Photocatalytic Reaction Rate Constant Research Articles

Mn doping and core-shell engineering of silane-modified Mn-TiO2@SiO2 nanoparticles with drastically reduced photocatalytic activity for transparent UV-shielding hybrid materials

The photocatalytic ability and incompatibility with the organic matrix of TiO2 limit its application in UV-shielding hybrid materials. Tuning the electronic structure and engineering the morphology of TiO2 are effective in reducing photocatalytic activity but remain challenging in drastic reduction. Herein, a Mn-TiO2@SiO2 structure with an average size of 24.4 nm is constructed via a combination strategy of Mn doping and core–shell engineering to accelerate the recombination of carriers and build surface barriers. Impressively, compared with pure TiO2, the 2 %Mn-TiO2@SiO2 shows 336, 447, and 237 times lower photocatalytic reaction rate constants (k) for the degradation of three dyes (reactive red 120, methyl orange, and methyl blue), respectively, demonstrating the drastically reduced photocatalytic activity of Mn-TiO2@SiO2 structure. The characterizations and density functional theory calculations reveal that Mn doping introduces an occupied deep level and an unoccupied shallow level, which facilitates the co-trapping of electrons and holes, accelerating the recombination of carriers, and the SiO2 shell serves as a barrier to mitigate the interfacial charge transfer. Additionally, surface modification using silanes enables monodisperse core–shell structure and improves its compatibility with substrates, providing the UV-shielding Mn-TiO2@SiO2-C12 silane/fluorocarbon hybrid coatings with high transparency and anti-UV aging ability.

Boosting bulk photocharge separation and transfer in heterojunctions for antibiotics removal: Enhanced internal electric field and interfacial electric field

The electric fields created by semiconductor heterojunctions often only separated photogenerated charges at component interface, not sufficiently inhibiting carriers’ recombination in their bulk phases. Herein, we introduced the enhanced bulk internal electric field into BixOyIz/g-C3N4 heterojunction, constructing a dual electric field structure through in-situ precipitation and calcination to boost photocharge separation and transfer at both the interface and the bulk. The interfacial electric field created by heterojunction boosted the photocharge separation, and the enhanced internal electric field resulting from iodine reduction improved the bulk charge dynamics of BixOyIz. The dual electric field endowed BixOyIz/g-C3N4 with high photocatalytic activity and broad application potential. Specifically, the photocatalytic reaction rate constants of BixOyIz/g-C3N4 calcined at 460 °C for tetracycline removal reached 0.024 min−1, which was 3.42 times higher than that of BiOI/g-C3N4. The electron paramagnetic resonance (EPR) and scavenging experiments proved that ·O2− was the predominant active species in oxidizing tetracycline. The experiments on simulated real water showed that BixOyIz/g-C3N4 has a broad range of pH applicability, strong resistance to anionic interference, and good cycling performance. This work provided new insights for inhibiting bulk phase photocharge recombination of individual components in heterojunctions.

Facile synthesis of ZnO/halloysite nanotube composite with greatly enhanced photocatalytic performance

ZnO/halloysite nanotube composites (ZH-X, X = 10, 30, 40, 50, 70), with different mass ratio of ZnO to halloysite nanotubes (HNTs), were fabricated successfully via a facile wet chemical technique in anhydrous ethanol under a mild reaction condition. ZnO nanoparticles about 9 nm in size were inhibited from agglomeration and loaded homogeneously on the surface of HNTs. The microstructure, specific surface area, light absorption ability, photocatalytic performance, etc. of the ZH-X composites varied with the mass ratio of ZnO to HNTs. All ZH-X composites displayed better photocatalytic performance than pure ZnO sample did. With the increasing of ZnO content, the photocatalytic activity of ZH-X composite toward degrading methylene blue (MB) solution strengthened gradually and reached the maximum by ZH-40 composite (with ZnO content of 28.57 wt%), then decreased step by step. ZH-40 (0.05 g) removed 99.88% of MB (100 mL, 15 mg/L) after adsorption in dark and then photocatalytic degradation for 60 min, and whose photocatalytic reaction rate constant was 5.73 times that of pure ZnO. The enhanced photocatalytic efficiency of ZH-40 composite was attributed to the interfacial effect of ZnO and HNTs as well as the dispersed ZnO nanoparticles, which maintained the adsorption ability of HNTs and improved the separation and migration of photo-generated electron and hole pairs. This work provides a feasible method for loading photocatalyst on clay mineral to realize efficient photocatalysis.

