Fabrication of microfibrillated cellulose from biomass by use of carbon nitride with high nitrogen/carbon ratio

Microfibrillated cellulose (MFC) as an attractive green bio-based material has attracted widespread attention in recent years due to its non-toxicity, degradability, excellent performance, and high aspect ratio. In this study, the g-C3N5 with a high nitrogen/carbon ratio was prepared as a catalyst through the self-polymerization of a nitrogen-rich precursor. The triazole groups at the edges of g-C3N5 were proven to exhibit strong adsorption to biomass and strong alkalinity. In a low-acidic aqueous system with g-C3N5, MFC with diameters of 100-200 nm and lengths up to 100 μm was fabricated from various biomasses within 5 min under microwave radiation. The ultimate yield of the MFC produced from viscose reached 90 %. Young's modulus of the MFC reaches 3.7 GPa. This work provides a particular method with high efficiency to prepare MFC with excellent properties from biomass by chemical method.

Efficient photocatalytic hydrogen peroxide production over S-scheme In2S3/molten salt modified C3N5 heterojunction

Graphitic phase carbon nitride (g-C3N5), as a novel n-type metal-free material, is employed as a visible light-receptive catalyst because of its narrow band gap and abundant nitrogen. To overcome the low carrier mobility efficiency of g-C3N5, its modification by K ions was adopted. In addition, In2S3 was selected to couple with modified g-C3N5 to overcome the recombination of photogenerated e-/h+. As a novel photocatalytic material, it was proven to possess a high visible light absorption capacity and a strong H2O2 production ability (up to 3.89 mmol⋅L-1 in 2 h). Moreover, a S-scheme heterojunction structure was successfully constructed between the two materials, which was tested and confirmed to be successful in raising the photogenerated e-/h+ separation efficiency. Ultimately, the primary processes of photocatalytic H2O2 production were summarized by superoxide radical and rotating disc electron measurements. This research provides a fresh perspective for the synthesis of C3N5-based S-scheme heterojunction photocatalysts for producing H2O2.

Core-Shell Structured Cobalt Sulfide/C. I. Pigment Yellow 53 Photocatalysts with Abundant Sulfur Vacancies for Efficient Photocatalytic Co-Production of Xylonic Acid and CO

Photocatalytic biorefinery has been gaining increasing attention as a promising method for utilizing biomass and solar energy, yet it still faces the key challenge of designing stable, efficient, and cost-effective photocatalysts. In this study, cobalt sulfide/ C. I. Pigment Yellow 53 composite photocatalysts (CoS/PY53-CSx) with a core-shell structure, which has abundant sulfur (S) vacancies, are developed using a simple hydrothermal method. The CoS nanocage with S vacancies not only offers numerous active sites but also enhances the light-trapping performance of PY53. Moreover, the internal electric field within the core-shell CoS/PY53-CSx further enhances charge separation/transfer efficiency while reducing electron transfer resistance, thereby boosting photocatalytic activity. Remarkably, 75.2% of xylonic acid and 22.8 µmol of CO from xylose are obtained using CoS/PY53-CS0.1 in an air atmosphere. Recycling experiments demonstrate that CoS/PY53-CS0.1 exhibits excellent recyclability due to the strong bonding force between the core and shell. In addition, electron spin resonance characterization combined with poisoning experiments suggests that h+ and ·O2 - serve as the main oxidation active species during this system. This work presents a simple and cost-effective method for efficient photocatalytic biorefinery.

Floating MIL-88A(Fe)@expanded perlites catalyst for continuous photo-Fenton degradation toward tetracyclines under artificial light and real solar light

In this work, MIL-88A(Fe) was immobilized onto the expanded perlites to fabricate the floating MIL-88A(Fe)@expanded perlites (M@EP) catalyst via high throughput batch synthesis method under room temperature. The as-prepared M@EP could efficiently activate H2O2 to achieve 100% tetracycline antibiotics (TCs) removal under both artificial low power UV light (UVL) and real sunlight (SL) irradiation. The toxicological evaluation, growth experiment of mung beans and antimicrobial estimation revealed the decreasing aquatic toxicity of the TCs intermediates compared to those of the pristine TCs. A self-designed continuous bed reactor was employed to investigate the long-term operation of the M@EP. The findings demonstrated that the antibiotics mixture can be continuously degraded up to 7 days under UVL and 5 daytimes under SL irradiation, respectively. More importantly, ca. 76.9% and 81.6% of total organic carbon (TOC) removal efficiencies were accomplished in continuous bed reactor under UVL and SL irradiation, respectively. This work advances the immobilized MOFs on floating supports for their practical application in large-scale wastewater purification through advanced oxidation processes. ENVIRONMENTAL IMPLICATION: This work presented the high throughput production and photo-Fenton degradation application of floating MIL-88A(Fe)@expanded perlites (M@EP). Three tetracycline antibiotics (TCs) were selected as model pollutants to test the degradation ability of M@EP in batch experiment and continuous operation under artificial light and solar light. The complete TCs degradation could be accomplished in self-designed device up to 7 d under UV light and 5 d under real solar light. This work tapped a new door to push MOFs-based functional materials in the real water purification.

Z-scheme heterojunction photocatalyst formed by MOF-derived C-TiO2 and Bi2WO6 for enhancing degradation of oxytetracycline: Mechanistic insights and toxicity evaluation in the presence of a single active species

In the work, Bi2WO6/C-TiO2 photocatalyst was successfully synthesized for the first time by loading narrow bandgap semiconductor Bi2WO6 on MOF-derived carboxyl modified TiO2. The phase structure, morphology, photoelectric properties, surface chemical states and photocatalytic performance of the prepared photocatalysts were systematically investigated using various characterization tools. The degradation efficiency of oxytetracycline by 6BT Z-scheme heterojunction photocatalyst under visible light could reach 93.6 % within 100 min, which was related to the high light harvesting and effective separation and transfer of photo-generated carriers. Furthermore, the effects of various environmental factors in actual wastewater were further investigated, and the results showed that 6BT exhibited good adaptability, durability and resistance to interference. Unlike most works, the degradation system with a different single active species were designed and constructed based on their formation mechanism. In addition, for the first time, a positive study was conducted on the priority attack sites, intermediate products, and degradation pathways for the photocatalytic degradation of oxytetracycline by a single active species through HPLC-MS and Fukui index calculations. The toxicity changes of intermediate products produced in three different single active species oxidation systems were evaluated using toxicity assessment software tools (T.E.S.T.), Escherichia coli growth experiments, and wheat growth experiments. Among them, the intermediate products formed through O2- oxidation had the lowest toxicity and the main active sites it attacked were the 20C, 38O, 18C, 41O, and 55O atoms with high f+ values in the oxytetracycline molecular structure. This work provided the insight into the role of each active species in the degradation of antibiotics and offered new ideas for the design and synthesis of efficient and eco-friendly photocatalysts.

