Study of the interfacial charge transfer in bismuth vanadate/reduce graphene oxide (BiVO4/rGO) composite and evaluation of its photocatalytic activity

Impact of graphene oxide on visible light photocatalytic performance of graphene oxide/graphitic carbon nitride three-dimensional structure composites

The non-metallic catalyst graphitic carbon nitride (g-C3N4) has attracted a significant amount of attention due to its excellent photocatalytic performance. The photocatalytic performance of g-C3N4 has been further enhanced by the incorporation of graphene oxide (GO) as a composite catalyst. However, the enrichment and recovery of these two-dimensional composites after photocatalysis is still a difficult challenge. In this work, a visible light responsive graphene oxide/graphitic carbon nitride coated sponge three-dimensional composite (PU-GO/g-C3N4) was prepared by electrostatic self-assembly using polyurethane sponge (PU) as a skeleton and g-C3N4 as a photocatalyst. The degradation rate of rhodamine B (RhB) under visible light was used as an index to evaluate the photocatalytic performance of PU-GO/g-C3N4. The results demonstrate that during the photocatalytic degradation of RhB by PU-GO/g-C3N4, g-C3N4 is the main photocatalyst, while the holes and the superoxide radicals generated by electron excitation are the main agents. As a bridge connecting PU and g-C3N4, GO improves the agglomeration phenomenon of g-C3N4 on PU. Meanwhile, GO has excellent carrier mobility and inhibits the recombination of photogenerated electrons and holes. Moreover, the presence of GO enhances the absorption of light and dyes. Overall, the addition of GO effectively enhances the photocatalytic performance of PU-GO/g-C3N4 due to it enhances dye absorption, improves light energy utilization rate, and expedites transfer of photogenerated electrons. After 5 cycles, PU-GO/g-C3N4 still exhibits an RhB degradation rate of 92.06%, demonstrating good stability and recycling performance. This material shows great promise for practical environmental remediation applications.

New light on the photocatalytic performance of NH4V4O10 and its composite with rGO

Solar-driven photocatalysis has shown great potential as a sustainable wastewater treatment technology that utilizes clean solar energy for pollutant degradation. Consequently, much attention is being paid to the development of new, efficient and low-cost photocatalyst materials. In this study, we report the photocatalytic activity of NH₄V₄O₁₀ (NVO) and its composite with rGO (NVO/rGO). Samples were synthesized via a facile one-pot hydrothermal method and successfully characterized using XRD, FTIR, Raman, XPS, XAS, TG-MS, SEM, TEM, N₂ adsorption, PL and UV‒vis DRS. The results indicate that the obtained NVO and NVO/rGO photocatalysts exhibited efficient absorption in the visible wavelength region, a high content of V⁴⁺ surface species and a well-developed surface area. Such features resulted in excellent performance in methylene blue photodegradation under simulated solar light illumination. In addition, the composite of NH₄V₄O₁₀ with rGO accelerates the photooxidation of the dye and is beneficial for photocatalyst reusability. Moreover, it was shown that the NVO/rGO composite can be successfully used not only for the photooxidation of organic pollution but also for the photoreduction of inorganic pollutants such as Cr(VI). Finally, an active species trapping experiment was conducted, and the photodegradation mechanism was discussed.

Bismuth vanadate/MXene (BiVO4/Ti3C2) heterojunction composite: enhanced interfacial control charge transfer for highly efficient visible light photocatalytic activity

We have synthesized BiVO4/Ti3C2 nanocomposite via a low-cost hydrothermal method and investigate its photocatalytic degradation activity against monoazo (methyl orange) and diazo dye (Congo red) in an aqueous solution under visible light. The physiochemical characterization exhibited that the addition of MXene in pristine BiVO4 nanocomposite led to an increase in specific surface area and reduction in optical band gap energy. MXene also helps in enhancing visible light response via a higher electron-hole pair generation rate and long lifetime. The synthesized BiVO4/Ti3C2 heterojunction composite exhibited 99.5 % degradation efficiency within 60 min for Congo red and 99.1 % for methyl orange solution in 130 min owed to a large specific surface area (1.79 m2/g), reduced band gap (1.99 eV), and low recombination rate of charge carriers. The chemical mechanism for BiVO4/Ti3C2 nanocomposite proposes that Ti3C2 role-plays as electron capture because of the higher potential of MXenes, tuning band gap energy which paves the way to excellent photocatalytic action. This work opens a new basis for developing Ti3C2 based promising and inexpensive co-catalyst for efficient solar utilization in photocatalytic-related applications in the future.

