Photogenerated Electron-hole Pairs Research Articles

Photocatalytic Performance of the BaSn-based Nanoscale Materials for the Organic Pollutants Enhanced by Sm (Er) Doping

Background: Sm (Er) doping is an effective strategy for enhancing the photocatalytic activity of the semiconductor photocatalysts for the degradation of organic pollutants. BaSnbased nanorods possess wide band gap energy, which limits the photocatalytic application. It is important to research the feasibility of the improved photocatalytic performance of the BaSnbased nanorods by doping with Sm (Er). Objective: The aim is to synthesize Sm (Er)-doped BaSn-based nanoscale materials through a simple hydrothermal process and research the photocatalytic performance of the Sm (Er)-doped BaSn-based nanoscale materials for the gentian violet degradation. Methods: Sm (Er)-doped BaSn-based nanoscale materials with a polycrystalline structure were synthesized through a simple hydrothermal process. The Sm (Er)-doped composites were analyzed by X-ray diffraction, electron microscopy, solid diffuse reflectance spectrum, X-ray photoelectron spectroscopy, photoluminescence, and electrochemical impedance spectroscopy. Results: Sm (Er) doping induces the morphological evolution of the BaSn-based nanoscale materials from the nanorods to irregular nanoscale particles. Sm (Er) in the doped BaSn-based nanoscale materials exists in the form of the cubic Sm2Sn2O7 and orthorhombic ErF3 phases. The band gap value is decreased with increasing the Sm (Er) dopant contents. Sm (Er)-doped BnSnbased nanoscale materials with the Sm (Er) content of 8wt.% have the lowest band gap and show the strongest light absorption ability. Compared with the un-doped BaSn-based nanoscale materials, the Sm (Er)-doped BnSn-based nanoscale materials exhibit higher photocatalytic activity for the gentian violet degradation. 8wt.% Sm-doped BnSn-based nanoscale materials show the highest photocatalytic activity for the degradation of the gentian violet. 20 mL gentian violet solution (concentration of 10 mg·L-1) can be totally degraded using 20 mg 8wt.% Sm-doped BnSnbased nanoscale materials under UV light illumination for 150 min. Conclusion: The enhanced photocatalytic activity of the Sm (Er)-doped BnSn-based nanoscale materials can be attributed to the decreased band gap, enhanced light absorption ability, and decreased recombination of the photo-generated electron-hole pairs.

Photodetectors Based on ZrS3/MoS2 Heterostructures.

High-performance photodetectors with the detection capability of linearly polarized light have broad applications in both military and civilian fields. Quasi-one-dimensional ZrS3 as an emerging anisotropic two-dimensional material has come under the spotlight owing to its intriguing properties. However, the performance of the ZrS3 photodetector is seriously restricted by its low responsivity. Herein, a novel high-performance photodetector based on the van der Waals ZrS3/MoS2 heterostructure is proposed. Attributed to the charge trapping-assisted photogating effect, interlayer carrier transitions, and fast spatial separation of the photogenerated electron-hole pairs, the device displays superior photoresponse characteristics ranging from the ultraviolet to the visible spectrum in terms of high responsivity up to 212 A/W, an extraordinary external quantum efficiency of 8.5 × 104%, and a prompt rise/decay time of 0.19/0.38 ms. In addition, owing to the profound birefringence and dichroism effects in ZrS3 together with strong light-matter interactions in the heterostructure, profound linear-polarization sensitivity is demonstrated with a dichroic ratio of about 2.8. Overall, this photodetector not only is integrated with the excellent properties of ZrS3 and monolayer MoS2 but also further enhances the advantages through interlayer couplings, which demonstrate the strong potential of the ZrS3-based devices for high-performance, ultrafast, and polarization-sensitive photodetection.

