Direct Sunlight Irradiation Research Articles

Engineering direct Z-scheme GCN/ bimetallic-MOF heterojunctions as efficient and recyclable photocatalysts for enhancing degradation of RR 195 under visible light

Direct Z-scheme heterojunction photocatalyst GCN/M-FeBTC (M: Ni, Co, Cu, Zn, Mn; BTC: 1,3,5-benzenetricarboxylate, GCN: graphitic carbon nitrides) were synthesized by in-situ hydrothermal method assisted using microwave. GCN/M-FeBTC materials exhibit excellent photocatalytic performance with nearly 100 % of reactive red 195 (RR-195) being removed after 30 min under direct sunlight irradiation. Tests for reactive radicals have shown that holes (h+) and superoxide radicals (•O2–) close a major function in the removal of RR-195. Based on the band structure (BS) of the material, a direct Z-scheme heterojunction photocatalyst mechanism has been proposed. The effects of catalyst mass, pH and RY-145 concentration on the photocatalytic activity of GCN/Mn-FeBTC materials were also researched. The innovation of the photocatalytic activity of the GCN/Mn-FeBTC materials may be due to the synergistic combination of factors such as: (i) the high surface area; (ii) visible light absorption and efficient splitting of electron (e–) and h+; (iii) increased oxygen vacancies and defects; (iv) shortening of charge transport distances. The decomposition pathway of RR-195 was determined based on liquid chromatography mass spectrometry (LC-MS) analysis. Chemical oxygen demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC) show high mineralization potential for the degradation of RR-195 on direct Z-scheme photocatalysts GCN/M-FeBTC.

Enhanced photocatalytic degradation of methylene blue dye using eco-friendly synthesized rGO@ZnO nanocomposites

Industrial chemical pollutants such as methylene blue (MB) dye are released into the water body and potentially cause harm to the human and aquatic biosphere. Therefore, this study aims to synthesize eco-friendly nanocatalysts, i.e., reduced graphene oxide (rGO), zinc oxide (ZnO), and reduced graphene oxide-zinc oxide (rGO@ZnO) nanocomposites, for efficient photocatalytic degradation of MB dye. A graphite rod was obtained from waste dry cell batteries for the electrochemical exfoliation synthesis of graphene oxide (GO) and rGO. For the eco-friendly synthesis of ZnO and rGO@ZnO nanocatalysts, Croton macrostachyus leaf extract was used as a reducing and capping agent. The synthesized nanocatalysts were characterized using a UV–Vis spectrophotometer, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray. The eco-friendly synthesized rGO, ZnO, and rGO@ZnO nanocatalysts were applied for the photocatalytic degradation of MB dye using direct sunlight irradiation. At optimum parameters, photocatalytic degradation of MB dye efficiency reached up to 66%, 96.5%, and 99.0%, respectively. Furthermore, kinetics of the photodegradation reaction based on rGO, ZnO, and rGO@ZnO nanocatalysts follow pseudo-first-order with a rate constant of 2.16 × 10–3 min−1, 4.97 × 10−3 min−1, and 5.03 × 10−3 min−1, respectively. Lastly, this study promotes a low catalyst load (20 mg) for the efficient photodegradation of MB dye.

Pore-Confined π-Chromophoric Tetracene as a Visible Light Harvester toward MOF-Based Photocatalytic CO2 Reduction in Water.