Polyimide/Ag2WO4 Z-Scheme Heterojunction for Efficient Photocatalytic Degradation of Tetracycline

It is of great significance to construct a Z-scheme heterojunction for improving solar light harvesting and achieving efficient separation of photogenerated carriers and then enhancement of the photocatalytic performance of semiconductor photocatalysts. Herein, the direct Z-scheme PI/Ag2WO4 heterojunction was designed and prepared according to the band edge potentials of the semiconductor. Due to the fact that the Z-scheme structure not only endowed the PI/Ag2WO4 composites with efficient separation of photogenerated electron-hole pairs but also reserved the redox ability of the valence band and conduction band of monophase catalysts, the 50% PI/Ag2WO4 heterojunction exhibited excellent photocatalytic activity, which were 2.9 and 1.5 times those of the PI and Ag2WO4 photocatalysts, respectively. The photocatalytic reaction mechanism of PI/Ag2WO4 composites was confirmed by the results of TEM, UV-vis, XPS, and EPR experiments. This work provides a feasible strategy to design high-performance photocatalysts in the field of practice purification of wastewater.

3D/1D Fe3O4@TiO2/TC-TiO2/SiO2 Magnetic Inorganic-Framework Molecularly Imprinted Fibers for Targeted Photodegradation

To achieve a selective degradation of pollutants in a water body, 3D/1D magnetic molecularly imprinted fibers Fe3O4@TiO2/TC-TiO2/SiO2 were fabricated by an electrospinning method. The molecularly imprinted layer was successfully prepared by a direct imprinting method using TiO2 as a functional monomer. Fe3O4 facilitates the catalyst recovery and light utilization. The as-prepared fibrous photocatalyst has a large specific surface area of 132.4 m2/g. The successful generation of imprinted sites was proven by various characterizations. The weak interaction between the inorganic functional monomer and tetracycline (TC) was determined to be van der Waals force and hydrogen bonds by the IGMH isosurface theory. The construction of the 3D/1D homojunction of molecularly imprinted materials is beneficial to charge transfer. The as-prepared photocatalyst exhibits a high selectivity coefficient α = 737.38 competing with RhB. The TC removal efficiency reached 100% within only 20 min. In addition, the possible degradation pathway and the degradation mechanism are reasonably proposed. This work not only provides an in-depth mechanism of the weak interaction between the inorganic molecularly imprinted functional monomer and pollutant molecules but also offers new thoughts on the fabrication of photocatalysts for the effective and selective treatment of pollutants in water bodies.

Progress on mechanism and efficacy of heterogeneous photocatalysis coupled oxidant activation as an advanced oxidation process for water decontamination

The rising debate on the dilemma of photocatalytic water treatment technologies has driven researchers to revisit its prospects in water decontamination. Nowadays, heterogeneous photocatalysis coupled oxidant activation techniques are intensively studied due to their dual advantages of high mineralization and high oxidation efficiency in pollutant degradation. This paved a new way for the development of solar-driven oxidation technologies. Previous reviews focused on the advances in one specific coupling technique, such as photocatalytic persulfate activation and photocatalytic ozonation, but lack a consolidated understanding of the synergy between photocatalytic oxidation and oxidant activation. The synergy involves the migration of photogenerated carriers, radical reaction, and the increase in oxidation rate and mineralization. This review systematically summarizes the fundamentals of activation mechanism, advanced characterization techniques and synergistic effects of coupling techniques for water decontamination. Besides, specific cases that lead researchers astray in revealing mechanisms and assessing synergy are critically discussed. Finally, the prospects and challenges are put forward to further deepen the research on heterogeneous photocatalytic activation of oxidants. This work provides a consolidated view of the existing heterogeneous photocatalysis coupled oxidant activation techniques and inspires researchers to develop more promising solar-driven technologies for water decontamination.

A novel visible-light-driven Z-scheme C3N5/BiVO4 heterostructure with enhanced photocatalytic degradation performance

As a visible-light response semiconductor materials, bismuth vanadate (BiVO4) is extensively applied in photodegradation organic dye field. In this study, we synthesized C3N5 nanosheets and coupled with decahedral BiVO4 to construct a Z-scheme C3N5/BiVO4 heterostructure with close interface contact. By introducing C3N5 into BiVO4, the built Z-scheme transfer pathway provides silky channel for charge carrier migration between different moieties and enables photoexcited electrons and holes accumulated on the surface of BiVO4 and C3N5. The accelerated separation of charge carriers ensures C3N5/BiVO4 heterostructures with a powerful oxidation capacity compared with pure BiVO4. Due to the synergistic effect in Z-scheme heterostructure, the C3N5/BiVO4 demonstrated an improved photodegradation ability of rhodamine B (RhB) and methylene blue (MB) that of bare BiVO4.

Nitrogen-rich carbon nitride (C3N5) coupled with oxygen vacancy TiO2 arrays for efficient photocatalytic H2O2 production

Developing efficient and facilitated recycling photocatalysts for H2O2 formation is an ideal strategy for solar-to-chemical energy conversion. In this work, we synthesized ultrathin C3N5 nanosheets through the process of thermal polymerization and polyvinylpyrrolidone (PVP)-assisted solvent exfoliation. Subsequently, the obtained ultrathin C3N5 nanosheets were tightly attached to the surface of TiO2-x arrays, resulting in an enhanced photocatalytic H2O2 production rate. The density functional theory (DFT) calculations demonstrate that an internal electric field (IEF) is generated between the TiO2-x array and the ultrathin C3N5 due to the different work functions. The presence of IEF provides an additional driving force for carrier separation and transfer in the heterointerface. Benefitting from this unique strategy, the optimal heterojunction obtains the highest H2O2 formation rate (2.93 μmol/L/min), which is about 4.1 times than that of TiO2-x arrays. The rotating disk electrode (RDE) analysis manifests H2O2 formation through 2e--dominated oxygen reduction reaction (ORR). This research provides an innovative strategy for assembling a type-II heterojunction with a useful IEF for efficient photocatalytic H2O2 production.

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.

