Photogenerated Electron-hole Pairs Research Articles

Porous carbon nanofiber/porphyrin-based metal organic frameworks/TiO2 nanoparticles ternary materials for selective detection and photoreduction of Cr(Ⅵ)

For the heavy metal ion Cr(Ⅵ), which is widely present in wastewater with acute toxicity, mutagenicity and carcinogenicity, we successfully constructed a ternary material of PCNFs/CuMOF/TiO2 for rapid detection and photoreduction of Cr(Ⅵ). The material has obvious advantages: on the one hand, ZIF-8/polyacrylonitrile (PAN) nanofibers and their derived porous carbon nanofibers (PCNFs) were synthesized by electrospinning and high temperature carbonization, which provided a loading platform for CuMOF and TiO2, effectively inhibited the agglomeration of CuMOF and TiO2, and ensured the exposure of active sites. Meanwhile, its excellent conductivity can promote the effective migration of photogenerated carriers in the photocatalytic process. On the other hand, CuMOF constructed with tetra-carboxyphenylporphyrin (TCPP) as the linking arm and Cu(NO3)2·3 H2O as the metal node was directly loaded on the surface of porous carbon nanofibers (PCNFs), and then TiO2 nanoparticles were introduced by hydrothermal method. CuMOF ensures the responsiveness of the composite to visible light. Moreover, the energy level structure of TiO2 matches with CuMOF, which effectively inhibits the recombination of photogenerated electron-hole pairs (e--h+). The results show that the colorimetric detection of Cr(Ⅵ) was achieved by using 3,3′,5,5′-tetramethylbenzidine (TMB) as the sensing probe. The method was highly selective for Cr(Ⅵ) ions with a limit of detection (LOD) of 24.1 nM. Encouragingly, PCNFs/CuMOF/TiO2 was further used as a photocatalyst. The reduction rate of Cr(Ⅵ) under visible light irradiation is 96.1 % in 60 min. The active species trapping experiments confirm the key role of e- photocatalytic reduction, upon which a possible photocatalytic mechanism is proposed. The degradation rate of Cr(Ⅵ) is still 86.4 % after the five times cycle, and the good stability and reproducibility allow it to be used as a potential green photocatalyst for the conversion of Cr(Ⅵ) to Cr(Ⅲ).

Unlocking enhanced photocatalytic power: Donor-acceptor synergy in non-metallic g-C3N4 hollow nanospheres

Selecting safe, non-toxic, and non-metallic semiconductor materials that facilitate the degradation of pollutants in water stands out as an optimal approach to combat environmental pollution. Herein, graphitic carbon nitride (g–C3N4)–based hollow nanospheres nonmetallic photocatalyst modified with covalent organic framework materials named TpMA, based on 1, 3, 5-trimethylchloroglucuronide (Tp) and melamine (MA), was successfully synthesized (abbreviated as CNTP). The ordered electron donor-acceptor structure inherent in TpMA contributed to enhancing the transport efficiency of photogenerated carriers in CNTP. The CNTP photocatalysts exhibited excellent performance in degrading rhodamine B and tetracycline in visible light, with optimal degradation rates reached more than 90% in 60 and 80 min, respectively, which were 5.3 and 3.0 times higher than those of pure CNNS. The increased photocatalytic efficiency observed in CNTP composites could be traced back to the covalently connection between the two molecules, forming a π-conjugated system that facilitated the separative efficiency of photogenerated electron-hole pairs and intensified the utilization of visible light. This study provided a new means to design and fabricate highly efficient and environmentally friendly non-metallic photocatalytic materials.

Unveiling the potential of a g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction photocatalyst for rechargeable zinc-air battery: Visible-light-driven photo-assisted charging for bifunctional ORR and OER at the air cathode