Biomass derived graphene like material supported Fe2O3 heterophase junction and the removal performance for phenol

Fe2O3@NC composites with different crystal forms were prepared in situ derived from biomass and Fe(NO3)3 by one-pot synthesis. In the process, biomass played important role in guiding the formation of γ-Fe2O3 beside the source of the graphene like nanosheets including N, C, O elements (NC). When the mass ratio of biomass and Fe(NO3)3 is proper, both of α- Fe2O3 and γ-Fe2O3 nanoparticles with the size of 3–10 nm deposit simultaneously on the graphene like nanosheets, forming uniform Fe2O3@NC nanosheets with the thickness of 15–30 nm. The specific area of Fe2O3@NC composite is improved drastically due to the synergistic effect between Fe2O3 nanoparticles and the graphene like nanosheets, resulting in the improvement of adsorption performance. The graphene like nanosheets as supporter of Fe2O3 nanoparticles enhance the separation and transfer of electrons and holes due to its good conductivity. On the other hand, the photoinduced electrons and holes could be separated and transferred quickly due to the effect of α-γ-Fe2O3 phase junction. Under the dual effects, the photocatalytic reaction rate constant of Fe2O3@NC composite with α-Fe2O3 and γ-Fe2O3 reaches to 1.44 × 10−3 L⋅ mg−1⋅ min−1, exhibiting far higher than pure Fe2O3 and Fe2O3@NC composite with single crystal form. Moreover, Fe2O3@NC composite could be recovered by magnet owing to the strong magnetism property of γ-Fe2O3, exhibited good reusability after five cycles by magnet recovery.

Superoxide radical induced redox processes for simultaneous reduction of Cr (VI) and oxidation of ciprofloxacin in wastewater

Simultaneous removal of antibiotics and heavy metals from the wastewater is still a sophisticated task with great challenge. Interestingly, •O2- as a long-lived and highly active specie can simultaneously remove antibiotics and heavy metals. Herein, we design a S-type heterojunction photocatalyst, which can efficiently generate •O2-. Characterizations and DFT calculation demonstrate that internal electric field provides powerful propulsion for migration of photo generated carriers between Zn0.78Cd0.22S and g-C3N4, effectively extends electronic life, thereby enhances the production of •O2-. Photocatalytic reaction rate constants under optimal composite ratio conditions were 3.1-times (ciprofloxacin) and 5.9-times (Cr (VI)) higher than Zn0.78Cd0.22S under the coexisting pollutant system. Benefiting from the inbuilt electric field to stimulate electron transfer and utilization as well as the dual function of •O2-, it reveals the possibility of practical wastewater treatment in the internal circulating fluidized bed reactor.

Machine learning analysis to interpret the effect of the photocatalytic reaction rate constant (k) of semiconductor-based photocatalysts on dye removal

Photocatalytic reactions with semiconductor-based photocatalysts have been investigated extensively for application to wastewater treatment, especially dye degradation, yet the interactions between different process parameters have rarely been reported due to their complicated reaction mechanisms. Hence, this study aims to discern the impact of each factor, and each interaction between multiple factors on reaction rate constant (k) using a decision tree model. The dyes selected as target pollutants were indigo and malachite green, and 5 different semiconductor-based photocatalysts with 17 different compositions were tested, which generated 34 input features and 1527 data points. The Boruta Shapley Additive exPlanations (SHAP) feature selection for the 34 inputs found that 11 inputs were significantly important. The decision tree model exhibited for 11 input features with an R2 value of 0.94. The SHAP feature importance analysis suggested that photocatalytic experimental conditions, with an importance of 59%, was the most important input category, followed by atomic composition (39%) and physicochemical properties (2%). Additionally, the effects on k of the synergy between the metal cocatalysts and important experimental conditions were confirmed by two feature SHAP dependence plots, regardless of importance order. This work provides insight into the single and multiple factors that affect reaction rate and mechanism.

