UV Vis Diffuse Reflectance Spectroscopy Research Articles

PREPARATION AND PHOTOCATALYTIC PERFORMANCE OF AG3PO4/MOS2 COMPOSITE PHOTOCATALYST

Ag3PO4 and MoS2 semiconductor materials were synthesized by hydrothermal method. The composite materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and UV–vis diffuse reflectance spectroscopy (UV–VIS DRS), and the photocatalytic degradation of organic dyes by rhodamine B was studied. The results showed that: Ag3PO4/MoS2 composite photocatalyst is formed by using MoS2 microspheres as the matrix and Ag3PO4 nanoparticles coated on its surface or embedded in its lamellar structure. When the molar fraction of Ag3PO4 in the composite product is 75%, the composite photocatalyst has better light absorption capacity and lower photogenerated carrier recombination rate (optical band gap is 1.24 eV), and shows better visible light photocatalytic degradation activity in the photocatalytic degradation of RhB experiment, the catalytic degradation rate is as high as 95.0%. At the same time, the degradation mechanism showed that H+ and O2− were the main active substances for RhB degradation. The photocatalyst has excellent performance and simple preparation method. It has broad application prospects in the field of photocatalysis.

Cu2O-Electrodeposited TiO2 Photoelectrode for Integrated Solar Redox Flow Battery

TiO2 photoelectrode has become an attractive platform due to its excellent photoelectric performance and has been widely used in battery, photocatalysis, and other photoelectric fields. However, when the TiO2 photoelectrode is used in solar flow batteries, the small photo-charging current is a potential problem, which will extend the charging process and lower the battery utilization efficiency. To address this issue, Cu2O is introduced to the surface of the TiO2 photoelectrode, and Cu2O-TiO2 forms a heterojunction to improve battery performance in this work. The formation mechanism of Cu2O-TiO2 is revealed and utilized to deposit Cu2O on pre-treated FTO glass covered with TiO2 films using electrochemical deposition (ECD). The photoelectrochemical properties of Cu2O-TiO2 photoelectrodes are characterized using XRD, UV-vis diffuse reflectance spectroscopy, XPS, and electrochemical characterizations. The successful deposition of Cu2O on the surface of TiO2 photoelectrode is confirmed, and the UV-vis spectroscopic test results show that the incorporation of Cu2O enhances and broadens the absorption and utilization of sunlight in the UV range by the TiO2 photoelectrode. Furthermore, the electrochemical test results manifest that the Cu2O-TiO2 photoelectrode possesses a higher carrier concentration under illumination conditions due to the formation of a heterojunction. Finally, a 30 min unbiased photocharging test demonstrates that the Cu2O-TiO2 photoelectrode charges in a current density of 425.03 μA·cm−2, indicating an increased photogenerated carrier concentration and a decreased photogenerated carrier recombination rate, which results from the enlarged doping concentration and improved charge transfer process at the electrolyte/semiconductor interface due to the incorporation of Cu2O. Compared with the current density of 116.21 μA·cm−2 for the bare TiO2 photoelectrode, the performance can be improved by over 365%.

Synergistic Effect of Catalytic Action of Copper and Cerium in the Oxidation of CO on Modified Zeolites Cu/Ce/ZSM-5

A series of mono- and bimetallic copper-cerium catalysts based on ZSM-5 zeolite with different aluminium content (SiO2/Al2O3 = 30 and 55) was synthesised by incipient wetness impregnation. The copper content was 0–4.3 wt %, and cerium loading varied in the range from 0 to 6 wt %. The obtained composites have been investigated by low temperature N2 sorption, XPS, EPR spectroscopy, UV-vis diffuse reflectance spectroscopy, DRIFT spectroscopy of adsorbed CO and tested in the reaction of catalytic oxidation of CO with oxygen. In the systems under study а pronounced synergistic effect of catalytic action of copper and cerium is observed, associated with the redox interaction between the metals. With an increase in the proportion of cerium in bimetallic systems from Сu : Ce = 6 to Сu : Ce = 1, the catalytic activity of the composites grows monotonically. The most active catalysts show 50% CO conversion at temperatures of 90–100°C. Decrease in the aluminium content in the zeolite contributes to higher catalytic activity. It has been shown that Cu+ ions bound to the surface of CeO2 particles play a key role in catalysis.

