Visible Light-driven Photocatalyst Research Articles

Visible light- and dark-driven degradation of palm oil mill effluent (POME) over g-C3N4 and photo-rechargeable WO3.

The investigations of real industrial wastewater, such as palm oil mill effluent (POME), as a recalcitrant pollutant remain a subject of global water pollution concern. Thus, this work introduced the preparation and modification of g-C3N4 and WO3 at optimum calcination temperature, where they were used as potent visible light-driven photocatalysts in the degradation of POME under visible light irradiation. Herein, g-C3N4-derived melamine and WO3 photocatalyst were obtained at different calcination temperatures in order to tune their light absorption ability and optoelectronics properties. Both photocatalysts were proven to have their distinct phases, crystallinity levels, and elements with increasing temperature, as demonstrated by the ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) results. Significantly, g-C3N4 (580°C) and WO3 (450°C) unitary photocatalysts exhibited the highest removal efficiency of POME without dilution due to good crystallinity, extended light absorption, high separation, and less recombination efficiency of electron-hole pairs. Furthermore, surprisingly, the superior energy storage photocatalytic performance with outstanding stability by WO3 achieved an approximately 10% increment during darkness, compared with g-C3N4 under visible light irradiation. Moreover, it has been proven that the WO3 and g-C3N4 photocatalysts are desirable photocatalysts for various pollutant degradations, with excellent visible-light utilization and favorable energy storage application.

Visible Light-Driven SnIn4S8 Photocatalyst Decorated on Polyurethane-Impregnated Microfiber Non-Woven Fabric for Pollutant Degradation.

In recent years, polyurethane has drawn great attention because of its many advantages in physical and chemical performance. In this work, firstly, polyurethane was impregnated in a non-woven fabric (NWF). Then, polyurethane-impregnated NWF was coagulated utilizing a wet phase inversion. Finally, after alkali treatment, microfiber non-woven fabrics with a porous polyurethane matrix (PNWF) were fabricated and used as substrates. SnIn4S8 (SIS) prepared by a microwave-assisted method was used as a photocatalyst and a novel SIS/PNWF substrate with multiple uses and highly efficient catalytic degradation ability under visible light was successfully fabricated. The surface morphology, chemical and crystal structures, optical performance, and wettability of SIS/PNWF substrates were observed. Subsequently, the photocatalytic performance of SIS/PNWF substrates was investigated by the decomposition of rhodamine B (RhB) under visible light irradiation. Compared with SIS/PNWF-2% (2%, the weight ratio of SIS and PNWF, same below), SIS/PNWF-5% as well as SIS/PNWF-15%, SIS/PNWF-10% substrates exhibited superior photocatalytic efficiency of 97% in 2 h. This may be due to the superior photocatalytic performance of SIS and the inherent hierarchical porous structure of PNWF substrates. Additionally, the hydrophobicity of SIS/PNWF substrates can enable them to float on the solution and further be applied on an open-water surface. Furthermore, tensile strength and recycle experiments demonstrated that SIS/PNWF substrates possessed superior mechanical strength and excellent recycle stability. This work provides a facile and efficient pathway to prepare SIS/PNWF substrates for the degradation of organic pollutants with enhanced catalytic efficiency.

Rational design of 2D Janus P3m1 M2N3 (M = Cu, Zr, and Hf) and their surface-functionalized derivatives: ferromagnetic, piezoelectric, and photocatalytic properties.

