Type-II surface heterojunction of bismuth-rich Bi4O5Br2 on nitrogen-rich g-C3N5 nanosheets for efficient photocatalytic degradation of antibiotics

Single-crystal oxygen-rich bismuth oxybromide nanosheets with highly exposed defective {10-1} facets for the selective oxidation of toluene under blue LED irradiation

Reactive radicals are crucial for activating inert and low-polarity C(sp3)-H bonds for the fabrication of high value-added products. Herein, novel single-crystal oxygen-rich bismuth oxybromide nanosheets (Bi4O5Br2 SCNs) with more than 85 % {10-1} facets exposure and oxygen defects were synthesized via a facile solvothermal route. The Bi4O5Br2 SCNs demonstrated excellent photocatalytic performance in the selective oxidation of toluene under blue light. The yield of benzaldehyde was 1876.66 μmol g-1 h-1, with a selectivity of approximately 90 %. Compared to that of polycrystalline Bi4O5Br2 nanosheets (Bi4O5Br2 PCNs), the activity of Bi4O5Br2 SCNs exhibit a 21-fold increase. Experimental studies and density functional theory (DFT) calculations have demonstrated that the defect Bi4O5Br2 (10-1) facets exhibits exceptional adsorption properties for O2 molecules. In addition, the single-crystal structure in the presence of surface defects significantly increases the separation and transport of photogenerated carriers, resulting in the effective activation of adsorbed O2 into superoxide radicals (•O2-). Subsequently, the positively charged phenylmethyl H is readily linked to the negatively charged superoxide radical anion, thereby activating the CH bond. This study offers a fresh perspective and valuable insights into the development of efficient molecular oxygen-activated photocatalysts and their application in the selective catalytic conversion of aromatic C(sp3)-H bonds.

Promoting the suitability of graphitic carbon nitride and metal oxide nanoparticles: A review of sulfonamides photocatalytic degradation

The widespread consumption of pharmaceutical drugs and their incomplete breakdown in organisms has led to their extensive presence in aquatic environments. The indiscriminate use of antibiotics, such as sulfonamides, has contributed to the development of drug-resistant bacteria and the persistent pollution of water bodies, posing a threat to human health and the safety of the environment. Thus, it is paramount to explore remediation technologies aimed at decomposing and complete elimination of the toxic contaminants from pharmaceutical wastewater. The review aims to explore the utilization of metal-oxide nanoparticles (MONPs) and graphitic carbon nitrides (g-C3N4) in photocatalytic degradation of sulfonamides from wastewater. Recent advances in oxidation techniques such as photocatalytic degradation are being exploited in the elimination of the sulfonamides from wastewater. MONP and g-C3N4 are commonly evolved nano substances with intrinsic properties. They possessed nano-scale structure, considerable porosity semi-conducting properties, responsible for decomposing wide range of water pollutants. They are widely applied for photocatalytic degradation of organic and inorganic substances which continue to evolve due to the low-cost, efficiency, less toxicity, and more environmentally friendliness of the materials. The review focuses on the current advances in the application of these materials, their efficiencies, degradation mechanisms, and recyclability in the context of sulfonamides photocatalytic degradation.

Highly efficient hydrogen production and selective CO2 reduction by the C3N5 photocatalyst using only visible light

The production of energy sources by metal-free photocatalysts based on graphitic carbon nitride (g-C3N4) has garnered substantial attention. In this study, nitrogen-rich carbon nitride (C3N5) was successfully synthesized through the thermal polycondensation of 3-amino-1,2,4-triazole. The structural and physical characterization has suggested that a portion of the triazine rings, which constitute the structural framework of g-C3N4, may be substituted with five-membered rings in C3N5. Furthermore, the polymerization of C3N5 proceeded more extensively than that of g-C3N4 from melamine precursors. The increased nitrogen content in C3N5 resulted in a heightened number of π-electrons and a narrowed energy bandgap, with the potential of the valence band maximum being negatively shifted. Additionally, photocatalytic assessments encompassing nitro blue tetrazolium reduction, H2 production from triethanolamine aqueous solution, and CO2 reduction in the liquid phase were performed. All findings demonstrated that C3N5 exhibits significantly superior photocatalytic properties compared to g-C3N4. It is particularly noteworthy that C3N5 selectively generates methanol and H2 from oversaturated CO2 solutions under visible light irradiation, while g-C3N4 selectively generates formaldehyde. These outcomes strongly indicate that C3N5 serves as a metal-free, visible-light-responsive photocatalyst, capable of contributing to both the production of renewable energy sources and the reduction of greenhouse effect gases.

