Construction of novel Zn2TiO4/g-C3N4 Heterojunction with efficient photodegradation performance of tetracycline under visible light irradiation

Construction of a direct Z-scheme Cs3Bi2Cl9/g-C3N4 heterojunction composite for efficient photocatalytic degradation of various pollutants in water: Performance, kinetics and degradation mechanism

The use of emerging composite materials has been booming to remove environmental pollutants. The aim of this research is to develop a new composite based on Cs3Bi2Cl9 perovskite and graphitic carbon nitride (g-C3N4) to investigate the photocatalytic performance under visible light irradiation. To achieve this, we produce the Cs3Bi2Cl9/g-C3N4 heterojunctions through a simple self-assembly synthesis. The as-synthesized composites are characterized using XRD, FTIR, FESEM, TEM, BET and EDX techniques. The photocatalytic performance of Cs3Bi2Cl9/g-C3N4 is examined in the degradation of various water contaminants, including 4-nitrophenol (4-NP), tetracycline antibiotic (TC), methylene blue (MB) and methyl orange (MO). The experimental results indicate the superior photocatalytic performance of the composites in the degradation of pollutants compared to pure Cs3Bi2Cl9 and g-C3N4. The 10% Cs3Bi2Cl9/g-C3N4 composite achieves the optimal degradation efficiency of 100, 92, 98.7, and 85.1% of 4-NP, TC, MB, and MO, respectively. This superior photocatalytic activity attributes to improved optical and electrochemical properties, including enhanced absorption ability, narrowing band gap, promoted separation efficiency of photogenerated carriers, and a high redox potential, which is confirmed by UV-vis DRS, PL, EIS, and CV analyses. The 10% Cs3Bi2Cl9/g-C3N4 composite also demonstrates high photocatalytic stability after four consecutive cycles. Radical trapping tests show that superoxide radicals (•O2-), holes (h+), and hydroxyl radicals (•OH) contribute to the photocatalytic process. Based on the obtained data, a direct Z-scheme heterojunction mechanism is proposed. Overall, this research offers a new stable photocatalyst with excellent prospect for photocatalytic applications.

Photo-Fenton degradation of tetracycline antibiotic over MIL-101(Cr)/FeOOH nanocomposite as stable and efficient visible light responsive photocatalyst

Designing an inexpensive, easily synthesized, stable and efficient photocatalyst is a major challenge in photocatalysis area, especially when photo-reaction is performed in aquatic medium to degrade organic pollutants. To this aim, nano-sized MIL-101(Cr) (MIL = Materials Institute Lavoisier), as chemically tolerant metal-organic framework (MOF), was simply prepared via HF-free hydrothermal synthesis procedure. In order to decorate amorphous FeOOH quantum dots (QDs) on the surface of this MOF, various amounts of FeOOH QDs (i.e., 5, 10, 15 and 20 wt%) were synthesized in the presence of MIL-101(Cr) to prepare MIL-101(Cr)/FeOOH(x%) nanocomposites. Decoration of such iron oxide quantum dots on the surface of MIL-101(Cr) and investigation of its activity in photo-Fenton degradation of tetracycline (TC) antibiotic is reported here for the first time. Among the synthesized nanocomposites, MIL-101(Cr)/FeOOH(15%) demonstrated superior photo-Fenton activity in degradation of TC (80%) at short reaction time under optimum reaction condition using the energy-efficient white LED lamps as visible light source. It was observed that the synergy between any component of this photo-Fenton system such as nanocomposite, hydrogen peroxide and visible light is the main reason for enhancement of TC removal over time. Also, neither MIL-101(Cr) nor FeOOH QDs exhibited poor degradation efficiency, which implies the positive role of the coupling of these materials. Furthermore, the stability and recoverability of MIL-101(Cr)/FeOOH(15%) nanocomposite was investigated in four photo-Fenton cycles, which no significant decrease in TC degradation performance was observed.