Enhancing the Visible Light Photocatalytic Activity of TiO2-Based Coatings by the Addition of Exfoliated g-C3N4

In the last few years, increasing interest from researchers and companies has been shown in the development of photocatalytic coatings for air purification and self-cleaning applications. In order to maintain the photocatalyst’s concentration as low as possible, highly active materials and/or combinations of them are required. In this work, novel photocatalytic formulations containing g-C3N4/TiO2 composites were prepared and deposited in the form of coatings on a-block substrates. The obtained photocatalytic surfaces were tested for NOx and acetaldehyde removal from model air. It was found that the addition of only 0.5 wt% g-C3N4 towards TiO2 content results in over 50% increase in the photocatalytic activity under visible light irradiation in comparison to pure TiO2 coating, while the activity under UV light was not affected. The result was related to the creation of a g-C3N4/TiO2 heterojunction that improves the light absorption and the separation of photogenerated electron-hole pairs, as well as to the inhibition of TiO2 particles’ agglomeration due to the presence of g-C3N4 sheets.

CuO nanoflowers: Multifaceted implications of various precipitating agents on rectification behaviour

In order to achieve the best possible use of traditional energy resources for the preservation of the environment, semiconductor-based optoelectronic devices are one of the most intriguing methods for converting light energy into electrical energy. CuO has been extensively explored as a material for energy conversion and the development of photo-detectors due to its notable characteristics among other metals, especially its non-toxicity, abundance, high efficiency, electrochemical stability and low cost/promising photodiode. However, some drawbacks limit its practical application in white light and photo-detector, including the rapid recombination rate of photo-generated electron-hole pairs and destitute response to visible light. As a result, several strategies have been developed from an optoelectronics perspective to eradicate these deficiencies and make an effort to enhance CuO photodiode activities. In this research work, the electrical characteristics and rectification behaviour of CuO with various precipitating agents have been examined. The CuO nanoparticles can be synthesized by co-precipitation technique prepared with different precipitants. Through this research, several parameters, such as the structural, functional, morphological, optical and electrical characteristics, were investigated by changing the precipitants. The functional group formation of pure CuO phase was confirmed by FT-IR studies. UV–Vis absorption measurements indicate that the band gap of the CuO nanoparticles was ranging from 2.40 to 2.85 eV. As a diode, CuO/p-Si exhibits a non-ideal behaviour and under light conditions with Na2CO3 precipitant, the better ideality factor is about 2.35. The barrier height is determined by the thermionic emission theory to be 0.77 and 0.79 eV in the dark and light conditions respectively.

Modified metal–organic frameworks for sonophotocatalytic elimination of wastewater pollutants

In recent decades, people have witnessed a rapid development of society, accompanied by the increase sharply of numerous organic/inorganic contaminants from industrial effluents. The high toxicity of pollutants has led to long‐term risk to human health. To connect with environment‐friendly green chemistry and sustainable development, photocatalysis technology has emerged. Metal–organic framework (MOF)‐based photocatalysts performed high efficiency for the elimination of wastewater pollutants. Nevertheless, the large band gap energy and high recombination rate of photogenerated electron–hole pair decrease the catalytic efficiency. Sonochemistry is regarded as a safe, highly efficient, clean, and eco‐friendly technology, which has aroused a lot of interest in the treatment of wastewater. The cavitation effect induced by ultrasonic waves promotes the generation of additional active radicals. The ultrasonic oscillation facilitates cleaning the surface of catalysts, dispersing catalyst particles, and increasing proton transport. Therefore, photocatalysis coupling with ultrasonic waves, known as sonophotocatalysis (SPC), is a promising means for enhancing the overall performance of wastewater treatments. This review discusses the recent advancements of hybrid MOF‐based photocatalysts driving the wastewater treatments in SPC system. The catalytic performance of hybrid MOF is discussed in the SPC process. The inner properties of phases in hybrid MOF such as the location of redox potential and transfer direction of electrons and energy after hybridization are elucidated. Additionally, the review discusses the existing challenges and obstacles of MOF‐based SPC system and proposes feasible improvements to meet the future requirements of practical applications.