Cobalt doped nitrogen-vacancies-rich C3N5 with optimizing local electron distribution boosts peroxymonsulfate activation for tetracycline degradation: Multiple electron transfer mechanisms

Heterogeneous photocatalysis coupled with peroxymonosulfate (PMS) activation is considered as an advanced water purification technology for emerging contaminates degradation. In this study, Cobalt (Co) doped nitrogen-vacancies-rich C3N5 photocatalysts (Co/Nv-C3N5) were designed to activate PMS for tetracycline removal. The photo-chemical oxidation system displayed superior advantage, in which the observed rate constant of tetracycline degradation (0.1488 min-1) was 10.86 and 1.82 times higher than that of photo-oxidation and chemical-oxidation systems. Density functional theory calculation results verified the reconstruction of local charge distribution during PMS activation, indicating Co doping and nitrogen-vacancy engineering not only promoted photoelectrons capture, but also boosted electron transfer from the C-N framework to PMS and the generation of active species. Furthermore, several unique multiple electron transfer mechanisms were found in nonradicals (h+, 1O2 and Co(IV)) pathways. Additionally, three possible tetracycline degradation pathways were proposed and the toxicity of the intermediates was evaluated. Overall, the findings from this study provided a novel strategy for developing high-efficient photocatalyst for the rapid degradation of organic pollutants.

Photoelectrochemical biosensor for DNA demethylase detection based on enzymatically induced double-stranded DNA digestion by endonuclease-exonuclease system and Bi4O5Br2-Au/CdS photoactive material

A novel photoelectrochemical (PEC) biosensor for the detection of DNA demethylase MBD2 was developed based on Bi₄O₅Br₂-Au/CdS photosensitive material. Bi₄O₅Br₂ was firstly modified with gold nanoparticles (AuNPs), following with the modification onto the ITO electrode with CdS to realize the strong photocurrent response as a result of AuNPs had good conductibility and the matched energy between CdS and Bi₄O₅Br₂. In the presence of MBD2, double-stranded DNA (dsDNA) on the electrode surface was demethylated, which triggered the digestion activity of endonuclease HpaII to cleave dsDNA and induced the further cleavage of the dsDNA fragment by exonuclease III (Exo III), causing the release of biotin labeled dsDNA and inhibiting the immobilization of streptavidin (SA) onto the electrode surface. As a results, the photocurrent was increased greatly. However, in the absence of MBD2, HpaII digestion activity was inhibited by DNA methylation modification, which further caused the failure in the release of biotin, leading to the successful immobilization of SA onto the electrode to realize a low photocurrent. The sensor had a detection of 0.3-200 ng/mL and a detection limit was 0.09 ng/mL (3σ). The applicability of this PEC strategy was assessed by studying the effect of environmental pollutants on MBD2 activity.

Engineered g-C3N5-Based Nanomaterials for Photocatalytic Energy Conversion and Environmental Remediation

Photocatalysis plays a vital role in sustainable energy conversion and environmental remediation because of its economic, eco-friendly, and effective characteristics. Nitrogen-rich graphitic carbon nitride (g-C₃N₅) has received worldwide interest owing to its facile accessibility, metal-free nature, and appealing electronic band structure. This review summarizes the latest progress for g-C₃N₅-based photocatalysts in energy and environmental applications. It begins with the synthesis of pristine g-C₃N₅ materials with various topologies, followed by several engineering strategies for g-C₃N₅, such as elemental doping, defect engineering, and heterojunction creation. In addition, the applications in energy conversion (H₂ evolution, CO₂ reduction, and N₂ fixation) and environmental remediation (NO purification and aqueous pollutant degradation) are discussed. Finally, a summary and some inspiring perspectives on the challenges and possibilities of g-C₃N₅-based materials are presented. It is believed that this review will promote the development of emerging g-C₃N₅-based photocatalysts for more efficiency in energy conversion and environmental remediation.

Dual S-scheme ZnO–g-C3N4–CuO heterosystem: a potential photocatalyst for H2 evolution and wastewater treatment

A ZnO–g-C3N4–CuO catalyst prepared by an ecofriendly solution combustion process is used for H2 evolution. The mechanism of H2 evolution over ZnO–g-C3N4–CuO is described under visible light illumination.

