Fabrication of dual Z-scheme photocatalyst via coupling of BiOBr/Ag/AgCl heterojunction with P and S co-doped g-C3N4 for efficient phenol degradation

Advances in noble metal mediated Z-scheme photocatalytic system have ushered in a climax on environmental remediation. Herein, graphitic carbon nitride (GCN) and phosphorus sulphur co-doped graphitic carbon nitride (PSCN) were synthesized via calcination process. GCN, PSCN and Z-scheme visible light driven (VLD) ternary BiOBr/PSCN/Ag/AgCl nanophotocatalyst were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–visible diffuse reflectance spectra (UV–vis DRS). BiOBr/PSCN/Ag/AgCl nanocomposite exhibited superior visible light driven photocatalytic ability as compared to pristine PSCN, AgCl and BiOBr towards degradation of phenol. The results explicated promising photocatalytic activity along with space separation of photocarriers caused via formation of BiOBr/PSCN/Ag/AgCl Z-scheme heterojunction. The visible light absorption efficacy of BiOBr/PSCN/Ag/AgCl photocatalyst was confirmed by photoluminescence (PL) spectra. Finally, recycling experiments were explored for the mechanistic detailing of phenol photodegradation employing BiOBr/PSCN/Ag/AgCl photocatalyst. After seven successive cycles photodegradation efficacy of photocatalyst was reduced to 90% from 98%. Proposed mechanism of BiOBr/PSCN/Ag/AgCl nanophotocatalyst for degradation of phenol was discussed. OH and O2− radicals were main reactive species responsible for photocatalytic phenol degradation

Magnetically separable ZnO/ZnFe204 and ZnO/CoFe204 photocatalysis supported onto nitrogen doped graphene for photocatalytic degradation of toxic dyes

Advanced oxidation processes (AOPs) counting heterogeneous photocatalysis has confirmed as one of the preeminent method for waste water remediation. In the present work, we have successfully fabricated novel visible-light-driven nitrogen-doped graphene (NG) supported magnetic ZnO/ZnFe2O4 (ZnO/ZF/NG) and ZnO/CoFe2O4 (ZnO/CF/NG) nanocomposites. ZnO synthesized via direct precipitation method. Hydrothermal method was used for the preparation of nitrogen-doped graphene supported magnetic ZnO/ZF (ZnO/ZnFe2O4) and ZnO/CF (ZnO/CoFe2O4) nanocomposites. The procured materials were scrutinized by assorted characterizations to acquire information on their chemical composition, crystalline structure and photosensitive properties. The absorption and photocatalytic performance of photocatalysts were studied via UV–Visible spectra. Photodegradation performance of the synthesized nanocomposites was estimated toward mineralization of methyl orange (MO) and malachite green (MG) dyes in aqueous solution. The high surface area of ZnO/ZF/NG and ZnO/CF/NG was suitable for adsorptive removal of MO and MG dyes. The photodegradation performance of heterojunction photocatalysts was superior to bare photocatalyst in 140 min under visible-light irradiation. Spectrophotometer, GC–MS (Gas chromatography–mass spectrometry) elucidation was carried out to expose the possible intermediates formed. Both ZnO/ZF/NG and ZnO/CF/NG were rapidly isolated from the aqueous phase by applying an external magnetic field in 20 sec and 2 min, respectively. The photocatalytic performance and stability of ZnO/ZF/NG and ZnO/CF/NG nanocomposites were confirmed by conducting 10 consecutive regeneration cycles. Owing to recyclability of ZnO/ZF/NG and ZnO/CF/NG, these heterogeneous nanocomposites might be used as cost-effective for treatment of discarded water. The observations endorse that the synthesized ternary heterogeneous nanocomposites facilitates wastewater decontamination using photocatalytic technology

Recent advances in noble metal free doped graphitic carbon nitride based nanohybrids for photocatalysis of organic contaminants in water: A review

Extensive contamination of water bodies by textile dyeing industries, organic pollutants and agricultural waste has emerged water pollution as one of the major global environmental crisis. The effect of this gross negligence is posing serious threats to human health therefore today; conserving water resources for the essence of life is of grave concern. Recently, advancements in photocatalytic properties of graphitic carbon nitride (g-C3N4) for wastewater treatment have gained tremendous interest in research. However, pristine g-C3N4 suffers from bottlenecks such as low surface area, rapid recombination of photo-generated electron–hole pairs and insufficient light absorption which thereby, reduces the photocatalytic degradation activity. Hitherto, noble metals have been widely utilized as dopants but are cost ineffective, rarely found and are difficult to recover. In this updated and all-inclusive review we have briefly discussed photocatalysis mechanism, primarily focused on non-precious elemental doping via various synthesis techniques of noble metal free doped g-C3N4 photocatalysts. Typically metal, non-metal, rare earth metal doping and co-doping have been explored, which demonstrates the synergistic behavior of the doped nanocomposites in modulation of electronic structure, broaden the visible light absorption range, enhancement in photocatalytic wastewater remediation ability to obtain maximum pollutant eradication. Summary remarks conclude the review with valuable knowledge of noble metal free doped g-C3N4 photocatalysts for water purification and sheds light on current challenges and crucial issues associated with its commercialization. The future aspect aims at designing of efficient solar light driven photocatalysts for application in various domains i.e. production of H2 and O2, reduction of CO2, practical use of solar cells, treatment of wastewater, air purification and environmental conservatio

