low-level concentrations of pollutants in water and air using titanium dioxide as a “model” semiconductor. The review considers charge transport characteristics on the semiconductor surface, photocatalyst reactor design and organic degradation mechanistic pathways. The effects of photoreactor operating parameters on the photocatalytic process are discussed in addition to mineralization and disinfection kinetics.
995 citations
TL;DR: The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out by new thermal decomposition method, which is simple and cost effective.
911 citations
TL;DR: In this paper, a review of surface-modified TiO2 photocatalysis based on photo-induced interfacial charge transfer has been conducted, which is mainly focused on environmental remediation, and various surface modifiers are classified according to the kind of surface modifiers and their effects on photocatalytic reaction mechanism and kinetics are discussed in detail.
Abstract: This paper reviews recent studies on the semiconductor photocatalysis based on surface-modified TiO2 of which application is mainly focused on environmental remediation. TiO2 photocatalysis that is based on the photoinduced interfacial charge transfer has been extensively studied over the past four decades. A great number of modification methods of semiconductor photocatalysts have been developed and investigated to accelerate the photoconversion, to enable the absorption of visible light, or to alter the reaction mechanism to control the products and intermediates. In this regard, various modification methods of TiO2 are classified according to the kind of surface modifiers (metal-loading, impurity doping, inorganic adsorbates, polymer coating, dye-sensitization, charge transfer complexation) and their effects on photocatalytic reaction mechanism and kinetics are discussed in detail. Modifying TiO2 in various ways not only changes the mechanism and kinetics under UV irradiation but also introduces visible light activity that is absent with pure TiO2. Each modification method influences the photocatalytic activity and mechanism in a way different from others and the observed modification effects are often different depending on the test substrates and conditions even for the same modification method. Better understanding of the modification effects on TiO2 photocatalysis is necessary to obtain reliable results, to assess the photoconversion efficiency more quantitatively, and to further improve the modification methods.
840 citations
TL;DR: The results show that after a spontaneous adsorption process g-C3N4 is successfully coated on CdS nanowires with intimate contact and can significantly improve the photocatalytic hydrogen-production rate of C dSnanowires, which reaches an optimal value of up to 4152 μmol h(-1) g(-1).
Abstract: CdS/g-C3N4 core/shell nanowires with different g-C3N4 contents were fabricated by a combined solvothermal and chemisorption method and characterized by X-ray powder diffraction, scanning electronic microscopy, transmission electron microscopy, and UV–vis diffuse reflection spectroscopy. The photocatalytic hydrogen-production activities of these samples were evaluated using Na2S and Na2SO3 as sacrificial reagents in water under visible-light illumination (λ ≥ 420 nm). The results show that after a spontaneous adsorption process g-C3N4 is successfully coated on CdS nanowires with intimate contact and can significantly improve the photocatalytic hydrogen-production rate of CdS nanowires, which reaches an optimal value of up to 4152 μmol h–1 g–1 at the g-C3N4 content of 2 wt %. More importantly, g-C3N4 coating can substantially reinforce the photostability of CdS nanowires even in a nonsacrificial system. The synergic effect between g-C3N4 and CdS, which can effectively accelerate the charge separation and tr...
780 citations
TL;DR: A new and simple synthetic pathway to form ordered, hollow carbon nitride structures, using a cyanuric acid-melamine (CM) complex in ethanol as a starting product, and it is shown that various CM morphologies can be obtained using different solvents, which leads to diverse orderedcarbon nitride architectures.
Abstract: Here we report a new and simple synthetic pathway to form ordered, hollow carbon nitride structures, using a cyanuric acid–melamine (CM) complex in ethanol as a starting product. A detailed analysis of the optical and photocatalytic properties shows that optimum hollow carbon nitride structures are formed after 8 h of condensation. For this condensation time, we find a significantly reduced fluorescence intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes. Enhanced charge transfer is seen as well from a drastic increase of the photocatalytic activity in the degradation of rhodamine B dye, which is shown to proceed via photoinduced hole transfer. Moreover, we show that various CM morphologies can be obtained using different solvents, which leads to diverse ordered carbon nitride architectures. In all cases, the CM-C3N4 structures exhibited superior photocatalytic activity compared to the bulk material. The utilization of C...
TL;DR: In this article, a new approach assisted by hydrogen plasma to synthesize unique H-doped black titania with a core/shell structure was presented, superior to the high H-2-pressure process (under 20 bar for five days).
