Solar Light Photocatalytic Activity Research Articles

Boosting solar-light photocatalytic activity of Ni2P-decorated ZnCr2O4 nanofibers for H2 evolution and tetracycline elimination

Photocatalysis is a promising route to convert solar light into chemical energy for H2 evolution and pollutants degradation. Hence, Ni2P decorated ZnCr2O4 (Ni2P/ZnCr2O4) nanofibers were prepared for boosting solar-light induced water splitting and tetracycline hydrochloride (TCH) degradation. For comparison to ZnCr2O4 nanofibers, Ni2P/ZnCr2O4 composites exhibited the better photocatalytic activities for water splitting and TCH removal. Owing to the co-catalytic effect of Ni2P for the efficient photon capture, the charge carriers were rapidly separated and migrated at the interface between Ni2P and oxygen-defected ZnCr2O4. H2 evolution rate of optimal C–Ni2P/ZnCr2O4 with a nominal Ni2P content of 9.0 wt% was 575.89 μmol g−1 h−1, and its apparent quantum yield at 420 nm was 15.25 %, while its H2 evolution decreased from 2815.13 to 2602.51 μmol g−1 after fifth cycle. In addition, the removal efficiency of C–Ni2P/ZnCr2O4 was 93.68 % within 90 min, and declined to 88.76 % after five cycles for solar-light driven degradation of 50 mg L−1 TCH solution. The deactivation of C–Ni2P/ZnCr2O4 was due to the photo-corrosion for the change in valence states of compositions.

Solvothermal synthesis of novel ternary BiOI–BiOBr–NiO nanophotocatalyst with improved solar light photocatalytic activity

A novel class of heterojunction BiOI–BiOBr–NiO has been synthesized through solvothermal-precipitation route. Novel as-prepared nanophotocatalysts are highly efficient under simulated sunlight illumination for (Acid Orange 7) AO7 degradation. Even though, NiO possess no photocatalytic efficiency, its combination with BiOBr–BiOI provides exceptional high photocatalytic performance due to more effective photo-generated electron–hole separation through the heterojunction semiconductor construction. XRD, FESEM, EDX, BET, FTIR and DRS analysis were applied to identify the physical, chemical and optical properties of the synthesized BiOI–BiOBr–NiO heterojunctions. The results showed remarkable increase of photoactivity of BiOI–BiOBr–NiO (6:3:1) in comparison with corresponding heterostructures. XRD confirms construction of BiOBr–BiOI over NiO nanoparticles. In addition, 3D image of synthesized samples affirms proper roughness and porosity. The effect of parameters including catalyst loading, pH and dye concentration has been examined. According to recycling tests and XRD of used sample, the novel heterojunction system considered to be photo table.

Enhanced solar light photocatalytic activity of TiO2 modified with ammonium carbamate for the removal of ketoprofen from water

This study was focused on the investigation on the influence of modification of TiO2 with ammonium carbamate on its physicochemical properties and photocatalytic activity under simulated solar light. A simple mechanochemical approach based on ball-milling combined with calcination was adapted to obtain novel C,N,S-modified TiO2-based materials. Ammonium carbamate was used as C and N source, while a crude TiO2 acquired from sulfate technology was applied as TiO2 and S precursor. The photoactivity of the prepared photocatalysts was examined towards ketoprofen decomposition under simulated solar light. Additionally, the most efficient photocatalysts were examined under the visible and UV light. The influence of the preparation conditions (rotation speed, ball-milling time, calcination temperature and ammonium carbamate dose) on the photoactivity of the photocatalysts was investigated for the first time. All novel photocatalysts revealed improved ketoprofen photodecomposition efficiency (67–72 %) compared to the TiO2 P25 (60 %), the crude TiO2 (29 %) and a synthesized referential photocatalyst (60 %). The highest photoactivity was achieved for the photocatalysts prepared through 1 h of ball-milling with the speed of 600 rpm and calcined at 600 °C. The ketoprofen decomposition efficiency was rising with the increasing TiO2:N weight ratio from 9:1 to 5:5 for all the investigated types of radiation.

Plant Photocatalysts: Photoinduced Oxidation and Reduction Abilities of Plant Leaf Ashes under Solar Light.