Rapid Hydrolysis Precipitation of BiOBr Nanosheets for Boosting Photocatalytic N2 Fixation

AbstractIn this paper, BiOBr nanosheets were synthesized through a novel hydrolysis precipitation method, which significantly reduced energy consumption and time cost compared to traditional hydrothermal synthesis methods. The subjected hydrothermal and high‐temperature calcination process promote the generation of surface oxygen vacancies, which inhibited the recombination of photogenerated electron hole pairs and improve the photocatalytic performance of BiOBr. Additionally, by adjusting the addition amount of KOH in the synthesis process, BiOBr can grow towards more complex crystal structure, which also provides a new path for the fabrication of 2D materials.

In Situ Photodeposition of Gold Nanoparticles with Exposed High-Activity Crystal Facets under Different Sacrificial Agents.

In situ photodeposition presents a powerful approach for integrating noble metal co-catalysts onto semiconductor surfaces. However, achieving precise control over the microstructure of the deposited co-catalyst remains a major challenge. Au nanoparticles (NPs) are deposited onto H-KCNO using HAuCl4 in the presence of various sacrificial agents in this study. Notably, the choice of sacrificial agent decisively influences the exposed crystal facets, loaded content, and particle size of the deposited Au NPs. Importantly, in situ photodeposition under an ethanol solution facilitates the exposure of the highly active (111) and (220) crystal facets of Au. The introduction of Au NPs significantly enhances photocatalytic hydrogen evolution, achieving rates of 4.93, 57.88, and 15.44 μmol/h for H-KCNO/Au-(water, ethanol, and lactic acid), respectively. The observed photocatalytic activity for hydrogen evolution indicates that the exposure of the highly active planes emerges as critical for significant performance enhancement. Photoelectrochemical and photoluminescence measurements suggest that the highly active (111) and (220) crystal facets effectively segregate sites for redox reactions, thereby impeding the recombination of photogenerated electron-hole pairs.

Interlayer Potassium Single-Atom-Coordinated g-C3N4 for Significantly Boosted Visible Light Photocatalytic H2 Production.

In recent years, graphitic carbon nitride (g-C3N4) has attracted considerable attention because it includes earth-abundant carbon and nitrogen elements and exhibits good chemical and thermal stability owing to the strong covalent interaction in its conjugated layer structure. However, bulk g-C3N4 has some disadvantages of low specific surface area, poor light absorption, rapid recombination of photogenerated charge carriers, and insufficient active sites, which hinder its practical applications. In this study, we design and synthesize potassium single-atom (K SAs)-doped g-C3N4 porous nanosheets (CM-KX, where X represents the mass of KHP added) via supramolecular self-assembling and chemical cross-linking copolymerization strategies. The results show that the utilization of supramolecules as precursors can produce g-C3N4 nanosheets with reduced thickness, increased surface area, and abundant mesopores. In addition, the intercalation of K atoms within the g-C3N4 nitrogen pots through the formation of K-N bonds results in the reduction of the band gap and expansion of the visible-light absorption range. The optimized K-doped CM-K12 nanosheets achieve a specific surface area of 127 m2 g-1, which is 11.4 times larger than that of the pristine g-C3N4 nanosheets. Furthermore, the optimal CM-K12 sample exhibits the maximum H2 production rate of 127.78 μmol h-1 under visible light (λ ≥ 420 nm), which is nearly 23 times higher than that of bare g-C3N4. This significant improvement of photocatalytic activity is attributed to the synergistic effects of the mesoporous structure and K SAs doping, which effectively increase the specific surface area, improve the visible-light absorption capacity, and facilitate the separation and transfer of photogenerated electron-hole pairs. Besides, the optimal sample shows good chemical stability for 20 h in the recycling experiments. Density functional theory calculations confirm that the introduction of K SAs significantly boosts the adsorption energy for water and decreases the activation energy barrier for the reduction of water to hydrogen.

