Degradation Rate Constants Research Articles

Storm: Incorporating transient stochastic dynamics to infer the RNA velocity with metabolic labeling information

The time-resolved scRNA-seq (tscRNA-seq) provides the possibility to infer physically meaningful kinetic parameters, e.g., the transcription, splicing or RNA degradation rate constants with correct magnitudes, and RNA velocities by incorporating temporal information. Previous approaches utilizing the deterministic dynamics and steady-state assumption on gene expression states are insufficient to achieve favorable results for the data involving transient process. We present a dynamical approach, Storm (Stochastic models of RNA metabolic-labeling), to overcome these limitations by solving stochastic differential equations of gene expression dynamics. The derivation reveals that the new mRNA sequencing data obeys different types of cell-specific Poisson distributions when jointly considering both biological and cell-specific technical noise. Storm deals with measured counts data directly and extends the RNA velocity methodology based on metabolic labeling scRNA-seq data to transient stochastic systems. Furthermore, we relax the constant parameter assumption over genes/cells to obtain gene-cell-specific transcription/splicing rates and gene-specific degradation rates, thus revealing time-dependent and cell-state-specific transcriptional regulations. Storm will facilitate the study of the statistical properties of tscRNA-seq data, eventually advancing our understanding of the dynamic transcription regulation during development and disease.

Chitosan-Promoted TiO2-Loaded Double-Network Hydrogels for Dye Removal and Wearable Sensors.

The loading of photocatalysts on hydrogels can significantly reduce the loss of catalysts and effectively prevent secondary contamination, thus demonstrating great application potential and advantages in the field of wastewater treatment, especially in the removal of dyes. Herein, the semiconductor TiO2 was successfully loaded into a polyacrylic acid/chitosan (PAA/CS) double-network (DN) hydrogel, which exhibited superior removal of dyes in wastewater such as MG, MB, MV, and RhB. The dye degradation process followed first-order kinetics, and the first-order rate constants for dye degradation were further calculated under UV light irradiation. Furthermore, the photocatalytic mechanism of the hydrogel was explored and analyzed. More interestingly, the PAA/CS-TiO2 DN hydrogel has excellent tensile properties and superior electrical conductivity, which can be assembled into flexible sensors for real-time monitoring of mechanical deformations and human joint motions. It is envisioned that these excellent properties make hydrogel photocatalysts promising for a wide range of applications.

Engineering Charge Transfer Characteristics in ZnO NRs/Ag2O NPs p-n Heterojunctions: Toward Highly Efficient and Recyclable Photocatalysts.

Staggered gap p-n heterojunction ZnO nanorods/Ag2O nanoparticles, a paradigm of photocatalysts, were developed via engineering the hydrothermal and coprecipitation method. Under simulated sunlight, the photocatalytic characteristics of ZnO/Ag2O(Zn/A) heterojunctions with varying mole ratios (from 8:1 to 8:4, named Zn/A-1-Zn/A-4) were systematically evaluated through the degradation of methylene blue (MB). The influence of key experimental variables, including photocatalyst concentration, MB concentration, and solution pH, on the photocatalyst performance was further analyzed. The incorporation of Ag2O enhanced visible-light absorption, improved electron-hole separation efficiency, and significantly improved the photocatalytic recyclability of the Zn/A heterojunctions. Additionally, metallic Ag generated during photodegradation was found to enhance the photocatalytic activity further. Kinetic studies indicated that the photocatalytic degradation of MB followed pseudo-first-order kinetics, with the Zn/A-3 heterojunction showing the highest photocatalytic activity, achieving a degradation rate constant (k) of 0.028 min-1. Scavenger experiments confirmed that •OH radicals, holes (h+), and superoxide radicals (•O2-) were the primary reactive species involved in the degradation process. The photocatalytic mechanism was identified as a Z-scheme charge transfer system, facilitating efficient charge separation. Moreover, the Zn/A-3 heterojunction exhibited remarkable recyclability, retaining >91% of the photocatalytic activity after five cycles. This study demonstrates the potential of Zn/A heterojunctions for practical applications in industrial wastewater treatment using solar energy.