Plant leaf ashes were obtained via the high temperature calcination of the leaves of various plants, such as sugarcane, couchgrass, bracteata, garlic sprout, and the yellowish leek. Although the photosynthesis systems in plant leaves cannot exist after calcination, minerals in these ashes were found to exhibit photochemical activities. The samples showed solar light photocatalytic oxidation activities sufficient to degrade methylene blue dye. They were also shown to possess intrinsic dehydrogenase-like activities in reducing the colorless electron acceptor 2,3,5-triphenyltetrazolium chloride to a red formazan precipitate under solar light irradiation. The possible reasons behind these two unreported phenomena were also investigated. These ashes were characterized using a combination of physicochemical techniques. Moreover, our findings exemplify how the soluble and insoluble minerals in plant leaf ashes can be synergistically designed to yield next-generation photocatalysts. It may also lead to advances in artificial photosynthesis and photocatalytic dehydrogenase.

Synthesis of highly efficient selenium oxide hybridized g-C3N4 photocatalyst for NADH/NADPH regeneration to facilitate solar-to-chemical reaction

An inexpensive graphitic carbon nitrite (g-C3N4) photocatalyst was hybridized with selenium oxide (SeO2) photocatalyst by a monolayer-dispersed technique. After hybridization of g-C3N4 with SeO2, the NADH/NADPH regeneration efficiency of SeO2 photocatalyst was enhanced under solar light illumination. The photocatalytic activity of SeO2/g-C3N4 photocatalyst under solar light illumination was enhanced by 3-fold higher than g-C3N4 photocatalyst, the solar light photocatalytic activity was produced and the photo-decomposition of SeO2 photocatalyst was completely stifled after hybridized SeO2 photocatalyst by g-C3N4 photocatalyst. The improvement in performance and photo-decomposition inhibition under solar light illumination was persuaded by efficiency separation of photo-persuaded holes from SeO2 to the valence bond (V.B.)/highest occupied molecular orbital (HOMO) of g-C3N4 under solar light illumination, the electron jumped from the V.B. to the conduction band (C.B.)/lowest unoccupied molecular orbital (LUMO) of g-C3N4 could directly insert into the C.B. of SeO2 photocatalyst, synthesized SeO2/g-C3N4 photocatalyst is highly active for NADH/NADPH regeneration under solar light.

ZnInGaS4 heterojunction with sulfide vacancies for efficient solar-light photocatalytic water splitting and Cr(VI) reduction

ZnInGaS4 heterojunction with S vacancies was prepared via the microwave hydrothermal route to boost the solar-light photocatalytic activity for water splitting and Cr (VI) reduction. The tight interface between ZnIn2S4 and ZnGa2S4 favors the rapid separation and transfer of photo-induced electron-hole pairs, and the narrowed band gap is suitable for visible-light harvesting. In addition, S vacancies serve as the adsorption sites and photons capture, leading to the efficient solar utilization. Compared with ZnIn2S4 (0.94 mmol g-1h−1) and ZnGa2S4 (0.33 mmol g-1h−1), the optimal ZnInGaS4 with a In/Ga molar ratio of 1:1 exhibits the better H2 evolution rate (4.47 mmol g-1h−1) and the apparent quantum yield of 20.16 % at wavelength of 400 nm. The removal efficiency of ZnInGaS4 for solar-light driven Cr (VI) reduction is 99.46 % within 140 min, which is higher than ZnIn2S4 (93.14 %) and ZnGa2S4 (89.31 %). The photo-corrosion induces to the deactivation of ZnGa2S4 for solar-light driven H2 evolution and Cr (VI) reduction after five cycles.

Solar light photocatalytic activity of CuO/TiO2 mixed oxide derived from conjugated azomethine metal complex for degradation of food colorants

