Photodegradation Rate Research Articles

Green synthesis and characterization of titanium dioxide nanoparticles and their photocatalytic activity

In this study, we compared two low-temperature synthesis procedures for the large-scale production of titania nanoparticles (NPs). The first takes place in an aqueous medium with an acidic environment, by using a triblock polymer surfactant (Pluronic 123). The second involves a polycondensation reaction of alkoxide precursors at 70 °C in a water-in-oil (W/O) microemulsion with a volume ratio of 1:1, using cetylpyridinium bromide (CPB) as a cationic surfactant. The morphological and structural characterization of the samples was carried out through Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The photoactivity of the nanostructured titania was evaluated by measuring the photodegradation of Methylene Blue (MB). The solvent-free synthetic approach provided spherical titania nanoparticles mainly constituted by rutile crystallites with a very good synthetic yield. However, the photodegradation rate of MB for such titania nanoparticles ranges from 30 % to 40 %, after 1h under solar irradiation. Conversely, titania nanoparticles obtained through microemulsion synthesis show a photodegradation rate of more than 90 % comparable to titania P25. This high-yield synthesis leads to the formation of TiO2 nanoparticles characterized by small crystallite aggregates (rutile and anatase).

Synergetic photocatalytic degradation of the tetracycline antibiotic over S-scheme based BiOBr/CuInS2/WO3 ternary heterojunction photocatalyst

The present research investigated the photodegradation capability of a ternary BiOBr/CuInS2/WO3 heterojunction against the tetracycline (TC) antibiotic. BiOBr/CuInS2/WO3 heterojunction is formed using a straightforward physical mixing method, whereas pure photocatalysts (CuInS2, WO3) were synthesized hydrothermally and BiOBr by a coprecipitation process. The Field Emission Scanning Electron Spectroscopy examination validated the nanorod and nanosheet shape of the fabricated BiOBr-CuInS2-WO3. The photodegradation capabilities of the BiOBr-CuInS2-WO3 heterojunction were superior to those of other pure photocatalysts, and it followed the S-scheme charge transfer route as indicated by the band alignments. After 120 min of light irradiation, the BiOBr/CuInS2/WO3 S-scheme ternary heterojunction obtained a photodegradation rate of 98.9 %, much greater than other pure photocatalysts. According to electron spin resonance investigations and scavenging experiments, the radicals hydroxyl radicals (•OH), hole (h+), superoxide (•O2−) play a significant role in the photodegradation of TC. The ternary heterojunction's improved light absorption, lower recombination rate, and higher photocarrier separation rate were due to the fabrication of S-scheme heterojunction. The ternary BiOBr/CuInS2/WO3 photocatalyst's photodegradation efficacy was consequently enhanced. Investigations for photocatalyst reusability demonstrated its exceptional stability, with a 93.8 % degradation rate after five catalytic cycles.

Characterization and photocatalytic properties of zno tetrapods synthesized by high-temperature pyrolysis

The presented work presents the structural and morphological characterization and the results of studies of luminescent, photocatalytic properties of ZnO tetrapods synthesized by the method of high-temperature pyrolysis. It has been shown that the morphology and structural parameters of ZnO tetrapods are determined by the location in the synthesis zone (correlated with the distance from the air inflow window). All samples were characterized by pseudo-three-dimensional morphology of tetrapods. A correlation was found between luminescent properties and photocatalytic activity of tetrapods. The highest photodegradation rates of methylene blue under ultraviolet radiation were demonstrated by ZnO tetrapods grown in the zones closest and farthest from the window (rate constants 54 × 10–3 min–1 and 50 × 10–3 min–1, respectively).