Nanomaterials significance; contaminants degradation for environmental applications

Nanotechnology provides an innovative platform that is inexpensive, reasonable, having least chances of secondary contamination, economical, and an effective method to concurrently eradicate numerous impurities from contaminated wastewater. Presently, different researches have been conducted exhibiting versatile multifunctional nanoparticles (NPs) that concurrently confiscate several impurities existing in the water. Nanotechnology helps in eliminating impurities from water through the rapid, low-cost method. Pollutants such as 2,4-dichlorophenol (death-causing contaminant as it quickly gets absorbed via the skin), or industrial dyes including methyl violet (MV) or methyl orange (MO) causing water contamination were also concisely explained. In this mini-review, nanomaterials were critically investigated, and the practicability and effectiveness of the elimination of contaminations were debated. The analysis shows that a few of these processes can be commercialized in treating diverse toxins via multifunctional nanotechnology innovations. Hence, nanotechnology shows a promising and environmental friendly method to resolve the restrictions of current and conventional contaminated water treatment. We can progress the technology, without influencing and affecting the natural earth environment conditions.

Bismuth-Graphene Nanohybrids: Synthesis, Reaction Mechanisms, and Photocatalytic Applications—A Review

Photocatalysis is a classical solution to energy conversion and environmental pollution control problems. In photocatalysis, the development and exploration of new visible light catalysts and their synthesis and modification strategies are crucial. It is also essential to understand the mechanism of these reactions in the various reaction media. Recently, bismuth and graphene’s unique geometrical and electronic properties have attracted considerable attention in photocatalysis. This review summarizes bismuth-graphene nanohybrids’ synthetic processes with various design considerations, fundamental mechanisms of action, heterogeneous photocatalysis, benefits, and challenges. Some key applications in energy conversion and environmental pollution control are discussed, such as CO2 reduction, water splitting, pollutant degradation, disinfection, and organic transformations. The detailed perspective of bismuth-graphene nanohybrids’ applications in various research fields presented herein should be of equal interest to academic and industrial scientists.

Construction of 1T-MoS2 quantum dots-interspersed (Bi1-x Fe x )VO4 heterostructures for electron transport and photocatalytic properties

The present study reports trigonal phase molybdenum disulfide quantum dots (MoS2/QDs)-decorated (Bi1-x Fe x )VO4 composite heterostructures. Initially, (Bi1-x Fe x )VO4 heterostructure nanophotocatalysts were synthesized through the hydrothermal method decorated with 1T-MoS2 via a sonication process. 1T-MoS2@(Bi1-x Fe x )VO4 heterostructures were characterized in detail for phase purity and crystallinity using XRD and Raman spectroscopy. The Raman mode evaluation indicated monoclinic, mixed monoclinic-tetragonal and tetragonal structure development with increasing Fe concentration. For physiochemical properties, SEM, EDX, XPS, PL, EPR, UV-visible and BET techniques were applied. The optical energy band gaps of 1T-MoS2@(Bi1-x Fe x )VO4 heterostructures were calculated using the Tauc plot method. It shows a blue shift initially within a monoclinic structure then a red shift with an increase of Fe concentration. 1T-MoS2@(Bi40Fe60)VO4 with 2 wt% of 1T-MoS2-QDs carrying a mixed phase exhibited higher photocatalytic activity. The enhanced photocatalytic activity is attributed to the higher electron transportation from (Bi1-x Fe x )VO4 surface onto 1T-MoS2 surface, consequently blocking the fast electron-hole recombination within (Bi1-x Fe x )VO4. 1T-MoS2 co-catalyst interaction with (Bi1-x Fe x )VO4 enhanced the light absorption in the visible region. The close contact of small 1T-MoS2-QDs with (Bi1-x Fe x )VO4 develops a high degree of crystallinity, with fewer defects showing mesoporous/nanoporous structures within the heterostructures which allows more active sites. Herein, the mechanism involved in the synthesis of heterostructures and optimum conditions for photocatalytic degradation of crystal violet dye are explored and discussed thoroughly.