Facile Fabrication of SrTiO3/In2O3 on Carbon Fibers via a Self-Assembly Strategy for Enhanced Photocatalytic Hydrogen Production

Photocatalytic water splitting by semiconductors is considered a promising and cost-effective method for achieving sustainable hydrogen production. In this study, a CF/SrTiO3/In2O3 photocatalytic material with a double-layer core–shell structure was developed. The experimental results indicated that the produced CF/SrTiO3/In2O3 composite fiber displayed superior photocatalytic hydrogen production performance, achieving a hydrogen evolution rate of approximately 320.71 μmol/g·h, which is roughly seven times higher than that of the CF/SrTiO3 fiber alone. The enhanced photocatalytic activity of the CF/SrTiO3/In2O3 fiber can be attributed to the heterojunction structure enriched with oxygen vacancies. It was found that these oxygen vacancies created defective states that served as traps for photogenerated electrons, facilitating their migration to the surface defect states and enabling the reduction of H+ in water to produce hydrogen. Furthermore, the synergy between the heterojunction structure and the conductivity of the carbon fiber promoted the generation and migration of photogenerated electrons, reduced the recombination of photogenerated electron–hole pairs, and ultimately improved photocatalytic hydrogen production. This study presents a new approach for designing efficient photocatalysts with surface oxygen vacancies on carbon fibers, providing new insights into the sustainable application of photocatalysts.

Spherical g-C3N4@PDA nanocarrier for synergistic chemo-photothermal tumor therapy

In this paper, by wrapping the near-infrared (NIR) response polydopamine (PDA) as a nanocoating on the surface of spherical nano graphitic phase carbon nitride (g-C3N4), a multifunctional g-C3N4/PDA (CNP) nanocarrier platform was prepared. The π-conjugation system in PDA and the electronegative hydroxyl groups on the surface of CNP promote the creation of abundant active sites, which had a high drug loading rate of about 98.5 % for the electropositive GA. Due to the strong NIR reaction of CNP, the release of GA from CNP/GA can be greatly accelerated by the rising temperature, bonding disruption and charge transfer. Moreover, the photo-generated electron-hole pairs could be excited by the NIR effect of CNP, which promotes the production of ROS (·OH, ·O2– and 1O2) to induce apoptosis in HepG2 cells. Thus, the present spherical CNP nanocarrier with a combination of enzyme-mimic activity and NIR-responsive properties has a great potential for chemo-photothermal synergistic tumor therapy.

The Synthesis of Ag/TiO2 via the DC Magnetron Sputtering Method and Its Application in the Photocatalytic Degradation of Methyl Orange in Na2SO4 Solution

TiO2 and TiO2 films modified with Ag (Ag/TiO2) were prepared via the DC magnetron sputtering method and the degree of modification was controlled via the sputtering power and time of Ag. The microstructures and properties of these films were characterized using field emission scanning electron microscopy, X-ray diffractometry, ultraviolet–visible diffuse reflectance spectrometry, atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The results show that the prepared films have an anatase structure. Compared with pure TiO2, Ag deposition can improve the utilization of light. The three-dimensional images of Ag/TiO2 clearly show that with the increase in Ag sputtering power and sputtering time, Ag particles on the surface of the film gradually increase, and the structure of the film is relatively dense. The photocatalytic effect of Ag/TiO2 films is the best when the Ag sputtering power is 5 W and the sputtering time is 50 s. Under high-pressure mercury lamp irradiation, the photocatalytic degradation rate of methyl orange (MO) in pure MO solution with Ag/TiO2-5 W-50 s can reach 100% within 55 min, whereas that in MO-Na2SO4 mixed solution can reach 99.55% within 65 min. The results suggest that the presence of Na2SO4 in MO solution can inhibit the degradation of MO using Ag/TiO2, the result of XPS suggests that Na2SO4 accelerates the oxidation of Ag, which may lead to an increase in the recombination rate of photogenerated electron–hole pairs and a decrease in the degradation rate. During the process of recycling photocatalysts, the degradation rate of MO was apparently reduced. A possible reason is that the Ag particles have been oxidized and products of photocatalytic degradation are on the surface of the photocatalyst. The photocatalytic degradation mechanism was studied.