Synergistic effects of Fe2O3 supported on dendritic fibrous SBA-15 for superior photocatalytic degradation of methylene blue

Environmental pollution caused by dye effluent has attracted much attention, and thus developing photocatalysts with superior photodegradation performance is an imperative task. A series of Fe supported on dendritic fibrous SBA-15 (Fe/DFSBA-15) catalysts with various Fe contents were prepared using a microemulsion coupled with ultrasonic-assisted impregnation methods. The findings revealed that the structural stability of DFSBA-15 was unaffected by the amount of Fe loaded. As the Fe loading increased, the size of Fe2O3 nanocrystals increased while the catalysts’ surface area decreased. The bandgap energy of the catalyst decreased with increasing Fe loading and became constant after reaching an optimal Fe loading of 10 wt%. The one-factor-at-a-time study revealed that 10Fe/DFSBA-15 degraded 94.72 % of methylene blue (MB) within 180 min at 1.5 g/L catalyst dosage, pH 8, and 10 mg/L of concentration, owing to Si-O-Fe coordination, modest Fe2O3 crystallite size, homogeneous metal distribution, slower recombination rate, and low bandgap energy. The advantageous features of 10Fe/DFSBA-15 resulted in accelerating the photodegradation rate, where 10Fe/DFSBA-15 is found as the optimal catalyst. The addition of Fe particles to the DFSBA-15 largely improved their photocatalytic activity toward MB degradation, making it a potential candidate for removing pollutants from aqueous solutions.

Construction of a novel multidimensional 1D/2D heterojunction FeVO4/In2S3 with significantly reinforced charge transport and excellent photocatalytic activity

Aiming at developing a highly efficient photocatalyst for the photocatalytic degradation of emerging contaminants, a novel 1D/2D heterojunction FeVO4/In2S3 was constructed by the in-situ growing of the small-sized In2S3 nanosheets on the rod-shaped FeVO4. The fabricated FeVO4/In2S3 was in detail characterized. The photodegradation of tetracycline (TC) in water was carried out for the evaluation of the photocatalytic performance of FeVO4/In2S3. Additionally, the photoinduced charge transfer mode at the interface of FeVO4/In2S3 was discussed. The prepared FeVO4/In2S3 exhibits exceptional photocatalytic capability for the elimination of TC. The optimum composite photocatalyst 20%FVO/IS displays the greatest activity, achieving a removal efficiency of 90 % toward TC in water. The photodegradation rate constant of TC by 20%FVO/IS is 0.01362 min−1, which is 3.98 and 2.87 folds that by FeVO4 and In2S3, individually. The significantly reinforced activity of FeVO4/In2S3 is attributed to the improved light-harvesting ability in the visible region and the considerably accelerated separation and transfer of the photo-excited carriers resulting from the formation of 1D/2D multidimensional heterostructure between FeVO4 and In2S3. Additionally, FeVO4/In2S3 displayed outstanding stability. Its photocatalytic activity decreased by only 6 % after four cycles of reuse. The predominant reactive species for TC degradation is superoxide radical, followed by holes. Furthermore, the transport pathway of the photoexcited charge carriers in FeVO4/In2S3 complies with the Type-II interfacial charge transfer mode. The prepared FeVO4/In2S3 is a potential photocatalytic material for the photodegradation of the contaminants in water environment.

Giant Photodegradation Rate Enabled by Vertically Grown 1T/2H MoS2 Catalyst on Top of Silver Nanoparticles

The exaltation of the photodegradation performance of dichalcogenide MoS2 grown on top of silver nanoparticles (Ag‐NPs) is reported on. The fabricated MoS2 nanosheets nucleate vertically from Ag‐NPs seeds, enabling the growth of both metallic and semiconductor phases 1T/2H‐MoS2. Findings reveal remarkable enhancement of the Raman scattering and an exceptional broadband optical absorption attributed to plasmonic effects induced by the presence of both metallic 1T‐MoS2 and Ag‐NPS at 2H‐MoS2 interfaces. To leverage this effect, photodegradation tests are conducted to remove methyl orange pollutant. Notably, results reveal a significant increase in photodegradation efficiency and rate constant, reaching up to 120% and 550% over pristine 2H‐MoS2, respectively. This finding underscores the role of Ag‐NPs and 1T‐MoS2 tandem to unlock the superior photodegradation properties of vertically aligned 2H‐MoS2 toward methyl orange, paving the way for the development of dichalcogenide‐based hybrid photocatalyst for wastewater treatment and environmental remediation.