Bi2ZnB2O7 – PVDF electrospun composite membrane for waste water treatment utilizing photo-piezocatalysis

To enhance the piezoelectric capabilities of the β-phase of poly(vinylidene fluoride), a new composite membrane was prepared via electrospinning. This consist of Bi2ZnB2O7 and poly(vinylidene fluoride). A comparison of electrospun and composite fibers showed a significant increase in β-phase content. XRD and FTIR were used to characterize the samples' structures. FE-SEM and HR-TEM were also used to examine sample morphology. The optical properties of the BBZO-PVDF membrane were further assessed using UV–visible diffuse reflectance spectroscopy. The composite membrane's effectiveness was tested using photocatalysis, piezocatalysis, and photo-piezocatalysis. Methylene blue (MB) dye was degraded by these methods. The synergy between light and piezoelectric actions improved degradation performance significantly. It achieved a 74% degrading efficiency and a kinetic rate constant of 7.3 × 10−3 min−1. The findings show that the BBZO-PVDF composite membrane has great potential for enhanced environmental remediation and catalytic processes.

Ultrasonic radiation assisted synthesis of (CH3NH3)2CuCl4, CH3NH3PbCl3, and CH3NH3SnCl3 perovskites for energy application

The present research provides an outline for the synthesis of organic-inorganic hybrid perovskites such as (CH3NH3)2CuCl4, CH3NH3PbCl3, and CH3NH3SnCl3 by using Ultrasonic radiation assisted method. An X-ray diffraction study reveals the presence of crystalline phase in the Cu, Pb and Sn based perovskites. The optical and electrical properties were carefully examined using UV–Vis diffuse reflectance spectroscopy. The optical band gaps of the synthesized sample were estimated using Tauc's plot. The current-voltage characteristics of all the samples demonstrate increase in photocurrent under UV light compared to darkness. The findings indicated that the addressed samples are improved in the visible absorption region and were in good agreement with earlier research. The photo-induced mechanisms that result in the remarkable charge separation efficiency of these materials are fundamental properties that provide insight into the special features of such a material which has driven this to the forefront of photovoltaic research.

Construction of novel an in-situ m-BiVO4/t-BiVO4 isotype heterojunction photocatalyst for improved visible light-dependent degradation of dye

In this article, we have studied the photocatalytic characteristics of isotype heterostructure Bismuth vanadate BiVO4 (m-BiVO4/t-BiVO4). The isotype Bismuth vanadate m-BiVO4/t-BiVO4 (MTBV) was formed by a facile hydrothermal method. It was observed that the crystalline phase of isotype MTBV could be controlled by modifying the pH values of the precursors in the hydrothermal method. The isotype MTBV heterojunction was investigated for its physicochemical features by different techniques including X-ray powder diffraction (XRPD), Field emission scanning electron microscopy (FESEM), Energy dispersive microscopy (EDS), Fourier transfer infrared (FTIR) spectroscopy, UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Photoluminance (PL), and Electrochemical impedance spectroscopy (EIS). Photocatalytic degradation of Congo red (CR) dye under visible light irradiation was used to determine the photocatalytic activity of a well-developed MTBV heterostructure. The isotype MTBV phase resulted in an increased response due to a faster electron-hole pair formation rate by reducing charge recombination processes, a reduction in optical energy band gap (2.52 eV), and good compatibility between Preston t-BiVO4 and m-BiVO4 photocatalyst. In 1 hr, the optimized isotype MTBV heterojunction showed a CR degradation of 98%. According to the results of the PL, EIS, and UV–Vis studies, isotype MTBV might be an excellent option for a blue/green visible light-dependent optical photocatalyst. A feasible photocatalytic mechanism was suggested and discussed in particular to relate the physiochemical properties and photocatalytic properties; furthermore, kinetics decomposition process study, scavenger effect, dye concentration, catalyst dose effect, reusability and stability were checked, respectively.