Localized surface-plasmon resonance effect as a new driver of Z-scheme electron transfer in cerium dioxide–graphitic carbon nitride heterojunctions

The intersecting interface between the two semiconductors of cerium dioxide (CeO2)–graphitic carbon nitride (g-C3N4) heterojunctions, which have demonstrated excellent photocatalytic activity, inhibits the rapid compounding of the photogenerated electron–hole pairs of g-C3N4. CeO2–g-C3N4 heterojunctions with Z-scheme and type-II electron-transfer routes were prepared via calcination in argon and air atmospheres, respectively. The built-in electric field theory cannot be used to explain the presence of a type-II electron-transfer route in CeO2–g-C3N4 heterojunctions. According the femtosecond transient absorption spectra, the localized surface-plasmon resonance (LSPR) effect of CeO2 drove the Z-scheme electron transfer in CeO2–g-C3N4 heterojunctions. The CeO2–g-C3N4 heterojunction exhibited a type-II electron-transfer route when the particle size of CeO2 increased, which attenuated the LSPR effect. The CeO2–g-C3N4 heterojunction with the Z-scheme electron-transfer route exhibited 4.4 times higher degradation efficiency for bamboo pulping wastewater than g-C3N4, and this result was attributed to the reduced complexation of photogenerated electron–hole pairs and extended photogenerated electron lifetime. Overall, this research provides a new idea for constructing Z-scheme electron-transfer heterojunctions.

MOF-on-MOF-derived Fe[sbnd]Zr bimetal oxides supported on hierarchically porous carbonized wood to promote photo-Fenton degradation of ciprofloxacin

MOF-on-MOF derivatives have served as promising heterogeneous Photo-Fenton (hetero-PF) catalysts, but its self-aggregation instability and limited photocatalytic activity inhibit the effective ciprofloxacin (CIP) removal. In this study, a novel hetero-PF catalyst, dual MOF-derived FeZr bimetal oxide embedded in a wood-converted porous carbon skeleton (ZrO2@Fe3O4/WPC), was successfully synthesized via a straightforward in-situ growth strategy combined with co-pyrolysis. The as-prepared hybrid photocatalysts, featuring a large surface area, effective porous structures, efficient light absorption and a narrow band gap demonstrated superior photo-Fenton activity, accomplishing approximately 99.1 % degradation of CIP within 120 min under neutral conditions. Furthermore, the ZrO2@Fe3O4/WPC hetero-PF system showed satisfactory performance in treating real water matrices. It can be inferred that the abundant heterojunctions, resulting from the synergistic effect of FeZr mixed oxide and the porous carbonized wood substrate, contributed to the rapid separation and migration of photogenerated electron-hole pairs. Meanwhile, the FeZr site in the graphitized carbon framework activates H2O2 to accelerate the generation of the OH and O2− radicals, leading to a heightened degradation efficiency of CIP. Besides, the photodegradation pathway of CIP is obtained by liquid chromatography-mass spectrometry (LC-MS). This study indicates that combining porous carbonized wood and heterometallic MOF derived materials provides a promising method for realizing high-efficiency photo-Fenton degradation of antibiotic water pollutions.

All-organic heterojunctions used for the excellent photocatalytic H2O2 synthesis: The key role of bay-position Cl in PDI

Melem is the basic structural unit of g-C3N4. When directly utilized as a photocatalyst, the separation efficiency of photogenerated electron-hole pairs is low. In this study, we constructed a Melem-based all-organic heterojunction (PICN) by reacting the -NH2 at the terminal of the Melem unit with the anhydride of PDA. The photocatalytic efficiency for H2O2 production of the heterojunction is 4.2 times that of CN. Introducing -Cl at the bay position of PDI further enhances the photocatalytic H2O2 production efficiency by 1.6 times. This enhancement is attributed to the introduction of -Cl, which not only broadens the UV–visible light absorption range of the sample but also improves the interface electron transfer efficiency between Melem and PDICl. Moreover, the introduction of -Cl can also reduce the overpotential of the O2 reduction reaction on the surface of the sample. These novel findings may provide insights for the design of organic heterojunction photocatalysts.