Oxidative degradation of glycine in aqueous KOH/K2CO3 solutions for CO2 capture

AbstractPotassium hydroxide and potassium carbonate, being cost‐effective and environmentally friendly CO2 capture solvents, are promising candidates for carbon capture applications. Their slow absorption kinetics, however, necessitate strategies to enhance their rates, thereby reducing the capital costs of absorption equipment and saving energy for regenerating large volumes of solvent. Glycine, a potential additive, is explored for this purpose. While glycine‐based solvents are more stable than MEA, their amino functional group renders them susceptible to oxidative degradation. This study investigates the degradation of these solvents and the influence of potassium hydroxide and potassium carbonate on their stability. The experiment was performed under 100% O2 at 90 °C and 3 bar for about 3 weeks. It was observed that glycinate degraded by 53% for the glycinate‐only solution. The results also show that the addition of potassium hydroxide and potassium carbonate to a glycinate‐only solution had a mixed effect on the degradation of glycinate. Potassium hydroxide increased degradation by 5% compared to the glycinate‐only solution, while potassium carbonate decreased degradation by 4%. This order is supported by the degradation rate constants. Meanwhile, under N2, no significant change was observed in glycine concentration. Glycine's susceptibility to oxidative degradation is likely attributed to its less compact and rigid structure, resulting in weaker bonding and increased vulnerability to external factors. This instability leads to the formation of formate, carbonate, acetate, and oxalate as the primary degradation products across all studied solutions. A proposed mechanism for glycinate oxidative degradation sheds light on this process. These findings are crucial for informed decision making regarding performance trade‐offs in point source carbon capture and direct air capture, where oxygen is a prevalent gas component and potassium‐based solutions are commonly employed as absorbents. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Enhancing photocatalytic degradation of beta-blocker drugs using TiO2 NPs/zeolite and ZnO NPs/zeolite as photocatalysts: optimization and kinetic investigations

This study delves into the development and optimization of photocatalysts, namely ZnO NPs/Zeolite and TiO2 NPs/Zeolite, for the degradation of two beta-blocker drugs, including Atenolol (AT) and Metoprolol (ME). Structural and morphological analyses of the catalysts were conducted, and optimal conditions for drug degradation were determined using a Box-Behnken design. The results underscored the significant influence of pH, catalyst amount, drug concentration, and H2O2 concentration on the degradation process using ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalysts. The optimal values of drug concentration, pH, catalyst amount, and H2O2 concentration, were determined to be 32 and 33 mg L−1, 4.2 and 4.6, 428 and 386 mg, and 2.6 and 2.5 mM utilizing ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalyst, respectively. Following optimization, the kinetics of the photodegradation process were investigated, revealing promising rates and half-life times for both drugs. The pseudo-first-order rate constants for Atenolol and Metoprolol degradation were 0.064 ± 0.007 min−1 and 0.065 ± 0.004 min−1 with ZnO NPs/Zeolite and 0.071 ± 0.007 min−1 and 0.071 ± 0.006 min−1 with TiO2 NPs/Zeolite, respectively. Furthermore, ZnO NPs/Zeolite and TiO2 NPs/Zeolite demonstrated reusability up to 5 and 6 times, respectively, without significant activity loss. The comparative analysis highlighted the superior performance of TiO2 NPs/Zeolite over ZnO NPs/Zeolite, attributed to lower consumption, shorter degradation time, improved reusability, and compatibility with milder acidic conditions. Overall, the research showcases the potential of ZnO NPs/Zeolite and TiO2 NPs/Zeolite as an effective and sustainable solution for removing Metoprolol and Atenolol contaminants.