Advancements in solar-driven energy storage technology have been achieved for rechargeable zinc-air batteries (RZABs), facilitating accelerated kinetic responses in both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we successfully synthesized a novel g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction through a facile hydrothermal process, demonstrating its efficacy as a bifunctional photocatalyst. Upon exposure to LED irradiation, this heterojunction triggers an effective separation of the photogenerated electron-hole pairs, resulting in enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance by 46.19 % and 65.69 % respectively, compared to non-LED conditions. Interestingly, the reduction in the potential gap under LED irradiation (0.06 V), correlating with a significant 2.71 % increase in round-trip efficiency (RTE), is observed. In addition, the optimized band alignment derived from g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction for photo-assisted charging rechargeable zinc-air batteries is proposed. Insightfully, photo-enhanced charging in RZABs mechanism during the charge/discharge process through in-situ X-ray absorption spectroscopy (XAS) is monitored, confirming the large interaction between O2 adsorption and Bi 6d orbitals of g-C3N4/BiOBr/Bi2O2CO3 in the presence of LED. In conclusion, our innovative g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction underscores the significant role that visible-light-driven photocatalysts can play in enhancing the efficiency of rechargeable zinc-air batteries.

Photoexcitation-induced efficient detoxification and removal of arsenite in contaminated water by a layered double hydroxide-supported polyacrylate stabilized ferrous sulfide composite

The effective detoxification and removal of arsenite (As(III)) has been widely concerned because of its strong toxicity and migration ability. In this study, we designed a layered double hydroxide-supported polyacrylate stabilized ferrous sulfide composite (PAA/FeS@LDH) and coupled it with UV excitation to purify As(III)-polluted water. The removal efficiency of As(III) under UV irradiation reached almost 100% in 120 min, and the first-order kinetic constant was 3.12 orders of magnitude higher than under dark. UV irradiation significantly accelerated the oxidation and detoxification of As(III) at the interface of PAA/FeS@LDH and treatment solution. It is attributable to the generation of reactive oxygen species (ROS) intermediates, including .O2–, .OH, and SO4.– under UV irradiation, because of the presence of the photogenerated electron-hole pairs and iron valence states cycles. Importantly, .O2– may be rapidly captured and oxidized to 1O2 on the surface of PAA/FeS@LDH that is also an important contributor to the oxidation removal of As(III). Noticeably, As(III) concentrations in the real water were rapidly reduced to below the guideline limitation of drinking water (10 μg/L) within 20 min under UV irradiation. Our outcomes provide a novel photoexcitation treatment system for the efficient detoxification and removal of As from actual wastewater.

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.

Zn-Mn bimetallic oxide derived from waste battery to activate peroxymonosulfate for bisphenol A removal under visible light irradiation

In this study, Zn-Mn bimetallic oxide (ZMBO) was synthesized from spent alkaline zinc-manganese batteries to effectively activate peroxymonosulfate (PMS) under visible light irradiation. PMS activation can be triggered by Mn-composition, which could be augmented thanks to the visible light response of Zn-composition. Meanwhile, the introduction of PMS could effectively hinder the rapid recombination of photogenerated electron-hole pairs. By adding 1.00 mM of PMS and 0.50 g/L of ZMBO, the Vis/ZMBO/PMS system could remove 90.0 % of bisphenol A (BPA) in 120 min under the neutral pH condition. Quenching experiment and electron paramagnetic resonance technique were used to identify the reactive species, and singlet oxygen as well as photogenerated hole were identified as the major reactive species which exhibited high selectivity towards electron-rich contaminants. X-ray photoelectron spectroscopy (XPS) confirmed that the cycles between manganese in Mn(II), Mn(III) and Mn(IV) promoted PMS activation. The ZMBO photocatalyst exhibited excellent reusability. The existence of common anions (Cl–, NO3– and SO42–) presented a slight inhibition for BPA degradation while little BPA was removed with the addition of 5.00 mM H2PO4–. This study provides an alternative for the feasible utilization of waste battery, and the Vis/ZMBO/PMS system shows great potential in the elimination of pollutant with electron-donating capability from water.

The transition from indirect band gap to direct band gap and effectively separating of electron-hole pairs in h-BC2N / MoSi2N4 heterojunction for photocatalytic water splitting