A green approach to synthesis of Ag-doped CeO2 nanorods embedded reduced graphene oxide nanocomposite for excellent photocatalytic and antimicrobial activity

In this paper, the Ag-doped cerium oxide nanorods embedded reduced graphene oxide (Ag@CeO2/rGO) nanocomposite was synthesized via Punica Granatum leaf extract for for photocatalytic degradation of methylene blue (MB) and 4-nitrophenol (4-NP). The microstructural results confirmed the successful decoration of Ag-doped CeO2 nanorods on rGO matrix. The photocatalytic properties, including photocatalytic degradation, charge transfer kinetics and photocurrent generation, are systematically investigated using electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD). The results of photocatalytic dye degradation measurements indicated that Ag@CeO2/rGO nanocomposite is more effective than pristine CeO2 to degrade the MB dye, and the degradation rate reached 100 % in 60 min. The decomposition of MB with Ag@CeO2/rGO nanostructure followed first-order reaction kinetics with a reaction rate constant (Ka) of 0.0198 min−1. The EIS and OCVD measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in CeO2 by the separation of photo-generated electron–hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity. The photocurrent density of Ag@CeO2/rGO, CeO2/rGO and pristine CeO2 are 215, 167.4 and 98.8 mAcm−2, respectively.

Facile construction of Bi2WO6/TiO2 microspheres heterojunction for boosting photocatalytic degradation of organic dyes

Flower-like Bi2WO6 microspheres and TiO2 spherical particles were prepared by a facile hydrothermal method without any surfactant or template. A unique Z-Scheme Bi2WO6/TiO2 heterojunction was successfully synthesized via a simple physical mixing method. The effect of mass ratio on the structure, morphology, optical properties, BET surface area and photocatalytic performance evaluated by degradation of organic dyes including Rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under solar irradiation was systemically investigated. When the mass ratio of Bi2WO6 to TiO2 was 1:4, the Bi2WO6/TiO2 composites exhibited the highest photocatalytic degradation efficiency, the highest degradation efficiency of RhB and MB reached 95.2 % and 89.3 %, which could be attributed to the construction of heterojunction structure between TiO2 and Bi2WO6. The optical absorption capacity of Bi2WO6/TiO2 composites was stronger than pure TiO2. Furthermore, the radical-quenching experiments proved that ·O2– and h+ played crucial roles in the photocatalytic reaction. The suitable band potential of Bi2WO6 (3.19 eV) and TiO2 (2.89 eV) revealed the Z-Scheme pathway and possible photocatalytic mechanism of Bi2WO6/TiO2 composites for organic dyes degradation. Thus, the direct Z-scheme Bi2WO6/TiO2 heterojunction effectively promoted separation of photogenerated electron-hole pairs, resulting in higher photocatalytic activity.

Impact of blue-shifted effective joint density of electronic states on the photoluminescence of nanostructured silicon

Light emission from nanostructured silicon has triggered tremendous research interest for three decades. Yet, the exact mechanism of photoluminescence from silicon-based nano-systems is still not completely understood. It is generally believed that quantum confinement and surface chemistry play a combined role in determining the luminescence characteristics on nano silicon. In this work, we show that the evolution of electron-hole effective joint density of states, resulting from the relaxation of k-selection rule, can account for the much-observed temperature dependent shift of the luminescence spectra of nanostructured silicon. Deconvolution of the emission characteristics reveals three distinct radiative recombination channels that can be attributed to band-to-band, band-to-trap and trap-to-trap transitions. At temperatures below ∼200 K, the peak due to band-to-band transition exhibit a nearly linear blue shift with increasing temperature while at higher temperatures this trend is reversed. The rate of variation of emission peak energy with temperature is also found to be dependent on average crystallite size. These results are explained in terms of shift in the effective joint density of state function of photogenerated electron-hole pairs. The shift provides experimental evidence of the pseudo-direct transitions in the quantum-confined nanostructure of silicon.