In this study, first-principles calculations were employed to rationally design two-dimensional (2D) Janus transition metal nitrides of P3m1 M2N3 phases, where M is a d-block element (Sc-Zn, Y-Cd, Hf-Hg). Among the 29 examined 2D M2N3, three 2D phases, namely P3m1 Cu2N3, Zr2N3, and Hf2N3, exhibit excellent thermodynamic, dynamic, mechanical, and thermal stabilities. These novel Janus 2D materials exhibit ferromagnetic metallic and half-metallic behavior. The related 2D Janus surface-functionalized derivatives, Cu2N3H, Cu2N3F, Cu2N3Cl, Zr2N3H, Hf2N3H, and Hf2N3F, are all dynamically stable. The 2D Janus P3m1 phases of Zr2N3H, Hf2N3H, and Hf2N3F, all with M in the +IV oxidation state, act as semiconductors in the visible region, with energy band gaps of 2.26-2.70 eV at the HSE06 level of theory. On the other hand, the 2D Janus P3m1 Cu2N3X phases (where X = H, F, and Cl) are ferromagnetic half-metals. Additionally, it has been unveiled that there are high hole mobilities (∼6 × 103 cm2 V-1 s-1) derived from the moderate deformation potential and effective mass in the 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases. Uniaxial strain engineering has demonstrated the outstanding in-plane piezoelectric properties of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F with high d11 values (∼99.91 pm V-1). Furthermore, the desirable band-edge alignments and high anisotropic carrier mobilities of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases indicate their potential as visible light-driven photocatalysts for water splitting reactions on different facets. These properties render 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases promising for use in optoelectronics, piezoelectric sensing, and photocatalysis applications.

SnS2 based SnS2/rGO/g-C3N4 Z-scheme ternary nanocomposites for efficient visible light-driven photocatalytic activity

Novel ternary composite photocatalyst SnS2/rGO/g-C3N4 in a Z-scheme configuration was synthesized using hydrothermal method for the degradation of dye pollutants from the industrial wastes. To enhance photocatalytic effectiveness, we employed Z-scheme architecture by utilizing SnS2 as a semiconductor with the unique electronic properties of rGO and g-C3N4 for promoting efficient charge separation. The synthesized ternary composite materials were characterized by various spectroscopic and microscopic techniques. The photocatalytic activities of these samples were evaluated through the degradation of Methylene Blue (MB) dye under visible light. Notably, the catalysts SnS2, SnS2/rGO, SnS2/g-C3N4, and SnS2/rGO/g-C3N4 exhibited degradation efficiencies of 55%, 57%, 64%, and 86%, respectively, after 70 min. Among these, the ternary composite catalyst of SnS2/rGO/g-C3N4 exhibited enhanced degradation performance. Furthermore, when exposed to visible light, the unique crisscross morphology and Z scheme architecture effectively promote light utilization efficiency, providing ample reactive sites and leading to a higher degradation percentage. Further optimization of experiments for this composite material involved in varying catalyst loadings, dye concentrations, and pH levels. The SnS2/rGO/g-C3N4 composite exhibited optimal degradation performance with 5 mg catalyst in a 25 ppm MB solution within 100 ml. This composite was identified for the first time as an excellent visible light-driven photocatalyst for MB, displaying high degradation efficiencies. These findings emphasize the promising potential of the SnS2/rGO/g-C3N4 ternary nanocomposite for applications in visible light-driven photocatalysis.

Visible light-driven photocatalyst δ‑Bi7VO13 nanoparticles synthesized by thermal plasma

Visible light-driven photocatalyst δ‑Bi7VO13 nanoparticles synthesized by thermal plasma

Constructing In2S3/CdS/N-rGO Hybrid Nanosheets via One-Pot Pyrolysis for Boosting and Stabilizing Visible Light-Driven Hydrogen Evolution

The construction of hybrid junctions remains challenging for the rational design of visible light-driven photocatalysts. Herein, In2S3/CdS/N-rGO hybrid nanosheets were successfully prepared via a one-step pyrolysis method using deep eutectic solvents as precursors. Benefiting from the surfactant-free pyrolysis method, the obtained ultrathin hybrid nanosheets assemble into stable three-dimensional self-standing superstructures. The tremella-like structure of hybrid In2S3/N-rGO exhibits excellent photocatalytic hydrogen production performance. The hydrogen evolution rate is 10.9 mmol·g−1·h−1, which is greatly superior to CdS/N-rGO (3.7 mmol·g−1·h−1) and In2S3/N-rGO (2.6 mmol·g−1·h−1). This work provides more opportunities for the rational design and fabrication of hybrid ultrathin nanosheets for broad catalytic applications in sustainable energy and the environment.