Calcination-Induced Oxygen Vacancies Enhancing the Photocatalytic Performance of a Recycled Bi2O3/BiOCl Heterojunction Nanosheet

With the rapid development of industry, bismuth-based semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi₂O₃/BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min^-1 compared with 0.05228 min^-1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

Direct Z-Scheme g-C3N5/Cu3TiO4 Heterojunction Enhanced Photocatalytic Performance of Chromene-3-Carbonitriles Synthesis under Visible Light Irradiation

In order to make the synthesis of pharmaceutically active carbonitriles efficient, environmentally friendly, and sustainable, the method is regularly examined. Here, we introduce a brand-new, very effective Cu3TiO4/g-C3N5 photocatalyst for the production of compounds containing chromene-3-carbonitriles. The direct Z-Scheme photo-generated charge transfer mechanism used by the Cu3TiO4/g-C3N5 photocatalyst results in a suppressed rate of electron-hole pair recombination and an increase in photocatalytic activity. Experiments showed that the current method has some advantages, such as using an environmentally friendly and sustainable photocatalyst, having a simple procedure, quick reaction times, a good product yield (82–94%), and being able to reuse the photocatalyst multiple times in a row without noticeably decreasing its photocatalytic performance.

Photocatalytic assessed adsorptive removal of tinidazole from aqueous environment using reduced magnetic graphene oxide-bismuth oxychloride and its silver composite

Antibiotics (tinidazole (TNZ)) in wastewater, exhibit adverse effects on humans and ecosystem. The current study was aimed to synthesize photocatalysts mrGO/BiOCl and mrGO/BiOCl/Ag. mrGO was coupled with BiOCl by hydrothermal method and Ag was deposited over it. The synthesized mrGO/BiOCl and mrGO/BiOCl/Ag were confirmed by Pzc analysis (5.5 and 4.4 for mrGO/BiOCl and mrGO/BiOCl/Ag, respectively), surface area analysis (380 m² g^-1, 227.7 m² g^-1, 220 m² g^-1 for mrGO, mrGO/BiOCl and mrGO/BiOCl/Ag respectively), elemental analysis (Ag, O, Bi, Fe), surface morphology (rough ball like sphere of mrGO/BiOCl and cubic Ag nanoparticles in mrGO/BiOCl/Ag), functional groups and band gap (Eg) determination. The Eg was determined using Kubelka-Munk equation as 3.5 and 2.8 eV for mrGO/BiOCl and mrGO/BiOCl/Ag respectively. During the adsorption study, the best experimental conditions for various operating parameters such as pH (2), contact time (5 min for mrGO/BiOCl and 10 min for mrGO/BiOCl/Ag under UV irradiation), TNZ concentration (18 μgL^-1) and catalyst dosage (0.001 g) were achieved. Kinetic study revealed that both composites followed pseudo second order kinetics (R² = 0.9979 and 0.9986, respectively). Data of rGO/BiOCl was fitted to Freundlich adsorption model (R² = 0.9687) and rGO/BiOCl/Ag fitted to Langmuir adsorption model (R² = 0.9994). Moreover, thermodynamic parameters confirmed that a photodegradation phenomenon was spontaneous and exothermic. The results confirmed that rGO/BiOCl and rGO/BiOCl/Ag are appropriate composites for TNZ removal from the aqueous environment with removal efficiency of 97 and 24%, respectively.

Visible-near-Infrared Light-Driven Photocatalytic Characteristics of Er3+/Yb3+-Codoped BiOBr Upconverting Microparticles for Tetracycline Degradation

To settle the unsatisfying efficiency and insufficient light harvesting ability of photocatalysts, we report on the development of Er³⁺/Yb³⁺-codoped BiOBr (BiOBr:Er³⁺/xYb³⁺) microparticles that were synthesized by a rational high-temperature solid-state reaction method. The prepared microcrystals exhibit high visible upconversion (UC) emissions with maximum intensities at x = 0.01 when excited by a 980 nm laser. Remarkably, the corresponding UC emission process is attributed to a two-photon absorption route. Furthermore, the photocatalytic activities of as-synthesized compounds were further evaluated through analyzing the visible-near-infrared light-triggered tetracycline degradation. Compared with BiOBr:Er³⁺ microparticles, BiOBr:Er³⁺/xYb³⁺ microparticles present superior photocatalytic properties and the optimal status is achieved when x = 0.05, in which h⁺, ·O₂^-, and ·OH active species contribute to the photocatalytic mechanism. Additionally, the designed microparticles exhibit better photocatalytic abilities than previously reported photocatalysts (i.e., TiO₂, SnO₂) upon full-spectrum light irradiation. These results reveal that Yb³⁺ codoping is able to not only enhance the UC emission properties of BiOBr:Er³⁺ microparticles but also reinforce their photocatalytic activities. Our findings may put forward a facile strategy to regulate the photodegradation capacity of photcatalysts.