Integrating photoactive π-chromophoric guest molecules inside the MOF nanopore can result in the emergence of light-responsive features, which in turn can be utilized for developing photoactive materials with inherent properties of MOF. Herein, we report the confining of π-chromophoric tetracene (TET) molecules inside the nanospace of postmodified Zr-MOF-808 (Zr-MOF) with MBA molecules (MBA = 2-(5'-methyl-[2,2'-bipyridine]-5-yl)acetic acid) for effectively utilizing its light-harvesting properties toward photocatalytic CO2 reduction. The confinement of the TET molecules as a photosensitizer and the covalent grafting of a catalytically active [Re(MBA)(CO)3Cl] complex, postsynthetically, result in a single integrated catalytic system named Zr-MBA-TET-Re-MOF. Photoreduction of CO2 over Zr-MBA-TET-Re-MOF showed the evolution of 805 μmol g-1 CO with 99.9% selectivity after 10 h of continuous visible light irradiation in water without any additional sacrificial electron donor and having the apparent quantum efficiency of 1.3%. In addition, the catalyst demonstrated an appreciable activity even under direct sunlight irradiation in aqueous medium with a maximum production of 362.7 μmol g-1 CO, thereby mimicking artificial photosynthesis. Moreover, electron transfer from TET to the catalytic center was supported by the formation of photoinduced TET radical cation, as inferred from in situ UV-vis spectra, electron paramagnetic resonance (EPR) analysis, and transient absorption (TA) studies. Additionally, the in situ diffuse reflectance infrared Fourier transform (DRIFT) measurements support that the photoreduction of CO2 to CO proceeds via *COOH intermediate formation. The close proximity of the light-harvesting molecule and catalytic center facilitated facile electron transfer from the photosensitizer to the catalyst during the CO2 reduction.

Zn-doped NiO nanocomposites for efficient solar light-assisted wastewater treatment and its profound for low phytotoxic and antibacterial applications

The present research aims to eradicate methylene blue toxins (test effluent) in aquatic environments using photocatalytic Zn-doped NiO nanoparticles. Ultrasonic-assisted co-precipitation process was adopted to synthesize Zn-doped NiO nanoparticles. The prepared samples were characterized by XRD, SEM, in vitro antibacterial, phytotoxicity, and photocatalytic analysis. XRD patterns exhibited a solitary phase of Fm3m space-group-cubic-structured Zn-doped NiO crystallites with a preferred orientation along the (200) plane. SEM analysis explored the formation of nanorods with hexagonal ends. Zn-doped NiO is capable of rendering significant antibacterial efficacy against Staphylococcus aureus (MTCC 25923) and Escherichia coli (MTCC 25922) bacterial strains. Zn-doped NiO nanocomposites are appropriate for decomposing methylene blue (MB) contaminants in 120 minutes under direct sunlight irradiation. Hydroponically grown Vigna radiata seedlings and Mentha piperita L plants in dye-deprived water show minimal phytotoxicity and enhanced physiological aspects of plants. The outcome of the current research encouraged bringing new ideas for further utilization of textile MB effluent after photocatalytic treatment to non-domestic applications, such as irrigating roadside plants, public parks, and gardens.

Effective catalysts for wastewater treatment under sunlight: Gas dependent preparation of mesoporous biphasic N-doped TiO2 nanoparticles

Photocatalysts are playing an indispensable role in tackling environmental and energy crises; however, they are associated with poor solar energy utilization. In this study, N-doped titanium dioxide (N-TiO2) nanocrystals were successfully prepared using benign N-source, guanidine chloride by simple sol-gel technique. The significance of annealing gases environment (air, argon, and nitrogen) on their physicochemical properties and photocatalytic activity under direct sunlight irradiation was investigated. XRD and Raman data revealed that the crystal structure of spheroidal N-TiO2 nanocrystals was transformed from monophase anatase with less crystallinity in argon, and nitrogen to dual-phase anatase/rutile (A/R) with higher crystallinity in air. Importantly, XPS confirmed the successful incorporation of N in interstitial sites of the bare titania structure. Moreover, DRS and PL results revealed that the introduction of N into the TiO2 matrix not only led to a red shift towards visible-light but also lowered the bandgap energy (2.35 eV) and suppressed charge carriers recombination. BET showed a typical IV isotherm of mesoporous N-TiO2 nanomaterials with a high specific surface area in the range of 80–103 m2 g−1. Furthermore, their rhodamine B (RhB) photodegradation performance and thermal-stability were dictated by the annealing gas type. Nobly, the N-TiO2 prepared in air demonstrated the highest degradation performance (99%) with the fastest rate (0.0158 min−1) which is twice faster as the control TiO2 material. Its real textile wastewater removal was 63% and 56.5% COD and TOC, respectively. These improved performances are mainly attributed to its higher crystallinity, A/R mixed phase, aqueous-dispersion character, and lower recombination rate. Such gas driven-synthesis of photocatalysts has practical applications in designing other solar energy conversion systems.