Impact of nitrogen doping on triazole-based graphitic carbon Nitride-TiO2 (P25) S-scheme heterojunction for improved photocatalytic hydrogen production

Establishing an S-scheme heterojunction is a promising method for increasing the photocatalytic activity of synthetic materials. In this study, nitrogen-doped g-C3N5/TiO2 S-scheme photocatalysts have been synthesized and examined for photocatalytic hydrogen production using thermal decomposition methods. Nitrogen-doped g-C3N5/TiO2 composites performed better than pure nitrogen-doped g-C3N5 and TiO2 alone. Using experiments and density functional theory (DFT) calculations, nitrogen (N) doping was identified as being introduced by replacing the carbon (C) atoms in the matrix of g-C3N5. In addition to its narrow band gap, N-doped g-C3N5 showed efficient carrier separation and charge transfer, resulting in the enhanced absorption of visible light and photocatalytic activity. DFT, XPS, optical property characteristics, and PL spectra confirmed these findings, which were attributed to the successful nitrogen doping, and the composite was proven to be a potential candidate for photocatalytic hydrogen generation under light irradiation. The quantity of H2 produced from the nitrogen-doped g-C3N5/TiO2 composite for 3 hours (3515.1 μmol g-1) was about three times that of N-doped g-C3N5. The H2 production percentage of the nitrogen-doped g-C3N5/TiO2 catalyst with Pt as the cocatalyst was improved by nearly ten times as compared to N-doped g-C3N5/TiO2 without a cocatalyst. Herein, we report the successful preparation of the N-doped g-C3N5/TiO2 S-scheme heterojunction and highlight a simple and efficient catalyst for energy storage requirements and environmental monitoring.

Recent advancements in the fabrication and photocatalytic applications of graphitic carbon nitride-tungsten oxide nanocomposites

The present review focuses on the widely used graphitic carbon nitride (g-C3N4)-tungsten oxide (WO3) nanocomposite in photocatalytic applications. These catalysts are widely employed due to their easy preparation, high physicochemical stability, nontoxicity, electron-rich properties, electronic band structure, chemical stability, low cost, earth-abundance, high surface area, and strong absorption capacity in the visible range. These sustainable properties make them predominantly attractive and unique from other photocatalysts. In addition, graphitic carbon nitride (g-C3N4) is synthesized from nitrogen-rich precursors; therefore, it is stable in strong acid solutions and has good thermal stability up to 600 °C. This review covers the historical background, crystalline phases, density-functional theory (DFT) study, synthesis method, 0-D, 1-D, 2-D, and 3-D materials, oxides/transition/nontransition metal-doped, characterization, and photocatalytic applications of WO3/g-C3N4. Enhancing the catalytic performance strategies such as composite formation, element-doping, heterojunction construction, and nanostructure design are also summarized. Finally, the future perspectives and challenges for WO3/g-C3N4 composite materials are discussed to motivate young researchers and scientists interested in developing environment-friendly and efficient catalysts.

Porous Host-Guest MOF-Semiconductor Hybrid with Multisites Heterojunctions and Modulable Electronic Band for Selective Photocatalytic CO2 Conversion and H2 Evolution

Optimizing catalysts for competitive photocatalytic reactions demand individually tailored band structure as well as intertwined interactions of light absorption, reaction activity, mass, and charge transport.  Here, a nanoparticulate host-guest structure is rationally designed that can exclusively fulfil and ideally control the aforestated uncompromising requisites for catalytic reactions. The all-inclusive model catalyst consists of porous Co3 O4 host and Znx Cd1- x S guest with controllable physicochemical properties enabled by self-assembled hybrid structure and continuously amenable band gap. The effective porous topology nanoassembly, both at the exterior and the interior pores of a porous metal-organic framework (MOF), maximizes spatially immobilized semiconductor nanoparticles toward high utilization of particulate heterojunctions for vital charge and reactant transfer. In conjunction, the zinc constituent band engineering is found to regulate the light/molecules absorption, band structure, and specific reaction intermediates energy to attain high photocatalytic CO2 reduction selectivity. The optimal catalyst exhibits a H2 -generation rate up to 6720 µmol g-1 h-1 and a CO production rate of 19.3 µmol g-1 h-1 . These findings provide insight into the design of discrete host-guest MOF-semiconductor hybrid system with readily modulated band structures and well-constructed heterojunctions for selective solar-to-chemical conversion.

Controlled Ni doping on a g-C3N4/CuWO4 photocatalyst for improved hydrogen evolution

The development of a low-cost, environment-friendly and suitable semiconductor-based heterogeneous photocatalyst poses a great challenge towards extremely competent and substantial hydrogen evolution. A series of environment-friendly and proficient S-scheme Ni-doped CuWO4 nanocrystals supported on g-C3N4 nanocomposites (Ni-CuWO4/g-C3N4) were constructed to ameliorate the photocatalytic efficacy of pure g-C3N4 and Ni-CuWO4 and their activity in H2 generation through photocatalytic water splitting was evaluated. The Ni-CuWO4 nanoparticles were synthesized through doping of Ni2+ on wolframite CuWO4 crystals via the chemical precipitation method. An elevated hydrogen generation rate of 1980 μmol h-1 g-1 was accomplished over the 0.2Ni-CuWO4/g-C3N4 (0.2NCWCN) nanocomposite with an apparent quantum yield (AQY) of 6.49% upon visible light illumination (λ ≥ 420 nm), which is evidently 7.1 and 17.2 fold higher than those produced from pristine g-C3N4 and Ni-CuWO4. The substantial enhancement in the photocatalytic behaviour is primarily because of the large surface area, limited band gap energy of the semiconductor composite and magnified light harvesting capability towards visible light through the inclusion of g-C3N4, thus diminishing the reassembly rate of photoinduced excitons. Further, density functional theory (DFT) calculations were performed to investigate the structural, electronic and optical properties of the composite. Theoretical results confirmed that the Ni-CuWO4/g-C3N4 composite is a potential candidate for visible-light-driven photocatalysts and corroborated with the experimental findings. This research provides a meaningful and appealing perspective on developing cost-effective and very proficient two-dimensional (2D) g-C3N4-based materials for photocatalytic H2 production to accelerate the separation and transmission process of radiative charge carriers.

Study on Photochemical Properties of a Sr-SnS2/CaIn2S4 Heterostructure to Improve Cr(VI) Removal

Compound semiconductor photocatalysis technology is considered to be a promising treatment for solving water problems efficiently. The point of designing high-efficiency catalysts is to optimize the band gap structure and facilitate the separation of charge carriers by establishing new electron migration pathways. Recently, 3D porous CaIn2S4 was found to have good photocatalytic ability. However, the quick recombination and agglomeration of carriers still limit its application. Herein, we prepared a heterostructure by introducing 2D Sr-doped SnS2 to 3D CaIn2S4 by a hydrothermal synthesis method. The optimal dosage of Sr-SnS2 is 3%, and the photocatalytic Cr(VI) removal efficiency of 3% Sr-SnS2/CaIn2S4 (SSCS-3) is 5.82 and 10.83 times those of pure CaIn2S4 and SnS2, respectively. According to the results of characterization tests and calculation verification, we inferred that the enhanced photocatalytic removal of Cr(VI) is due to the introduction of Sr-SnS2 that can promote the rapid transfer of photogenerated electrons to the surface of CaIn2S4, and the heterostructure formed between 2D Sr-SnS2 and 3D CaIn2S4 can also provide abundant reaction sites. The promotion of carrier separation is mainly due to the formation of a built-in electric field of the Sr-SnS2/CaIn2S4 heterostructure. This work provides new ideas and technologies for the treatment of Cr(VI) in wastewater.