This work illustrates the preparation of an effective photocatalyst, CuO/TiO2 nano metal mixed oxide (NMMO). The desired synthesis was carried out by calcination assisted reaction of Cu[DBAPD]/TiO2 at 650 °C. Additionally, the prepared nano metal mixed oxide material has also been confirmed by numerous characterization techniques such as XRD, FTIR, HRTEM, FESEM with EDS, XPS, BET, ESR and Photoluminescence which revealed the occurence of strong interfacial interactions between CuO and TiO2. The optical properties of the prepared NMMO have also been measured by UV–vis. spectroscopy. The prepared NMMO exhibited excellent photo-response for the total degradation of amaranth (99.21 %) as well as brilliant blue (99.68 %) after just 40 min during intense solar irradiation. It has been found that the photocatalytic degradation mechanism over the surface of CuO and TiO2 can be well explained by considering the charge flow from TiO2 to CuO. Such type of structure offered higher redox capability as well as improved separation of photogenerated charge carriers, thus providing phenomenal photocatalytic performance. In addition to this, the degradation process has been investigated utilizng mass spectrometry and UV–vis. spectral analysis. Moreover, the CuO/TiO2-NMMO photocatalytic material offered good stability and reusability and can therefore act as a strong contender to be use in environmental remediation.

Enhanced solar light photocatalytic and antimicrobial activity of green noble metal/TiO2 nanorods

Au/TiO2 and Pt/TiO2 nanocomposites have been processed using a green method. Au and Pt colloidal nanoparticles have been primarily synthesized by mixing their corresponding metal ions with an aqueous solution of corn husk extract, followed by anchoring on the as-synthesized TiO2 nanorods. The structural and morphological properties of green-prepared nanomaterials were systematically investigated by various techniques. The UV–VIS absorption measurements confirmed the formation of colloidal Au and Pt with λmax at 550 and 345 nm, respectively. TEM results show anchoring of spherical Au particles (40 nm) on TiO2 nanorods while smaller Pt particles have been observed on Pt/TiO2 composite. It has been shown that the highest visible light harvesting capability was earned for Au/TiO2 composite due to the surface plasmon resonance (SPR) of Au nanoparticles. The photocatalytic and antimicrobial activity of the nanomaterials was investigated for disinfection of Escherichia coli under solar light irradiation. The green synthesized nanocomposites showed enhanced solar light photocatalytic and antimicrobial activity. The best photocatalytic and antimicrobial activity was obtained for Au/TiO2. This evidences the enhanced SPR of Au nanoparticles and hence an enhancement in the solar light accessible by TiO2 so that a higher amount of reactive oxygen species can be generated, which enhances photocatalytic and antibacterial activity.

Construction of α-Fe2O3/Sulfur-Doped Polyimide Direct Z-Scheme Photocatalyst with Enhanced Solar Light Photocatalytic Activity.

A novel two-dimensional α-Fe2O3/sulfur-doped polyimide (FO/SPI) direct Z-scheme photocatalyst was successfully constructed by a facile thermal treatment method. The effects of α-Fe2O3 nanosheets on the morphology, chemical structure, and photoelectronic properties of FO/SPI composites were systematically characterized by different spectroscopic means. These methods include X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transient fluorescence spectra, and so forth. It was confirmed that the small amounts of α-Fe2O3 can availably facilitate exfoliation of bulk SPI, resulting in a transformation of SPI from bulk to 2D layered composite that illustrates tight interface through the coordination Fe–N bond and an all-solid-state direct Z-scheme junction. Thus, the transfer and separation efficiency of photogenerated electron/hole pairs were significantly enhanced, which greatly promoted improvement of the photocatalytic activity of the FO/SPI composite for methyl orange degradation under solar light. This work provides a new approach to constructing efficient inorganic–organic Z-scheme photocatalyst based on strong interface interaction.

Phase stabilization and exposed {1 0 0} facet growth of α-Ag3VO4 photocatalyst: A low-temperature, template-free hydrothermal synthesis approach

The low-temperature phase stabilization, exposed {100} facet growth and solar light photocatalytic activity of α-Ag3VO4 microcrystals synthesized by a template-free hydrothermal procedure from AgNO3, NH4VO3 and ammonia were reported. By simply selecting a stoichiometric AgNO3/NH4VO3 molar ratio and a suitable amount of ammonia, pure α-Ag3VO4 powders were received readily at temperature as low as 100 °C while the competitive phase formation of the less photoactive Ag4V2O7 was inhibited completely. Especially, by increasing hydrothermal temperature from 100 to 160 °C, the crystallographic orientation growth of α-Ag3VO4 microcrystals along a-axis occurred and gradually diminished. For optimized sample, α-Ag3VO4 microcrystals were enclosed by exposed {100} facets, providing a significant enhancement in photocatalytic activity for methyl orange photodegradation under simulated solar light irradiation with respect to that of the random-oriented bulk sample. The role of ammonia on the low-temperature phase stabilization and exposed {100} facet growth of Ag3VO4 was also discussed.

