Physical investigations on annealed structure Cu/La2O3 for photocatalytic application under sunlight (original) (raw)
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Nano-Structures & Nano-Objects, 2019
g r a p h i c a l a b s t r a c t h i g h l i g h t s • Nanostructured CuO thin films were prepared by thermal evaporation and annealing. • XRD and Raman studies revealed monoclinic CuO nanoparticles in the prepared thin films. • Annealing at 400 • C led to enhancement in absorbance in the UV-Visible region and narrowing of band gap. • CuO nanostructured thin film annealed at 400 • C showed excellent photocatalytic efficiency for degradation of MB and MG in water.
Journal of Saudi Chemical Society, 2019
A simple precipitation-reduction method was used to prepare cubic and polyhedral Cu 2 O structures. Their morphological, structural, optical and electronic properties were analyzed and compared with those of commercial Cu 2 O by means of SEM, TEM, XRD, UV-vis DRS, Photoluminescence Spectroscopy and Time Resolved Microwave Conductivity. Methyl orange (MO) photodegradation with visible light (blue-light LEDs, k = 450-470 nm) was taken as a model reaction to study the photocatalytic activity. According to the results, Cu 2 O edge-and corner-truncated polyhedral particles significantly decreased the MO initial concentration by adsorption and photocatalysis, whereas, Cu 2 O cubic particles did not show MO adsorption but slightly higher photocatalytic activity than the polyhedral particles. Commercial Cu 2 O showed MO adsorption and high electron mobility but it was completely inactive. These results were explained in terms of the crystalline defects that influence both, the adsorption capacity and the photocatalytic activity.
Journal of Materials Science: Materials in Electronics, 2019
In this study, Cu 2 O nanostructures on Cu wire were formed with in situ chemical and then thermal oxidation to obtain the desirable structure, morphology and optical properties in order to enhance visible-light photocatalytic activity. The findings suggested that the procedure involved solution phase treatment and formation of Cu 2 O on pure Cu wire with two-step oxidation in controlled environment of nitrogen and air. Results showed that Cu 2 O nanostructure on Cu substrate were formed from transformation of as-synthesized Cu(OH) 2 nanostructures. The kinetic studies for Cu(OH) 2 formation and the synthesis mechanism of Cu 2 O nanostructures were investigated. The results show that the heterogeneous Cu/Cu 2 O nanostructures display nanorod and polyhedral morphology. The MB degradation reaches 77-82% after 240 min visible light irradiation. The band gap values of the heat treated samples under nitrogen and air were obtained 1.75 and 2.00 eV, respectively. Intensity of PL spectra for the heat treated sample under nitrogen was obviously lower. Furthermore, it is observed that the first order and modified-Freundlich model fit the kinetic data well.
Synthesis and comparative photocatalytic activity of CuO layers on SiO2 substrates
Nanosystems: Physics, Chemistry, Mathematics, 2020
Using the thermodynamic and kinetic approaches, it was found that Cu(NH 3) 2+ 4 aq complex predominating at 23 • C spontaneously decomposes at elevated temperatures, forming CuO precipitate in a bulk solution and a layer (CuO||SiO 2) on the surface of silica glass. The rates of these heterogeneous processes are fairly well described by the 1st-order reaction of decay of the Cu(NH 3) 2+ 4 aq complex. The formation of the CuO precipitate and layer is a two-step kinetic process. The rate of precipitate formation dominates above 65 • C while the rate of the layer formation prevails below this value. The CuO||SiO 2 material synthesized below 65 • possesses an optical bandgap of (1.25±0.05) eV, which is smaller compared to the crystals of commercial CuO. The CuO||SiO 2 material displays a photocatalytic activity in the reaction of UV-decomposition of benzoquinone-hydroquinone. It was discovered that the photocatalytic activity depends on the thickness of the photocatalyst layer.
Materials Science and Engineering: B, 2006
The present paper describes processing, properties and photocatalytic application of Cu doped TiO 2 thin films on glass substrate. Cu doped TiO 2 coatings were successfully prepared on glass slide substrates using sol-gel method. The obtained solutions exhibit acidic characteristics. The phase structure, thermal, microstructure and surface properties of the coatings were characterized by using XRD, DTA/TG, SEM and AFM. Their adhesion properties and spectroscopic analysis were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Cu/Ti ratios. Glass substrates were coated by solutions of Ti-alkoxide, Cu-chloride, glacial acetic acid and isopropanol. The obtained gel films were dried at 300 • C for 10 min and subsequently heat-treated at 500 • C for 5 min in air. The oxide thin films were annealed at 600 • C for 60 min in air. TiO 2 , CuO, Cu 4 Ti, Ti 3 O 5 and Cu 3 TiO 4 phases were found in the coating. The organic matters were burned at temperatures between 200 and 350 • C and TiO 2 crystallization was formed at 450 • C. The weight loss of the powder during process up to 600 • C is approximately 70%. The microstructural observations demonstrated that CuO content was led an improved surface morphology while thickness of the film and surface defects were increased in accordance with number of dipping. According to AFM results, it was found that as the Cu/Ti content increases the surface roughness of the films increases. In addition structural, thermal and microstructural results, it was found that the films of 0.73 ratio have better adhesion strength to the glass substrate among other coatings. The oxide films were found to be active for photocatalytic decomposition of metylene blue.