Interfacial modulation of α-Ag1.82Cu0.09WO4 with high active BiOClxI1−x for boosting photocatalytic activity and degradation of emerging contaminants under direct sunlight

Removal of organic contaminants in wastewater using sunlight-driven photocatalysts has received significant attention in recent years. However, the rational design of photocatalysts to attain high light absorption, lower charge carrier recombination with efficient photocatalytic activity and good recycling capability is crucial for the practical photocatalysis process. Herein, solid-state Z-scheme BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 heterojunction is synthesized by assembling hierarchical 3D-BiOCl0.6I0.4 nanoflowers on cube-like 3D-α-Ag1.82Cu0.09WO4 surface through a hydrothermal method. A wide range of characterization techniques confirms the successful synthesis of BiOClxI1−x (0 ≤ x ≤ 1.0), α-Ag1.82Cu0.09WO4 and BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composites. The TC antibiotic removal efficiency of 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composite reaches 95.91% within 120 min under natural sunlight irradiation and the rate constant is 1.81 and 3.33 times higher than the pristine BiOCl0.6I0.4 and α-Ag1.82Cu0.09WO4, respectively. The optimized binary heterojunction exhibits excellent photocatalytic performance for toxic pollutants like MB (η = 97.27%) and RhB (η = 95.75%) under direct sunlight irradiation. The favorable photocatalytic activity of binary heterojunction is ascribed to enhancing the sunlight absorption range, the tight contact interface and the effective separation of electron/hole pairs. Notably, 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composite exhibits attractive recycling ability and good photostability for prolonged sunlight irradiation. Furthermore, the total organic carbon results also confirm that the 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 efficiently mineralized the model pollutants (TC antibiotic, MB and RhB) into other unharmful compounds under sunlight irradiation. In summary, this work offers an effective strategy to prepare solid-state Z-scheme heterojunction with favorable photocatalytic activity, which can increase wastewater purification efficiency.

Synthesis and characterization of quaternary GO/CoCrO3/SiO2/Ag2WO4Nanocomposite based on energy storage and photocatalytic applications

This paper embellished to present novel graphene oxide/cobalt chromium oxide/silicon dioxide/silver tungstate nanocomposite using urea as a reducing agent and tetraethylorthosilicate to enhance stability via hydrothermal approach along with modified hummer’s method, co-precipitation and sol–gel routes. The existence of oxygen, cobalt, chromium, carbon, silicon, silver, and tungsten are confirmed by the nanocomposite elemental composition whereas reduction in particle size up to 4.28 nm indicated by surface morphology. Nanocomposite material had an average crystallite size of 6.85 nm with band gap of 2.5 eV possessing zeta potential value of −16.9 mV. Peak intensity has decreased indicated by Pl spectra whereas FTIR confirms existence of functional groups. The material exhibited excellent electrochemical performance with a specific capacitance of 5124F/g and electrochemical active surface area of 0.02 cm2. The power density ranges from 2881.8 to 2117 W/kg and the energy density ranges from 117.6 to 160.1 Wh/Kg whereas charge transfer resistance value of 1.67 Ω results in electron rate constant 4.98 × 10-9 cms−1. Nanomaterial shows photocatalytic activity about 88.27% degradation efficiency achieved for methylene blue dye under direct sunlight irradiation for 180 min obtaining pseudo kinetics constant value of 1.43x10-2 min−1. Overall results suggest that the GO/CoCrO3/SiO2/Ag2WO4 nanocomposite material has promising potential as energy storage material for supercapacitors and as a photocatalytic material for environmental remediation.