Slow photon photocatalytic enhancement of H2 production in TaON inverse opal photonic crystals

In this study, tantalum oxynitride inverse opal (TaON IO) photonic crystals with different macropore diameters (D) were synthesized in a two-step process involving colloidal crystal templating and thermal nitridation, then applied as visible light-driven photocatalysts for hydrogen production. The TaON inverse opals showed photonic band gaps (PBGs) at visible wavelengths, with the PBG position redshifting as the diameter of the macropores increased in accordance with a modified Bragg's law expression. By aligning the electronic absorption edge of TaON (Eg ∼ 2.4 eV) with the blue edge (short-wavelength side) or red edge (long-wavelength side) of the PBGs, slow photon enhancement of photocatalytic H2 generation was realized. H2 production tests conducted in 10 vol% methanol containing H₂PtCl6 under Xe lamp irradiation (150 W) showed that the hydrogen production rate was enhanced by ∼1.3–1.4 times when the TaON absorption edge (∼510 nm) aligned with blue edge of the PBG (0.3421 mmol g−1 h−1) or the red edge of the PBG (0.3254 mmol g−1 h−1) in the inverse opals. The red edge enhancement was due to increased light absorption and charge carrier generation in TaON, whereas the blue edge effect was likely due to suppression of electron-hole pair recombination. Results demonstrate that photonic crystal engineering to exploit slow photon effects is a viable approach for boosting photocatalytic hydrogen production rates.

Ce-doped TiO2-zeolite fibers: visible light-driven photocatalysts for indigo dye degradation.

Indigo dye is a poisonous dye that threatens human health by polluting the environment. Therefore, we prepared a visible light-sensitive photocatalyst to eliminate indigo dye especially from water sources. In this study, sol-gel and electrospinning methods have been performed to synthesize Ce-doped TiO2-zeolite fibers for indigo degradation. The structural and optical properties of the synthesized fibers were investigated by XRD, SEM, EDX, and UV-Vis spectrophotometer techniques. It has been shown that 3% Ce-doped TiO2/zeolite fibers have the highest photocatalytic activity with 100% degradation after 150h, showing that the light absorption of TiO2 expands into the visible light area by Ce doping and absorption into the zeolite. The recyclability analyses of the spent photocatalyst exhibited 87.0% degradation of indigo after four cycles, demonstrating the stability of the fiber. An effective photocatalyst has been obtained by improving the photocatalytic and electrochemical properties thanks to the fibers' high surface area and the zeolite's porous structure. Based on these findings, the study reveals the significant potential of Ce-doped TiO2/zeolite fibers for the purification of wastewater under visible light.

Anti-fouling and self-cleaning ability of BiVO4/rGO and BiVO4/g-C3N4 visible light-driven photocatalysts modified ceramic membrane in high performance ultrafiltration of oily wastewater

Oily wastewater is one of the most harmful and resistant types of wastewater that cannot be treated with the usual and traditional methods. In this study, the visible light-driven photocatalysts BiVO4/rGO and BiVO4/g-C3N4 were made using the hydrothermal method. After that, a simple sol-gel method was used to make a photocatalytic ultrafiltration membrane with good self-cleaning and anti-fouling properties that can effectively separate oily wastewater. Photocatalyst properties were identified by using XRD, FTIR, DRS, N2 absorption-desorption, and zeta potential analysis. The performance of photocatalytic membranes was then investigated in oily wastewater treatment. Antifouling parameters, underwater oil contact angle, surface roughness, and electrochemical properties were measured to look into the membrane's antifouling properties. The use of a BiVO4/rGO composition with 20 wt% of rGO produced an underwater oil contact angle of 158°. Also, after 3 h of 3000 ppm oily wastewater filtration, the permeate flux was double that of the UF membrane without a photocatalytic coating, and the TOC removal efficiency was more than 99%. Measurement of antifouling parameters revealed that flux recovery was 89% compared to 51% for the UF membrane, and the total fouling ratio was reduced from 57% to 21%.