Studies on the substrate-dependent photocatalytic properties of Cu2O heterojunctions
RSC Advances, 2021
is a promising material for photocatalysis because of its absorption ability in the ultraviolet (UV)-visible light range. Cu 2 O deposited on conductive Ti and fluorine-doped tin oxide (FTO) substrates behaves as a photocathode. Cu 2 O deposited on an n-type semiconductor such as TiO 2 nanotube arrays (TNA)/Ti behaves as a photoanode and has demonstrated better photocatalytic activity than that of TNA/Ti. The substrate-dependent photocatalytic properties of Cu 2 O heterojunctions are not well studied. In this work, the photocatalytic properties of a Cu 2 O/TNA/Ti junction as a photoanode and of Cu 2 O/Ti and Cu 2 O/FTO junctions as photocathodes without bias were systematically studied to understand their performance. The Cu 2 O/TNA/Ti photoanode exhibited higher photocurrent spectral responses than those of Cu 2 O/Ti and Cu 2 O/FTO photocathodes. The photoanodic/photocathodic properties of those junctions were depicted in their energy band diagrams. Time-resolved photoluminescence indicated that Cu 2 O/TNA/Ti, Cu 2 O/Ti, and Cu 2 O/FTO junctions did not enhance the separation of photogenerated charges. The improved photocatalytic properties of Cu 2 O/TNA/Ti compared with TNA/Ti were mainly attributed to the UV-visible light absorption of Cu 2 O.
Photocatalytic generation of hydrogen under visible light on La2CuO4
Bulletin of Materials Science, 2015
The semiconducting properties of La 2 CuO 4 prepared by a chemical route are investigated for the first time by the photo-electrochemical technique. The optical gap is found to be 1.27 eV and the transition is directly allowed. p-Type conductivity is demonstrated from the Mott-Schottky plot in alkaline KOH solution (0.1 M), extrapolation of the linear region to the potential axis gives a flat band potential of −0.41 V SCE , a holes density of 1.75 × 10 19 cm −3 and a space-charge region of 18 nm. The electrochemical impedance spectroscopy, measured over the frequency range (1 mHz-10 5 Hz), reveals the predominance of the bulk contribution with a constant phase element. The energy diagram shows the feasibility of La 2 CuO 4 for the H 2 evolution under visible light. The best performance occurs at pH 12.5 in the presence of S 2 O 2− 3 as holes scavenger. A liberation rate of 20.6 μmol mn −1 (g catalyst) −1 is obtained under full light (29 mW cm −2).
Desalination and Water Treatment, 2015
In this paper, various morphologies of copper oxide (CuO) were synthesized from acetate, sulfate, and nitrate precursors using hydrothermal bath method. The photoluminescence spectra revealed that CuO-Ni sample contains the strongest surface defect peak which can be related to its highest active surface area. The Fourier transform infrared (FT-IR) results showed that the concentration of the surface OH − group on the samples varies considerably according to CuO-Ac > CuO-Ni > CuO-Su. From structural results, it could be observed that all the samples crystallized into a monoclinic crystal structure. The photocatalytic activity of CuO samples was evaluated by the catalytic oxidation of methylene blue in the presence of hydrogen peroxide. Concerning the nearly same optical band gap for the samples, the best photocatalytic performance of CuO-Ni nanorods was assigned to its highest active surface area and surface hydroxyl groups.
Applied Surface Science, 2019
In the present work Cu 2 O shape tailored microcrystals were obtained and investigated. The used shape-tailoring approach was based upon the variation of the starting precursor (copper(II) acetate and copper(II) chloride, the latter one being also much more cheaper and easily accessible), the synthesis temperature (60, 70 and 80°C, respectively) and the shape tailoring agent applied (PVP vs. EDTA). It was found that cubic and polyhedral monodisperse microcrystals were obtained, which showed enhance visible light photocatalytic activity in the degradation of methyl orange. The activity was dependent of the formation of metallic Cu (the formed metallic nanoparticles were obtained when PVP was used), the microcrystals' size and morphology. The band-gap values were directly linkable to the obtained photocatalytic activity, while in the first derivative DRS spectra the electron transition contribution of facet (111) was also found, alongside of the polycrystalline Cu 2 O electron transition contribution. Also, the surface hydrophylicity played a crucial role in the determination of the photocatalytic properties as evidenced by IR measurements and DLS investigations as well.