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Switching on efficient photocatalytic water oxidation reactions over CaNbO2N by Mg modifications under visible light illumination
摘要： In spite of a strong visible light absorbance as far as 600 nm, CaNbO2N generally exhibits poor photocatalytic activity under normal conditions because of various structural defects and poor charge mobility. In this work, we have synthesized a series of Mg-modified CaNbO2N, i.e. CaNb1-xMgxO2+yN1-y (0 ≤ x ≤ 0.2), and performed a detailed investigation on their crystal structures, optical absorption and other physicochemical properties. Our results show that there is a slight shrinkage of the unit cell and a blue-shift of absorption edges upon Mg incorporation into CaNbO2N. The nitrogen contents as well as defects levels can be effectively tuned by altering the content of Mg. More strikingly, photocatalytic oxygen productions are much improved after Mg modifications under visible light irradiation (λ ≥ 420 nm). An average oxygen production rate as much as ~126.8 umol h?1 and an apparent quantum efficiency as high as ~3.4 % at 420 ± 20 nm is achieved for CaNb0.9Mg0.1O2+yN1-y (x = 0.1). These improvements probably stem from a substantial decrease of Nb4+ defects in CaNbO2N as well as slight positive shift of valence band maximum (VBM) after Mg modifications. Meanwhile, photoelectrochemical analysis suggests charge migration is somewhat enhanced in response to Mg modifications.
关键词： water oxidation,CaNbO2N,photocatalyst,water splitting,Mg modification
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A FFT-Based Approach to Explore Periodicity of Vines/Soil Properties in Vineyard from Time Series of Satellite-Derived Spectral Indices
摘要： From literature, NDVI proved to be correlated to vigour and midday stem water potential of vines; NDWI to soil water content. It is thus expected that significant periodicities can be found looking at spectral indices time series. This can be useful to better interpret vines behaviour and, possibly, relate intra-vineyard macroscopic differences to this type of information. To preliminarily test this hypothesis 25 Landsat 8 OLI images, Level-2 Data Products, were processed to compute NDVI and NDWI time series. An interpolation step aimed at generating daily estimates of indices in the explored period (May 2013-February 2016) was performed. Successively vegetation effects were removed from NDWI to emphasize soil signal. Finally a FFT analysis of both NDVI and NDWI interpolated time series was achieved to explore their periodicity, giving a first agronomic interpretation of results.
关键词： NDVI,volumetric water content,water potential,Landsat 8 OLI,NDWI,FFT
更新于2025-09-04 15:30:14
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Modern Purification Methods for Liquid Scintillators Intended for Recording Rare Events
摘要： Chromato-mass-spectrometry and UV/VIS spectroscopy are used to study the composition and properties of linear alkyl benzene (LAB) produced in Russia as the basic solvent for production of low-background liquid scintillators. The efficiency of LAB purification by reducing intrinsic radioactivity (U, Th) via water extraction (with addition of a strong chelate, dimethylaminomethylendiphosphonic acid) and sorption on Al2O3 in silica gel is studied. The purification method for removing potassium from scintillation fluors (PPO, BPO, p-terphenyl) is developed. It is shown that U and Th can be efficiently extracted from NdCl3 water solutions with 0.1 M TOPO solution in pseudocumene.