Decoration of CeO2 nanoparticles on g-C3N4 for degradation of microcystins through photocatalytic activation of peroxymonosulfate

As the most common cyanobacterial toxin, microcystin LR (MC-LR) has dangerous neurotoxicity and hepatotoxicity, posing a serious threat to human and ecosystem health. Therefore, we constructed a type-II CeO2/g-C3N4 heterojunction for highly efficient degradation of MC-LR via peroxymonosulfate (PMS) assisted-visible light-driven photocatalysis process. Multi techniques were conducted to analyze the microstructures, optical and electrochemical properties of CeO2/g-C3N4. The experimental results indicate that the composite material has appropriate energy levels and establishes a well-established interfacial band structure, facilitating the migration and separation of photogenerated electron-hole pairs. The coupled photocatalysis and PMS activation system presented a dramatically enhanced catalytic performance. Within 60minutes, 10% CeO2/g-C3N4/PMS could degrade 99% of the MC-LR present in the solution under visible light irradiation, which was about 3.8 times higher than that in a single photocatalytic system. The optimal conditions for this degradation process were a PMS dosage of 3.0mM and an initial pH of 2.5. EPR analysis revealed that SO4•ˉ, O2•ˉ, h+, and 1O2 were involved in the degradation process. Moreover, the intermediates of its degradation were analyzed through UPLC-MS. This study provides a valuable resource for the intelligent development of type-II heterojunction and its practical implications in the photodegradation of MC-LR through synergistic activation with PMS.

Efficient peracetic acid activation by high-index facets of Cu2O under simulated solar light: The crucial role of uncoordinated Cu atoms

Tuning the facets of transition-metal catalysts to achieve effective micropollutant removal via peracetic acid (PAA) activation is a promising approach. However, within this process, the correlation between PAA activation and the atomic arrangement of the exposed facets is ambiguous. Herein, we present a comprehensive study wherein a series of Cu2O materials, with typical high-index facets ({211}, {311}, and {332}) and low-index facets ({100}, {110}, and {111}), were synthesized. These materials were used to investigate facet-dependent PAA activation for tetracycline (TC) degradation under simulated solar light irradiation. The results demonstrate that Cu2O with high-index {332} facets exhibit the optimal TC degradation (96.65 % within 20 min), and its kobs values are 1.52 and 2.01 times those of Cu2O with {311} and {211} facets, respectively. Detailed identification of the active species proved that •OH, 1O2, and the electron transfer process induced by the reactive Cu (I)–PAA* complexes were involved in TC degradation. In contrast to the {211} and {311} facets, PAA demonstrated a heightened tendency for adsorption and activation into active species on the {332} facets because of the denser uncoordinated Cu atoms. In addition, the facet heterojunction composed of {332} and {100} facets was conducive to the separation of photogenerated electron-hole pairs and charge migration, thus promoting the Cu(II)/Cu(I) cycle. In the practical applicability evaluation, Cu2O with {332} facets effectively removed multiple pollutants as well as actual pharmaceutical wastewater. This study provides a novel strategy for PAA activation by regulating the exposed facets of the catalyst.

Ultrathin-Shelled Zn-AgIn5S8/ZnS Quantum Dots with Partially Passivated Trap States for Efficient Hydrogen Production

The manipulation of trap states plays a crucial role in the development of efficient photocatalysts. An ultrathin-shelled Zn-AgIn5S8/ZnS quantum dots (QDs) photocatalyst was synthesized via in situ growth using a low-temperature hydrothermal method. The optical properties of the samples coated with ZnS shell were studied vis UV-vis absorption and fluorescence spectra. The ultrathin ZnS shell plays an important role in the Zn-AgIn5S8/ZnS core–shell heterostructure photocatalytic water splitting system, which could reduce surface defects, prolong the carrier lifetime and improve the photo-generated electron–hole pair separation effectively, resulting in the improved photocatalytic efficiency and enhanced stability of the catalyst. The results provide an effective guideline for shell thickness design in future constructions of the core–shell heterostructure photocatalyst.