A simple and green photoreduction approach for synthesis of Au/g-C3N4 hybrid nanocomposites with high solar light photocatalytic activity

In this study, we developed a green and easy to scale up approach for producing Au/g-C3N4 (Au/GCN) hybrid plasmonic photocatalyst without using the chemical reducing agents via the growing of Au nanoparticles (Au NPs) on the surface of GCN nanosheets under the photo-reduction of ultraviolet (UV)-radiation. Different characterization techniques were conducted for investigating the structure, morphology, surface chemistry and optical properties of the as-prepared catalysts. The scanning electron microscope image shows that the homogeneous Au NPs anchored on the surface of the GCN nanosheet increased with the UV illumination time. The x-ray photoelectron spectroscopy results prove the coexistence of GCN nanosheets with heptazine heterocyclic ring (C6N7) units and Au NPs in the Au/GCN. The photoluminescence intensity decreased sharply with the time of UV irradiation, indicating that the recombination rate of photogenerated electron–hole recombination decreased. The photocatalytic activity of the hybrid catalysts was evaluated by degrading rhodamine B (RhB) under simulated sunlight irradiation. The results show that the Au/GCN photocatalyst exhibits superior sunlight photocatalytic activity than that of bare GCN. The 6 h irradiated fabricating sample exhibited the strongest photocatalytic activity, completely decomposing the 10 ppm RhB in 30 min of irradiation. This report can provide the design of a simple and green synthesis method for the highly active Au/GCN photocatalyst.

Efficient solar-light photocatalytic activity of FeS/S-doped MgO composites for tetracycline removal

To overcome the poor visible-light harvesting and the inferior charge transfer and separation of MgO, MgO nanosheets were co-modified by S and FeS (FeS/S-MgO) via a high-temperature sulfurized route. Compared with pure S-MgO, FeS/S-MgO exhibited higher photocatalytic capacity for tetracycline hydrochloride (TCH) under solar light irradiation. It’s attributed to the junction interface between FeS and O-defected S-MgO for promoting the transfer and separation of photo-induced carriers and enhancing the visible-light absorption capacity. The photocatalytic activity of FeS/S-MgO was greatly affected by FeS content, TCH concentration, pH, inorganic salts, and quenchers. The optical 3-FeS/S-MgO with a FeS content of 7.94 wt% degrade 97.10% TCH solution of 40 mg L −1 , and declined to 94.21% after five cycles under the same conditions. •OH and h + played the crucial role in 3-FeS/S-MgO assisted photocatalytic system. • FeS/S-MgO composites were prepared by high-temperature sulfurization. • FeS/S-MgO enhanced the visible-light harvesting and the charge transfer. • •OH and h + played the vital role in solar-light driven degradation of TCH.

Nonthermal plasma sulfurized CuInS2/S-doped MgO nanosheets for efficient solar-light photocatalytic degradation of tetracycline

To enhance the adsorption-photocatalytic capacity of tetracycline hydrochloride (TCH) under solar light irradiation, ultrafine CuInS2 nanoparticles of 5 nm modified MgO with S doping (CIS/S-MgO) nanosheets were in-situ sulfurized in the nonthermal plasma. Compared with pure MgO, In2S3/S-MgO and CuS/S-MgO, CIS/S-MgO exhibited the better photocatalytic activity while worse adsorption capacity. The optimal 2-CIS/S-MgO could remove 98.4% of 200 mg L−1 TCH solution within 180 min, and declined to 92.3% after five cycles. The attenuated surface discharge and small BET surface area of CIS/S-MgO induced to the inferior adsorption capacity, while the Z-structured junction formed between CuInS2 and S-MgO was favorable for the charge transfer and separation of electron-hole pairs. •O2− was vital for enhancing the solar-light photocatalytic activity of 2-CIS/S-MgO.