Modulating electronic structure of NiFe layered double hydroxide membrane by interlayer-confinement for enhanced water decontamination

Herein, the role of nanoconfinement on modulating the electronic structure of the catalyst that influences the efficiency of advanced oxidation processes (AOPs) was investigated. Peroxymonosulfate (PMS)-based AOP was conducted within the nanoconfined sub-nanometer interlayer channels of a 2D NiFe layered double hydroxide membrane (NiFeM). The interlayer-confined NiFeM exhibited complete removal of sulfamethoxazole, with a degradation rate constant of 211.67 s−1 that was 2.6–946.2 times higher than previously reported nanoconfined AOPs systems, and also demonstrated broad pH working range and anti-interference ability with excellent catalytic stability in 25 h. Theoretical calculations suggested such interlayer confinement upshifted the catalyst metal d-band center, accounting for strengthened PMS adsorption and electron transfer from catalyst to PMS molecules. This work embodies the interlayer confinement effect on modulating the electronic structure of catalyst and provides insights for designing catalysts with excellent capability for environmental remediation, energy conversion and chemical synthesis.

Synergistic degradation of refractory organic pollutant by underwater bubbling plasma combined with heterogeneous Fenton process

Excessive discharge of the refractory organic pollutants endangers the development of the society and economy, thus seeking an efficient wastewater abatement method is an urgent need. Herein, Iron (Ⅱ) sulfide (FeS) was employed as the heterogeneous catalyst and coupled with underwater bubbling plasma (UBP) for the elimination of the refractory organic pollutant, malachite green (MG). FeS catalyst was synthesized using the solvothermal method and subsequently characterized comprehensively, focusing on its microstructure, specific surface area, chemical bonds and elements valence states. The UBP system combined with FeS (UBP/FeS) exhibited the robust synergism with a maximum synergistic factor of 1.89. The MG degradation percentage and rate constant were up to 94.7% and 0.237 min−1 within 12 min. The parameter experiments revealed that FeS dosage, pulse frequency, initial MG concentration and solution conductivity of 150 mg/L, 56 Hz, 5 mg/L and 21.8 μS/cm, respective, were more conducive for MG elimination. The MG removal efficiency reached 86.2% after five consecutive applications of FeS. Reactive substances including ·OH, ·O2−, eaq, O3 and H2O2 were confirmed to contribute to MG elimination. Additionally, the conversion circle between ≡ Fe(Ⅱ) and ≡ Fe(Ⅲ) promoted the catalytic conversion of H2O2 and O3 into ∙OH. The comparison of UV–vis spectra and total organic carbon of MG solution before and after reaction revealed the superior degradation of MG in the UBP/FeS system. Hypotheses regarding to the decomposition pathways of MG were formulated based on the identified intermediates. The toxicity level of MG solution was lightened after reaction. The above results indicate that UBP/FeS has the advantages of quick degradation and high efficiency, representing a promising approach for refractory pollutants treatment.

Comparing theeffect of applying different types of amendments on carbon emissions and kinetics of degrading total petroleum hydrocarbons in artificial petroleum-contaminated soil.