To improve the photocatalytic efficiency of MoSi2N4, we decided to use the organic material h-BC2N to form a new photocatalytic heterojunction, h-BC2N/MoSi2N4. Firstly, we calculated the phonon spectra of h-BC2N, MoSi2N4, and h-BC2N/MoSi2N4 heterojunction to determine their dynamical stability. Next, using the HSE06 density functional theory method, we calculated the band structures and DOS of h-BC2N, MoSi2N4, and h-BC2N/MoSi2N4 heterojunction to determine their band structures and types. To analyze the electron transfer in the h-BC2N/MoSi2N4 heterojunction, we calculated the work function and differential charge density to determine the direction of the built-in electric field and the electron transfer between h-BC2N and MoSi2N4. Furthermore, we discussed the interaction between h-BC2N and MoSi2N4, and the results showed that the VBM and CBM of h-BC2N and MoSi2N4 changed with the formation of the heterojunction. Then, we analyzed the reaction mechanism of the h-BC2N/MoSi2N4 heterojunction and found that the built-in electric field promotes the electron transition from the CBM of MoSi2N4 to the VBM of h-BC2N, effectively separating the photo-generated electron-hole pairs of MoSi2N4 in space, making h-BC2N/MoSi2N4 heterojunction a classical Type Z heterojunction. These results suggest that h-BC2N/MoSi2N4 heterojunction can improve the photocatalytic efficiency of MoSi2N4.

High-Efficient photocatalytic degradation of Levofloxacin via a novel ternary Fe2O3/CeO2/ZnO Heterostructure: Synthesis Optimization, Characterization, toxicity assessment and mechanism insight

Considering the serious problem of lack of freshwater worldwide and the effectiveness of the photocatalysis process in water purification, we prepared a novel Ternary Fe2O3/CeO2/ZnO photocatalyst toward degradation of Levofloxacin (LEF) antibiotic. In this study, the CeO2 was synthesized through the hydrothermal route and the nanocomposite was prepared using a simple-impregnation method. Then the synthesized materials with various weight percentages 5 %FeCe (10, 20, 30 and 40 %) on the ZnO were completely characterized in the aspects of structural, morphological and optical properties with the aid of XRD, XPS, BET, TEM, SEM, EIS, ESR, Band-gap, Photocurrent, Mott Schottky, etc. The XPS analysis depicts the successful construction of required bonds among FeCe/ZnO materials. The enhancement of LEF decomposition was investigated utilizing RSM-CCD method, considering factors such as the amount of catalyst used, irradiation time, pH levels, and the initial concentration of LEF. The trapping experiments of free radicals highlight the significant contributions of the •OH and •O2– radicals. A notable degradation rate of 98.9 % was achieved under optimal operational conditions, which included catalyst dosage of 0.69 g/L, irradiation period of 83.64 min, initial LEF concentration of 37.9 mg/L, and pH of 6.18. Furthermore, the findings of EIS, photocurrent, and Mott-Schottky analyses allowed for proposing a suitable charge transfer mechanism and demonstrated effective separation of photo-generated electron-hole pairs. Additionally, LC-MS analysis was utilized to elucidate the intermediate products generated during the photodegradation of LEF, leading to the proposal of plausible degradation pathways. The exceptional efficiency of the 30FeCe/ZnO photocatalyst highlights its promising potential for the efficient treatment of persistent organic pollutants on a large scale in wastewater treatment plants.

Experimental and theoretical study on potentiated photocatalytic nitrogen fixation of Mo doped InVO4 nanorods

Photocatalytic nitrogen fixation is acknowledged as an eco-friendly substitute for the conventional Haber-Bosch procedure for nitrogen (N2) conversion into ammonia (NH3). Localized electron-rich oxygen vacancies (OVs) on the surface of indium-based semiconductors have been proven to possess the capacity to capture and activate N2. Herein, oxygen vacancy-enriched Mo doped InVO4 nanorods with preferred orientation have been successfully synthesized via a simple hydrothermal reaction. Doping Mo into InVO4 nanorods can not only generate numerous OVs but also simultaneously modulate their electronic structure, significantly improving the efficiency of photocatalytic nitrogen fixation. Benefiting from the optimal Mo doped content, the 5 %Mo/InVO4 sample presents the optimal photocatalytic performance with the NH3 yield of 162.00 μmol·g−1·h−1, which is 2.4 times higher than that of pristine InVO4 sample. The characterization results reveal that the introduction of OVs augments light consumption and impedes the recombination of photogenerated electrons-hole pairs. Furthermore, the effect of OVs by doping Mo on the nitrogen fixation performance is also verified by the density functional theory (DFT) theoretical calculation. This work provides a new platform for the development of promising catalysts in the photocatalytic nitrogen fixation field, and has certain theoretical and practical value.