Synthesis of Solar Light Active Reduced Graphene Oxide-ZnS Nanomaterial for Photocatalytic Degradation and Antibacterial Applications.

Good water quality is essential for life; therefore, decolorizing and detoxifying organic dye wastes (textile effluents) have gained immense environmental importance in recent years. Thus, the degradation of wastewater has become a potential need for our environment. This research aims to synthesize and investigate a ceramic-based nanomaterial catalyst for the degradation of dye solution under exposure to sunlight. A reduced graphene oxide-ZnS (rGO-ZnS) nanomaterial was qualitatively synthesized using a solvothermal method. The prepared nanomaterial was characterized using XRD, SEM, HR-TEM, EDX, XPS, and FT-IR techniques. The photocatalytic activity of the rGO-ZnS nanomaterial was checked using oxidative photocatalytic degradation of naphthol blue black dye (NBB) under direct sunlight irradiation. Here, the rGO/ZnS composite showed a significant photocatalytic performance to degraded NBB (93.7%) under direct solar light. Chemical Oxygen Demand (COD) measurements confirmed the mineralization of the dye. The influence of different radical scavengers on NBB degradation was studied. Optimum conditions for efficient degradation were determined. The antibacterial property of the prepared catalyst was studied.

Photo- or Electrochemical Cyclization of Dienes with Diselenides to Access Seleno-Benzo[b]azepines.

A cascade selenylation/cyclization of dienes with diselenides has been realized under visible-light irradiation or electrolysis conditions. Employing O2 or electricity as a "green" oxidant, this protocol provides a green and efficient method for an array of biologically important seleno-benzo[b]azepine derivatives in moderate to good yields. The direct sunlight irradiation and gram-scale reaction render the approach practical and attractive.

Interface engineering and photocatalytic properties of novel Bi4(V1.5Fe0.5O10.5)/g-C3N4 under direct sunlight irradiation

The development of heterostructured catalysts can reduce the recombination of photo-generated charge carriers and preserve the strong redox potential of a photocatalytic system, thus significantly enhancing photocatalytic performance. In the present study, a novel Aurivillius Bi4(V1.5Fe0.5O10.5)/g-C3N4 catalyst was prepared using a cost-effective method. The structural, morphological, compositional, and optical properties of the samples were characterized, verifying the formation of a Bi4(V1.5Fe0.5O10.5)/g-C3N4 interface. The prepared Bi4(V1.5Fe0.5O10.5)/g-C3N4 catalyst exhibited exceptional performance in the photocatalytic removal of the organic pollutants methylene blue and Rhodamine B under direct sunlight, removing 97.6% and 98.4%, respectively, over the test period, which was 1.49 and 1.36 times higher, respectively, than that achieved by g-C3N4 alone. The ability of the prepared catalyst to remove Ciprofloxacin, Amoxicillin, and 4-nitrophenol was also tested. The possible degradation pathways for the generated charge carriers were identified by determining the roles of intermediates such as •O2–, h+, and •OH. The stronger photocatalytic activity of the proposed catalyst was attributed to the high-quality interface between Bi4(V1.5Fe0.5O10.5) and g-C3N4, which allowed for efficient charge-carrier separation and maintained a high redox potential. The Bi4(V1.5Fe0.5O10.5)/g-C3N4 photocatalyst thus represents a new potential pathway for the production of high-quality photocatalysts.

Combined action of cerianite, uv and direct sunlight irradiation for the removal of violet crystal and methylene blue from aqueous solution

Combined action of cerianite, uv and direct sunlight irradiation for the removal of violet crystal and methylene blue from aqueous solution

Modeling of Solar Photocatalytic Degradation of Rhodamine B Dye by TiO2 Nanoparticles Using an Artificial Neural Network

AbstractAn artificial neural network (ANN) model was developed for the photocatalytic degradation of rhodamine B by TiO2 nanoparticles synthesized by the electrochemical method, under direct sunlight irradiation. The four inputs are: irradiation time, initial dye concentration, pH of the initial solution, and catalyst loading. The ANN model with 20 hidden neurons and with R2 of 0.999 shows minimum values of the performance metrics of 0.169, 2.020, 1.531, and 0.215 for the mean square error, the root mean square error, the mean absolute error, and the mean absolute percentage error, respectively. The optimized ANN configuration of 4‐20‐1 shows a good fit with the experimental data. The result shows that the sunlight irradiation time has the main impact on rhodamine B degradation at ∼55 %.