Contamination byspent engine oil represents a significant global environmental challenge as it poses a major hazard to human health, animals, plants, microorganisms, the soil ecosystem, and aquatic ecosystems. This study assumes that some amendments differ significantly in their ability to degrade petroleum hydrocarbons. Therefore, this incubation study was conductedto investigate the effect of different types of inorganic and organic amendments (zeolite, bone char, banana leaves biochar, and wood chips biochar) on carbon emissions (CO2-C) and the kinetics of total petroleum hydrocarbons (TPHC) degradation in artificial petroleum-contaminated soil. These amendments wereadded to the soil under study at adose of 3% (w/w). At the end of the incubation period, applying zeolite, bone char, banana leaves biochar, and wood chips biochar to artificial petroleum-contaminated soil significantly reduced cumulative CO2-C emissions compared to the control. The banana leaves biochar significantly decreased TPHC concentrations in artificial petroleum-contaminated soil compared to the control treatment. At the end of the incubation period, adding banana leaves biochar to the soil showed high degradation efficiencies of TPHC which was36% higher than soil before incubation. The effectiveness of applying amendments used in this experiment on the degradation of TPHC increase was in the order of banana leaves biochar > bone char > wood chips biochar > control > zeolite. The second-order model described the kinetics of total petroleum hydrocarbons better than thefirst-order model. Banana leaves biochar added to the soil resulted in a significant increase in the degradation rate constant of total petroleum hydrocarbons (k2) compared with the control. A higher k2 value indicates that TPHC degrades more rapidly. The half-life of TPHC degradation in the soil was decreased significantly by adding banana leaves biochar. According to the second-order equation, the half-lives of control, zeolite, bone char, banana leaves biochar, and wood chips biochar were 4.0, 5.3, 2.7, 1.0, and 3.6 years, respectively. The banana leaves biochar amendment might be cheaper and more environmentally friendly than other organic amendments because it has the high potential for carbon sequestration and remediate petroleum-contaminated soil, which would increase the sustainable use of petroleum-contaminated soil leading to preserving the environment.

Breakdown cost and recycling processes of Bentonite/TiO2 quantum dots of photo and solar degradation of Congo Red dye and industrial dyes wastes

This research presents the preparation, characterization, and application of a novel bentonite- TiO2 quantum dot (Bent/TQ) nanocomposite for the efficient photodegradation of Congo Red dye, a common pollutant in industrial wastewater. The composite was prepared via a co-precipitation method followed by calcination, which facilitated the uniform dispersion of TiO2 quantum dots within the bentonite matrix. The resulting material exhibited a high specific surface area of 205.45 m2/g and an optimized band gap of 3.15 eV, making it suitable for visible light photocatalysis. The photocatalytic efficiency of Bent/TQ was evaluated under both xenon lamp irradiation and natural sunlight. The composite demonstrated a significant degradation rate constant of 23.35 × 10⁻³ s⁻1, which is comparable to that of pure TiO2 quantum dots (28.86 × 10⁻³ s⁻1). Mechanistic studies revealed that the primary active species responsible for the degradation were hydroxyl radicals (•OH), generated through the interaction of photogenerated electron-hole pairs with H2O molecules and molecular oxygen. Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) analyses were employed to assess the mineralization efficiency of the composite. The Bent/TQ catalyst achieved a COD removal efficiency of 84.5% and a TOC reduction of 76.2% after 240 minutes of irradiation under natural sunlight. Reusability tests indicated that the photocatalyst retained approximately 80% of its original efficiency after seven consecutive cycles, though a slight decline was observed due to particle agglomeration under prolonged light exposure. The economic analysis suggested that the use of Bent/TQ nanocomposites could reduce operational costs by 29.12% compared to conventional TiO2-based systems, making it a cost-effective solution for large-scale wastewater treatment. This work highlights the potential of Bent/TQ nanocomposites as sustainable and efficient photocatalysts for environmental remediation, with future efforts aimed at enhancing their long-term stability and expanding their applicability to a broader range of pollutants.

Enhanced photocatalytic performance of TiO2 with tunable oxygen vacancies induced by H2/N2 mixture treatment

Surface treatment can effectively modulate the surface properties of a photocatalyst to hasten the separation and transfer of photoinduced charges, ultimately achieving high photocatalytic performance. Herein, surface treatment of anatase-phase TiO2 prepared by a hydrothermal method was performed under H2/N2 mixed atmosphere. The experimental results demonstrate that roasting TiO2 in a H2/N2 atmosphere can effectively reduce partial Ti4+ to Ti3+, thereby facilitating the production of tunable oxygen vacancies (OVs) by disrupting Ti-O-Ti bonds. OVs can construct defective energy levels to bring about a decrease in the bandgap of TiO2 and an extension of light absorption range. Moreover, OVs remarkedly improve the separation of photoinduced charges of TiO2 and accelerate the photocatalytic reaction as active sites. The photocatalytic experimental results demonstrate that TiO2 exhibits the highest performance when roasting TiO2 in a H2/N2 atmosphere for 2 h, and the photocatalytic degradation rate constant of rhodamine B (RhB) and tetracycline (TC) on this sample under simulated solar light irradiation is 2.24 and 1.11 times higher than that on the reference TiO2, respectively. These findings provide valuable insights for designing highly efficient photocatalysts for effective water pollution treatment.