Characterization of ZnO/rGO Nanocomposite and Its Application for Photocatalytic Degradation

Zinc oxide (ZnO) nanorods (NRs) with reduced graphene oxide (rGO) were successfully synthesized using a hydrothermal method with an additional spray coating. This paper focuses on the effect of rGO coating on charge transfer and interaction between ZnO and rGO that remarkably contributes to the enhancement of the electrical and optical properties of ZnO-based NRs. The synthesized ZnO/rGO nanocomposite was characterized using FESEM, PL spectroscopy and XPS. FESEM analysis results showed that the surface morphology of the synthesized NRs had a hexagonal rod structure covered with rGO layers on the tip of the rod. The Tauc Plot analysis revealed that the rGO layers reduced the bandgap of ZnO NRs from 3.25 eV to 3.17 eV, where the light absorption increased. The chemical composition, electronic state, and interactions between the elements in the ZnO NRs/rGO nanocomposites were investigated using XPS. The presence of oxygen species due to the rGO deposition layers is indicated by the shift of the peak position toward a greater binding energy. The hybridization of this semiconductor and graphene material reduced the bandgap and lowered the PL emission. Finally, the photocatalytic activity of ZnO NRs/rGO has been studied for methylene blue degradation via oxidation. The results showed that the photocatalytic reaction rate constant of ZnO NRs/rGO > pristine ZnO NRs.

Single-Crystal Ferroelectric-Based (K,Na)NbO3 Microcuboid/CuO Nanodot Heterostructures with Enhanced Photo-Piezocatalytic Activity.

Developing single-crystal-based heterostructured ferroelectrics with high-performance photo-piezocatalytic activity is highly desirable to utilize large piezopotentials and more reactive charges that can trigger the desired redox reactions. To that end, a single-crystal-based (K,Na)NbO3 (KNN) microcuboid/CuO nanodot heterostructure with enhanced photo-piezocataytic activity, prepared using a facile strategy that leveraged the synergy between heterojunction formation and an intense single-crystal-based piezoelectric effect, is reported herein. The catalytic rhodamine B degrading activity of KNN/CuO is investigated under light irradiation, ultrasonication, or co-excitation with both stimulations. Compared to polycrystalline KNN powders and bare KNN single-crystals, single-crystal-based KNN/CuO exhibits a higher piezocurrent density and an optimal energy band structure, resulting in 5.23 and 2.37 times higher piezocatalytic degradation activities, respectively. Furthermore, the maximum photo-piezocatalytic rate constant (≈0.093 min-1 ) of KNN/CuO under 25min ultrasonication and light irradiation is superior to that of other KNN-based catalysts, and 1.6 and 48.6 times higher than individual piezocatalytic and photocatalytic reaction rate constants, respectively. The excellent photo-piezocatalytic activity is attributed to the enhanced charge-carrier separation and proper alignment of band structure to the required redox levels by the appropriate p-n heterojunction and high piezoelectric potential. This report provides useful insight into the relationships between heterojunctions, piezoelectric responses, and catalytic mechanisms for single-crystal-based heterostructured catalysts.