Abstract: Black TiO2 attracts enormous attention due to its large solar absorption and induced excellent photocatalytic activity. Herein, a new approach assisted by hydrogen plasma to synthesize unique H-doped black titania with a core/shell structure (TiO2@TiO2-xHx) is presented, superior to the high H-2-pressure process (under 20 bar for five days). The black titania possesses the largest solar absorption (approximate to 83%), far more than any other reported black titania (the record (high-pressure): approximate to 30%). H doping is favorable to eliminate the recombination centers of light-induced electrons and holes. High absorption and low recombination ensure the excellent photocatalytic activity for the black titania in the photo-oxidation of organic molecules in water and the production of hydrogen. The H-doped amorphous shell is proposed to play the same role as Ag or Pt loading on TiO2 nanocrystals, which induces the localized surface plasma resonance and black coloration. Photocatalytic water splitting and cleaning using TiO2-xHx is believed to have a bright future for sustainable energy sources and cleaning environment.
TL;DR: In this article, the photocatalytic mechanism analysis revealed that the interreaction between BiOBr and g-C3N4 is a kind of facet coupling, and active species trapping and quantification experiments indicated that the photoinduced charges transfer between these facets resulted in the efficient charge separation.
Abstract: BiOBr-g-C3N4 inorganic–organic composite photocatalysts were synthesized by a one-step chemical bath method at low temperature and characterized by X-ray diffraction patterns (XRD), Fourier transform infrared (FT-IR), thermo gravimetric (TG), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectra (DRS). The BiOBr-g-C3N4 composite showed much higher visible-light-driven (VLD) photocatalytic activity than pure g-C3N4 and BiOBr for rhodamine B (RhB) degradation. The photocatalytic mechanism analysis revealed that the interreaction between BiOBr and g-C3N4 is a kind of facet coupling between BiOBr-{0 0 1} and g-C3N4-{0 0 2}. The active species trapping and quantification experiments indicated that the photoinduced charges transfer between these facets resulted in the efficient charge separation.
TL;DR: In this article, a mass production approach to synthesize black titania by aluminium reduction is reported, and the obtained sample possesses a unique crystalline core-amorphous shell structure (TiO2@TiO 2−x).
Abstract: Utilizing solar energy for hydrogen generation and water cleaning is a great challenge due to insufficient visible-light power conversion. Here we report a mass production approach to synthesize black titania by aluminium reduction. The obtained sample possesses a unique crystalline core–amorphous shell structure (TiO2@TiO2−x). The black titania absorbs ∼65% of the total solar energy by improving visible and infrared absorption, superior to the recently reported ones (∼30%) and pristine TiO2 (∼5%). The unique core–shell structure (TiO2@TiO2−x) and high absorption boost the photocatalytic water cleaning and water splitting. The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen efficiency (1.7%). A large photothermic effect may enable black titania “capture” solar energy for solar thermal collectors. The Al-reduced amorphous shell is proved to be an excellent candidate to absorb more solar light and receive more efficient photocatalysis.
TL;DR: The photocatalytic activity of the AgX/g-C 3 N 4 hybrid materials was evaluated using methyl orange as a target organic pollutant in this article, which was attributed to the synergic effect between g-C and AgX, which included the optical property, the better dispersion and the small size.
Abstract: Novel visible-light-driven AgX/g-C 3 N 4 (X = Br, I) hybrid materials were synthesized by the facile water bath method. The AgX/g-C 3 N 4 hybrid materials were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Fourier transform infrared spectra (FTIR), Raman and the special surface area. The XRD, EDS, TEM, FTIR, Raman and XPS analyses indicated that AgX nanoparticles were evenly distributed on the surface of g-C 3 N 4 and the heterostructures were formed. The photocatalytic activity of the AgX/g-C 3 N 4 hybrid materials was evaluated using methyl orange as a target organic pollutant. The as-prepared AgX/g-C 3 N 4 hybrid materials displayed much higher photocatalytic activity than the pure g-C 3 N 4 and AgX nanoparticles. After the introduction of AgX nanoparticles, the photocurrent of the AgBr/g-C 3 N 4 and AgI/g-C 3 N 4 hybrid materials was found to increase by 21 and 8 times than that of the pure g-C 3 N 4 , respectively. The increased photocatalytic activity of the AgX/g-C 3 N 4 hybrid materials was attributed to the synergic effect between g-C 3 N 4 and AgX, which included the optical property, the better dispersion and the small size. A photocatalytic mechanism and the kinetics of AgX/g-C 3 N 4 hybrid materials were also proposed.
TL;DR: In this article, a template free in situ precipitation method has been developed for the synthesis of Ag3PO4 nanoparticles on the surface of a g-C3N4 photocatalyst at room temperature.