Improved naphthalene photodegradation rate of CN/Pt-P25 photocatalyst by effectively tuning Pt chemical states via H2 secondary annealing

Photocatalytic technology holds promising prospects for remediating naphthalene pollution in water bodies. In this work, the CN/Pt-P25 photocatalyst was successfully prepared via photodeposition combined with co-pyrolysis methods, and employed for naphthalene photodegradation under simulated sunlight. The chemical state of Pt was found to have a significant impact on the photocatalytic activity. H2 secondary annealing effectively tuned Pt chemical states, increasing the proportion of Pt0 species on the CN/Pt-P25 photocatalyst from 41.91 % to 62.24 %. The improved proportion of Pt0 species proportion led to a reduction in the bandgap, which induced changes in the band positions and notably enhancing the separation efficiency of photogenerated electron-hole pairs. Under simulated sunlight irradiation, (H2) CN/Pt-P25 photocatalyst achieved complete naphthalene photodegradation within 100 min. Thus, photocatalysts containing a high proportion of Pt0 species exhibited an improved performance in naphthalene photodegradation. These findings provide new insights into the application of photocatalytic technology for the remediation of PAHs.

Exploring photocatalytic tetracycline removal performance under simulated sunlight irradiation: Milling time effect on metallic reduction of MnO/ZrO2 mixed oxide

In the present research, it is reported that ball milling technique can be applied to enhance the photocatalytic properties of MnO and ZrO2 metal oxide powders (MZOx) furthermore the fabricated photocatalyst can be used for the degradation of tetracycline (TTC). XRD analyses revealed that increasing the milling time resulted in the formation of a pure metallic Mn crystal phase, which boosted the antibiotic degradation rate. It was confirmed by SEM technique that the morphological structures of the particles were generally small and uniform. The band gap energy was calculated as 3.70 eV for the hybrid metal oxide. Additionally, the adsorptive and photoluminescence features were illuminated via DRS and PL analyses. The effect of milling time had a major impact on the photodegradation rate of TTC, and the 8 h milling sample (MZOx-8h) exhibited the highest catalytic degradation activity (79.4 %). Low photocatalytic activity was obtained at acidic pHs and increased at alkaline pHs. The presence of H2O2 sharply decreased photocatalytic process time (60 min) and 94.3 % of the TTC was degraded at 7.5 mM H2O2. The photocatalytic degradation process proceeded through superoxide radicals and was supported by holes. The stability of MZOx-8h almost remained constant (70.02 %) even after seven cycles. It was determined that the presence of oxalic acid positively affected the progress of TTC degradation reactions. Further, practical application areas were investigated and MZOx-8h doped on support materials was found to be suitable for such applications in proportion to the doping ratio. Finally, it was demonstrated that MZOx-8h exhibited remarkable performance in photocatalytic reactions of different types of organic pollutants. The synergistic nature of MnO and ZrO2 with the contribution of ball milling time effect resulted in high photocatalytic activity.

Preparation of Functionalized Ethylene-Vinyl-Alcohol Nanofibrous Membrane Filter for Rapid and Cyclic Removing of Organic Dye from Aqueous Solution.

A functionalized ethylene-vinyl-alcohol (EVOH) nanofibrous membrane (NFM) was fabricated via co-electrospinning H4SiW12O40 (SiW12) and EVOH first, and then grafting citric acid (CCA) on the electrospun SiW12@EVOH NFM. Characterization with FT-IR, EDX, and XPS confirmed that CCA was introduced to the surface of SiW12@EVOH NFM and the Keggin structure of SiW12 was maintained well in the composite fibers. Due to a number of carboxyl groups introduced by CCA, the as-prepared SiW12@EVOH-CCA NFM can form a high number of hydrogen bonds with CR, and thus can be used to selectively absorb congo red (CR) in aqueous solutions. More importantly, the CR enriched in the NFM can be rapidly degraded via photocatalysis. SiW12 in the NFM acted as a photocatalyst, and the hydroxyl groups in the NFM acted as an electron donor to accelerate the photodegradation rate of CR. Meanwhile, the SiW12@EVOH-CCA NFM was regenerated and then exhibited a relatively stable adsorption capacity in five cycles of filtration-regeneration. The bifunctional nanofibrous membrane filter showed potential for use in the thorough purification of dye wastewater.