A novel noble-metal-free FeS2/Mn0.5Cd0.5S heterojunction for enhancing photocatalytic H2 production activity: Carrier separation, light absorption, active sites

BackgroundThe development of efficient and noble-metal-free photocatalysts is greatly essential for photocatalytic hydrogen production. However, the photocatalytic activity of a single photocatalyst is usually limited for various reasons. MethodsHerein, FeS2/Mn0.5Cd0.5S (FSMCS) heterojunctions were constructed by a simple solvent evaporation method. The morphological characterizations revealed a raspberry-like hollow microsphere structure for FeS2 and irregular granularity for Mn0.5Cd0.5S. Photoluminescence (PL) and electrochemical experiments indicated that the FSMCS composite effectively facilitated the separation of photogenerated electron-hole pairs. The UV–vis diffuse reflectance spectrum (DRS) showed that, in FSMCS composite, the visible light absorption range was effectively expanded to the full visible light. Significant findingsExcellent photocatalytic activity in FSMCS heterojunctions without loading noble metals because FeS2 could serve an active site for hydrogen production. The optimum FSMCS composite had excellent photocatalytic hydrogen production activity (6.1 mmol·g−1·h−1), which was 5.6 and 2.3 times higher than that of the pristine Mn0.5Cd0.5S (1.1 mmol·g−1·h−1) and Mn0.5Cd0.5S-1 %Pt (2.7 mmol·g−1·h−1). Meanwhile, in four round-robin tests, the activity of the 5FSMCS photocatalyst did not significantly decrease. This work proved that combining Mn0.5Cd0.5S and non-precious metal cocatalysts to construct heterojunctions is a promising strategy for photocatalytic hydrogen production.

Polyimide/Ag2WO4 Z-Scheme Heterojunction for Efficient Photocatalytic Degradation of Tetracycline.

It is of great significance to construct a Z-scheme heterojunction for improving solar light harvesting and achieving efficient separation of photogenerated carriers and then enhancement of the photocatalytic performance of semiconductor photocatalysts. Herein, the direct Z-scheme PI/Ag2WO4 heterojunction was designed and prepared according to the band edge potentials of the semiconductor. Due to the fact that the Z-scheme structure not only endowed the PI/Ag2WO4 composites with efficient separation of photogenerated electron-hole pairs but also reserved the redox ability of the valence band and conduction band of monophase catalysts, the 50% PI/Ag2WO4 heterojunction exhibited excellent photocatalytic activity, which were 2.9 and 1.5 times those of the PI and Ag2WO4 photocatalysts, respectively. The photocatalytic reaction mechanism of PI/Ag2WO4 composites was confirmed by the results of TEM, UV-vis, XPS, and EPR experiments. This work provides a feasible strategy to design high-performance photocatalysts in the field of practice purification of wastewater.

Facile synthesis of CuOx-decorated TiO2 nanoparticles via oxygen-limited pyrolysis of Cu(II) complex for efficient photocatalytic hydrogen evolution

CuOx-decorated TiO2 (CuOx/TiO2) nanoparticles have been prepared by the pyrolysis of Cu(II) complex on TiO2 in an oxygen-limited atmosphere. A solution phase deposition method combined with freeze drying was employed for depositing the 2-methylimidazole-Cu(II) complex onto TiO2 nanoparticles. The effect of decoration of CuOx on TiO2 nanoparticles in terms of the crystal phase, morphology, chemical compositions, surface area, surface elemental states, optical absorption and emission properties, was investigated using a series of characterization tools. The oxygen-limited pyrolysis of 2-methylimidazole resulted in the reduction of partial Ti4+ and Cu2+ ions into Ti3+, Cu+ and Cu0 species, respectively. The surface decoration of CuOx was found to improve the separation and migration of photogenerated electron-hole pairs and increase the life time of excitons. Furthermore, the photocatalytic performance of CuOx/TiO2 nanoparticles was evaluated for hydrogen evolution in aqueous methanol solution under UV–visible light irradiation. The CuOx/TiO2 photocatalyst with the optimal cocatalyst loading achieved hydrogen evolution rate of 4.34 mmol h−1 g−1, with 71- and 5.5-fold enhancement in activity over neat TiO2 and CuOx/P25, respectively. It is expected that the combination of deposition and pyrolysis of 2-methylimidazole-Cu(II) complex could be an effective approach for the decoration of Cu and its oxides on other supports.