Recyclable waste Dry-cell batteries derived carbon dots (CDs) for detection of Two-fold metal ions and degradation of BTB dye

In modern era, electronic wastes are one of the major threats around us, most of them are reused with less efficiency instead of re-usage, and conversion into valuable products is highly recommended. In this work, we report an innovative approach for the synthesis of highly photoluminescent CDs from waste dry-cell batteries through one-step hydrothermal treatment for the detection and degradation of environmental pollutants. The as-prepared CDs were studied by X-ray photoelectron spectroscopy (XPS), HR-TEM studies, X-ray diffractometer (XRD), Raman spectrometer, FTIR spectroscopy, UV–visible spectrophotometer, and spectrofluorometric measurements. The calculated quantum yield for synthesized CDs was around 13 %. The CDs have uniform particle size distribution, strong photoluminescent behavior, and possess high stability against various environmental conditions. Also, CDs display the selective and sensitive detection of Cr6+ and Co2+ and ions with a detection limit of around 0.11 µM and 0.10 µM respectively. The possible mechanism of CDs was also examined. Moreover, the photocatalytic activity of CDs with Bromothymol Blue (BTB) dye was studied. The degradation efficiency of BTB dye can be achieved at around 84 % over 180 min under the irradiation of direct sunlight in presence of H2O2. To date, it’s the first time we have recycled waste dry-cell batteries into CDs as an effective probe for the detection and decomposition of environmental pollution. Furthermore, this work provides not only an easier route to make good quality and improved photoluminescent CDs from waste material like used batteries and also paves way for the reconversion of global treating waste. Finally, the outstanding detection capability with multiple properties of as-prepared CDs provides various environmental applications like the detection of pollutants and carcinogenic polluted water treatment.

Incorporating CdS and anchoring Pt single atoms into porphyrinic metal–organic frameworks for superior visible-light and sunlight-driven H2 evolution

Water splitting by photocatalytic semiconductors to produce hydrogen is considered one of the best ways to utilize solar energy. However, the recombination of electron-hole pairs in semiconductors such as cadmium sulfide (CdS) reduces the light-driven reaction efficiency. In addition, nanoparticles (NPs) of semiconductors tend to aggregate, resulting in decreased atom utilization. Rationally building composite photocatalysts by reducing nanoparticle aggregation and maximizing charge transport efficiency is thus seen as an attractive strategy for achieving high hydrogen evolution rates. Herein, we designed a new composite photocatalyst, CdS@PCN-222(Pt), by growing CdS in situ on a metal–organic framework (MOF) containing single Pt atoms. This catalyst exhibits an excellent hydrogen evolution activity of 71645 μmol/gCdS/h under visible light irradiation (λ ≥ 420 nm), which is around 110 times higher than pure CdS. Remarkably, CdS@PCN-222(Pt) also has an extremely high hydrogen evolution activity of 31326 μmol/gCdS/h under direct sunlight irradiation, far surpassing those of reported MOF-based photocatalysts. The charge-separation mechanisms were revealed by spectroscopic measurements, DFT calculations, and single crystal X-ray diffractions. The highly porous structure of PCN-222(Pt) results in the uniform distribution of CdS, and the anchored Pt single atoms achieve photo-induced electron transfer, inhibiting the recombination of photogenerated charge carriers. The results show that the synergistic effects between inorganic semiconductors and MOFs containing anchored single atoms enhance the photocatalytic activity for H2 generation under visible light and even sunlight. As a result, the findings offer important new perspectives that can be utilized in the design of high-performance composite photocatalysts in the future.

