Solid state route for synthesis of YFeO3/g-C3N4 composites and its visible light activity for degradation of organic pollutants

Graphitic carbon nitride (g-C3N4)-assisted materials for the detection and remediation of hazardous gases and VOCs

Graphitic carbon nitride (g-C3N4)-based materials are attracting attention for their unique properties, such as low-cost, chemical stability, facile synthesis, adjustable electronic structure, and optical properties. These facilitate the use of g-C3N4 to design better photocatalytic and sensing materials. Environmental pollution by hazardous gases and volatile organic compounds (VOCs) can be monitored and controlled using eco-friendly g-C3N4- photocatalysts. Firstly, this review introduces the structure, optical and electronic properties of C3N4 and C3N4 assisted materials, followed by various synthesis strategies. In continuation, binary and ternary nanocomposites of C3N4 with metal oxides, sulfides, noble metals, and graphene are elaborated. g-C3N4/metal oxide composites exhibited better charge separation that leads to enhancement in photocatalytic properties. g-C3N4/noble metal composites possess higher photocatalytic activities due to the surface plasmon effects of metals. Ternary composites by the presence of dual heterojunctions improve properties of g-C3N4 for enhanced photocatalytic application. In the later part, we have summarised the application of g-C3N4 and its assisted materials for sensing toxic gases and VOCs and decontaminating NOx and VOCs by photocatalysis. Composites of g-C3N4 with metal and metal oxide give comparatively better results. This review is expected to bring a new sketch for developing g-C3N4-based photocatalysts and sensors with practical applications.

Facile synthesis of N vacancy g-C3N4 using Mg-induced defect on the amine groups for enhanced photocatalytic •OH generation

Photocatalysis offers opportunities to degrade recalcitrant organic pollutants without adding treatment chemicals. Nitrogen (N) vacancy is an effective point-defect engineering strategy to mitigate electron-hole recombination and facilitate hydroxyl radical (•OH) production via superoxide radical (O₂^•-) generation during photocatalytic application of graphitic carbon nitride (g-C₃N₄). Here, we report a novel strategy for fabrication of N-vacancy-rich g-C₃N₄ (NvrCN) via post-solvothermal treatment of Mg-doped g-C₃N₄. The addition of the Mg precursor during the polycondensation of urea created abundant amine sites in the g-C₃N₄ framework, which facilitates formation of N vacancies during post-solvothermal treatment. Elemental analysis and electron paramagnetic resonance spectra confirmed a higher abundance of N vacancies in the resultant NvrCN. Further optical and electronic analyses revealed the beneficial role of N vacancies in light-harvesting capacity, electron-hole separation, and charge transfer. N vacancies also provide specific reaction centers for O₂ molecules, promoting oxygen reduction reaction (ORR). Therefore, •OH generation increased via enhanced formation of H₂O₂ under visible light irradiation, and NvrCN photocatalytically degraded oxytetracycline 4-fold faster with degradation rate constant of 1.85 × 10^-2 min^-1 (light intensity = 1.03 mW/cm², catalyst concentration = 0.6 g/L, oxytetracycline concentration = 20 mg/L) than pristine g-C₃N₄. Overall, this study provides a facile method for synthesizing N-vacancy-rich g-C₃N₄ and elucidates the role of the defect structure in enhancing the photocatalytic activity of g-C₃N₄.

"Magnetic Ni-Zn ferrite anchored on g-C3N4 as nano-photocatalyst for efficient photo-degradation of doxycycline from water"

In the present work, mixed-spinel ferrite anchored onto graphitic carbon nitride (GCN) was synthesized for mineralization of antibiotic pollutant from waste water. A Z-scheme g-C₃N₄/Ni_0.5Zn_0.5Fe₂O₄ nano heterojunction was fabricated by three step procedure: pyrolysis, solution combustion and mechanical grinding followed by annealing. The prepared photocatlyst was tested for degradation of Doxycycline (DC) drug under the natural sun light. Results revealed that the prepared heterojunction has maximum degradation efficiency of 97.10% pollutant in 60 min experiment. The Z-scheme heterojunction between g-C₃N₄ and Ni-Zn ferrite improves the photoinduced charges separation and protection of redox capability and therby increases the photo degradation efficiency. The scavenging experiments suggested that O₂^-● and h⁺ as main active species responsible for degradation of the antibiotic. In addition, the dopant variation can drive the shists in band gap and energy band positiong too which makes then excellent candidates for synthesizing tunable heterostructures with organic semiconductors. The work focusses on designing and developing of saimpler but efficient magnetic heterojunctions with superior redox capability for solar powered waste water treatment.