Photoelectrochemical performance of BiOI/TiO2 nanotube arrays (TNAs) p-n heterojunction synthesized by SILAR-ultrasonication-assisted methods

In order to extend the visible region activity of titania nanotube array (TNAs) films, the successive ionic layer adsorption and reaction (SILAR)-ultrasonication-assisted method has been used to prepare BiOI-modified TiO2 nanotube arrays (BiOI/TNAs). The band gap of BiOI/TNAs for all the variations reveals absorption in the visible absorption. The surface morphology of BiOI/TNAs is shown in the nanoplate, nanoflake and nanosheet forms with a vertical orientation perpendicular to TiO2. The crystalline structure of BiOI did not change the structure of the anatase TNAs, with the band gap energy of the BiOI/TNAs semiconductor in the visible region. The photocurrent density of the BiOI/TNAs extends to the visible-light range. BiOI/TNAs prepared with 1 mM Bi and 1 mM KI on TNAs 40 V 1 h, 50 V 30 min show the optimum photocurrent density. A tandem dye-sensitized solar cell (DSSC)-photoelectrochemical (PEC) was used for hydrogen production in salty water. BiOI/TNAs optimum was used as the photoanode of the PEC cell. The solar to hydrogen conversion efficiency (STH) of tandem DSSC-PEC reaches 1.34% in salty water.

"Quasi-In Situ Synthesis of Oxygen Vacancy-Enriched Strontium Iron Oxide Supported on Boron-Doped Reduced Graphene Oxide to Elevate the Photocatalytic Destruction of Tetracycline"

The efficient use of visible light is necessary to take advantage of photocatalytic processes in both indoor and outdoor circumstances. Precisely manipulating the in situ growth method of heterojunctions is an effective way to promote photogenerated charge separation. Herein, the SrFeO₃@B-rGO catalyst was prepared by an in situ growth method. At a loading of 10 wt % B-rGO, the nanocomposites revealed an excellent morphology and thermal, optical, electrochemical, and mechanical properties. X-ray diffraction analysis revealed the cubic spinel structure and a space group of Pm̅3m for SrFeO₃. High-resolution scanning electron microscopy and high-resolution transmission electron microscopy show the core-shell formation between SrFeO₃ and B-rGO. Furthermore, density functional theory of SrFeO₃ was performed to find its band structure and density of states. The SrFeO₃@B-rGO nanocomposite shows the degradation rate of tetracycline (TC) reaching 92% in 75 min and the highest rate constant of 0.0211 min^-1. To improve the catalytic removal rate of antibiotics, the efficiency of e^- and h ⁺ separation must be improved, as well as the generation of additional radicals. Radical trapping tests and the electron paramagnetic resonance method indicated that the combination of Fe²⁺ and Fe³⁺ in SrFeO₃ effectively separated e^- and h⁺ while also promoting the development of the superoxide anion (^•O₂^-) to accelerate TC degradation. The entire TC degradation pathway using high-performance liquid chromatography and its mechanism were discussed. As a whole, this study delineates that photocatalysis is a viable strategy for the treatment of environmental antibiotic wastewater.

Liquid exfoliation of bulk g-C3N5 to nanosheets for improved photocatalytic antibacterial activity

Liquid exfoliation of bulk g-C₃N₅ was applied to synthesize g-C₃N₅ nanosheets. In order to characterize the samples, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectra (XPS), UV-Vis absorption spectra (UV-Vis), and photoluminescence spectra (PL) were examined. g-C₃N₅ nanosheets exhibited enhanced performance in the inactivation of Escherichia coli (E. coli) with visible light irradiation relative to bulk g-C₃N₅ and promoted complete inactivation of E. coli within 120 min. h⁺ and •O₂^- were the principal reactive species in the antibacterial process. In the early stages, SOD and CAT played a defensive role in resisting oxidative damage of active species. With the prolonged light exposure time, the antioxidant protection system was overwhelmed leading to the destruction of the cell membrane. The leakage of cell contents such as K⁺, protein, and DNA caused bacterial apoptosis ultimately. The enhanced photocatalytic antibacterial performance of g-C₃N₅ nanosheets is ascribed to the stronger redox property by the upward shift of CB and downward shift of VB compared with bulk g-C₃N₅. On the other hand, larger specific surface area and better separation efficiency of photoinduced carriers are helpful to the improved photocatalytic performance. This study systematically revealed the inactivation process toward E. coli and expanded the application range of g-C₃N₅-based materials with abundant solar energy.

Construction of an La-BiVO4/O-Doped g-C3N4 Heterojunction Photocatalyst Embedded in Electrospinning Nanofibers

BiVO₄ has been widely used in the field of photocatalysis due to its nontoxic and moderate band gap. However, single BiVO₄ has the disadvantages of a high recombination rate of photogenerated carriers and weak response to visible light, inhibiting its photocatalytic applications. To explore viable solutions, a hybrid material composed of lanthanum-doped bismuth vanadate (La-BiVO₄) and oxygen-doped porous graphite carbon nitride (O-doped g-C₃N₄), i.e., La-BiVO₄/O-doped g-C₃N₄ powder, was prepared by a facile hydrothermal reaction and low-temperature calcination. Then, the powder was loaded on polyacrylonitrile nanofibers (NFs) through the electrospinning fiber technique. Various surface science characterizations, including transmission electron microscopy and nitrogen absorption and desorption analysis, confirmed the successful synthesis of a mesoporous heterojunction material. The La³⁺-doping as well as the porous morphologies and larger specific surface area of the O-doped g-C₃N₄ ultimately improve the photocatalytic abilities via a proposed Z-scheme heterojunction mechanism. The roles of La³⁺-doping and morphology modification in promoting the separation of the photogenerated carriers and broadening the optical absorption range were experimentally discussed. The RhB degradation experiment indicated that the La-BiVO₄/O-doped g-C₃N₄ powder has excellent photocatalytic activity, which is about 2.85 and 2 times higher than that of the pure BiVO₄ and O-doped g-C₃N₄, respectively. Meanwhile, the La-BiVO₄/O-doped g-C₃N₄ NF shows good stability and recoverability after a 10-cycle testing. Such a hybrid photocatalyst with a proposed Z-scheme heterojunction mechanism and good plasticity might pave a feasible way to fabricate a new library of photocatalysts.