Abstract: A facile and reproducible template free in situ precipitation method has been developed for the synthesis of Ag3PO4 nanoparticles on the surface of a g-C3N4 photocatalyst at room temperature. The g-C3N4–Ag3PO4 organic–inorganic hybrid nanocomposite photocatalysts were characterized by various techniques. TEM results show the in situ growth of finely distributed Ag3PO4 nanoparticles on the surface of the g-C3N4 sheet. The optimum photocatalytic activity of g-C3N4–Ag3PO4 at 25 wt% of g-C3N4 under visible light is almost 5 and 3.5 times higher than pure g-C3N4 and Ag3PO4 respectively. More attractively, the stability of Ag3PO4 was improved due to the in situ deposition of Ag3PO4 nanoparticles on the surface of the g-C3N4 sheet. The improved performance of the g-C3N4–Ag3PO4 hybrid nanocomposite photocatalysts under visible light irradiation was induced by a synergistic effect, including high charge separation efficiency of the photoinduced electron–hole pair, the smaller particle size, relatively high surface area and the energy band structure. Interestingly, the heterostructured g-C3N4–Ag3PO4 nanocomposite significantly reduces the use of the noble metal silver, thereby effectively reducing the cost of the Ag3PO4 based photocatalyst.
TL;DR: In this article, the photocatalytic reduction of carbon dioxide to fuels using solar energy is evaluated using Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS).
TL;DR: In this article, a facile and effective hydrothermal method for the fabrication of the Ag3PO4-graphene visible light photocatalyst has been developed to improve the photocatalytic performance and stability of Ag-PO4, and also to reduce the high cost of Ag 3PO4 for practical uses.
Abstract: A facile and effective hydrothermal method for the fabrication of the Ag3PO4-graphene (Ag3PO4-GR) visible light photocatalyst has been developed to improve the photocatalytic performance and stability of Ag3PO4, and also to reduce the high cost of Ag3PO4 for practical uses. The size and morphology of Ag3PO4 particles could be tailored by the electrostatically driven assembly of Ag+ on graphene oxide (GO) sheets and by the controlled growth of Ag3PO4 particles on the GO surface. The generation of Ag3PO4 and the transformation of GO to GR can be achieved simultaneously in the hydrothermal process. The improved photocatalytic activity of Ag3PO4-GR composites under visible light irradiation is attributed to high-surface-area GR sheets, enhanced absorption of organic dyes, and more efficient separation of photogenerated electron–hole pairs. The transfer of photogenerated electrons from the surface of Ag3PO4 to GR sheets also reduces the possibility of decomposing Ag+ to metallic Ag, suggesting an improved stab...
TL;DR: A direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anataseTiO2 and rutile TiO2.
Abstract: The sole effect of surface/bulk defects of TiO2 samples on their photocatalytic activity was investigated. Nano-sized anatase and rutile TiO2 were prepared by hydrothermal method and their surface/bulk defects were adjusted simply by calcination at different temperatures, i.e. 400–700 °C. High temperature calcinations induced the growth of crystalline sizes and a decrease in the surface areas, while the crystalline phase and the exposed facets were kept unchanged during calcination, as indicated by the characterization results from XRD, Raman, nitrogen adsorption–desorption, TEM and UV-Vis spectra. The existence of surface/bulk defects in calcined TiO2 samples was confirmed by photoluminescence and XPS spectra, and the surface/bulk defect ratio was quantitatively analyzed according to positron annihilation results. The photocatalytic activity of calcined TiO2 samples was evaluated in the photocatalytic reforming of methanol and the photocatalytic oxidation of α-phenethyl alcohol. Based on the characterization and catalytic results, a direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anatase TiO2 and rutile TiO2. The surface defects of TiO2, i.e. oxygen vacancy clusters, could promote the separation of electron–hole pairs under irradiation, and therefore, enhance the activity during photocatalytic reaction.
TL;DR: In this paper, the localised surface plasmon resonance (LSPR) effect of noble metal nanoparticles (NPs) was used to improve the performance of semiconductor photocatalysts (for example, TiO2 and Ag halides).
TL;DR: In this study, the catalysts were prepared by thermal decomposition method, which was employed for the first time in the preparation of ZnO/Ag nanocomposite catalysts, and results suggest better photocatalytic properties for 10 wt.% Ag sample compared to other samples.
TL;DR: Improved photocatalytic activity could be attributed to the improved visible light utilization, oxidation power, and electron transport property, due to the significantly narrowed bandgap, positively shifted valence band-edge potential, and enhanced electronic conductivity.