Effects of the surface of solar-light photocatalytic activity of Ag-doped TiO2 nanohybrid material prepared with a novel approach

Surface modification with a nanomaterial has been confirmed to be an effective strategy to enhance the visible-light photodegradation efficiency of titanium dioxide nanoparticles (TiO2-NPs). In this regard, we used silver as an additive into TiO2-NPs to improve their photodegradation activity under visible light irradiation. Here, a novel and eco-friendly process was developed to prepare the Ag-doped TiO2 nanohybrid and named as photon-induced method (PIM). The XRD technique showed that the prepared Ag-doped TiO2 has mixed phases of anatase and rutile. However, the rutile-only phase was detected for the pure TiO2-NPs at 700 °C of calcination. Ultraviolet–visible (UV–Vis) absorption spectra revealed a reduction in the energy bandgap of TiO2 after Ag doping. Besides, the addition of Ag resulted in a significant improvement of TiO2 morphology. Methylene blue (MB) dye was chosen to be an organic target to investigate the photocatalyst activity of the TiO2-NPs. In this regard, the degradation rate of MB was found to be 100% for the Ag-doped TiO2, which is higher than that of pure rutile TiO2. The incorporation of Ag additive plays a significant role in the improvement of TiO2 stability and photodegradation performance due to the surface plasmon resonance phenomenon.

Solar light sensitive hybrid Ce4+/3+ doped perovskite magnesium zirconate nano cubes for photocatalytic hydrogen evolution and organic pollutant degradation in water

Dispersion of petite quantity (Mg1−xCexZryO3) of cerium dopant in the lattice of magnesium zirconate (MgZrO3) is an efficient strategy to stimulate solar light photocatalytic activity of the material and achieve superior charge carrier separation. In this research, we demonstrate the tailoring of MgZrO3 to become a solar light sensitive material for the degradation of methyl orange (MO) dye and hydrogen evolution from water. Cerium doped MgZrO3 nanocubes (Mg1−xCexZryO3NCs) showed 93% efficiency for the degradation of MO and was able to show a maximum hydrogen evolution rate of 13,318 µmol h−1 g−1. It was found that, concentration of cerium plays a key role in the overall performance of the photocatalyst. A systematic characterization by Brunauer–Emmett–Teller (BET), Scavenger experiments, Electron Spin Resonance Spectroscopy (ESR), Photoluminescence (PL) and photocurrent measurements of the Mg1−xCexZryO3 NCs showed that, it possesses high surface area, promotes transfer of photo-stimulated electrons and provides rich photo-active centers for the enhanced photocatalytic redox activity. Retention of structure and morphology even after rigorous cycling of the catalyst with respect to MO degradation and hydrogen evolution makes Mg1−xCexZryO3 NCs a robust photocatalytic material.

Solar light irradiated photocatalytic activity of ZnO–NiO/rGO nanocatalyst

The current study is based on the synthesis and characterization of ZnO–NiO/rGO nanohybrid for photocatalytic degradation of organic pollutants. The physicochemical properties of synthesized products were estimated by X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), field emission-scanning electron microscopy (FESEM), and Ultraviolet–Visible spectroscopy. The diffraction data showed the formation of binary metal oxide nanocomposite, containing ZnO in hexagonal whereas NiO in the cubic crystalline phase. XRD results revealed that the calculated crystallite size of NiO and ZnO in the ZnO–NiO nanocomposite was <20 nm. The spectroscopic results were found to be in close agreement with XRD data. The morphological analysis exposed the nano-island morphology of the product. The solar light assisted photocatalytic degradation outcome showed 89% degradation of methylene blue and 51% degradation of benzimidazole under similar conditions using ZnO–NiO/rGO nanohybrid. Moreover, the experiment showed that hydroxyl radicals, electrons, and holes were the main active species during the degradation mechanism. In contrast to the ZnO–NiO nanocomposite, the ZnO–NiO/rGO nanohybrid exhibited greater degradation efficiency. This superb photocatalytic performance of ZnO–NiO/rGO nanohybrid proved to be a durable candidate in the field of catalysis.

Ternary NiTiO3@g-C3N4–Au nanofibers with a synergistic Z-scheme core@shell interface and dispersive Schottky contact surface for enhanced solar photocatalytic activity

Ternary photocatalyst NiTiO3@g-C3N4–Au nanofibers were designed with synergistical Z-scheme and Schottky heterojunctions for synergistically enhanced solar light photocatalytic activity reactions.