Enhanced plasmonic photocatalytic performance of C3N4/Cu by the introduction of a reduced graphene oxide interlayer

Cu nanoparticles (NPs) are low-cost surface plasmonic resonance (SPR) metal nanostructures, and their SPR properties can be used to enhance the photocatalytic hydrogen evolution performance of carbon nitride (C₃N₄). But their actual performance is usually limited, and one key factor is their poor interfacial quality. In this work, a highly conductive reduced graphene oxide (RGO) interlayer is introduced between protonated C₃N₄ (PCN) nanosheets and Cu NPs, which can act as an efficient sink for photogenerated electrons from C₃N₄ and hot electrons from Cu NPs, and simultaneously serve as reaction sites for the hydrogen evolution reaction, and accelerate the charge transport by the formed C-O-C and C-O-Cu bonds. The optimal hydrogen evolution rate of the optimized PCN/RGO/Cu is 1.30 mmol g^-1 h^-1, which is 6.76, 2.47 and 2.41 times that of PCN, PCN/RGO and PCN/Cu, respectively, and it can further reach up to 13.22 mmol g^-1 h^-1 by loading moderate Pt NPs. Meanwhile, the introduced RGO can effectively anchor Cu NPs to enhance the stability of the photocatalyst. In addition, due to the broad SPR response of Cu NPs, a near-infrared photocatalytic performance is realized for PCN/RGO/Cu with an apparent quantum efficiency of 0.46% at 765 nm.

Engineered Cobalt Single-Atoms@BiFeO3 Heteronanostructures for Highly Efficient Solar Water Oxidation

Efficient charge-carrier separation and their utilization are the key factors in overcoming sluggish four-electron reaction kinetics involved in photocatalytic oxygen evolution. Here, a novel study demonstrates the significance of Na₂ S₂ O₈ as a sacrificial agent in comparison to AgNO₃ . Resultantly, BiFeO₃ (BFO) and titanium doped-oxygen deficient BiFeO₃ (Ti-BFO-R) nanostructures achieve ≈64 and 44.5 times higher O₂ evolution in the presence of Na₂ S₂ O₈ compared to AgNO₃ as a sacrificial agent, respectively. Furthermore, the presence of Co single atoms (Co-SAs) deposited via immersion method on BFO and Ti-BFO-R nanostructures led to achieving outstanding O₂ evolution at a rate of 16.11 and 23.89 mmol g^-1 h^-1 , respectively, which is 153 and 227.5 times higher compared to BFO (in the presence of AgNO₃ ), the highest O₂ evolution observed for BFO-based materials to date. The successful deposition of Co-SAs is confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and X-ray absorption near-edge structure (XANES). The charge transfer investigations confirm the significance of Co-SAs on BFO-based photocatalysts for improved charge-carrier separation, transport, and utilization. This novel study validates the excellent role of Na₂ S₂ O₈ as a sacrificial agent and Co-SAs as a cocatalyst for BFO-based nanostructures for efficient O₂ evolution.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO₂ nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti₃C₂@TiO₂ nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti₃C₂@TiO₂ were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti₃C₂ and TiO₂. The optimized Ti₃C₂@TiO₂-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO₂ with a rate constant (k) of 0.02463 min^-1. The major contribution of ^•O₂^- and ^•OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 μmol h^-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti₃C₂@TiO₂ originated from the superior electrical conductivity of cocatalyst Ti₃C₂, which facilitated spatial photogenerated e^-/h⁺ separation and transfer at the Ti₃C₂ MXene@TiO₂ interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

S-Scheme and Schottky Junction Synchronous Regulation Boost Hierarchical CdS@Nb2O5/Nb2CTx (MXene) Heterojunction for Photocatalytic H2 Production

Photocatalytic water cracking hydrogen (H₂) production is a promising clean energy production technology. Therefore, a ternary CdS@Nb₂O₅/Nb₂CT_x (MXene) heterojunction with hierarchical structure was designed to promote photocatalytic H₂ evolution. When Na₂S/Na₂SO₃ and lactic acid were used as sacrificial agents, the hydrogen evolution reaction (HER) rates of the optimized photocatalyst were 1501.7 and 2715.8 μmol g^-1 h^-1, with 12.4% and 26.1% apparent quantum efficiencies (AQE) at 420 nm, respectively. Its HER performance was 10.9-fold higher than that of pure CdS and remained 87% activity after five rounds of cycle tests. Such an enhancement stems from the excellent light absorption properties, tight interfacial contact, fast charge transfer channel, and sufficient active sites. Mechanism analysis demonstrates that S-scheme and Schottky junction synchronous regulation boost hierarchical CdS@Nb₂O₅/Nb₂CT_x for photocatalytic H₂ production. This work creates possibilities for manufacturing Nb-based MXene photocatalysts for converting solar energy and other applications.

C,N co-doped TiO2 hollow nanofibers coated stainless steel meshes for oil/water separation and visible light-driven degradation of pollutants

Complex pollutants are discharging and accumulating in rivers and oceans, requiring a coupled strategy to resolve pollutants efficiently. A novel method is proposed to treat multiple pollutants with C,N co-doped TiO₂ hollow nanofibers coated stainless steel meshes which can realize efficient oil/water separation and visible light-drove dyes photodegradation. The poly(divinylbenzene-co-vinylbenzene chloride), P(DVB-co-VBC), nanofibers are generated by precipitate cationic polymerization on the mesh framework, following with quaternization by triethylamine for N doping. Then, TiO₂ is coated on the polymeric nanofibers via in-situ sol-gel process of tetrabutyl titanate. The functional mesh coated with C,N co-doped TiO₂ hollow nanofibers is obtained after calcination under nitrogen atmosphere. The resultant mesh demonstrates superhydrophilic/underwater superoleophobic property which is promising in oil/water separation. More importantly, the C,N co-doped TiO₂ hollow nanofibers endow the mesh with high photodegradation ability to dyes under visible light. This work draws an affordable but high-performance multifunctional mesh for potential applications in wastewater treatment.

The Collision between g-C3 N4 and QDs in the Fields of Energy and Environment: Synergistic Effects for Efficient Photocatalysis

Recently, graphitic carbon nitride (g-C₃ N₄ ) has attracted increasing interest due to its visible light absorption, suitable energy band structure, and excellent stability. However, low specific surface area, finite visible light response range (<460 nm), and rapid photogenerated electron-hole (e^- -h⁺ ) pairs recombination of the pristine g-C₃ N₄ limit its practical applications. The small size of quantum dots (QDs) endows the properties of abundant active sites, wide absorption spectrum, and adjustable bandgap, but inevitable aggregation. Studies have confirmed that the integration of g-C₃ N₄ and QDs not only overcomes these limitations of individual component, but also successfully inherits each advantage. Encouraged by these advantages, the synthetic strategies and the fundamental of QDs/g-C₃ N₄ composites are briefly elaborated in this review. Particularly, the synergistic effects of QDs/g-C₃ N₄ composites are analyzed comprehensively, including the enhancement of the photocatalytic performance and the avoidance of aggregation. Then, the photocatalytic applications of QDs/g-C₃ N₄ composites in the fields of environment and energy are described and further combined with DFT calculation to further reveal the reaction mechanisms. Moreover, the stability and reusability of QDs/g-C₃ N₄ composites are analyzed. Finally, the future development of these composites and the solution of existing problems are prospected.