In Situ Coupling Carbon Defective C3N5 Nanosheet with Ag2CO3 for Effective Degradation of Methylene Blue and Tetracycline Hydrochloride

The development of novel catalysts for degrading organic contaminants in water is a current hot topic in photocatalysis research for environmental protection. In this study, C₃N₅ nanosheet/Ag₂CO₃ nanocomposites (CNAC-X) were used as efficient photocatalysts for the visible-light-driven degradation of methylene blue (MB), and tetracycline hydrochloride (TC-HCl) was synthesized for the first time using a simple thermal oxidative exfoliation and in situ deposition method. Due to the synergistic effect of nanosheet structures, carbon defects, and Z-scheme heterojunctions, CNAC-10 exhibited the highest photocatalytic activity, with photodegradation efficiencies of 96.5% and 97.6% for MB (60 mg/L) and TC-HCl (50 mg/L) within 90 and 100 min, respectively. The radical trapping experiments showed that ·O₂^- and h⁺ played major roles in the photocatalytic effect of the CNAC-10 system. Furthermore, intermediates in the photodegradation of MB and TC-HCl were investigated to determine possible mineralization pathways. The results indicated that C₃N₅ nanosheet/Ag₂CO₃ photocatalysts prepared in this work could provide an effective reference for the treatment of organic wastewater.

Semiconductor facet junctions for photocatalytic CO2 reduction

Photocatalytic carbon dioxide (CO2) conversion has been recognized as one of the promising strategies for unraveling current environmental and energy problems attributed to the growing fossil fuel consumption of the human society because it can directly harness incident sunlight energy for converting waste CO2 into valuable compounds. Increasing attention has been provoked to the semiconductor facet junction photocatalysts due to their unique feature in enhancing the photogenerated electron–hole pair utilization toward improving the photocatalytic CO2 conversion performance. In the past decade, significant breakthroughs in the semiconductor facet junction photocatalysts for photocatalytic CO2 conversion. In this review, we give a brief introduction on the development and the idea of the semiconductor facet junction photocatalysts. Then, the unique advantages of the semiconductor facet junction photocatalysts for photocatalytic CO2 conversion are summarized. Subsequently, the recent development of semiconductor facet junction photocatalysts in photocatalytic CO2 conversion is overviewed. We end this review by presenting the perspectives and challenges in this field for its future advancement toward practical applications. This review is expected to push forward the development of not only photocatalytic CO2 conversion but also other energy and environmental photocatalytic applications.

N-CQDs from reed straw enriching charge over BiO2-x/BiOCl p-n heterojunction for improved visible-light-driven photodegradation of organic pollutants

Green bismuth-based photocatalysts have attracted extensive attention in the field of PPCPs photodegradation. The improved carrier separation efficiency still remains a key factor to enhance photocatalytic performance. Herein, N-doped biomass carbon quantum dots (N-CQDs) decorated p-n heterojunction photocatalyst BiO_2-x/BiOCl was prepared using a facile ion-etching strategy, and it displayed a markedly enhanced catalytic activity in the photodegradation of sulfonamide antibiotics. Calculated by the differential charge density, the doped N-CQDs could gather photogenerated electrons, which indicated that the introduction of N-CQDs into BiO_2-x/BiOCl would effectively inhibit the recombination of photogenerated charge carriers. In addition, photocatalytic performance and density functional theory (DFT) calculation results revealed that the photogenerated electrons tended to transfer from p-BiOCl to n-BiO_2-x through N-CQDs, which could generate ·O₂^- and photogenerated h⁺ to oxidize the target pollutants. Benefiting from the synergistic effect of accelerated separation of e^--h⁺ in p-n heterojunction and the electron-rich performance of N-CQDs, the superb TOC removal efficiencies (89.40% within 120 min visible-light irradiation) and toxicity reduction performance of photodegradation intermediates were achieved. As a consequence, this work will provide a design of high-quality photocatalysts and a green-promising strategy for bismuth-based photocatalysts in the water treatment of PPCPs.