Metaheuristic optimization algorithms-based prediction modeling for titanium dioxide-Assisted photocatalytic degradation of air contaminants

Airborne contaminants pose significant environmental and health challenges. Titanium dioxide (TiO2) has emerged as a leading photocatalyst in the degradation of air contaminants compared to other photocatalysts due to its inherent inertness, cost-effectiveness, and photostability. To assess its effectiveness, laboratory examinations are frequently employed to measure the photocatalytic degradation rate of TiO2. However, this approach involves time-consuming requirements, labor-intensive tasks, and high costs. In literature, ensemble or standalone models are commonly used for assessing the performance of TiO2 photocatalytic degradation of water and air contaminants. Nonetheless, the application of metaheuristic hybrid models has the potential to be more effective in predictive accuracy and efficiency. Accordingly, this research utilized hybrid machine learning (ML) algorithms to estimate the photo-degradation rate constants of organic air pollutants using TiO2 nanoparticles and exposure to ultraviolet light. Six metaheuristics optimization algorithms, namely, nuclear reaction optimization (NRO), differential evolution algorithm (DEA), human felicity algorithm (HFA), lightning search algorithm (LSA), Harris hawks algorithm (HHA), and tunicate swarm algorithm (TSA) were combined with random forest (RF) technique to establish the hybrid models. A database of 200 data points was acquired from experimental studies for model training and testing. Furthermore, multiple statistical indicators and 10-fold cross-validation were employed to examine the established hybrid model's accuracy and robustness. The TSA-RF model demonstrated superior prediction accuracy among the six suggested models, achieving an impressive correlation (R) of 0.90 and a lower root mean square error (RMSE) of 0.25. In contrast, the HFA-RF, HHA-RF, and NRO-RF models exhibited a slightly lower R-value of 0.88, with RMSE scores of 0.32. The DEA-RF and LSA-RF models, while effective, showed a marginally lower R-value of 0.85, with RMSE values of 0.45 and 0.44, respectively. Moreover, the SHapley Additive exPlanation (SHAP) results indicated that the degradation rates of air contaminants through photocatalysis were most notably influenced by factors such as the reactor sizes, photocatalyst dosage, humidity, and intensity.

Lanthanum anchored NiCo2S4 nanocomposite and their structural, optical, and enhanced photodegradation of Indigo Carmine (InC) dye

The focus of this study is to explore the potential of lanthanum-anchored NiCO2S4 (L-NCS) as a photocatalyst for Indigo carmine (InC) dye under visible radiation. Different analytical techniques including XRD, SEM, TEM, and PL were used to confirm the uniform distribution of lanthanum on NiCO2S4. A study of the optical and photochemical properties of L-NCS revealed a reduction in charge carrier recombination and an increase in visible light sensitivity due to the introduction of soft metal dopants into NCS. The optimized L-NCS catalyst showed a significant increase in photodegradation rate, about 7.2 times higher than that of pure NCS when exposed to visible light. Furthermore, the reproducibility of L-NCS shows excellent stability as a photocatalyst for environmental remediation.

Innovative chelation strategies for facile synthesis of bimetallic nanomaterials with remarkable photocatalytic and biochemical activities

Biological and chemical chelations of nanoparticles are becoming increasingly popular due to their low cost and absence of harsh chemicals. In this study, palladium-nickel nanoparticles (PdNi NPs) were synthesized using a semi-organic auto-chelation method with Glycyrrhiza glabra L. plant as a biological chelating agent and oxalic acid (OA) for chemical chelation. The aim was to compare biological chelation and chemical chelation. The synthesized NPs were then compared for their photocatalytic and antibacterial applications. The nanomaterials synthesized for each method were analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and UV–VIS spectroscopy. The particle size of NPs synthesized with OA from the obtained structures was calculated as 22.48 nm. At the same time, the antibacterial activities of the acquired NPs against Escherichia coli and Staphylococcus aureus were evaluated. The results showed that NPs obtained by different synthesis methods provided 99.9 % inhibition against Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) within 24 h. Additionally, the photocatalytic effects of PdNi NPs on the removal of methylene blue (MB) dye were assessed. Furthermore, the photocatalytic activity towards MB was similar in the nanoarchitectures obtained with both chelation agents. When biological and chemical chelation were compared after 90 min under sunlight, photodegradation rates were found to be approximately 50 % the same. The obtained results demonstrated that PdNi NPs synthesized using biological agents yielded similar outcomes in photocatalytic and antibacterial applications when compared to PdNi NPs synthesized using chemical agents. The findings provide evidence that NP synthesis with favorable characteristics can be accomplished without the requirement of chemical agents, showcasing the feasibility of a cost-effective and eco-friendly synthesis.