Synthesis and characterization of ZnO nanorods via hydrothermal route for wastewater recycling

In this work, highly efficient ZnO nanorods (NRs) were prepared using an easy and costeffective hydrothermal process. The Synthesized ZnO NR have been analyzed for their structure, morphology, and optical characteristics using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FTIR), and ultraviolet-visible (UV-visible) spectroscopy, respectively. Additionally, a test is conducted on the ZnO nanorod's photocatalytic efficiency towards the degradation of certain dyes, Methylene Blue (MB) and Methyl Orange (MO). The FESEM investigation revealed that the ZnO nanostructures show nanorods with varying diameters (needle-like shape) with an estimated size of (10 to 20) µm. According to the XRD examination, the NRs had a hexagonal-shaped wurtzite pattern, exhibiting an average crystallite diameter of about 50 nm. FTIR spectra confirmed that functional groups from the substance being extracted were present in the ZnO NRs. The band-gap value of 3.37 eV was determined through the TAUC plot model from the ultraviolet-visible spectrum data. In the presence of as-synthesized ZnO NRs, the MO dye degraded by 100 percent in 46 minutes, but the MB dye significantly degraded by approximately 100 % in 20 minutes with high degradation rate constants kMO = 0.086 min-1 and kMB = 0.180 min-1, respectively.

MoS2–CdS Composite Photocatalyst for Dye Degradation: Enhanced Apparent Quantum Yield and Reduced Energy Consumption

AbstractThis study investigates the visible light‐assisted photocatalytic degradation of rhodamine B (Rh B) dye using MoS2–CdS nanocomposite. Two crucial operational parameters, illumination time and the weight ratio of MoS2 to CdS, are systematically examined. Approximately, 91.9% of Rh B solution with a concentration of 10 mg/L is degraded by the MoS2–CdS photocatalyst under 60 min of illumination, with a photocatalyst dosage of 0.5 g/L. The results are consistent with a pseudo‐first‐order kinetic model, wherein the degradation rate constant of CdS increases fourfold after amalgamation with MoS2. The formation of the composite with MoS2 results in 1.72 times increase in the apparent quantum yield and 3.15 times decrease in the electrical energy consumption per order of CdS nanorods under similar experimental conditions. The investigation also comprehensively explores the reactive species responsible for Rh B degradation under visible light in the presence of MoS2–CdS photocatalyst. This analysis confirms that both hydroxyl and superoxide anion radicals play a dominant role in Rh B degradation. These findings underscore the potential practical applications of MoS2–CdS nanorods in eco‐friendly water treatment technologies, offering efficient and sustainable solutions to contemporary environmental challenges.

Evaluation of photocatalytic efficiency of TiO2 applied over cement plaster for mitigating urban air pollutant: TVOC