Photoluminescence and light absorption edges of Bi2O2CO3 regulated by pressure-induced oxygen vacancies

In this work, Bi2O2CO3 (BOC) was subjected to high-pressure treatment using a diamond anvil cell at pressures of 0, 4.2, and 25.6 GPa to improve the photocatalytic performance. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed for in-depth analysis. The results indicated that after treatment at 25.6 GPa, oxygen vacancies were induced in the powder, and defect energy levels were formed within the band gap of the BOC, thereby expanding its absorption of visible light. The light absorption edge shifted from 377 nm to 562 nm, which have enhanced the ability of separating photogenerated electron-hole pairs. This study demonstrates that high-pressure treatment is beneficial for improving the photocatalytic performance of Bi2O2CO3.

Efficient photocatalytic reforming of cellulose for H2 production enabled by oxygen-vacancy rich SrMoO4/palygorskite nanocomposite

Photocatalytic reforming of biomass into hydrogen along with the simultaneous production of high-value chemicals, plays a significant role in advancing a sustainable economy. A major challenge in this process is the effective utilization of photogenerated holes while simultaneously preventing the rapid recombination of photoinduced carriers, which is crucial for optimizing solar-to-hydrogen conversion efficiency. In this study, an exquisite oxygen-rich vacancy (OV) plasmonic SrMoO4/phosphor acidized palygorskite (H-Pal) nanocomposite was prepared for efficient photocatalytic H2 evolution while producing high value-added lactic acid (LA) simultaneously. Results showed that the integration of local surface plasmon resonance (LSPR) effect and OV enhanced the photothermal catalytic conversion of cellulose reaching as high as 87%. Notably, the selectivity of LA reached as high as 31% while the H2-evolution efficiency reached 906 μmol•g-1•h-1. The local thermal effect improved the conversion efficiency of cellulose, and the OV in SrMoO4 introduced instantaneous Lewis acid sites during light irradiation, which improved the selectivity for LA. Moreover, the formation of an S-scheme SrMoO4-OV/H-Pal heterostructure effectively inhibited the recombination of photogenerated electron-hole pairs and maintained a high redox potential. This work demonstrates a promising strategy for efficient photocatalytic H2-evolution, coupled with production of high-valuable chemicals from biomass resources by taking advantage of clay materials.

Edge-Rich 3D Structuring of Metal Chalcogenide/Graphene with Vertical Nanosheets for Efficient Photocatalytic Hydrogen Production.

Constructing pertinent nanoarchitecture with abundant exposed active sites is a valid strategy for boosting photocatalytic hydrogen generation. However, the controllable approach of an ideal architecture comprising vertically standing transition metal chalcogenides (TMDs) nanosheets on a 3D graphene network remains challenging despite the potential for efficient photocatalytic hydrogen production. In this study, we fabricated edge-rich 3D structuring photocatalysts involving vertically grown TMDs nanosheets on a 3D porous graphene framework (referred to as 3D Gr). 2D TMDs (MoS2 and WS2)/3D Gr heterostructures were produced by location-specific photon-pen writing and metal-organic chemical vapor deposition for maximum edge site exposure enabling efficient photocatalytic reactivity. Vertically aligned 2D Mo(W)S2/3D Gr heterostructures exhibited distinctly boosted hydrogen production because of the 3D Gr caused by synergetic impacts associated with the large specific surface area and improved density of exposed active sites in vertically standing Mo(W)S2. The heterostructure involving graphene and TMDs corroborates an optimum charge transport pathway to rapidly separate the photogenerated electron-hole pairs, allowing more electrons to contribute to the photocatalytic hydrogen generation reaction. Consequently, the size-tailored heterostructure showed a superior hydrogen generation rate of 6.51 mmol g-1 h-1 for MoS2/3D graphene and 7.26 mmol g-1 h-1 for WS2/3D graphene, respectively, which were 3.59 and 3.76 times greater than that of MoS2 and WS2 samples. This study offers a promising path for the potential of 3D structuring of vertical TMDs/graphene heterostructure with edge-rich nanosheets for photocatalytic applications.

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.