Green synthesis of zinc oxide nanoparticles using Brassica oleracea var. botrytis leaf extract: Photocatalytic, antimicrobial and larvicidal activity

Green synthesis of nanomaterials has emerged as an ecofriendly sustainable technology for the removal of dyes in the last few decades. Especially, plant leaf extracts have been considered as inexpensive and effective materials for the synthesis of nanoparticles. In this study, zinc oxide nanoparticles (ZnO NPs) were prepared using leaves extract of Brassica oleracea var. botrytis (BO) by co-precipitation and applied for photocatalytic/antibacterial activity. The synthesized BO-ZnO NPs was characterized by different instrumental techniques. The UV–vis Spectrum of the synthesized material showed maximum absorbance at a wavelength of 311 nm, which confirmed the formation of BO-ZnO NPs. The XRD pattern of BO-ZnO NPs represents a hexagonal wurtzite structure and the average size of particles was about 52 nm. FT-IR spectrum analysis confirms the presence of hydroxyl, carbonyl, carboxylic, and phenol groups. SEM images exhibited a flower like morphology and EDX spectrum confirming the presence of the elements Zn and O. Photo-catalytic activity of BO-ZnO NPs was tested against thiazine dye (methylene blue-MB) degradation under direct sunlight irradiation. Around 80% of the MB dye got degraded at pH 8 under 75 min of sunlight irradiation. Further, the study examined that the antimicrobial and larvicidal activity of BO-ZnO NPs obtained through green synthesis. The antimicrobial study results showed that the BO-ZnO NPs formed zones against bacterial pathogens. The results showed the formation of an inhibition zone against B. subtills (16 mm), S.aureus (13 mm), K. pneumonia (13 mm), and E. coli (9 mm) respectively at a concentration of 100 μg/mL of BO-ZnO NPs. The larvicidal activity of the BO-ZnO NPs was tested against the fourth instar of Culex quinquefasciatus mosquito larvae The LC50 and LC90 values estimated through the larvicidal activity of BO-ZnO NPs were 76.03, 190.03 ppm respectively. Hence the above findings propose the synthesized BO-ZnO NPs by the ecofriendly method can be used for various environmental and antipathogenic applications.

Study of phytotoxicity, remarkable photocatalytic activity, recycling process and energy consumption cost of TiO2 quantum dots photocatalyst for photodegradation of Coomassie brilliant blue R dye

The phytotoxicity experimental assessment revealed that the water used in the germination of Lycopersicon esculentum tomato seeds which was treated with TiO2 quantum dots, TDs1 (2.7 nm), TDs2 (3.1 nm) and TiO2 (Degussa) respectively, had no impact on the germination process. TiO2 quantum dots with a high BET Specific surface area of 462.3 m2/g for TDs1 (2.7 nm) and 338.22 m2/g for TDs2 (3.1 nm) were synthesized through the sol-gel method using TiCl4 in different polar solvents. The structure, shape, and size of the prepared TDs samples have been characterized by techniques such as XRD, FE-SEM, HRTEM, and EDX, confirming no additional phases or impurities in TDs. The optical band gaps of TDs samples were determined from their diffuse reflectance spectral data using Kubelka-Munk Equation. Photocatalytic activities of 91 and 89% were achieved in the mineralization of Coomassie brilliant blue R (CBBR), a model commercial dye, under direct sunlight and xenon lamp irradiation, respectively. The reactive species on the photodegradation mechanism for the TDs prepared samples were determined by different trapping agents. The photocatalytic activity of the TDs samples remained strong after eight repetitions with a Xenon photoreactor and direct solar light. The assessment of the photodegradation efficiency of CBBR dye in terms of its beneficial influence on energy consumption (EE/O) and price estimates has been reported.