Photocatalysis emerged as a prominent method for mitigating air pollution stemming from emissions of total volatile organic compounds (TVOCs) in both indoor and outdoor environments. Given the slow degradation rate of certain TVOCs, which pose health risks, including carcinogenicity, there is a pressing need for effective air purification strategies, particularly within built environments where individuals spend substantial amounts of time. This study delves into the efficacy of TiO2 photocatalysis in reducing air pollutants when applied to building surfaces. Cement mortar samples, incorporating varied doses of TiO2 ranging from 7.83E-03 g/cm2 to 4.92E-02 g/cm2, were prepared and examined within batch reactors, both under sunlight exposure and in the absence thereof, to gauge their degradation rates towards TVOCs. Furthermore, surface characterization techniques were employed to explicate the microstructural properties of TiO2-coated plastered samples. The results obtained demonstrated the variation in the rate of degradation from 1.09E-04±0.1 % to 3.1E-4 ± 1.13 % min−1cm−2 for various initial concentrations of total volatile organic compounds (TVOCs) in the range of 600 ppm to 2900 ppm over a period of 100 min. The selected approach demonstrated the maximum degradation rate constant of 5.2E-04 min−1cm−2 corresponding to 15 % of TiO2 dose by weight of cement. These findings underscore the promise of TiO2 in purifying polluted air and advocate for its widespread implementation on building surfaces to enhance air quality.

Rape straw biochar-assisted preparation of flower-like BiOCl with enriched oxygen vacancies for efficient photocatalytic CO2 reduction and pollutants degradation

Utilizing photocatalytic technology to transform CO2 into high added value chemical products has represented an effective strategy for alleviating the climate problems that have arisen due to excessive CO2 emissions. As a typical bismuth-based photocatalyst, BiOCl has garnered widespread attention due to its unique layered structure and low toxicity. However, the low light utilization efficiency and the rapid recombination of e−/h+ pairs severely hinder the practical application of BiOCl. Introducing oxygen vacancies (OVs) into BiOCl has been demonstrated to be one of the effective strategies for enhancing the photocatalytic performance of BiOCl. However, introduction of OVs through a mild and cost-effective approach remains a significant challenge. In this work, we developed a strategy for introducing OVs on BiOCl, which indues the growth of BiOCl into flower-like spherical structures and introduction of abundant OVs through addition of rape straw biochar (RC) under hydrothermal conditions. The synergistic interaction of RC and OVs endows with BiOCl more active sites as well as higher photogenerated carriers (e−/h+) separation efficiency. When the mass ratio of RC to BiOCl is 0.5 % (RC-0.5), the sample demonstrates the best performance, conversion of CO2 to CO on the sample is 4.0 μmol g−1 h−1, which is 3.08 times higher than that on the reference BiOCl. Additionally, versatility of the photocatalysts was further evaluated through photocatalytic degradation of rhodamine B (RhB) and perfluorooctanoic acid (PFOA). The degradation rate constant of RhB and PFOA on the RC-0.5 sample is 0.0642 min−1 and 0.00566 min−1, respectively, which is 2.26 times and 0.43 times higher than that on the reference BiOCl. Total organic carbon (TOC) experiments demonstrate that RhB can be effectively mineralized into CO2, H2O and small molecules on the photocatalyst. The main reactive species involved in the photocatalytic degradation process were investigated through active free radical trapping experiments and electron paramagnetic resonance (EPR). This work provides a viable strategy for the development of high-performance BiOCl photocatalysts for environmental applications.

Fe/Mo bimetallic synergy system for ultra-highly efficient degradation of Rhodamine B

The traditional Fenton process, which depends on the use of Fe2+/H2O2, is constrained by the consumption of ferrous ions and the requirement for large amounts of H2O2. However, the assembly of bimetallic synergy systems with adjustable valence metal cations and enhanced dispersion of active sites has been evidenced to address these limitations. In this work, the Fe/Mo bimetallic synergy system in FexMo-CN materials is explored, utilized for the degradation of dyes with the assistance of H2O2. The cooperative effect of Fe/Mo bimetallic and the highly dispersed FeMoO4 as active sites make materials to achieve ultra-highly efficient degradation of dyes, approximately 100 % Rhodamine B (RhB) degradation within 6 min. And the corresponding degradation rate constant is 1.3471 min−1. Additionally, FexMo-CN materials exhibit excellent stability and versatility in solutions containing various cations, anions, or other dyes. Quenching experiments and EPR tests demonstrate that singlet oxygen (1O2) serves as the main reactive oxygen species (ROS) to degrade RhB. And the mechanism of generated 1O2 is revealed. The degradation path and mechanism of RhB are analyzed and the toxicology of intermediate products are calculated in detail. This work presents a novel approach for enhancing efficiency in Fenton-like reactions within the field of environmental remediation.