Unraveling charge transfer pathways and mechanisms in visible-light-responsive Bi4O5I2/GO/Bi2Sn2O7 all-solid-state Z-scheme heterojunction photocatalysts for high-efficiency antibiotic degradation

An all-solid-state Z-scheme Bi4O5I2/GO/Bi2Sn2O7 (BI41/1.5GO/BS41) ternary heterojunction was constructed by hydrothermal-ultrasonic assisted aqueous precipitation-heat treatment method. Taking the degradation effect of tetracycline hydrochloride (TC-HCl) as a reference, the BI41/1.5GO/BS41 composite catalyst exhibits the best photocatalytic performance, and its photocatalytic reaction rate constant is 3.82 that of Bi2Sn2O7. When the dosage of BI41/1.5GO/BS41 was 0.8 g/L, the degradation rate of TC-HCl solution with initial concentration of 15 mg/L was 90.31 % (pH=8) under visible light irradiation for 120 min. Moreover, the BI41/1.5GO/BS41 also has excellent salt tolerance, universality and recycling stability. The free radical capture experiments and electron paramagnetic resonance (EPR) tests found that •O2 and h+ were the main active substances for photocatalytic degradation of TC-HCl. The characterization results show that the improvement of photocatalytic performance of BI41/1.5GO/BS41 is due to the successful construction of all-solid-state Z-scheme heterojunction with graphene oxide (GO) as an electron transport medium, which not only reduces the transfer resistance of photogenerated electrons but also improves the separation efficiency of photogenerated carriers. Finally, the TC-HCl solution after visible light degradation was detected by the liquid chromatography mass spectrometry (LC-MS), and the possible intermediate products and degradation pathways were speculated. This work provides a new perspective on the application of all-solid-state Z-scheme heterojunction photocatalysts to environmental remediation.

Solution combustion synthesis of novel PrFeO3/CeO2 nanocomposite with enhanced photo-Fenton activity under visible light

In this study, we successfully synthesized PrFeO3/CeO2-based nanocomposites with different mass contents of СeO2 (0–18 wt%) via solution combustion with subsequent heat treatment in air. The results of EDXS and PXRD confirmed the presence of two phases in nanocomposites: a PrFeO3 orthorhombic phase with an average crystallite size of 13.6–36.6 nm and a СeO2 cubic phase in the form of an ultradisperse phase with an average particle size of 7.4–11.5 nm depending on the mass content of СeO2. We characterized the morphology, porosity, and specific surface structure of the powders by scanning electron microscopy, transmission electron microscopy, and adsorption–structural analysis, which established the foam-like morphology of nanopowders with a predominantly mesoporous structure. The specific surface area varied in the range of 8.8–19.4 m2/g for different СeO2 contents. We studied the optoelectronic properties of the nanocomposites with UV–visible diffuse reflection spectroscopy, which determined the values of the band gap of the PrFeO3 phase actively absorbing radiation in the visible region (2.07–2.13 eV). Based on the adsorption–photocatalytic properties of the obtained nanocomposites, we established the presence of a synergistic effect from the addition of CeO2 to PrFeO3. We studied the adsorption capacity of the samples during the adsorption of methyl violet, and we analyzed the resulting adsorption isotherm in accordance with the Freundlich model. The obtained results indicated increased dye adsorption in the presence of CeO2, with the maximum value of Kf = 45.7 observed at 15 wt%. We studied the photocatalytic Fenton-like activity of nanopowders during the degradation of methyl violet under the influence of visible light. We established he presence of a positive effect of CeO2 additive. At 9 wt% content, the maximum photocatalytic reaction rate constant was reached at 0.056 min−1, which was previously unavailable for analogical Fenton-like photocatalysts based on REE orthoferrites. Based on the conducted studies, we propose a possible mechanism of the photo-Fenton-like decomposition of organic pollutants in the presence of PrFeO3/CeO2 under the influence of visible light. The obtained nanocomposite materials were also characterized by high cyclic stability and the potential for magnetically controlled separation from the reaction solution, showing their potential as a basis for photocatalysts in wastewater treatment from dyes and other organic pollutants.