Hydrothermally synthesized Ag-TiO2 nanofibers (NFs) for photocatalytic dye degradation and antibacterial activity

This work successfully utilised eco-friendly green synthesis to produce Ag–TiO2 nanofibers (NFs). As pollution and energy limitations have become global issues, there is an ongoing need to develop more effective catalysts through straightforward and environmentally friendly methods. The Ag–TiO2 nanofibers (NFs) XRD pattern exhibits an anatase TiO2 and FCC crystal structure of Ag nanoparticles. The SEM investigation revealed a nanofiber-like surface morphology. The Ag–TiO2 nanofibers (NFs) exhibits an optical band gap energy is 2.5 eV. Methylene blue (MB), malachite green (MG), Congo red (CR), and crystal violet (CV) dye aqueous solutions were used to evaluate the photocatalytic performance of the synthesized Ag-modified TiO2 nanofibers (NFs) under direct sunlight irradiation. The effects of catalyst size on the efficient breakdown of MB dye were also investigated. The optimum catalyst concentration was found to be at 0.02 mg/mL. At 120 min of direct sunlight, the highest photosynthetic degradation efficiency (DE percentage) of 94% was achieved for MB dye. Ag–TiO2 nanofibers (NFs) have been demonstrated to have exceptional antibacterial activity against Gram-positive bacteria such as Staphylococcus aureus and Gram-negative bacteria E-Coli. Because of these great qualities, it seems likely that the Ag–TiO2 nanofibers (NFs) made could be a great photocatalyst for getting dye pollutants out of wastewater.

Interface engineering of 0D–1D Cu2NiSnS4/TiO2(B) p–n heterojunction nanowires for efficient photocatalytic hydrogen evolution

The photocatalytic hydrogen production is one of the clean and renewable methods of converting solar energy to chemical fuels. Herein, an 0D/1D Cu2NiSnS4/TiO2(B) p-n heterojunction photocatalyst was prepared by a hydrothermal route. The FE-SEM, and HR-TEM analysis revealed that the 1D nanowire morphology of TiO2(B) was coated uniformly with Cu2NiSnS4 (CNTS) nanoparticles. With an average particle size of 5 nm, CNTS nanoparticles improved the interfacial contact and formed an efficient p-n heterojunction with TiO2(B), which greatly improved the charge carrier separation, as evident from the transient photocurrent, photoluminescence, and impedance spectroscopies. The optimized Cu2NiSnS4/TiO2(B) sample produced an average of 7144 µmol/g of hydrogen in 4 h of reaction time under direct sunlight irradiation, which is nearly five times higher than bare TiO2(B). Based on the Mott-Schottky and UV–visDRS spectra, a Z-scheme p-n junction charge transfer mechanism has been proposed.

Sun irradiated high efficient photocatalyst ZnO nanoparticles obtained by assisted microwave irradiation

In this research microwave assisted zinc oxide synthesis applied to methylene blue dye mineralization is reported. This technique strongly influences the presence of certain intrinsic defects that is similar to those obtained by techniques where a rich oxygen atmosphere is used. These defects play a strong role in photocatalysis, showing a short time (70 min) at 95.3 % efficiency in methylene blue degradation under direct sunlight irradiation. Through X-ray diffraction, crystallinity, and nanoparticle size (5 nm) were obtained, meanwhile the morphology and elemental composition was observed by Scanning Electron Microscopy and Energy-Dispersive X-ray respectively. Additionally, Ultraviolet–Visible and Photoluminescence methods complete the analysis letting calculate the band gap (3.5 eV) and the presence/contribution of intrinsic defects. Such defects are identified as direct and strong contributors to carrier’s concentration separation and alternatively provoking low recombination levels, which is a characteristic desired in organic materials mineralization.

Construction of p–n junction type Ag2O/SnO2 heterostructure photocatalyst for enhanced organic dye degradation under direct sunlight irradiation: Experimental and theoretical investigations

Construction of p–n junction type Ag2O/SnO2 heterostructure photocatalyst for enhanced organic dye degradation under direct sunlight irradiation: Experimental and theoretical investigations