Construction of S-Scheme CuS/Bi5O7I Heterojunction for Boosted Photocatalytic Disinfection with Visible Light Exposure

In this paper, a novel S-scheme CuS/Bi5O7I heterojunction was successfully constructed using a two-step approach comprising the alkaline hydrothermal method and the adsorption–deposition method, and it consisted of Bi5O7I microrods with CuS particles covering the surface. The photocatalytic antibacterial effects on Escherichia coli (E. coli) were systematically examined with visible light exposure. The results suggested that the 3%-CuS/Bi5O7I composite showed the optimal antibacterial activity, completely inactivating E. coli (5 × 108 cfu/mL) in 180 min of irradiation. Moreover, the bacterial inactivation process was scientifically described. •O2− and h+ were the major active species for the inactivation of the bacteria. In the early stages, SOD and CAT initiated the protection system to avoid the oxidative destruction of the active species. Unfortunately, the antioxidant protection system was overwhelmed thereafter, which led to the destruction of the cell membrane, as evidenced by the microstructure changes in E. coli cells. Subsequently, the leakage of intracellular components including K+, proteins, and DNA resulted in the unavoidable death of E. coli. Due to the construction of the S-scheme heterojunction, the CuS/Bi5O7I composite displayed the boosted visible light harvesting, the high-efficiency separation of photogenerated electrons and holes, and a great redox capacity, contributing to an outstanding photocatalytic disinfection performance. This work offers a new opportunity for S-scheme Bi5O7I-based heterojunctions with potential application in water disinfection.

Enhanced Photocatalytic Degradation of Emerging Contaminants Using Ti3C2Tx MXene-Supported CdS Quantum Dots

The synthesis of efficient and stable catalysts for photocatalytic reactions is still a challenge. In this study, a new photocatalyst composed of two-dimensional titanium carbide (Ti₃C₂T_x) and CdS quantum dots (QDs) was fabricated, in which CdS QDs were intimately anchored on the Ti₃C₂T_x sheet surface. Due to the specific interface characteristics of CdS QDs/Ti₃C₂T_x, Ti₃C₂T_x can considerably facilitate the generation of photogenerated charge carriers, their separation, and their transfer from CdS. As expected, the obtained CdS QDs/Ti₃C₂T_x exhibit outstanding photocatalytic performance for carbamazepine (CBZ) degradation. Moreover, the quenching experiments demonstrated that superoxide radicals (^•O₂^-), H₂O₂, ¹O₂, and ^•OH are the reactive species involved in CBZ degradation, while ^•O₂^- made a major contribution. In addition, the sunlight-driven CdS QDs/Ti₃C₂T_x photocatalytic system is widely suitable for the elimination of different emerging pollutants in various water matrices, suggesting its potential practical environmental applications.

A general way to realize the bi-directional promotion effects on the photocatalytic removal of heavy metals and organic pollutants in real water by a novel S-scheme heterojunction: Experimental investigations, QSAR and DFT calculations

Heavy metals (HMs) often coexist with organic pollutants (OPs) in real surface water. Is it possible to find a general way that the removal of one from these two pollutants will promote the elimination of another pollutant? Herein, the bi-directional promotion effects (BPEs) on synchronous removal of Cr(VI) (i.e., hexavalent chromium) and OPs were achieved by a SnNb₂O₆/CuInS₂ S-scheme heterojunction. Specifically, the apparent rate constants are 0.161 min^-1 [(Cr(VI)] and 0.019 min^-1 [Tetracycline hydrochloride (TCH)] in coexisting Cr(VI)/TCH system (which are 3.74 and 1.58 times, respectively, compared to the mono-pollutant system), indicating OPs indeed can act as hole scavengers (electron donors) to consume plenty of photoinduced holes and enable more photoexcited electrons to attend to Cr(VI) photoreduction. More significantly, OPs (i.e., TCH, atrazine and 4-chlorophenol) with different molecular structures possess different adiabatic ionization potentials (AIPs), in an inversely linear relationship with BPEs, i.e., the lower AIP value is, the higher electron-donating ability is, the better BPEs present. Finally, TCH and its degradation intermediates toxicity was forecasted via quantitative structure-activity relationship, demonstrating the toxicity decrease of TCH during the photocatalytic process. This work provides a general strategy for simultaneous removal of contaminants, contributing to wastewater purification.

Immobilization of Bacillus amyloliquefaciens protease "Neutrase" as hybrid enzyme inorganic nanoflower particles: A new biocatalyst for aldol-type and multicomponent reactions

Organic-inorganic hybrid nanoflowers (hNFs) with commercial protease "Neutrase" is proposed and characterized as efficient and green biocatalysts for promiscuous catalysis in aldol-type and multicomponent reactions. Neutrase hNFs [Neutrase-(Cu/Ca/Co/Mn)₃(PO₄)₂] are straightforwardly prepared through mixing metal ion (Cu²⁺, Ca²⁺, Co²⁺ or Mn²⁺) aqueous solutions with Neutrase in phosphate buffer (pH 7.4, 10 mM) resulting in precipitation (3 days). The hNFs were characterized by various techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX), element mapping, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). In SEM images, the metal-Neutrase complexes revealed flower-like or granular structures after hybridization. The effect of metal ions and enzyme concentrations on the morphology and enzyme activity of the Neutrase-hNFs was examined. The synthesized Neutrase-Mn hNFs showed superior activity and stability compared to free Neutrase. Traditional organic CC coupling reactions such as aldol condensation, decarboxylative aldol, Knoevenagel, Hantzsch-type reactions and synthesis of 4H-pyran derivatives were used to test the generality and scope of Neutrase promiscuity, while optimizing conditions for the Neutrase-Mn hNF biocatalyst. Briefly, Neutrase-Mn₃(PO₄)₂ hNFs showed excellent enzyme activity, stability and reusability, qualifying as effective reusable catalysts for coupling reactions under mild conditions.

Enhanced photocatalytic degradation of tetracycline by a H2O2-assisted Bi3NbO7/Bi2Sn2O7 composite under visible light

A Z-scheme BNO/BSO composite photocatalyst has been successfully prepared using an in situ solvothermal method. The phase component, microstructure and optical properties of the as-prepared samples were characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and other means. The photocatalytic performance of the BNO/BSO composite was evaluated via the degradation of the typical antibiotic tetracycline (TC) under hydrogen peroxide assistance and visible light irradiation. The "cata + H₂O₂ + vis" system shows the best photocatalytic activity, and its apparent rate constant reaches 0.03164 min^-1, which is 4.9 times and 5.7 times that of the "cata + vis" system and the "cata + H₂O₂" system, respectively. Compared with pristine that of BSO alone, the reaction rate constant of the 15% BNO/BSO composite increases 1.8 times. The enhanced photocatalytic activity is attributed to the construction of a unique Z-scheme-type heterojunction, which effectively suppresses the recombination of electron-hole pairs. In addition, the addition of H₂O₂ promotes the generation of more active species. Moreover, a possible photocatalytic degradation mechanism is also further proposed.