Qualitative and quantitative contributions of intermolecular interactions, quantum chemical calculation, biological activity and visible-light driven photo catalysts studies of nickel complex of 4-amino-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide

This study reports the successful synthesis and characterization of a nickel complex of the sulfamethizole (smtz) ligand. The complex was characterized using 1H NMR and FT-IR spectroscopic analyses. The synthesized complex exhibited promising properties as a biological and visible light-driven photocatalyst. Under visible light radiation, it displayed remarkable photo-degradation capabilities, achieving a degradation efficiency of 91.2% within 80 min against a solution of methylene blue (MB) with a concentration of 10 PPM in 100 mL. To understand the complex's biological response, viscosity measurements were conducted to investigate its mode of binding with CT-DNA. The results demonstrated that the nickel complex exhibited stronger inhibitory activity and lower cytotoxicity compared to the smtz ligand, as evidenced by cytotoxic analysis and minimum inhibitory concentration (MIC) data against a range of gram-positive and gram-negative pathogens. Furthermore, the crystal structure of the complex was determined through single-crystal X-ray diffraction analysis, revealing its crystallization in the triclinic space group P-1. The asymmetric part of the unit cell consisted of a Ni0.5 metal atom, one -Picoline solvent molecule, one smtz ligand, and one coordinated water molecule. To gain further insights into the complex's properties, Hirshfeld surfaces (HS) and a 3D energy framework approach were utilized to visualize its active and inactive surfaces. The analysis indicated that the dispersion energy contribution in molecular packing was significantly greater than that of electrostatic energy. Additionally, calculations of the HOMO-LUMO energy and other quantum chemical parameters were performed to understand the molecule's stability. Overall, the synthesized nickel complex of the sulfamethizole ligand exhibited remarkable photocatalytic properties, strong inhibitory activity against pathogens, and a stable crystal structure. These findings contribute to the understanding of the complex's potential applications in photocatalysis and biomedical research.

Visible light-driven photocatalysts, quantum chemical calculations, ADMET-SAR parameters, and DNA binding studies of nickel complex of sulfadiazine

A 3D-supramolecular nickel integrated Ni-SDZ complex was synthesized using sodium salt of sulfadiazine as the ligand and nickel(II) acetate as the metal salt using a condensation process and slow evaporation approach to growing the single crystal. The metal complex was characterized for its composition, functional groups, surface morphology as well as complex 3D structure, by resorting to various analytical techniques. The interacting surface and stability as well as reactivity of the complex were carried out using the DFT platform. From ADMET parameters, human Intestinal Absorbance data revealed that the compound has the potential to be well absorbed, and also Ni-SDZ complex cannot cross the blood–brain barrier (BBB). Additionally, the complex's DNA binding affinity and in-vivo and in-vitro cytotoxic studies were explored utilizing UV–Vis absorbance titration, viscosity measurements, and S. pombe cells and brine shrimp lethality tests. In visible light radiation, the Ni-SDZ complex displayed exceptional photo-degradation characteristics of approximately 70.19% within 70 min against methylene blue (MB).

La1.33-xNa3xTi2O6/Na3La2(BO3)3 heterostructure transformed from La2Ti2O7 plates for enhanced photocatalytic H2 evolution

Perovskite-type oxide semiconductors, as promising photocatalysts, possess flexible structures with corner-shared BO6 octahedrons and A cations, but are limited by the broad band gaps and severe photo-induced carrier recombination. Herein, a series of La1.33-xNa3xTi2O6/Na3La2(BO3)3 composites were synthesized by annealing the layered La2Ti2O7 with NaBH4. The doping of Na+ ions in perovskite's A-site promotes the transformation of La2Ti2O7 into La1.33-xNa3xTi2O6 phase, meanwhile, substituted La species turn into Na3La2(BO3)3 phase. The crystalline degree of perovskite structure evolves with the ratio of Na+ ions in the A site, and La2Ti2O7 undergoes amorphization, recrystallization, and further decomposition as the Na species increases. In well-crystallized La1.17Na0.48Ti2O6/Na3La2(BO3)3, intimate interfacial contacts induce extended optical absorption and optimized charge transfer. Under visible light irradiation, the sample exhibits significantly enhanced photocatalytic H2 evolution activity, with hydrogen production rate reaching 660 μmol∙g−1·h−1, whereas La2Ti2O7 has almost no catalytic activity. This work presents a novel strategy to transform the perovskite oxides at a relatively low temperature by exchanging cations with reductive NaBH4. It demonstrates applications in the development of visible light-driven perovskite-based heterogeneous photocatalysts.

Cobalt Hydrogen-Bonded Organic Framework as a Visible Light-Driven Photocatalyst for CO2 Cycloaddition Reaction.