2D g-C3N4 nanosheets functionalized with nickel-doped ZrO2 nanoparticles for synergistic photodegradation of toxic chemical pollutants

The photocatalytic removal of toxic chemical pollutants from wastewater has garnered significant attention in recent times owing to its notable removal efficiency, cost-effectiveness, and eco-friendly characteristics. Nonetheless, this catalytic process necessitates augmented charge separation and distinctive interface properties to facilitate catalytic reactions for water treatment applications. Therefore, in the current study, novel g-C3N4/Ni-doped ZrO2 heterostructured hybrid catalysts have been synthesized via a hydrothermal approach. Microscopic studies reveal that ZrO2 nanospheres were distributed on the layered-like 2D structure of g-C3N4 nanosheets. Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) characterizations were employed to investigate the impact of bandgap, electron-hole recombination, charge transfer, and interface properties on the catalytic performance of g-C3N4/ZrO2 hybrids. XRD analysis confirmed that the Ni-ions do not disturb the host lattice crystal structure and heterostructure development between g-C3N4 and doped ZrO2 sample. Structurally, Ni-doped nanoparticles were found to be equally superficially dispersed on g-C3N4 sheets. Optical analysis results suggest that the hybrid catalyst possesses a narrow bandgap of 2.56 eV. The synthesized photocatalyst degraded rhodamine B (RhB) and tetracycline (TC) with ∼92% and ∼89% degradation efficiency, respectively. Heterostructured hybrid catalysts showed superior degradation rate constants than other catalysts. This might be attributed to the sufficient separation of electron-hole due to the development of a heterojunction. The radical scavenging experiments suggested that O2●- and ●OH radicals contributed substantially to the dye elimination activity of the composite. Therefore, the synthesized novel nanohybrid catalysts in this study present an efficient and straightforward synthesis method for the efficient removal of toxins from wastewater under visible light irradiation.

Ag@rGO coral reef morphology exhibits excellent optical properties and photocatalytic activity against methyl orange under sunlight

The modified hummers method was used to synthesize GO, and the coral reef shape morphology of Ag@rGO was synthesized through the chemical reduction method. As-synthesized GO, rGO, Ag NPs, and Ag@rGO were characterized using various characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectra, UV–Vis diffuse reflectance spectroscopy (UV-DRS), X-ray photoelectron spectrometer (XPS), N2 adsorption-desorption isotherms (BET), liquid chromatography with mass spectrometry LCMS, Moreover, thermal stability was studied using a thermogravimetric analyzer (TGA). The growth size, shape, and extent were studied using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The obtained material was partially in de-agglomerated and agglomerated form, and aggregation was due to electrostatic forces of attraction. Besides this, the synthesized GO (70 %), rGO (85 %), Ag NPs (92 %), and Ag@rGO (99 %) were utilized to investigate photocatalytic activity for the degradation of Methyl orange dye (MO) under sunlight. Ag@rGO shows effective catalytic activity as it degrades the azo dye effectively. The degradation was found to be maximum using Ag@rGO, showing 99 % (120 min).