Synthesis of Eu3+−doped ZnO/Bi2O3 heterojunction photocatalyst on graphene oxide sheets for visible light-assisted degradation of 2,4-dimethyl phenol and bacteria killing

We reported the immobilization of binary heterojunction Eu3+-ZnO/Bi2O3 over the surface of graphene oxide (GO) sheets by precipitation method to compose a visible light drive photocatalyst. The ternary nanocomposites were characterized by different spectral technique like FESEM, FTIR, XRD, XPS, EDX, HRTEM, UV–visible, PL, HPLC and LCMS analysis. The high specific surface area of 106.0 m2g-1 of Eu3+-ZnO/Bi2O3/GO nanocomposites was ascertained by BET adsorption-desorption isotherm. The nano-composite exhibit excellent photo-efficiency for the photodegradation of 2, 4-dimethyl phenol (DMP) under visible region and was almost completely mineralized in 100 min as compared to the bare and binary system. The mineralized products of DMP were analyzed by HPLC and LCMS analysis. The kinetic model suggests the degradation pathway obeys pseudo-first order kinetic. Their antibacterial property were assessed against E. coli bacteria and nearly 90% of gram negative bacteria were killed by using ternary photocatalyst as determined by CFU method. Also, Eu3+-ZnO/Bi2O3/GO nanocomposites possessed significant recycle efficiency up to six consecutive cycles which is beneficial to minimize the tariff. The improved photo-efficiency is due to the extension towards visible region, increase surface area, and high charge separation in ternary heterojunction

Persulfate-aided modified graphitic carbon nitride-based photocatalysts for wastewater treatment:synergistic mechanism

The metal-free graphitic carbon nitride (GCN) has ignited research in the realm of sulfate radical-based AOPs for aqueous pollutant degradation owing to the tunable optoelectronic properties. Upon light irradiations, the electronic excitations in GCN cause peroxo (O-O) bond cleavage in peroxydimonosulfate (PDS) and peroxymonosulfate (PMS) oxidants to release SO4 − and ·OH reactive oxidative species. The SO4 − radicals benefited from higher oxidation potential (2.5–3.1V), longer half-life period (4×10−5s), and responsiveness in the pH range. The synergistic mechanism of GCN-mediated PS/PMS photoactivation confirms the generation of ·OH to overcome the poor reductive potential of GCN and fastens the degradation rate of the reaction. With the advancement in surface modification strategies, researchers have explored the methods of introducing functional groups for increasing the surface-active sites to activate PMS/PDS over GCN.</p

GdVO4 modified fluorine doped graphene nanosheets as dispersed photocatalyst for mitigation of phenolic compounds in aqueous environment and bacterial disinfection

The agglomeration of graphene based photocatalysts is major bottleneck for their applicability in slurry type photoreactors. In this work, we have prepared fluorine doped graphene (FG) as high dispersed adsorbent by sonochemical exfoliation method. GdVO4 nanoparticles were anchored on FG to fabricate GdVO4/FG photo catalyst. The high-dispersion of FG and GdVO4/FG was ascertained by zeta potential measurements and Tyndall effect. The atomic force microscope analysis depicted that thickness of FG and GdVO4/FG was less than 2.0 nm. The band gap of GdVO4/FG was 2.1 eV. The high surface area of GdVO4/FG was suited for adsorption coupled photocatalysis involving mineralization of phenol and 2, 4-dinitrophenol (DNP) in aqueous medium. The photodegradation process followed pseudo first order kinetics. The simultaneous adsorption and photocatalysis was most efficient process for degradation of selected phenolic compounds. Under visible light, both phenol and DNP mineralized in 7 and 9 h, respectively. The high performance liquid chromatography and mass spectrometry confirmed the formation of intermediate during degradation process which ultimately mineralized into CO2 and H2O. The photocatalytic activity of GdVO4/FG was also tested for bacterial disinfection of Pseudomonas fluorescence, Staphylococcus aureus, Streptococcus enterica, Bacillus subtilis and Escherichia coli bacteria. The oxidative radical species OH center dot and O-2(center dot-) played vital role in photodegradation and disinfection process. Due to high dispersion and recyclability, GdVO4/FG could be used as an efficient photocatalyst for removal of both biotic and abiotic pollutants present in water

A Review on Carbon Quantum Dots Modified g-C₃N₄-Based Photocatalysts and Potential Application in Wastewater Treatment

Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in size) with unique optical, electrical, and physicochemical properties. In addition to these properties, CQDs exhibit the desired advantages of aqueous stability, low toxicity, high surface area, economic feasibility, chemical inertness, and highly tunable photoluminescence behaviour. Recently, graphitic carbon nitride (g-C3N4) has appeared as one of the required stable carbon-based polymers due to its varied applications in several fields. In this regard, modification strategies have been made in the g-C3N4 semiconductor using CQDs to enhance the adsorptive and photocatalytic activity. In comparison to other semiconductor quantum dots, g-C3N4 shows strong fluorescent properties, such as wide excitation spectra, photostability, and tunable photo-luminescent emission spectra. The interaction inside this multicomponent photocatalyst further promotes the photocatalytic activity by improving charge transference, which plays a vital role in electrochemistry. Therefore, CQDs are auspicious nanomaterials in the field of photocatalysis, wastewater treatment and water adsorption treatment. This particular article featured the recent progression in the field of CDs/g-C3N4-based photocatalysts focusing on their luminescent mechanism and potential applications in wastewater treatment