Construction of a novel S-scheme heterojunction piezoelectric photocatalyst V-BiOIO3/FTCN and immobilization with floatability for tetracycline degradation

A high-performance piezoelectric photocatalyst (V-BiOIO₃/FTCN) was constructed to improve removal efficiency of tetracycline hydrochloride (TCH). The role of V-BiOIO₃ in the composite was to introduce piezoelectric effect and construct S-scheme heterojunction photocatalyst with fish scale tubular carbon nitride (FTCN). The morphology, structure, chemical composition and optoelectronic characteristics of the as-prepared photocatalysts were studied by SEM, TEM, XRD, XPS and UV-Vis DRS. Combined with UV-Vis DRS, XPS valence band, Mott-schottky curve and theoretical calculations, the mechanism of TCH degradation was deeply analyzed. A series of degradation experiments showed that the V-BiOIO₃/FTCN could effectively degrade TCH, and the removal efficiency was further improved under the action of ultrasound. Importantly, the further immobilized V-BiOIO₃/FTCN/MS could float on the water surface to degrade TCH without additional stirring, which facilitated the recovery of photocatalysts and showed excellent practical application value. This work provided a reference for the design and immobilization of carbon nitride-based piezoelectric photocatalysts.

Novel La3+/Sm3+ co-doped Bi5O7I with efficient visible-light photocatalytic activity for advanced treatment of wastewater: Internal mechanism, TC degradation pathway, and toxicity analysis

Controlling semiconductor photocatalysts by doping rare-earth ions is an effective strategy to improve photocatalytic performance. Simple solvothermal and calcination methods were used to prepare La³⁺ and Sm³⁺ modified Bi₅O₇I nanomaterials. Some characterizations such as XRD, XPS, SEM, TEM, UV-vis, etc. were carried out to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was investigated by simulating the degradation of TC and RhB under visible-light irradiation. The degradation results showed that the photocatalytic efficiency of 4S4L-Bi₅O₇I was the best among the samples with the 100% degradation rate of TC (Tetracycline hydrochloride) and 93% of RhB (Rhodamine B). The capture experiment and ESR test proved that the active substances that play a role in the photocatalytic degradation of pollutants were ·O₂^-, ¹O₂ and h⁺, and on this basis, the possible degradation mechanism was proposed. The final results showed that La/Sm co-doping expanded the light absorption range of Bi₅O₇I and improved the charge separation efficiency and the specific surface area. Besides, the surface defects were formed on the surface of Bi₅O₇I due to ion-doping, which could catch e^- to promote the separation and transfer of carriers and improve the photocatalytic activity. LC-MS was used to analyze the possible degradation pathways of TC. And the toxicity of TC was also analyzed via T.E.S.T and Toxtree. The results showed comprehensive toxicity of TC was decreased by 4S4L-Bi₅O₇I so that the overall water pollution was reduced. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Ternary nanocomposites of CdS/WO3/g-C3N4 for hydrogen production

The sustainable rise in global warming and the consumption of fossil fuels considerably contribute to energy and environmental issues. To address these issues, semiconductor heterostructures can be used to generate clean energy sources as alternative energy sources and to reduce environmental impacts. Herein, we report the synthesis of a ternary semiconductor of the CdS/WO₃/g-C₃N₄ (i.e. C-CNW) nanostructured composite for hydrogen production and dye degradation under visible-light irradiation. The structural properties of the prepared materials were studied using a series of investigational analyses. The 3C-CNW nanostructure photocatalyst exhibited faster malachite green (MG) dye photodegradation within 105 min and the highest hydrogen production rate is 868.23 μmol g^-1 h^-1 under visible light illumination. Moreover, the photocatalytic hydrogen production of the 3C-CNW nanostructure photocatalyst with various scavengers was analyzed. Its higher photocatalytic activity is ascribed to the Z-scheme mechanism, which induces rapid diffusion of photoinduced charges within the ternary photocatalyst with its optical bandgap. This proposed strategy is useful to improve photocatalysts that play a role in mitigating energy and environmental issues.

Synergetic Catalytic and Photocatalytic Performances of Tin-Doped BiFeO3/Graphene Nanoplatelet Hybrids under Dark and Light Conditions

Because of a rapidly growing need for water, it is essential to find new fast and reliable ways of water purification from organic pollutants. For removing organic azo dyes from water, various catalysts and photocatalysts have been designed to meet crucial water needs. In this study tin (Sn) doped bismuth ferrite (BFO) nanoparticles have been synthesized using the sol-gel technique. Further, BFSO/GNP nanohybrids were synthesized by mixing BFSO nanoparticles with graphene nanoplatelets (GNPs) via a simple and cost effective coprecipitation process. XRD and SEM showed that BFSO/GNP nanohybrids are well grown in crystal structure along with uniform and homogeneous morphology. XPS supported the elemental composition and interface bonding of both materials present inside the nanohybrids. DRS and catalytic activities showed that BFSO/GNP nanohybrids are both dark and light active species for performing dye degradation activities during water purification. The as-synthesized nanohybrids provided efficient dye removal from water even in the absence of light owing to the presence of defects and trap-state carriers (electrons) inside the graphene sheets. The optimized nanohybrid BFSO-15/GNP showed 100% dye removal in 60 min with 90% catalytic activity under dark. The recyclability test showed stable and repeatable performance of BFSO/GNP nanohybrids up to 10 cycles of catalytic activities.

Effect of Sr and Ti substitutions on optical and photocatalytic properties of Bi1-x Sr x Fe1-x Ti x O3 nanomaterials

The potential use of down-sized BFO-xSTO systems (x ≤ 25%) as highly efficient photoanodes for photocatalytic water splitting is investigated. BFO-xSTO is prepared by a solid-state method and subsequently deposited by spray coating. The compounds possess rhombohedral symmetry for x ≤ 15% and phase coexistence for x > 15%, as demonstrated by Raman spectroscopy and transmission electron microscopy. Our findings revealed a drastic grain size decrease with increasing STO content, namely 260 nm for BFO to 50 nm for BFO with 25% STO. Moreover, BFO-xSTO, x > 10% exhibited high optical absorption (> 80%) in the full spectrum and interestingly a very promising band alignment with water redox potentials. Moreover, the photochemical measurements revealed a photocurrent density of ∼0.17 μA cm-2 achieved for x = 15% at 0 bias. Using DFT calculations, the substitution effects on the electronic, optical, and photocatalytic performances of the BFO system were investigated and quantified. Surprisingly, a high hydrogen yield (∼191 μmol g-1) was achieved by BFO-12.5%STO compared to 1 μmol g-1 and 57 μmol g-1 for BFO and STO, respectively. This result highlights the beneficial effects of both the downsizing and substitution of BFO on the photocatalytic water splitting and hydrogen production performances of Bi1-x Sr x Fe1-x Ti x O3 systems.