Mg0.5NixZn0.5-xFe2O4 spinel as a sustainable magnetic nano-photocatalyst with dopant driven band shifting and reduced recombination for visible and solar degradation of Reactive Blue-19

Focussing on visible light active ferrites for high performance removal of noxious pollutants, we report the synthesis of Mg0.5NixZn0.5-xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, & 0.5) ferrite nanoparticle for degradation of reactive blue-19 (RB-19). Lattice parameters calculated using intense X-ray diffraction (XRD) peaks and Nelson-Riley plots (N-R plot) are in well agreement with each other. The sample Mg0.5Ni0.4Zn0.1Fe2O4 (M5N4) exhibits best performance with 99.5% RB-19 degradation in 90 min under visible light. Photoluminescence (PL) results confirm that recombination of charge carriers is highly reduced in the photocatalyst. Scavenging experiments suggest that O2− radicals were the dominant species responsible for photocatalytic performance. The photocatalytic mechanism was explained in terms of dopant driven shifting of conduction bands and valence bands (calculated by Mott-Schottky plots). The thermodynamic probability of radical generation along with role of redox cycles of metal ions has been discussed in the mechanism. The dye degradation was ascertained by detection of intermediates via mass spectrometry analysis and a possible degradation route was also predicted. The findings in this work provide intriguing opportunities to modify the electronic band structure of spinel ferrites for visible and solar light photocatalytic activity for environmental detoxification.

RETRACTED: Atomic layer deposition of Cu2O on NH2-MIL-101(Fe) for enhanced photocatalytic performance and decreased electron/hole recombination

Coupling appropriate semiconductor nanoparticles with massive surface-area support has become a promising but challenging strategy to photocatalyst design for enhanced photocatalytic activity in environmental cleaning applications, owing to the severe aggregation issues of nanoparticles. Herein, the atomic layer deposition (ALD) approach was applied to uniformly disperse ultrafine Cu 2 O nanoparticles (5–10 nm) on metal-organic frameworks without aggregation, forming NH 2 -MIL-101(Fe)/Cu 2 O nanocomposite photocatalysts. The Cu 2 O mass within the nanocomposites can be well controlled by merely adjusting the ALD cycles. The optimal NH 2 -MIL-101(Fe)/Cu 2 O displays a high photodegradation efficiency of 92% for RhB and excellent stability under visible light. The reaction kinetics and photocurrent response experimental results reveal that the optimal NH 2 -MIL-101(Fe)/Cu 2 O photocatalyst exhibits effective charge separation/transfer and suppressed recombination rate of charge carriers, which will significantly increase the solar light utilization efficiency and photocatalytic activity. We believe the presented photocatalyst synthesis strategy here can be generalized to construct other photocatalysts for various photocatalytic applications.

Pulsed laser synthesis of reduced graphene oxide supported ZnO/Au nanostructures in liquid with enhanced solar light photocatalytic activity

ZnO/Au/rGO ternary nanocomposites possessing a high photocatalytic response under solar irradiation were synthesized by a two-step process via a pulsed laser synthesis and a wet chemical process. The crystalline structure, surface morphology, size distribution, elemental composition, and optical properties of the prepared ZnO/Au/rGO ternary nanocomposites were characterized using X-ray diffraction, field-emission scanning electron microscope, high-resolution transmission electron microscope, energy-dispersive X-ray spectroscopy, UV–vis diffuse reflectance spectra, and photoluminescence analysis. The photocatalytic activity of the as synthesized nanocomposites was evaluated for the degradation of methylene blue (MB) under solar light irradiation (SLI). The density of the elemental and carbonaceous components, such as the Au nanoparticles (NPs) and the rGO nano-matrix on ZnO, could be altered by changing the concentration of HAuCl4.3H2O (5, 10, 15, and 20 wt%) or rGO (2.5, 5, and 7.5 wt%) using the same synthetic processes. The ZnO/Au15/rGO5 nanocomposite showed the highest photocatalytic degradation efficiency of 95% MB after 120 min under SLI, potentially due to the increased absorption of solar light or the efficient separation and migration of charge carriers by the anchored Au NPs and rGO onto the ZnO NPs. Further, the observed results and reusability of ZnO/Au15/rGO5 makes it an exceptionally promising material for diverse applications in the field of wastewater treatment and other types of environmental remediation.