ZnFe2O4/TiO2 composites with type-I heterojunction for photocatalytic reduction of CO2

The composites of ZnFe2O4 (ZFO) with TiO2 (anatase, rutile) were synthesized and tested towards the photocatalytic reduction of CO2 to CO in the gas phase. ZFO was obtained through the precipitation from zinc and iron nitrates(V) precursors, followed by hydrothermal treatment, and its physicochemical properties were examined using XRD, FT-IR, XPS, SEM-EDS, and XRF techniques. ZFO was simply ground in the agate mortar with one of the TiO2 polymorphs, forming ZFO/anatase and ZFO/rutile. Spectroelectrochemical (SE-DRS), surface photovoltage (SPV), transient photocurrent and diffuse reflectance UV–vis spectroscopy (DRS) measurements were applied to understand the fate of photogenerated electrons and holes. The results point to the type-I heterojunction that is formed in the case of all ZFO/TiO2 systems. This type of band alignment is responsible for boosted photoactivity of the composites compared to the components used separately. The results confirm that the selection of anatase favours reaching higher yields of CO production, which is attributed rather to better electron mobility within anatase compared to rutile than to preferential, reducing properties of the rutile’s conduction band.

Core-shell Fe3O4/SiO2/TiO2 Magnetic Modified Ag for the Photocatalytic Degradation of Congo Red Dye and Antibacterial Activity

Disposal of dye wastewater can induce detrimental consequences for human health and the environment. The study aims to synthesize composites consisting of core-shell Fe3O4/SiO2/TiO2 modified with Ag. The composites comprise a Fe3O4 core, a SiO2 interlayer, and a TiO2 shell, with Ag being mobilized on the surface of the core and shell structures. Fe3O4/SiO2/TiO2@Ag composite was employed in the photocatalytic degradation of Congo red dye and antibacterial activity test. The degradation was facilitated by visible light irradiation while considering different factors such as pH solution, the photocatalyst dosage, and the dye's initial concentration. The composite was characterized using X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy-Electron Dispersive X-ray Spectroscopy (SEM-EDS), Vibrating Sample Magnetometer (VSM), and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS). The findings indicated that the composite exhibited strong magnetic, measuring 49.4 emu/g, with a band gap of 2.92 eV. The composite showed commendable catalytic properties, with degradation efficiency of 96.52% for Congo red dye under conditions: a pH solution of 4, a dosage of 0.5 g/L, and a dye concentration of 10 mg/L at 100 min of irradiation. The photocatalytic degradation kinetic is align with pseudo-first-order reactions. The composite also exhibits remarkable stability and efficiency with 4.83% decline in degradation efficiency after five cycles. Fe3O4/SiO2/TiO2@Ag composite exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus with a Minimum Inhibitory Concentration (MIC) value of 250 mg/L. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Influence of cobalt doping on chemical and green synthesized magnesium oxide nanoparticles for enhanced photocatalytic evaluation, adsorption studies, antimicrobial analysis and corrosion inhibition study

In this study, Cobalt-doped magnesium oxide nanoparticles (Co-MgO-Nps) were successfully synthesized using two different methods: co-precipitation via chemical synthesis and co-precipitation via a green synthesis approach. The originality of this research lies in the diverse applications that were explored using these nanoparticles. The study investigated various potential uses of Co-MgO-Nps, thereby highlighting their versatility and broad range of applications. X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray (EDX) analysis, UV–Vis Diffusion Reflectance Spectroscopy, BET adsorption isotherm, Transmission Electron Microscope (TEM), Photoluminescence (PL), Zeta potential and particle size determination were used to investigate and characterize the synthesizedCo-MgO-Nps. The photocatalytical degradationability of Co-MgO-Npsunder UV light irradiation wasstudied on potentially dangerous malachite green dye. The synthesizedCo-MgO-Nps showed outstanding photocatalytic performance in various ppm concentrations. Adsorption studies using malachite green dye at numerous ppm levels revealed that the Co-MgO-Nps synthesized by green approach degraded the dye more quickly than those synthesized chemically. Antimicrobial activities were evaluated against E. coli with different concentrations; the findings confirmed that the Co-MgO-Nps produced from green synthesis approach showed superior antimicrobial activity than the chemically synthesized Co-MgO-Nps. The synthesized Co-MgO-Nps showed good efficiency for inhibiting corrosion of maraging steel by hydrochloric acid.