Enhanced Photocatalytic Degradation of P-Chlorophenol by ZnIn2S4 Nanoflowers Modified with Carbon Quantum Dots

The removal of chlorophenol (CP) contaminants from water is a great challenge owing to their natural robustness and the toxic chlorinated by-products generated in degradation processes. In this work, a series of three-dimensional nanoflower-like structured photocatalysts (CQDs/ZnIn2S4-x, x = 1, 2, or 3 wt%) were fabricated via a facile hydrothermal approach. Excellent photocatalytic abilities toward 4-CP degradation under Xe lamp irradiation were achieved over the as-prepared composites. The removal efficiency of total organic carbon for 4-CP on the optimized CQDs/ZnIn2S4-2 was 49.1%, which was 16.0% higher than that of ZnIn2S4. The presence of CQDs could not only be used to adjust controllable band structures for enhancing light absorption, but it could also serve as an electron acceptor to promote the transition of electron–hole pairs. Moreover, a possible degradation mechanism of 4-CP was also proposed according to the analyses of active species, electron paramagnetic resonance characterization, degradation products, and attacked sites. Overall, this work unveils a superior function of an efficient photocatalyst for refractory organic pollutants.

Application of perovskite oxides and their composites for degrading organic pollutants from wastewater using advanced oxidation processes: Review of the recent progress

In the recent years, perovskite oxides are gaining an increasing amount of attention owing to their unique traits such as tunable electronic structures, flexible composition, and eco-friendly properties. In contrast, their catalytic performance is not satisfactory, which hinders real wastewater remediation. To overcome this shortcoming, various strategies are developed to design new perovskite oxide-based materials to enhance their catalytic activities in advanced oxidation process (AOPs). This review article is to provide overview of basic principle and different methods of AOPs, while the strategies to design novel perovskite oxide-based composites for enhancing the catalytic activities in AOPs have been highlighted. Moreover, the recent progress of their synthesis and applications in wastewater remediation (pertaining to the period 2016-2022) was described, and the related mechanisms were thoroughly discussed. This review article helps scientists to have a clear outlook on the selection and design of new effective perovskite oxide-based materials for the application of AOPs. At the end of the review, perspective on the challenges and future research directions are discussed.

Hydrogen production via water splitting over graphitic carbon nitride (g-C3N4 )-based photocatalysis

Photocatalytic splitting of water into hydrogen and oxygen using semiconductor photocatalysts and light irradiation has been attracted much attention and considered to be an alternative for nonrenewable fossil fuel to solve environmental problems and energy crisis and also an as promising approach to produce clean, renewable hydrogen fuel. Owing to their various advantages such as low cost and environmental friendly, chemical, and thermal stability, appropriate band structure, graphitic carbon nitride (g-C3N4 ) photocatalysts have gained multitudinous attention because of their great potential in solar fuels production and environmental remediation. However, due to its fast charge carrier’s recombination, low surface, and limited absorption of the visible light restrict their activity toward hydrogen evolution and numerous modification techniques were applied to solve these problems such as structural modification, metal/nonmetal doping, and noble metal loading, and coupling semiconductors. In this chapter, we summarize recent progress in the synthesis and characterization of the g-C3N4-based photocatalyst. Several modification methods used to enhance the photocatalytic hydrogen production of g-C3N4-based photocatalyst were also highlighted. This chapter ends with the future research and challenges of hydrogen production over g-C3N4-based photocatalyst.

g-C3N4/Ca2Fe2O5 heterostructures for enhanced photocatalytic degradation of organic effluents under sunlight

g-C₃N₄/Ca₂Fe₂O₅ heterostructures were successfully prepared by incorporating g-C₃N₄ into Ca₂Fe₂O₅ (CFO). As prepared g-C₃N₄/CFO heterostructures were initially utilized to photodegrade organic effluent Methylene blue (MB) for optimization of photodegradation performance. 50% g-C₃N₄ content in CFO composition showed an enhanced photodegradation efficiency (~ 96%) over g-C₃N₄ (48.15%) and CFO (81.9%) due to mitigation of recombination of photogenerated charge carriers by Type-II heterojunction. The optimized composition of heterostructure was further tested for degradation of Bisphenol-A (BPA) under direct sunlight, exhibiting enhanced photodegradation efficiency of about 63.1% over g-C₃N₄ (17%) and CFO (45.1%). The photoelectrochemical studies at various potentials with and without light illumination showed significant improvement in photocurrent response for g-C₃N₄/Ca₂Fe₂O₅ heterostructures (~ 1.9 mA) over CFO (~ 67.4 μA). These studies revealed efficient solar energy harvesting ability of g-C₃N₄/Ca₂Fe₂O₅ heterostructures to be utilized for organic effluent treatment.