Rational Design of Mesoporous ZnFe2O4@g-C3N4 Heterojunctions for Environmental Remediation and Hydrogen Evolution.

Mesoporous catalysts with a high specific surface area, accessible pore structures, and appropriate band edges are desirable for optimal charge transfer across the interfaces, suppress electron-hole recombination, and promote redox reactions at the active sites. The present study demonstrates the rational design of mesoporous ZnFe2O4@g-C3N4 magnetic nanocomposites (MNCs) with different pore sizes and pore volumes following a combination of facile thermal itching and thermal impregnation methods. The MNCs preserve the structural, morphological, and physical attributes of their counterparts while ensuring their effectiveness and superior catalytic capabilities. The morphological analysis confirms the successful grafting and confinement of ZnFe2O4 nanoparticles with the polymeric g-C3N4 nanosheets to form heterojunctions with numerous interfaces. The MNCs possess uniformly distributed small mesopores (pore size <4 nm), ample active sites, and a high specific surface area of 62.50 m2/g. The mesoporous ZnFe2O4@g-C3N4 notably improve hydrogen evolution rate and methylene blue dye degradation. The optimal loading weight of ZnFe2O4 is 20 %, in which the MNCs display the highest hydrogen evolution rate of 1752 μmol g-1 h-1 and photo-Fenton dye degradation rate constants of 0.147 min-1, upon solar-light illumination. Furthermore, the photocatalysts demonstrate recyclability over five consecutive cycles, confirming their stability, while easy separation using a simple magnet underscores practical utility.

Piezoelectric field accelerating charge transfer in Z-scheme heterojunction 2D-KNbO3/1D-CdS for efficient piezo-photocatalytic H2 evolution and TCH degradation

The piezo-phototronic effect utilizes the piezoelectric polarization field to tune the photogenerated carrier separation and transport performance in heterojunctions, which portrays a promising strategy for addressing energy shortage and environmental pollutants. Herein, a novel Z-scheme piezoelectric semiconductor heterojunction, 2D-KNbO3/1D-CdS-x (KNCS-x), was fabricated using hydrothermal and solvothermal methods, resulting in enhanced redox capacity. Under the simultaneous light and strain, KNCS-15 exhibits the highest piezo-photocatalytic activity, with degradation rates of tetracycline hydrochloride degradation rate constant, H2O2 as well as H2 production rates being 1.806 × 10−2s−1, 45.56 mM·h−1·g−1 and 8.87 mmol·h−1·g−1, respectively, which are 1.4, 2.4 and 1.9 times of photocatalysis alone, and 9.8, 9.2 and 9.8 times of piezocatalysis alone. DFT calculations, EPR and PALS indicate that the Z-scheme structure realizes effective separation of electron-hole pairs with strong redox ability and a higher carrier concentration. The enhanced catalytic activity is attributed to the introduction of piezoelectric potential, which facilitates improved spatial separation of electrons with high reduction and holes with high oxidation potential.

CoFe2O4/carbon nitride Z-scheme heterojunction photocatalytic PMS activation for efficient tetracycline degradation: Accelerated electron transfer