Superior photocatalytic performance of Dy2O3/graphitic carbon nitride nanohybrid for the oxidation Rhodamine B dye under visible light irradiation: A superoxide free radicals approach

Organic-inorganic hybrid semiconductor nanomaterials have emerged as promising candidates for next-generation energy and environmental solutions. These materials combine organic and inorganic components to form a new class of hybrid nanomaterials with enhanced photocatalytic activity under visible-light irradiation. In this study, g-C3N4 was integrated with different ratios of Dy2O3 using a hydrothermal process. The prepared hybrid composite materials were analysed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), UV–vis diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET) surface area analysis, field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray analysis (EDAX) high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Photoluminescence Spectroscopy (PL) and Electron Paramagnetic Resonance spectroscopy (EPR). The synthesized Dy2O3/g-C3N4 (DYCN) nanohybrid composite has a bandgap energy and surface area of 2.63 eV and 51.8 m2/g respectively. FE-SEM analysis showed nanorods connected to the sheet-like morphology of the prepared DYCN nanohybrid composite material. When exposed to visible light, the organic dye rhodamine B was used as a model pollutant to assess the photocatalytic activity of the synthesized materials. The oxidation of organic molecules was initiated by superoxide (•O2−) free radicals rather than hydroxyl radicals generated during the reaction, which was confirmed by EPR analysis. Due to its narrow bandgap, larger surface area, and presence of f shells in Dy2O3, the synthesized 5 % Dy2O3/g-C3N4 (DYCN 5) nanohybrid composite material showed more visible-light photocatalytic activity than pure g-C3N4 and various ratios of synthesized nanomaterials.

Periodate-Mediated Aerobic Oxidation of Sulfides over a Bifunctional Porphyrin-polyoxometalate Catalyst: Photosensitized Singlet Oxygen Oxidation of Iodate to Periodate.

Regeneration of terminal oxidants by molecular oxygen in metal-catalyzed oxidations of organic substrates has the advantage of avoiding the use of stoichiometric amounts of hazardous and/or expensive reagents to meet (some of) the green chemistry requirements. In the present study, photosensitized singlet oxygen oxidation of iodate to periodate has been used to regenerate the oxidant in polyoxometalate (POM)-catalyzed oxidation of sulfides to sulfoxides with periodate in water. To the best of our knowledge, it is the first report on singlet oxygen oxidation of iodate to periodate. In order to determine the contribution of photooxidation and oxidation pathways in the formation of sulfoxide, the oxidation of diphenyl sulfide with a very low reactivity toward aerobic photooxidation was studied; a sevenfold increase in the conversion of the sulfide to the diphenyl sulfoxide was observed for the reaction conducted in the presence of H2TMPyP-PW12O40/IO3-/O2/hν compared to that in the presence of H2TMPyP-PW12O40/O2/hν. Also, under the same conditions, a ca. 1.5-fold increase was observed in the case of methyl phenyl sulfide, which shows high reactivity toward both the oxidation and photooxidation reactions. A porphyrin-POM nanocomposite formed by the electrostatic immobilization of meso-tetra(N-methylpyridinium-4-yl)porphyrin (H2TMPyP) on PW12O40 was employed for the one-pot oxidation and photooxidation reactions. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), diffuse-reflectance UV-vis spectroscopy, thermal gravimetric analysis, and Fourier transform infrared were used to characterize the formation of the hybrid compound. An average particle size of 42 nm was estimated for H2TMPyP-PW12O40 from XRD peak broadening using the Scherrer equation. Also, FESEM images showed the formation of nearly spherical nanoparticles with a size of ca. 200 nm. The redshift of the Soret band of H2TMPyP upon immobilization on POM was attributed to strong N-H···O hydrogen-bond interactions between POM and porphyrin.