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.

Preparation of Au-RGO/TiO2 nanotubes and study on the photocatalytic degradation of ciprofloxacin

Au-RGO/TiO₂ nanotubes were prepared by anodic oxidation and electrochemical deposition, and their performance in the photocatalytic degradation of ciprofloxacin was investigated. The results showed that, compared with TiO₂ nanotubes and RGO/TiO₂ nanotubes, the Au-RGO/TiO₂ nanotubes had the highest ciprofloxacin degradation rate, reaching 96.93% in 180 min of photocatalysis. In addition, the possible degradation products of ciprofloxacin were analyzed by liquid chromatography-mass spectrometry, and the mechanism of degradation of ciprofloxacin by Au-RGO/TiO₂ nanotubes was analyzed.

Removing chemical and biological pollutants from swine wastewater through constructed wetlands aiming reclaimed water reuse

Reusing reclaimed wastewater is needed to fight water scarcity, reduce freshwater consumption and conserve water resources, but one must ensure that hazardous substances are fully removed/eliminate before that reuse. The potential of lab-scale constructed wetlands (CWs) for the removal of chemical and biological contaminants from livestock wastewater, while maintaining nutrient levels for fertilization, was assessed, evaluating changes in microbial communities, with particular focus on potential pathogens. CW microcosms with two different substrates (lava rock or light expanded clay aggregate), both planted with Phragmites australis, were tested. After 15 days of treatment, removal rates were higher than 80% for Cd, Cr, Cu, Fe, Pb and Zn, in general with no significant differences between the two different substrates. Organic matter and nutrients were also removed but their levels still allowed the used of the treated wastewater as a fertilizer Removal of bacterial contamination was estimated through enumeration of cultivable bacteria. High removal rates of fecal indicator bacteria were observed, reaching >95% for enterococci and >98% for enterobacteria after 15 days of treatment, decreasing hazardous biological contaminants initially present in the wastewater. In addition, the microbial communities in the initial and treated wastewater, and in the plant roots bed substrate, were characterized by using 16SrRNA gene amplicon sequencing. Microbial communities in the CW systems showed a clear shift comparatively with the initial wastewater showing system adaptation and removal potentialities. This also revealed an important removal of the most represented potential pathogenic genus, Clostridium, which relative abundance decreased from 33% to 1% through the treatment. Overall, CWs showed potential to be efficient in removing chemical and biological contaminants, while maintaining moderated levels of nutrients, allowing the reuse of reclaimed water in agriculture, namely as fertilizer. Current results will contribute for the optimization and use of CWs for a sustainable treatment of liquid wastes, promoting the circular economy.

Solvent-Free Combustion-Assisted Synthesis of LaFe0.5Cr0.5O3 Nanostructures for Excellent Photocatalytic Performance toward Water Decontamination: The Effect of Fuel on Structural, Magnetic, and Photocatalytic Properties

The present study reports the synthesis of nanocrystalline LaFe0.5Cr0.5O3 via a solvent-free combustion method using glycine, poly(vinyl alcohol), and urea as fuels, with superior photocatalytic activity. Rietveld refinement and powder X-ray diffraction data of nanomaterials demonstrate the existence of an orthorhombic phase that corresponds to the Pbnm space group. The crystallite size of nanoperovskite samples lies in the range of 20.9-36.4 nm. The Brunauer-Emmett-Teller (BET) surface area of the LaFe0.5Cr0.5O3 fabricated using urea is found to be higher than that of the samples prepared using other fuels. The magnetic measurements of all samples done using a SQUID magnetometer showed a dominant antiferromagnetic character along with some weak ferromagnetic interactions. The optical band gap of all nanosamples lies in the visible range (2-2.6 eV), making them suitable photocatalysts in visible light. Their use as a photocatalyst for the degradation of the rhodamine B dye (model pollutant) is studied, and it has been observed that the catalyst fabricated using urea shows excellent degradation efficiency for rhodamine B, i.e., 99% in 60 min, with high reusability up to five runs. Additionally, the degradation of other organic dyes such as methylene blue, methyl orange, and a mixture of these dyes (rhodamine B + methylene blue + methyl orange) is also investigated with the most active photocatalyst, i.e., LFCO-U, to check its versatility.

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.

Fabrication of a highly dispersed Co3O4-modified MOF-derived ZnO@ZnS porous heterostructure for efficient photocatalytic hydrogen production

A highly dispersed Co3O4-modified ZnO@ZnS porous heterostructure was prepared via a designed bimetallic ZnCo-ZIF@ZIF-8 precursor for water splitting.

Construction of BiOIO3/AgIO3 Z-Scheme Photocatalysts for the Efficient Removal of Persistent Organic Pollutants under Natural Sunlight Illumination

The efficient removal of persistent organic pollutants (POPs) in natural waters is vital for human survival and sustainable development. Photocatalytic degradation is a feasible and cost-effective strategy to completely disintegrate POPs at room temperature. Herein, we develop a series of direct Z-scheme BiOIO₃/AgIO₃ hybrid photocatalysts via a facile deposition-precipitation method. Under natural sunlight irradiation, the light intensity of which is ∼40 mW/cm², a considerable rate constant of 0.185 min^-1 for photodecomposing 40 mg/L MO is obtained over 0.5 g/L Bi@Ag-5 composite photocatalyst powder, about 92.5 and 5.3 times higher than those of pristine AgIO₃ and BiOIO₃. The photoactivity of Bi@Ag-5 for photodecomposing MO under natural sunlight illumination surpasses most of the reported photocatalysts under Xe lamp illumination. After natural sunlight irradiation for 20 min, 95% of MO, 82% of phenol, 78% of 2,4-DCP, 54% of ofloxacin, and 88% of tetracycline hydrochloride can be photodecomposed over Bi@Ag-5. Relative to the commercial photocatalyst TiO₂ (P25), Bi@Ag-5 exhibits greatly higher photoactivity for the treatment of MO-phenol-tetracycline hydrochloride mixture pollutants in the scale-up experiment of 500 mL of solution, decreasing COD, TOC, and chromaticity value by 52, 19, and 76%, respectively, after natural sunlight irradiation for 40 min. The photodegradation process and mechanism of MO have been systematically investigated and proposed. This work provides an archetype for designing efficient photocatalysts to remove POPs.