Synthesis of CoMnFe2O4 hollow microstructure decorated GO for photocatalytic degradation of organic dyes

Over the past decade, safeguarding marine life and aquatic ecosystems against deleterious dye pollutants has emerged as a paramount concern. Methylene blue dye stands out as one such pollutant capable of inflicting irreversible damage to marine ecosystems even at minute concentrations. Addressing this pressing issue, we synthesized a novel CoMnFe2O4/graphene oxide nanocomposite employing a microwave-ultrasonic method. This composite, comprising soft superparamagnetic CoMnFe2O4 hollow microstructures integrated onto graphene oxide surfaces, revealed a mesoporous structure with a notably high surface area, which was about 96.4654 m2.g−1. Various analytical techniques were employed to scrutinize the crystal structure, functional groups, surface chemical composition, and morphologies of the synthesized CoMnFe2O4/graphene oxide nanocomposite (X-ray diffraction, Fourier-Transform Infrared Spectroscopy, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy). The CoMnFe2O4 crystal phase appears to be cubic in the X-ray diffraction with a 28.91 nm Avg. crystallite size. The measured band gap energies for the CoMnFe2O4, graphene oxide, and CoMnFe2O4/graphene oxide nanocomposite are 2.23 eV, 2.90 eV, and 1.89 eV, respectively. Remarkably, under visible light irradiation, the nanocomposite exhibited an impressive degradation efficiency of 97.54 % within just fifty minutes (at pH = 7, Methylene blue conc. = 15 mg/L, and catalyst dose = 0.05 g.), attributed to a photo degradation rate constant (k value) reaching 0.07330 min−1. Notably, this efficiency nearly doubled with the introduction of H2O2 peroxide. The outstanding recyclability of the CoMnFe2O4/graphene oxide nanocomposite, sustaining optimal performance over four cycles without significant degradation, underscores its potential for long-term environmental remediation efforts. Moreover, its magnetic extractability from contaminated solutions enhances its suitability for advanced environmental applications.

Enhanced photocatalytic degradation of methylene blue dye using CuO nanoparticles from the fruit extracts of Diplocyclos palmatus (L) C. Jeffrey for wastewater remediation

ABSTRACT The degradation of synthetic organic dyes through photocatalysis requires structured nanoparticles (NPs). Copper oxide (CuO) NPs were used as the newest developed catalyst for the organic dye degradation under the irradiation of sunlight: The metal oxide NPs were synthesized using the fruit extract of Diplocyclos palmatus (L) C. Jeffrey. UV–visible light spectra showed an absorption band for CuO NPs at 277 nm. X-ray diffraction confirmed the monoclinic phase of CuO NPs. Scanning electron microscopy confirmed rod-shaped stacked particles. Energy-dispersive X-ray spectra indicating the presence of Cu in oxide form. For the degradation of methylene blue dye (MB), CuO NPs were used as photocatalyst for dye degradation under sunlight irradiation. This study confirmed the effects, such as irradiation time, concentration, pH, and catalyst dosage. The CuO NPs showed high photocatalytic degradation, degrading 90% of the dye in 120 min. The increased degradation of dye was observed on exposure to longer irradiation time. The increased concentration of dye resulted in a decreased rate of photodegradation. 95% degradation achieved at pH 9 showing that the pH medium also enhances the degradation. A higher dye degradation percentage was achieved by increasing the higher catalyst dosage of 0.013 g degraded 93% of dye. Thus in the treatment of wastewater containing pollutants, the synthesized CuO NPs acted as an efficient photocatalyst.