Riboflavin and Eosin Y Supported on Chromatographic Silica Gel as Heterogeneous Photocatalysts.

The application of photocatalysis for organic synthesis, both in the laboratory and on an industrial scale, will depend on the achieving of good yields and the ease with which it can be applied. Selective irradiation of the photocatalyst with LED light has made it possible to activate the reactions easily, without the need for UV or heat filters. However, a common problem is the need to separate the photocatalyst from the reaction products through extraction and chromatography isolation processes. These procedures make it difficult to recover and reuse the catalyst, which is not compatible with scale-up applications. Photocatalysts attached to heterogeneous supports resulted in an alternative, which facilitates their removal and reuse. In this study, we use chromatographic silica gel as a low-cost heterogeneous support to bind photosensitizers such as Riboflavin or Eosin Y. The modified silica gel was analyzed by FTIR-ATR and diffuse reflectance UV-visible spectroscopy, thermogravimetric analysis, and optical microscopy. These hybrid materials have a suitable size for easy separation by decantation and were found to be photoactive against two photooxidation reactions. These easy-to-handle materials open the door to effective applications for photoinduced organic synthesis methods at medium to large scale.

Structural and optical properties of sol-gel synthesized TiO2 nanocrystals: Effect of Ni and Cr (co)doping

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. Powder XRD technique reveals that the modified catalyst majorly contains the anatase polymorph with the transition metal ion either substituting Ti or located as interstitials in the lattice of TiO2. Raman and UV–Vis absorption spectra of the doped and codoped catalyst a show λmax shift towards longer wavelength when in the metal ion concentration is increased from 0.25 to 10 wt%. FTIR patterns show the stretching and vibration patterns of hydroxyl radicals present in the nanocrystals. The BET surface areas of the doped and codoped TiO2 nanocrystals have substantially higher surface areas compared with that of the undoped TiO2. Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5% + 5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the incorporation of transition metal ions in the TiO2 nanocrystals.

Towards an efficient p-n heterojunction in ternary composite material based polypyrrole, metal oxide and surface functionalized graphene for thermoelectric properties enhancement

The thermoelectric properties of ternary p-n heterojunction composites based on [p-type polymer/surface treated graphene/metal oxide in ceramic form] were investigated in this study. In the presence of ceramic tungsten oxide (WO3) particles and diazonium salt surface treated graphene, a simple in-situ pyrrole polymerization method was carried out. FTIR, Raman scattering, X-ray diffraction analysis (XRD), diffuse reflectance UV-Vis spectroscopy, I-V characteristics, and scanning electron microscopy - energy dispersive spectrometer (SEM-EDS) have all been used to characterize composites. Based on the comparison of observed thermoelectric parameters, the ternary composite created by PPy-FrGO (DS-SO3H)-WO3 based on functionalized graphene with diazonium salt (DS-SO3H) was chosen as having superior thermoelectric capabilities than the other samples. This advancement was made possible by combining two strategies: graphene functionalization with a conjugated diazonium salt and thermochemical treatment of tungsten oxide with the sol-gel method and sintering procedure. Functionalization reduced thermal conductivity (= 0.127 W.m−1. K−1) while adding ceramic tungsten oxide boosted electrical conductivity ( = 1087 S/m), resulting in a merit coefficient (ZT) of 1.63 × 10−4.

Green synthesis of CuO nanoparticles using citrus maxima peel aqueous extract

Discarded fruit peels caused pollution problem and reused of waste product reduces pollution and sustain environmental balance. In most cases, fruits peels are land filled or composted which lead to environmental problems like methane emission to the atmosphere due to anaerobic digestion and leachate formation, which percolates into the bottom of the earth during rainfall. This communication reports on the synthesis of copper oxide nanoparticles (CuO NPs) using citrus maxima peel. The prepared CuO NPs were characterized by XRD, SEM, EDS, UV–visible spectroscopy, FTIR and PL. The characterization results confirmed that the prepared CuO NPs have a monoclinic crystalline structure with a spherical shape and the average crystallite size of CuO NPs was about 20 nm. The optical band gap (Eg) of CuO NPs calculated from UV–Visible diffuse reflectance spectroscopy was 1.5eV. The photo response V-I characteristics of CuO NPs showed good photo response under illumination conditions, which might be due to the maximum number of exciting photoelectrons due to illumination.