Bi-functional super-hydrophilic/underwater super-oleophobic 2D lamellar Ti3C2Tx MXene/poly (arylene ether nitrile) fibrous composite membrane for the fast purification of emulsified oil and photodegradation of hazardous organics

Developing the multi-functional membranes including oil/water emulsion separation and removal of hazardous organic pollutants is essential to the purification of the complicated wastewater. However, it remains a daunting challenge to combine these intended functions while maintaining high separation efficiency. Herein, we developed a new 2D lamellar MXene/poly (arylene ether nitrile) (PEN) fibrous composite membrane through the self-assembly of TiO₂ nanoparticles intercalated MXene nanosheets onto the porous PEN nanofibrous mats and bioinspired polydopamine triggered chemical-crosslinking with polyethyleneimine (PEI). Such nano-intercalation and mussel-inspired crosslinking could effectively regulate the interlayer spacing of the MXene nanosheet skin layer and surface wettability of the composite membrane, which also further contributed to the fast separation and unique bifunctional feature. It was found that the MXene@TiO₂/PEN fibrous composite membrane exhibited low oil-adhesion and superhydrophilic (WCA = 0°)/underwater superoleophobic (UOCA > 155°) properties, which could efficiently separate various surfactant-stabilized oil-in-water emulsions under low pressure of 0.04 MPa while keeping good stability (Under 1 M HCl and 2 M NaOH solutions) and recyclability. Interestingly, the fibrous composite membrane achieved favorable permeation flux of 908-1003 Lm^-2h^-1 (2270-2507.5 Lm^-2h^-1bar^-1) in comparison to other reported MXene based multifunctional composite membranes. Moreover, owing to the synergistic effect of MXene nanosheets and TiO₂ nanoparticles, the MXene@TiO₂/PEN membrane showed excellent photocatalytic degradation performance for various dyes under visible light, i.e. the photocatalytic degradation efficiency for 15 ppm MB, MO, CV, and MeB solutions achieved 92.31%, 93.50%, 98.06%, and 99.30% within 60 min, respectively. Such 2D MXene bio-functional composite membranes with outstanding oil/water emulsions separation and photocatalytic degradation of dyes pave an avenue for treating complicated oily wastewater.

Pilot-Scale Studies of WO3/S-Doped g-C3N4 Heterojunction toward Photocatalytic NOx Removal

Due to the rising concentration of toxic nitrogen oxides (NO_x) in the air, effective methods of NO_x removal have been extensively studied recently. In the present study, the first developed WO₃/S-doped g-C₃N₄ nanocomposite was synthesized using a facile method to remove NOx in air efficiently. The photocatalytic tests performed in a newly designed continuous-flow photoreactor with an LED array and online monitored NO₂ and NO system allowed the investigation of photocatalyst layers at the pilot scale. The WO₃/S-doped-g-C₃N₄ nanocomposite, as well as single components, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller surface area analysis (BET), X-ray fluorescence spectroscopy (XRF), X-ray photoemission spectroscopy method (XPS), UV-vis diffuse reflectance spectroscopy (DR/UV-vis), and photoluminescence spectroscopy with charge carriers' lifetime measurements. All materials exhibited high efficiency in photocatalytic NO₂ conversion, and 100% was reached in less than 5 min of illumination under simulated solar light. The effect of process parameters in the experimental setup together with WO₃/S-doped g-C₃N₄ photocatalysts was studied in detail. Finally, the stability of the composite was tested in five subsequent cycles of photocatalytic degradation. The WO₃/S-doped g-C₃N₄ was stable in time and did not undergo deactivation due to the blocking of active sites on the photocatalyst's surface.

Sustainable and reusable electrospun g-C3N5/MIL-101(Fe)/poly(acrylonitrile-co-maleic acid) nanofibers for photocatalytic degradation of emerging pharmaceutical pollutants

To fabricate sustainable and reusable photocatalyst materials is urgent and desirable for removal of emerging pharmaceutical pollutants (EPPs) in environment water samples. In this work, we described the fabrication of...

In situ construction of a C3N5 nanosheet/Bi2WO6 nanodot S-scheme heterojunction with enhanced structural defects for the efficient photocatalytic removal of tetracycline and Cr(vi)

A novel 2D/0D C3N5/Bi2WO6 S-scheme heterojunction with enhanced structural defects has been designed for the efficient elimination of pharmaceutical antibiotics and Cr(vi).