A simple method to prepare and characterize ZnO/V2O5 nanostructure thin films for photoelectrochemical and photocatalytic uses in visible light

In this research, we investigated the enhancement of the photocatalytic efficiency of ZnO nanorods by incorporating vanadium pentoxide (V2O5). Zinc oxide (ZnO) nanorods were initially prepared by the chemical bath deposition (CBD) method. Subsequently, vanadium pentoxide (V2O5) nanoparticles, produced by laser ablation, were deposited onto the ZnO nanorods via drop casting. Scanning electron microscopy (SEM) images verified that ZnO grew in the morphology of nanorods and nanotubes, while V2O5 exhibited the structure of tree leaves and nanoparticles. The XRD technique was used to investigate the crystalline structure of the produced ZnO/ V2O5 nanostructure. The high band gap in ZnO limits the efficiency of photocatalysis under visible light. Building a core–shell structure with materials such as V2O5 can boost their performance in such conditions. The prepared samples appeared photodegradation rate of the MB dye reached 39% after 9 h of exposure to visible light. The photoelectrochemical cell measurement of the prepared ZnO/ V2O5 nanostructures demonstrated a positive response to light and achieved a relatively high photoconversion efficiency of 0.084% at 0.35 V, surpassing the results of earlier investigations. The M-S analysis revealed that the ZnO/ V2O5 nanostructure thin films exhibited n-type conductivity, characterized by a negative flat band potential VFB.

Tuning Stark effect by defect engineering on black titanium dioxide mesoporous spheres for enhanced hydrogen evolution

Defects can strongly affect the lattice, strain, and electronic structures of nanomaterials photocatalysts, like a double-edged sword of both positive significance and negative influence on photocatalytic performances. To date, most studies into defects only partially elucidated their beneficial or detrimental roles in photocatalysis. However, a quantitative understanding of the photocatalytic performances modulated by defect concentration still needs to be discovered. Here, a series of TiO2−X mesoporous spheres (MS) with different oxygen vacancy concentrations for photocatalytic applications were prepared by high-temperature chemical reduction. The link between oxygen vacancy concentration and photocatalytic performance was successfully established. The localization of carriers dominated by the Stark effect is first enhanced and then weakened with increasing oxygen vacancy concentration, which is a crucial factor in explaining the double-edged sword role of defect concentration in photocatalysis. As the reduction temperature rises to 300 °C, carrier localization dominated by the quantum-confined Stark effect maximizes the separation ability of photo generated electron hole pairs, thus exhibiting the best catalytic performance for photocatalytic hydrogen production and the degradation of organic pollutants, as demonstrated by a hydrogen evolution rate of 523.7 µmol g-1 h-1 and a ninefold higher RhB photodegradation rate compared to TiO2 MS. The work offers excellent flexibility for precisely constructing high-performance photocatalysts by understanding vacancy engineering.

Formulation of Polymeric Micelles to Increase the Solubility and Photostability of Caffeic Acid.

Caffeic acid (CA), a hydrophobic polyphenol with various pharmacological activities, exhibits a low aqueous solubility and sensitivity to light. In order to improve its chemical properties and overcome the limits in its application, the compound was loaded in P123 micelles (MCs) prepared using two polymer concentrations (10 and 20% w/w, MC10 and MC20). The micelles were characterised in terms of the size distribution, zeta potential, drug encapsulation efficiency, rheology, and cumulative drug release. Micellar formulations exhibited sizes in the range of 11.70 and 17.70 nm and a good polydispersion, indicating the formation of relatively small-sized micelles, which is favourable for drug delivery applications. Additionally, the stability and antioxidant profiles of the free CA and the CA loaded in micelles were studied. The results obtained on the free CA showed the formation of photodegradation products endowed with higher DPPH scavenging activity with respect to the pure compound. Instead, it was found that the incorporation of CA into the micelles significantly increased its solubility and decreased the photodegradation rate. Overall, the results indicate the successful formation of P123 micelles loaded with CA, with promising characteristics such as a small size, good encapsulation efficiency, sustained release profile, and improved light stability. These findings suggest the potentiality of these micelles as a delivery system for CA, thus enhancing its bioavailability.