Nanostructured MnWO4 as a Bifunctional Electrocatalyst for Water Splitting

Metal oxides have been considered as photo/electrocatalysts for water splitting because of their compositional and structural flexibility, and consequently, their tunable band gaps. These semiconductor nanomaterials could be used as electrocatalysts for artificial photosynthesis, which mainly includes the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. In this study, we synthesized nanostructured manganese tungstate (MnWO4) using the hydrothermal method as a bifunctional electrocatalyst for HER and OER reactions, which exhibit the Tafel slopes of 160 and 83 mV dec−1, respectively, in alkaline medium. Prepared nanomaterials were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). We demonstrated an approach to sketch the electronic diagram of nanostructured MnWO4 by using a combination of UV–Vis diffuse reflectance spectroscopy (DRS) and Mott–Schottky analysis via electrochemical impedance spectroscopy.

Photocatalytic Systems Based on ZnO Produced by Supercritical Antisolvent for Ceftriaxone Degradation

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has been used as a model contaminant. Moreover, there is particular interest in combining small-size ZnO particles and β-cyclodextrin (β-CD), creating a hybrid photocatalyst. Zinc acetate (ZnAc) (subsequently calcinated into ZnO) and β-CD particles with a mean diameter of 0.086 and 0.38 µm, respectively, were obtained using the supercritical antisolvent process (SAS). The produced photocatalysts include combinations of commercial and micronized particles of ZnO and β-CD and commercial and micronized ZnO. All the samples were characterized through UV–Vis diffuse reflectance spectroscopy (DRS), and the band gap values were calculated. Raman and FT-IR measurements confirmed the presence of ZnO and the existence of functional groups due to the β-cyclodextrin and ZnO combination in the hybrid photocatalysts. Wide-angle X-ray diffraction patterns proved that wurtzite is the main crystalline phase for all hybrid photocatalytic systems. In the photocatalytic degradation tests, it was observed that all the photocatalytic systems exhibited 100% removal efficiency within a few minutes. However, the commercial ZnO/micronized β-CD hybrid system is the photocatalyst that shows the best performance; in fact, when using this hybrid system, ceftriaxone was entirely degraded in 1 min.

Improvement of the photocatalytic activity of CeO2 on the degradation of chlorophenolic compounds obtained by solution combustion synthesis (SCS). Effect of urea as fuel

This work presents a detailed study to determine the optimal urea content in the synthesis of CeO2 by the solution combustion method and thus obtain the highest photocatalytic activity in the degradation of phenolic compounds. Four CeO2 with different molar ratios urea:Ce(IV) = 0:1, 2:1, 4:1, and 7:1 were synthesized. The synthesized oxides were evaluated in the photocatalytic degradation of 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol using UV light. The synthesized materials were characterized by XRD, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, FTIR spectroscopy, N2 physisorption, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. Raman characterization showed that using urea as fuel favors the formation of oxygen vacancies, increasing up to the urea:Ce(IV) = 4:1 ratio. Photoluminescence studies indicated a decrease on the recombination of photogenerated charges when the oxides are synthesized with urea. The CeO2 synthesized without urea showed 26.6% degradation of 3-chlorophenol, which increased up to 73.6% when it was synthesized with urea. The photocatalytic activity improved mainly due to a higher content of oxygen vacancies and lower recombination of the photogenerated charges. The synthesis method used led to the formation of CeO2 with improved physicochemical properties, so its implementation in the synthesis of other metal oxides and the use of other fuel agents is of great interest for its investigation.