Abstract: Cross-linked rather than non-covalently bonded graphitic carbon nitride (g-C3 N4 )/reduced graphene oxide (rGO) nanocomposites with tunable band structures have been successfully fabricated by thermal treatment of a mixture of cyanamide and graphene oxide with different weight ratios. The experimental results indicate that compared to pure g-C3 N4 , the fabricated CN/rGO nanocomposites show narrowed bandgaps with an increased in the rGO ratio. Furthermore, the band structure of the CN/rGO nanocomposites can be readily tuned by simply controlling the weight ratio of the rGO. It is found that an appropriate rGO ratio in nanocomposite leads to a noticeable positively shifted valence band edge potential, meaning an increased oxidation power. The tunable band structure of the CN/rGO nanocomposites can be ascribed to the formation of C-O-C covalent bonding between the rGO and g-C3 N4 layers, which is experimentally confirmed by Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) data. The resulting nanocomposites are evaluated as photocatalysts by photocatalytic degradation of rhodamine B (RhB) and 4-nitrophenol under visible light irradiation (λ > 400 nm). The results demonstrate that the photocatalytic activities of the CN/rGO nanocomposites are strongly influenced by rGO ratio. With a rGO ratio of 2.5%, the CN/rGO-2.5% nanocomposite exhibits the highest photocatalytic efficiency, which is almost 3.0 and 2.7 times that of pure g-C3 N4 toward photocatalytic degradation of RhB and 4-nitrophenol, respectively. This improved photocatalytic activity could be attributed to the improved visible light utilization, oxidation power, and electron transport property, due to the significantly narrowed bandgap, positively shifted valence band-edge potential, and enhanced electronic conductivity.
TL;DR: The as-prepared g-C3N4/Ag2O composites showed excellent stability toward the photodegradation of methyl orange (MO) and a possible photocatalytic and charge separation mechanism was proposed.
Abstract: Highly efficient visible-light-driven g-C3N4/Ag2O heterostructured photocatalysts were prepared by a simple liquid phase synthesis method at room temperature. The composition, structure, morphology, and optical absorption properties of the as-prepared g-C3N4/Ag2O composites were characterized by XRD, FTIR, XPS, TEM, and UV–vis DRS, respectively. We found interestingly that the photogenerated charge carriers separations of the as-prepared g-C3N4/Ag2O composites were closely related to the mass ratio of g-C3N4 and Ag2O. When the mass ratio of g-C3N4 and Ag2O reached 1:4, the as-prepared composite exhibited the highest photocatalytic activity, which was almost 11 and 1.2 times as high as that of individual g-C3N4 and Ag2O, respectively. The enhancement of photocatalytic activity could be attributed to the synergetic effects between g-C3N4 and Ag2O as well as the improved dispersibility and the decreased particle size of Ag2O. Moreover, the as-prepared composites showed excellent stability toward the photodeg...
TL;DR: The active light band of the novel hybrid photocatalyst with high photocatalytic activity covers full-spectrum solar light including the UV, visible, and near-infrared ranges.
Abstract: Near-infrared active photocatalytic properties of Bi2 WO6 nanosheets owing to the oxygen vacancies of the Bi2 WO6 nanosheets are reported. The broad spectrum photocatalyst, Bi2 WO6 -TiO2 nanobelt heterostructures, are obtained by assembling Bi2 WO6 nanocrystals on TiO2 nanobelts. The active light band of the novel hybrid photocatalyst with high photocatalytic activity covers full-spectrum solar light including the UV, visible, and near-infrared ranges.
TL;DR: The TiO2 photocatalysis was found to be a promising process for removing TC and its intermediates from aqueous solution by nanosized TiO 2 under UV irradiation.
TL;DR: In this article, the photocatalytic activity of non metal doped titania for a wide variety of pollutants degradation under UV/visible light, with special emphasis on nitrogen doped TiO 2.
Abstract: The multifunctional and advanced semiconductor titania with superior physicochemical and opto-electronic properties is extensively investigated in wastewater purification mainly due to its non-toxicity, favorable band edge positions, water insolubility, multifaceted electronic properties, surface acid–base properties, super hydrophilicity and so on. However, large band gap and massive photogenerated charge carrier recombination hinders its wide application under natural solar light. Thus, altering the surface-bulk structure of titania is a major goal in the area of both materials and environmental chemistry for its better applications. The substitution of p block elements (B, C, N, F, S, P, and I) either at Ti 4+ and O 2− sites is a promising approach to overcome the aforementioned drawbacks. This review focuses on the photocatalytic activity of non metal doped titania for a wide variety of pollutants degradation under UV/visible light, with special emphasis on nitrogen doped TiO 2 . Further improvement in photoactivity of N–TiO 2 is achieved via depositing with noble metals, co-doping with foreign ions, sensitization, surface modifications and heterostructuring with other semiconductors. The mechanism governing the photocatalytic reactions is discussed in the light of charge carrier generation–separation–transfer–recombination dynamics together with pollutant adsorption and their reactions with reactive oxygenated species in liquid or gaseous regime. We are positive that this review article will further stimulate our research interest on this intriguing hot topic.