Efficient degradation of roxarsone and simultaneous in-situ adsorption of secondary inorganic arsenic by a combination of Co3O4-Y2O3 and peroxymonosulfate

Roxarsone (ROX), as one of aromatic organoarsenic compounds (AOCs), is extensively used in livestock industry, which tends to transform into high-toxic inorganic arsenic in environments. Herein, a bifunctional Co₃O₄-Y₂O₃, possessing extremely excellent catalytic and adsorption performance due to the synergy of Co₃O₄ and Y₂O₃, was designed and employed to activate peroxymonosulfate (PMS) for the elimination of ROX and the simultaneous in-situ adsorption of secondary inorganic arsenic, in which Co₃O₄ acted as the primary catalyst, and Y₂O₃ served as the main adsorbent. 50 μM (3.75 mg-As/L) of ROX was almost completely degraded, coupled with the conversion of As(III) to As(V) in the system of Co₃O₄-Y₂O₃ (0.2 g/L) and PMS (0.5 mM) within 15 min at initial pH 7. Meanwhile, > 99.3% of the secondary As(V) would be removed within 120 min. The reactive oxygen species (ROS) were identified to be ^•OH, SO₄^•-, and ¹O₂, which were responsible for the ROX degradation and the formation of As(V). Simultaneously, the produced As(V) were effectively adsorbed via the ligand/anion exchange with surface -OH and CO₃^2- anions of Co₃O₄-Y₂O₃. The possible degradation pathways of ROX were further proposed on the basis of the intermediates identification. Our findings may provide an insight into the degradation of AOCs and the simultaneous removal of secondary inorganic arsenic via the PMS activation with Co₃O₄-Y₂O₃.

Ultrasound-Assisted Hydrothermal Fabrication of AgI/MFeO3/g-C3N4 (M = Y, Gd, La) Nano Sheet–Sphere–Sheet Photocatalysts with Enhanced Photodegradation Activities for Norfloxacin

AgI/MFeO3/g-C3N4 (M = Y, Gd, La) nano sheet–sphere–sheet photocatalysts were synthesized by a simple ultrasound-assisted hydrothermal approach. We characterized the microstructure, surface morphology, and optical absorption capacity of the obtained samples. According to the characterization results, AgI/MFeO3/g-C3N4 (M = Y, Gd, La) nano sheet–sphere–sheet photocatalysts were successfully obtained. MFeO3 nanospheres and AgI nanosheets were dispersed evenly on the surface of g-C3N4 nanosheets. AgI/MFeO3/g-C3N4 showed remarkable photocatalytic. Especially, 95% of NOF was photodegradated over AgI/LaFeO3/g-C3N4 within 3 h and the higher photocatalytic performance still remained after six cycles. Additionally, The N2 adsorption–desorption isotherms of AgI/MFeO3/g-C3N4 showed that AgI/LaFeO3/g-C3N4 possessed the highest specific surface area (79.32 m2/g). The result of scavenging experiment revealed that ·O2−, h+, and ·OH were the main roles in the photodegradation process. Benefitting from the nice energy band matching, MFeO3 acted as the center of photogenerated electrons migration and separation provided more direct electron channels. This work proposes an effective approach for the design and configuration of dual Z-scheme photocatalysts to accomplish the removal of organic contaminants based on g-C3N4.

A facile synthesis method for fabrication of LaFeO3/g-C3N4nanocomposite as efficient visible-light-driven photocatalyst for photodegradation of RhB and 4-CP

A solid state method for the large scale synthesis of LaFeO₃/g-C₃N₄nanocomposite with enhanced visible-light photocatalytic degradation activity.

Pt nanoparticles supported on YCoxFe1−xO3 perovskite oxides: highly efficient catalysts for liquid-phase hydrogenation of cinnamaldehyde

The Pt/YCo_0.3Fe_0.7O₃ catalyst furnished ca. 95% selectivity to cinnamyl alcohol at nearly full conversion for the selective hydrogenation of cinnamaldehyde.