The escalating consumption of antibiotics and their subsequent discharge into the water supply is a matter of significant concern. This study presents an innovative visible light (VL) activated peroxymonosulfate (PMS) system for efficient degradation of the targeted antibiotic tetracycline (TC). CoFe2O4/carbon nitride (CFO/CN) Z-scheme heterojunctions were designed and synthesized through a simple co-precipitation and calcination strategy. Surface and analytical techniques were employed to comprehensively characterize the prepared CFO/CN, demonstrating its enhanced efficiency in separating photoinduced charge carriers. CFO/CN exhibited a 27-fold enhancement in TC degradation rate constants with PMS under VL. The effects of various factors including catalyst dosage, PMS concentration, initial pH, and content of CFO on TC degradation efficiency were investigated. Reactive species quenching and EPR measurements revealed the main contribution of superoxide radicals (•O2−) made to TC degradation. TC degradation pathways were proposed based on oxidized product analysis. The assessment of acute toxicity demonstrated the reduced toxicity of the formed intermediates. A plausible mechanism for TC degradation over CFO/CN-PMS-VL was discussed. This work provides a comprehensive guide for heterojunction photocatalytic activation of PMS for efficient micropollutant degradation.

Nitrogen–oxygen vacancy and S-scheme heterostructure synergistically enhance solar photocatalysis

Introducing vacancies and constructing S-scheme heterojunctions are promising approaches for enhancing photocatalytic activity. However, the application of this synergistic strategy to realize inexpensive and efficient photocatalysts remains challenging. In this study, a straightforward hydrothermal and calcination modification strategy was used to prepare a photocatalyst in which abundant nitrogen–oxygen vacancies were coupled with a Ce-ZnO@C-g-C3N4 composite with an S-scheme heterojunction. Under sunlight irradiation, the prepared composite achieves 98.3% and 86.4% degradation of methylene blue and ciprofloxacin, with degradation rate constants of 0.3464 and 0.0893 min−1, respectively. Compared with ZnO and g-C3N4, the degradation rates of methylene blue over the composite catalyst are 34.8 and 22.7 times higher, respectively, and those of ciprofloxacin are 2.4 and 4.9 times higher, respectively. Based on a detailed examination of the catalyst structure and photoelectric properties, the high photocatalytic efficiency is attributed to nitrogen–oxygen vacancies, an enhanced surface area, and synergistic S-scheme heterojunction effects. These factors broaden the spectral range, increase the number of active sites, and facilitate efficient charge transfer, thereby enhancing the photocatalytic reaction. This system demonstrates the feasibility of integrating doping and heterojunction formation to enhance photocatalytic performance synergistically.

Synergistic impact of lanthanum and cerium co-doping ZnO for improved photocatalytic rhodamine B degradation efficiency under UV light

In this study, the influence of different La and Ce co-doping amounts on the structural, morphological, optical, and photodegradation properties of ZnO nanostructures was evaluated. Zn1-2xLaxCexO nanoparticles (NPs) were prepared using sol-gel auto-ignition process, where x = 0.00 (pure ZnO), 0.01 (LC1), 0.03 (LC3), and 0.05 (LC5). The X-ray diffraction (XRD) and Raman results revealed that the prepared ZnO NPs crystallize in the hexagonal wurtzite structure. The size of crystallites is affected by the increment of La and Ce and it decreased from 24.29 nm to 10.40 nm with the increase in the concentration of La and Ce. Transmission electron microscopy (TEM) showed that the samples exhibit an irregular distribution of NPs with a dominant spherical shape morphology. The simultaneous incorporation of La and Ce in ZnO NPs led to a slight variation in the absorption edge and a slight shift in the values of the band gap energy from 3.20 to 3.24 eV. Furthermore, a reduction in the recombination rate of photogenerated charge carriers and the creation of fewer additional defects upon the appropriate insertion of Ce and La ions are highlighted by the analysis of photoluminescence spectra, Nyquist plots, and transient photocurrent measurements. The photocatalytic activity of samples was evaluated against rhodamine B organic dye under UV light irradiation. The analysis showed that LC1 sample exhibited superior photocatalytic performance with 99.1% degradation efficiency and a degradation rate constant of 0.0762 min-1. This enhancement has been ascribed to the surface defects and the optimized crystallite size achieved, which help to generate reactive entities such as •OH and O2•− in addition to the great role of holes (h+) and impede the recombination of charge carriers e-/h+.