Effective sunlight photodegradation of methylene blue dye using zinc oxide doped with mono- and bi-metals of Ag and Ce

Nanosized spherical particles of pure ZnO and their doped ZnO photocatalysts with mono- or bi- Ag and Ce-metal oxides at different weight portions (i.e., 2 and 4 wt%) through the sol-gel route followed by a calcination at 500 °C for 2 h were employed for exploring the photodegradation of methylene blue (MB) dye under direct sunlight. The produced photocatalysts were characterized by X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) surface area, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), fourier transform infrared (FTIR), and UV-Vis diffuse reflectance spectroscopy (DRS). XRD patterns confirmed the formation of hexagonal wurtzite polycrystalline structure of ZnO with good crystallinity. Bi-doped ZnO photocatalysts with smaller particle sizes showed efficient improving in the photocatalytic activity of ZnO under direct sunlight irradiation. The enhanced photodegradation performance of doped samples could be attributed to the reduction in the crystallite size and band gap, as well as the presence of excess oxygen vacancies and Zn interstitial sites in the nanoparticles obtained. The calculated band gap of pure ZnO decreased from 3.07 to 2.79 eV for 2 %Ag-4 %Ce/ZnO. This doped sample degraded the MB dye completely at 60 min, whereas pure ZnO exhibited 100 % degradation of MB at 180 min. Moreover, 2 % Ag-4 %Ce/ZnO photocatalyst has the highest kinetic rate of photodegradation as compared to other samples over two initial concentrations of MB dye (0.09667 min−1 at Co= 10 mg/L and 0.04433 min−1 at Co= 20 mg/L). Hence, the obtained 2 % Ag-4 % Ce doped ZnO showcased the superb breakdown of MB dye under sunlight irradiation for positioning it as a promising material for water remediation.

Enhanced Photocatalytic Performances of SnS2/TiO2 Composites via a Charge Separation Following Z-Scheme at the SnS2/TiO2{101} Facets

The formation of heterojunctions for efficient charge separation has been practiced for the preparation of efficient semiconductor-based photocatalysts for applications such as hydrogen production and environmental remediation. In this study, we synthesized a composite structure with a heterojunction between SnS2 and TiO2 through a microwave-assisted hydrothermal process, in which SnS2 nanoparticles grew on nanocrystalline TiO2 nanosheets preferentially at the exposed {101} facets. Appropriate exposure of the {001} and {101} facets of the TiO2 nanosheet in the composite with a preferential growth of SnS2 nanoparticles at the {101} facets was the origin of the charge separation following a direct Z-scheme mechanism to result in enhanced photocatalytic performances in photodegradation of organic dyes such as methylene blue (MB) and rhodamine B (RhB) compared to that of SnS2 and TiO2 alone. A plot of photodegradation rates vs. SnS2 ratios in the composites gave an overall volcano-shaped curve with a maximum at the SnS2 ratio of about 33% at which small SnS2 nanoparticles were populated at the {101} facets of the TiO2 nanosheets with a high surface area (118.2 m2g−1). Our results suggest the microwave-assisted hydrothermal process can be a good synthetic approach for composite-based photocatalysts with a preferential heterojunction structure.

Highly efficient Bi/BiOCl with oxygen vacancies photocatalyst with synergetic effects of oxygen vacancy, surface plasmon resonance, and electron sink effects of metallic Bi

Bi/BiOCl with oxygen vacancies composite was synthesized through a facile and rapid in situ surface reduction of BiOCl, utilizing NaBH4 as the reductant. The reduction process yielded metallic Bi nanoparticles on the surface of BiOCl and meanwhile created the oxygen vacancies within the BiOCl lattice. As a consequence, the as‐synthesized Bi/BiOCl composites exhibited a substantially enhanced visible‐light absorption capacity, whereas pure BiOCl was only responsive to ultraviolet light. Additionally, the Bi/BiOCl composite demonstrated a markedly accelerated photodegradation rate of Rhodamine, exceeding that of pure BiOCl and P25 by a factor of 6.10 and 19.74, respectively. The density functional theory (DFT) calculation was carried out to estimate the band structural and electronic properties of samples. Based on systematic analysis, the underlying mechanism was attributed to the extended responsive light range due to the surface plasma resonance of metallic Bi and the formation of oxygen vacancy energy level. Moreover, the electron sink effect of Bi nanoparticles was found to suppress the recombination of photoinduced charges, further contributing to the enhanced photocatalytic performance of Bi/BiOCl.