关键词： NdCl3 water solutions,liquid scintillators,purification methods,sorption,potassium removal,radioactivity,linear alkyl benzene,water extraction
更新于2025-09-04 15:30:14
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PHOTOELECTROCHEMICAL ANALYSIS OF TITANIUM DIOXIDE BY USING OXALIC ACID AS A SACRIFICIAL DONOR
摘要： Photoelectrochemical (PEC) water splitting is a very promising green method to produce solar fuel. Titanium dioxide (TiO2) has been widely used as photocatalyst for this type of reaction. Improving the performance of TiO2 for PEC water splitting has been ongoing and addition of sacrificial donor especially from waste is an attractive option to achieve this. Oxalic acid is one component in organic waste stream that can be used as sacrificial donor. The TiO2 thin films has been fabricated by coating TiO2 paste on Fluorine Tin oxide (FTO) glass surface. The morphology of the TiO2 thin films were porous and rough with uniform particles size with crystallite size of about 20 nm and dominant anatase peak. The TiO2 photoelectrode undergo PEC testing to measure its photolectroactivity by using oxalic acid as a sacrificial donor in two different type of electrolytes which are distilled water and sodium sulfate (NA2SO4) aqueous solution. The photocurrent produced without addition of oxalic acid is much lower than with the acid. The saturation photocurrent for aqueous NA2SO4 solution and water electrolyte is 0.1 mA/cm2 and negligible respectively. While the photocurrent for addition of oxalic acid in NA2SO4 aqueous solution is 0.5 mA/cm2 and the photocurrent for oxalic acid in water only is 0.9 mA/cm2, which is almost double compared to in NA2SO4 and tenfold in water only. The highest photocurrent produced by TiO2 photoelectrode is by addition of oxalic acid in aqueous (H2O) electrolyte.
关键词： photoelectrochemical cell,titanium dioxide,donor,oxalic acid,Water splitting
更新于2025-09-04 15:30:14
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Fabrication of SnS <sub/>2</sub> /SnS Heterojunction with Enhanced Light-Assisted Electrochemical Water Splitting Performance
摘要： Semiconducting metal sul?des have raised strong research interest among researchers as a promising candidate for light-assisted electrochemical water splitting, because they have wide band gap. In order to harvest more light wavelengths for improvement of light-assisted electrochemical water splitting capacity, we fabricated SnS2/SnS heterojunction nanosheets via facile and environmental route. The SnS2/SnS heterojunction nanosheets were used as photo-electrocatalytic material which exhibited low over potential of ?0.64 V at the current density of 10 mA · cm?2 in 0.5 M NaSO4 solution. Moreover, the SnS and SnS2 nanosheets displayed high over potential values of ?0.80 and ?0.88 V at the current density of 10 mA · cm?2, respectively. This research ?nding may therefore show the potential for use of SnS2/SnS heterojunction nanosheets as low cost and environmentally friendly photo-electrocatalysis.
关键词： SnS2/SnS Heterojunction,SnS2 Nanosheet,SnS Nanosheet,Light-Assisted Electrochemical Water Splitting
更新于2025-09-04 15:30:14
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Enhanced Quenching Effect of Neonicotinoid Pesticides on Time-Resolved Terbium Luminescence in Presence of Surfactants
摘要： A luminescence analytical method for the quantification of neonicotinoid pesticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) in water samples is proposed. The method is based on the quenching effect that these analytes produce on the time-resolved luminescence signal of terbium ions (excitation/emission wavelengths of 256/545 nm/nm). An enhancement on the analytical signal is observed when surfactants are used in the system. The use of a 0.01 mol·L?1 sodium dodecyl sulfate produced approximately a 30% increase in the sensitivity of the method. Under the optimum conditions, the method presented detection limits between 0.03 and 0.23 μg·mL?1. Interference studies were performed for ions commonly present in waters, observing no interferences. In addition, recovery experiments were performed in different waters, well, spring, and swamp, observing recovery yields close to 100%, with relative standard deviations lower than 4% in all cases. No sample treatment except a filtration step was required. Hence, this method may represent an alternative to other existing methods for the quick and simple analysis of these ubiquitous insecticides in environmental waters.
关键词： neonicotinoid pesticides,surfactants,time-resolved luminescence,terbium luminescence,water samples
更新于2025-09-04 15:30:14
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Round‐the‐clock Photocatalytic Hydrogen Production with High Efficiency by a Long Afterglow Material
摘要： Long afterglow materials can store and release light energy after illumination. Here, a brick-like, micron-sized Sr2MgSi2O7:Eu2+,Dy3+ long afterglow material is used for hydrogen production via the photocatalytic reforming of methanol under round-the-clock conditions for the first time, achieving a solar-to-hydrogen (STH) conversion efficiency of 5.18%. This material is one of the most efficient photocatalysts and provides the possibility of practical use on a large scale. Its remarkable photocatalytic activity is attributed to its unique carrier migration path and large number of lattice defects. Our findings expand the application scope of long afterglow materials and provide a new strategy to design efficient photocatalysts by constructing trap levels that can prolong carriers’ lifetimes.