Modulation of reactive species in peroxymonosulfate activation by photothermal effect: A case of MOF-derived ZnFe2O4/C

Tuning reactive oxygen species in peroxymonosulfate (PMS) activation by the structure of catalysts has been extensively studied. But in photocatalysis, the photothermal effect is lack of attention on the alteration of reactive species produced by PMS activation. In this work, ZnFe2O4/C photocatalyst with oxygen vacancy (ZFOv/C) was synthesized via the calcination of bimetallic Zn/Fe-metal–organic framework. The photocatalytic performance of the catalyst had been studied under several conditions, and the experimental results demonstrated that the photocatalytic reaction rate constant of ZFOv/C photocatalyst without temperature control was 21.3 % higher than that under temperature control. Reactive species quenching experiments and electron paramagnetic resonance indicated that 1O2 and h+ are the primary reactive species without temperature control, while only 1O2 are the dominant reactive species under temperature control conditions. The possible activation site was speculated by in-situ Raman spectroscopy, XPS spectra and cycling experiment. This paper analyzes the reasons for photocatalysis to improve the degradation rate of pollutant from the perspective of the change of reactive species generated by photothermal effect on PMS activation, which may open up opportunities to explore the maximum utilization of sunlight in PMS activation.

Chemical oxidants (H2O2 and persulfate) activated photo-Fenton like degradation reaction using sol-gel derived g-C3N4/ZnCo2O4 nanocomposite

In this report, sol-gel method is used to prepare a g-C3N4/ZnCo2O4Z-scheme heterojunction nanocomposite for hydrogen peroxide (H2O2)/persulfate (PS) assisted photocatalytic RhB dye degradation. Structural, crystalline, optical, and chemical compositions of the prepared nanocomposite are discussed with the help of several characterization techniques. The nanocomposite exhibits higher photocatalytic reaction rate constant of about 0.03 min−1 through H2O2 activation under neutral pH condition. Whereas, PS activated photocatalytic degradation reaction shows higher degradation efficiency of 93 % under acid condition. Both H2O2 and PS activated photocatalytic reactions shows OH and SO− radicals are the key active species for the dye degradation reaction which is confirmed through elemental trapping experiment. The recycle tests are performed to show the stability of the nanocomposite. At last, the possible photocatalytic degradation mechanism is proposed through the Z-scheme mechanism.

Double-sided assembly of 0D polydopamine on 1D hexagonal tubular carbon nitride for boosting photocatalytic Cr(VI) reduction

The low efficient transfer/separation of photogenerated carriers and the inferior interfacial attraction between Cr(VI) and carbon nitride are the dominant limiting factors in the photocatalytic Cr(VI) reduction. Herein, a metal-free 0D/1D heterostructure of polydopamine (PDA) modified hexagonal carbon nitride tubes (HCN) was constructed for improving the photoreduced efficiency of Cr(VI). In the 0D/1D heterostructure, HCN exhibited a one-dimensional hexagonal tubular structure, and the zero-dimensional PDA nanoparticles were widely distributed on the outside and inside of HCN. After verified, the introduced PDA modified on the double surfaces of HCN played multiple roles in boosting the photocatalytic Cr(VI) reduction. Firstly, the 0D/1D heterostructure was conducive to accelerating the transfer/separation and spatially separating the photogenerated carriers. Secondly, PDA could regard as an “electron acceptor”, and enhance visible light absorption. Thirdly, PDA could promote the adsorption capacity of Cr(VI) which was attributed to the plentiful amino and catechol groups in the constitutional unit of PDA, and then improve the interfacial attraction between photocatalyst and Cr(VI). As expected, the photoreduced efficiency of Cr(VI) was markedly enhanced by the 0D/1D heterostructure. The photocatalytic reaction rate constant of Cr(VI) by the optimal PDA modified HCN was about 6.6 times than HCN.

Effectively compound the heterojunction formed by flower-like Bi2S3 and g-C3N4 to enhance photocatalytic activity.