TL;DR: This study provides a better understanding of photocatalytic CO2 reduction over MOF-based photocATalysts and also demonstrates the great potential of using MOFs as highly stable, molecularly tunable, and recyclable photoc atalysts inCO2 reduction.
Abstract: Metal-organic framework (MOF) NH2 -Uio-66(Zr) exhibits photocatalytic activity for CO2 reduction in the presence of triethanolamine as sacrificial agent under visible-light irradiation. Photoinduced electron transfer from the excited 2-aminoterephthalate (ATA) to Zr oxo clusters in NH2 -Uio-66(Zr) was for the first time revealed by photoluminescence studies. Generation of Zr(III) and its involvement in photocatalytic CO2 reduction was confirmed by ESR analysis. Moreover, NH2 -Uio-66(Zr) with mixed ATA and 2,5-diaminoterephthalate (DTA) ligands was prepared and shown to exhibit higher performance for photocatalytic CO2 reduction due to its enhanced light adsorption and increased adsorption of CO2 . This study provides a better understanding of photocatalytic CO2 reduction over MOF-based photocatalysts and also demonstrates the great potential of using MOFs as highly stable, molecularly tunable, and recyclable photocatalysts in CO2 reduction.
TL;DR: In this paper, Zhao et al. used Zn11−xCdxS solid solutions as the visible-light-driven photocatalysts and a mixed Na2S and Na2SO3 aqueous solution as the sacrificial reagent.
Abstract: Photocatalytic hydrogen (H2) production from water splitting under visible-light irradiation is considered to be an attractive way to solve the increasing global energy crises in modern life. In this study, highly efficient photocatalytic H2 production without the assistant of a cocatalyst was achieved using Zn11–xCdxS solid solutions as the visible-light-driven photocatalysts and a mixed Na2S and Na2SO3 aqueous solution as the sacrificial reagent. The Zn1–xCdxS samples were prepared by a simple zinc–cadmium–thiourea (Zn–Cd–Tu) complex thermolysis method using thiourea, zinc acetate (Zn(Ac)2), and cadmium acetate (Cd(Ac)2) as the precursors. The obtained Zn1–xCdxS solid solutions feature a small crystallite size and precisely controllable band structure, which are beneficial for the photocatalysis. When the Zn/Cd molar ratio is 1:1, the prepared Zn0.5Cd0.5S sample exhibits the highest H2-production rate of 7.42 mmol·h–1·g–1, exceeding that of the pure CdS and ZnS samples by more than 24 and 54 times, resp...
TL;DR: The nanohybrids show superior photocatalytic activities for the decomposition of methyl orange under visible-light irradiation to bulk g-C3N4, g-N4 nanosheets, and AuNP/bulk g- C3N 4 hybrids.
Abstract: Au nanoparticles (AuNPs) were loaded on graphitic carbon nitride (g-C3N4) nanosheets prepared by ultrasonication-assisted liquid exfoliation of bulk g-C3N4 via green photoreduction of Au(III) under visible light irradiation using g-C3N4 as an effective photocatalyst. The nanohybrids show superior photocatalytic activities for the decomposition of methyl orange under visible-light irradiation to bulk g-C3N4, g-C3N4 nanosheets, and AuNP/bulk g-C3N4 hybrids.
TL;DR: For the first time, the remarkable photocatalytic efficiency of such Fe(III)-based MOFs under visible light illumination (350 up to 850 nm) is shown.
Abstract: Herein, a new group of visible light photocatalysts is described. Iron(III) oxides could be promising visible light photocatalysts because of their small band gap enabling visible light excitation. However, the high electron–hole recombination rate limits the yield of highly oxidizing species. This can be overcome by reducing the particle dimensions. In this study, metal–organic frameworks (MOFs), containing Fe3-μ3-oxo clusters, are proposed as visible light photocatalysts. Their photocatalytic performance is tested and proven via the degradation of Rhodamine 6G in aqueous solution. For the first time, the remarkable photocatalytic efficiency of such Fe(III)-based MOFs under visible light illumination (350 up to 850 nm) is shown.