关键词： round-the-clock,water,Long afterglow,photocatalytic hydrogen evolution,methanol
更新于2025-09-04 15:30:14
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Electrochemical and photoelectrochemical water oxidation of solvothermally synthesized Zr-doped α-Fe2O3 nanostructures
摘要： To investigate the oxygen evolution reaction of overall water-splitting process, Zr-doped α-Fe2O3 nanostructures were synthesized by employing one-pot solvothermal route. This work reported the electrochemical and photoelectrochemical (PEC) properties of synthesized photoanodes depending on solvothermal treatment time (i.e., 12, 16, and 20 h) maintained during synthesis. The treatment time influenced the morphology of Zr-doped α-Fe2O3 nanostructures, which directly exert an effect on the electrochemical and PEC performance of the synthesized photoanodes. The high conductivity and lowest Tafel slope value (83 mV/decade) were attained from electrochemical studies for the nanoflake morphology. The highest photocurrent of about 0.52 mA/cm2 at 1.5 V Vs RHE was obtained for Zr-doped α-Fe2O3 nanoflakes and 16.17% intrinsic photon conversion efficiency was achieved for the same sample with high photostability for 2 h under continuous irradiation of light. We reported the treatment time-dependent morphology effect on both electrochemical and PEC water oxidation of Zr-doped hematite nanoflakes in this work.
关键词： IPCE,Zr-doped hematite,Nanostructures,Water oxidation
更新于2025-09-04 15:30:14
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Mechanistic insights into light-activated catalysis for water oxidation
摘要： The development of catalysts for water oxidation to oxygen has been the subject of intense investigation in the last decade. In parallel to the search for high catalytic performance, many works have focused on the mechanistic analysis of the process. In this perspective, the oxidation of water through light-assisted cycles composed of an electron acceptor (EA), a photosensitizer (PS), and a water oxidation catalyst (WOC) can provide insightful and complementary information with respect to the use of chemical oxidants or to electrochemical techniques. In this microreview, we discuss the mechanistic aspects of the EA/PS/WOC photoactivated cycles, and in particular: (i) the general elementary steps; (ii) the required features and the nature of the PS employed; (iii) the electron transfer processes and kinetics from the WOC to PS+ (hole scavenging); (iv) the detrimental quenching of the PS by the WOC and the alternative mechanistic routes; (v) the identification of WOC intermediates and, finally, (vi) the transposition of the above processes into a dye-sensitized photoanode embedding a WOC.
关键词： reaction mechanisms,intermediates,water oxidation,Electron transfer,photocatalysis
更新于2025-09-04 15:30:14
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Photocatalytic Performance on Visible Light Induced ZnS QDs-MgAl Layered Double Hydroxides Hybrids for Methylene Blue Dye Degradation
摘要： Semiconductor hybrids based photocatalytic reaction is one of the prominent methods to treat wastewater, containing the organic pollutants. In the present work, we report the development of ZnS QDs-LDH hybrid structure for the photocatalytic treatment of methylene blue (MB) dye. The as-synthesized ZnS QDs-LDH hybrid structure was characterized by XRD, FESEM, HRTEM, EDX, XPS, and FTIR to analyze the formation, morphology and chemical structure. The UV-Vis DRS was used to investigate the optical absorption characteristics of the ZnS QDs-LDH hybrid. The photocatalytic performance of the as-prepared samples was investigated against the methylene blue dye molecule under UV-Vis light irradiation. The scavenging experiments were carried out in order to probe the radical formation by using EDTA, benzoquinone, and 2-proponal. The cycling experiments were performed to check the stability of the ZnS QDs-LDH hybrid photocatalyst after repeated photodegradation experiments.
关键词： ZnS Quantum dots,Layered double hydroxides,Photocatalytic activity,Methylene blue dye degradation,Water treatment
更新于2025-09-04 15:30:14