In this study, the flower-shaped Bi2S3/g-C3N4-2.6 heterojunction obtained by solvothermal method and its photocatalytic degradation efficiency of rhodamine B (RhB) and tetracycline (TC) in aqueous solution within 40min is as high as 98.8% and 94.6%. For RhB degradation, the photocatalytic reaction rate constant (k) of Bi2S3/g-C3N4-2.6 is approximately 1.8 and 45.5 times that of Bi2S3 and g-C3N4. For TC, k is 3.1 and 2.4 times that of Bi2S3 and g-C3N4, respectively. The key to determining the high catalytic activity of Bi2S3/g-C3N4 lies in the formation of a good heterojunction between Bi2S3 and g-C3N4, which accelerates the electron transfer rate between the heterojunction interface and effectively avoids electron-hole recombination. The effects of catalyst dosage, different pH values, inorganic anions, and capture agents on the photodegradation performance of RhB were investigated. The results show that the catalyst dosage is 1.33g/L, and the solution pH is in the range of 5-9, which has the best removal effect on pollutants, and the isolation of holes (h+) with strong oxidizing ability promotes the collapse of pollutant molecules. Combined with electrochemical tests, a possible degradation mechanism was advised.

Carbon quantum dots induce in-situ formation of oxygen vacancies and domination of {0 0 1} facets in BiOBr microflower for simultaneous removal of aqueous tetracycline and hexavalent chromium

Crystal facet engineering and defect engineering are promising strategies to enhance the photocatalytic performance of BiOBr, but limited work has been reported to realize the simultaneous exposure of highly active facets and the introduction of oxygen vacancies by a single approach. In this work, carbon quantum dots-modified bismuth oxybromide (CQDs/BiOBr) with {001} exposed facets and surface oxygen vacancies was synthesized by a two-step hydrothermal method. The characterization and density functional theory calculation results verified that the introduction of CQDs promoted the growth of BiOBr with highly exposed {001} crystal facets and induced the in situ formation of oxygen vacancies by extracting O atoms from the [Bi2O2]2+ layer. The dual functionality of the CQDs allowed them to simultaneously remove tetracycline hydrochloride (TCH) and Cr(VI) under visible light irradiation. The photocatalytic reaction rate constants in the coexisting pollutant system were 3.71 (TCH) and 13.6-times (Cr(VI)) higher than those of the mono-pollutant systems. This work provides a candidate method to design highly efficient catalysts for environmental remediation.

Construction of plasmonic Bi/Bismuth oxycarbonate/Zinc bismuth oxide ternary heterojunction for enhanced charge carrier separation and photocatalytic performances

In this work, a novel plasmonic ternary Bi/Bismuth oxycarbonate/Zinc bismuth oxide (Bi-Bi2O2CO3-ZnBi2O4) is synthesized synergistically by a one-step hydrothermal method. The results show that the metallic Bi spheres and ZnBi2O4 nanoparticles are uniformly distributed on the surface of flower-like Bi2O2CO3 layer. Compared with the bare ZnBi2O4 and Bi-Bi2O2CO3, the ternary Bi-Bi2O2CO3-ZnBi2O4 heterojunction displays a significantly improved solar energy harvesting efficiency and enhanced photocatalytic degradation activity for environmental organic pollutants. The degradation efficiency of organics reaches to 98.4% under simulated solar light illumination. The degradation kinetics indicates that the photocatalytic reaction rate constant of ternary system is about 4.4 and 29.5 times higher than that of pure ZnBi2O4 and Bi-Bi2O2CO3, respectively. Moreover, O2− and h+ are the main active species in the photodegradation reaction. The improvement of the photocatalytic activity of the composites is attributed to the synergistic effect of ternary heterostructure and surface plasmon resonance (SPR), which promotes charge transfer and effectively inhibits the recombination of photogenerated carriers.

Photocatalytic performance of carbon nanotubes/activated carbon composite carrier carrying cadmium sulfide

The in-situ reaction process was used to prepare composite materials loaded with cadmium sulfide, which were respectively loaded by carbon nanotubes, activated carbon, and carbon nanotube/activated carbon composites for the study of photocatalytic degradation of methyl orange. The results show that when carbon nanotubes and activated carbon are used as carriers, the photocatalytic degradation reaction rate constants are 3.6 times and 8.8 times higher than those without a carrier. The photocatalytic performance of the carbon nanotube/activated carbon composite carrier with a mass ratio of 20: 80 to support cadmium sulfide is significantly higher than that of cadmium sulfide supported by carbon nanotubes and activated carbon respectively, and its photocatalytic degradation reaction rate constant is 30% – 40% higher than that under the condition of activated carbon alone as carrier. It shows that when the modified activated carbon is used as a photocatalyst carrier, carbon nanotubes have a significant effect in improving the efficiency of degrading organic matter.