Revolutionizing the Role of Solar Light Responsive BiVO4/BiOBr Heterojunction Photocatalyst for the Photocatalytic Deterioration of Tetracycline and Photoelectrocatalytic Water Splitting

In this study, a series of BiVO4/BiOBr composites with varying mole ratios were successfully synthesized using a hydrothermal method. The in-situ synthesis strategy facilitated the formation of a close interfacial contact between BiVO4 and BiOBr at the depletion zone, resulting in improved charge segregation, migration, reduced charge recombination, enhanced solar light absorption capacity, promoting narrow band gap, and large surface area. This study investigates the influence of different mole ratios of BiVO4 and BiOBr in a BiVO4/BiOBr nanocomposite on the photocatalytic degradation of tetracycline (TC), a pharmaceutical pollutant, and photoelectrocatalytic water splitting (PEC) under solar light irradiation. Maximum decomposition efficiency of ~90.4% (with a rate constant of 0.0159 min-1) for TC was achieved with 0.5 g/L of 3:1 BiVO4: BiOBr (31BVBI) photocatalyst within 140 min. The degraded compounds resulting from the TC abatement were analyzed using GC-MS. Furthermore, TC standards exhibited 78.2% and 87.7% removal of chemical oxygen demand (COD) and total organic carbon (TOC), respectively, while TC tablets showed 64.6% COD removal and 73.8% TOC removal. The PEC water splitting experiments demonstrated that the 31BVBI photoanode achieved the highest photocurrent density of approximately 0.2198 mA/cm2 at 1.23 V vs. RHE, resulting in the generation of approximately 1.864 mmolcm-2 s-1 of hydrogen, while remaining stable for 21,600 s. The stability of the photocatalyst was confirmed by post-degradation characterizations, which revealed intact crystalline planes, shape, and surface area. Comparisons with existing physicochemical methods used in industries indicate that the reported photocatalyst possesses strong surface catalytic properties and has the potential for application in industrial wastewater treatment and hydrogen generation, offering an advantageous alternative to costly and time-consuming processes.

Novel gC3N4/MgZnAl-MMO derived from LDH for solar-based photocatalytic ammonia production using atmospheric nitrogen

The development of catalysis technologies for sustainable environmental applications, especially an alternative to ammonia (NH3) production under the Haber-Bosch process, has gained a lot of scope in recent days. The current work demonstrated a green synthesis of graphitic carbon nitride (gC3N4) containing magnesium-zinc-aluminium mixed metal oxides (MgZnAl-MMO) derived from layered double hydroxide (LDH) for visible light aided catalytic production of ammonia. Pyrolysis-hydrothermal techniques were adopted for the synthesis and fabrication of the gC3N4/MgZnAl-MMO catalytic composite. Characterization results of field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), UV-visible spectroscopy, photoluminescence (PL), etc. showed the desired properties and functionalities like semi-crystalline structure with rough surface morphology that enhance the sorption reactions. Catalytic composite gC3N4/MgZnAl-MMO showed a bandgap energy of 2.16 eV that is considerably shifted toward the visible range when compared to gC3N4 (2.39 eV) and MgZnAl-MMO (2.93 eV). The results were also well complied with XPS results obtained that promote solar-based photocatalysis. The gC3N4/MgZnAl-MMO assisted photocatalytic production of NH3 in an aqueous media proved to be acceptable by the production of a maximum 47.56 μmol/L NH3 under visible spectrum employing a light emitting diode (LED) source. The results showed that the advancement of catalyst for desired functionalities and NH3 production using LED simulating solar light-aided catalysis would be an alternative to the Haber-Bosch process and solar-based sustainable processes for NH3 production.

Efficient bacterial inactivation with S-doped g-C3N4 nanosheets under visible light irradiation

The pathogenic bacteria in water that threatens the human health and photocatalytic disinfection have been proven to be a cost-effective and promising green technology. It is significant and necessary to develop efficient, safe, and visible light-driven photocatalysts. In this study, Escherichia coli was used as model bacterium and the disinfection performance of prepared S-doped g-C₃N₄ nanosheets (S-CNNs) under visible light was investigated. The results showed that the synergistic effects of S doping and the unique 2D structure of S-CNNs enhanced the visible light absorption, enlarged the specific surface area and reduced the recombination of photogenerated charge carriers which is beneficial for promoting the photocatalytic disinfection of the E. coli. Scavenger experiments indicated •O₂^- and h⁺ were the predominant reactive species in the photocatalytic disinfection process. In addition, the kinetics of disinfection activity were fitted by the modified Hom model and the k₂ value of S-CNNs is 0.0219 min^-1, which is much higher than that of the bulk g-C₃N₄ (CN). This work has demonstrated efficient bacterial inactivation with S-CNNs under visible light irradiation.