Layered and poriferous (Al,C)-Ta2O5 mesocrystals supported CdS quantum dots for high-efficiency photodegradation of organic contaminants

Preparation of high-performance composites photocatalysts for organic pollutants degradation is of great significance. In this work, elemental doping was employed to realize the visible-light harvesting and visible-light photocatalysis of the (Al,C)-Ta2O5 mesocrystals following by introduction of CdS quantum dots (QDs) into layered and poriferous (Al,C)-Ta2O5 nanosheets for fabrication of S-scheme charge transfer pathways. In this work, the higher temperatures treatment induced the successful transformation of (Al,C)-Ta2O5 nanosheets from Ta3AlC4 MAX. The experimental results also revealed that CdS QDs/(Al,C)-Ta2O5 composites showed highly enhanced visible-light absorption and visible-light photocatalytic tetracycline degradation performance. The optimal photocatalytic reaction rate constant of the CdS QDs/(Al,C)-Ta2O5-30% composite reached as high as 0.1117 min−1, which was approximately 27.24 times of the (Al,C)-Ta2O5 nanosheets and 2.43 times of CdS QDs, far better than those of commercial Ta2O5 and pristine Ta3AlC4. Meanwhile, the prepared CdS QDs/(Al,C)-Ta2O5 composites were also employed for efficient photodegradation of norfloxacin. Besides, the effects of various experimental parameters, reactive species determination, and band structures were also investigated. The improved visible-light photocatalytic performance of the CdS QDs/(Al,C)-Ta2O5 composites was mainly attributed to fabrication of S-scheme charge transfer pathways for efficient charge separation.

Superhydrophobic STA@PF@Cu2O modified wood with photocatalytic degradation properties for efficiency oil/water separation

The potential for coatings using Cu2O nanostructures combined with stearic acid (STA) and phenol formaldehyde (PF) resin to selectively sorb oils from oil/water mixtures was explored on balsa wood (Ochroma pyramidale). Wood samples coated by immersion in STA@PF@Cu2O nanostructures absorbed 1.6–3.9 times their weight from a wide range of oil and organic solvents with absorption capacity generally increasing with oil density. Separation efficiency of the coated balsa was above 90% for several oil/water mixtures, and the material surface could be regenerated up to 30 times by exposure to visible light while still retaining up to ~94% efficiency. For example, a 320 min light exposure of coated samples used to sorb methylene blue resulted in 99.8% degradation with photocatalytic reaction rate constants reaching 0.013 min–1. The coating represents an easily applied, cost effective and efficient system for oil sorption or oil/water sorption for spill-cleanup or wastewater treatment.

Visible-light photocatalytic tetracycline degradation over nanodots-assembled N-ZrO2−x nanostructures: Performance, degradation pathways and mechanistic insight

Nanodots-assembled N-ZrO2−X nanostructures were designed and prepared by facile modified solvothermal method with g-C3N4 as the nitrogen source. The prepared sample showed accumulated porous structures with nanodots and part of the sample presented oriented assembling features among nanodots. Besides, the experimental results also indicated that the N-ZrO2−X nanocrystals showed much narrower bandgap energy and visible-light absorption to compare with that of commercial ZrO2, mainly attributed to N doping and formation of oxygen vacancy species. These above findings contributed to the easy excitation of N-ZrO2−X nanocrystals by visible-light irradiation, accelerating the charge separation, and providing abundant reactive sites for efficient visible-light photodegradation of tetracycline. The photocatalytic reaction rate constant of N-ZrO2−x nanocrystals was calculated to be approximately 0.01563 min−1, which is 5.52 times of pristine g-C3N4, and far better than that of commercial ZrO2. Finally, possible visible-light photodegradation pathways and photocatalytic mechanism were also proposed.