A novel cobalt hydrogen-bonded organic framework (Co-HOF, C24H14CoN4O8) was synthesized from a mixed linker, that is, 2,5-pyridinedicarboxylic acid (PDC) and 2,2'-bipyridyl (BPY) linkers and cobalt ion through a simple, one-pot, low-cost, and scalable solvothermal method. The Co-HOF was fully characterized using several analytical and spectroscopic techniques including single-crystal X-ray diffraction, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. The Co-HOF exhibits high thermal and chemical stabilities compared to previously reported HOF materials. Moreover, Co-HOF shows excellent photocatalytic activity under visible light irradiation due to its narrow band gap of 2.05 eV. The cycloaddition reaction of CO2 to variable epoxides was investigated to evaluate the photocatalytic performance of Co-HOF under visible light radiation and was found to produce the corresponding cyclic carbonates in yields up to 99.9%.

Band-gap engineering of zirconia by nitrogen doping in reactive HiPIMS: a step forward in developing innovative technologies for photocatalysts synthesis.

In the global context of climate change and carbon neutrality, this work proposes a strategy to improve the light absorption of photocatalytic water-splitting materials into the visible spectrum by anion doping. In this framework, reactive high power impulse magnetron sputtering (HiPIMS) of a pure Zr target in Ar/N2/O2 gas mixture was used for the deposition of crystalline zirconium oxynitride (ZrO2-xNx) thin films with variable nitrogen doping concentration and energy band-gap. The nitrogen content into these films was controlled by the discharge pulsing frequency, which controls the target surface poisoning and peak discharge current. The role of the nitrogen doping on the optical, structural, and photocatalytic properties of ZrO2-xNx films was investigated. UV-Vis-NIR spectroscopy was employed to investigate the optical properties and to assess the energy band-gap. Surface chemical analysis was performed using X-ray photoelectron spectroscopy, while structural analysis was carried out by X-ray diffraction. The increase in the pulse repetition frequency determined a build-up in the nitrogen content of the deposited ZrO2-xNx thin films from ∼10 to ∼25at.%. This leads to a narrowing of the optical band-gap energy from 3.43 to 2.20eV and endorses efficient absorption of visible light. Owing to its narrow bandgap, ZrO2-xNx thin films obtained by reactive HiPIMS can be used as visible light-driven photocatalyst. For the selected processing conditions (pulsing configuration and gas composition), it was found that reactive HiPIMS can suppress the hysteresis effect for a wide range of frequencies, leading to a stable deposition process with a smooth transition from compound to metal-sputtering mode.

Natural marmatite photocatalyst for treatment of mineral processing wastewater to help zero wastewater discharge

Mineral processing wastewater (MPW) with large discharge and high toxicity affects environmental safety, and the realizing zero discharge of MPW is of great significance for reducing environmental pollution, saving water resources, and promoting the sustainable development of the mining industry. In this study, we reported natural marmatite (NM) as a low-cost and efficient photocatalyst for the treatment of MPW to help zero wastewater discharge. The photocatalytic activity of NM was evaluated by the removal of total organic carbon (TOC) from MPW under visible-light illumination, and the optimal degradation conditions were discussed. Results showed that superoxide free radicals (·O2−) were the dominant active species responsible for organic pollutants degradation, and 74.25% TOC removal was obtained after 120 min reaction under the optimum treatment conditions. Meanwhile, the wastewater treated by NM photocatalysis can be reused in the flotation system without adverse impact on the product index. Based on these findings, a model of zero wastewater discharge for flotation with the help of photocatalytic treatment was established, it indicated that the water of the whole system can be balanced without affecting the ore dressing index, which showed that visible light-driven photocatalyst has a promising application prospect in the treatment and recycling of industrial wastewater.

Physical properties and photocatalytic activity of Cr doped TiO2 nanoparticles.

Nanocrystalline Ti1-x Crx O2 (0≤ x ≤0.20) samples are synthesized via acid-modified sol-gel process and characterized with various techniques, such as HRTEM, FESEM, Raman, XPS, DTA and VSM. The TEM image of TiO2 exhibits elongated nanoparticles with an average size of 10 nm. The HRTEM in combination with selected area electron diffraction (SAED) patterns reveals the interplanar spacing and polycrystalline nature of the samples, respectively. FESEM micrographs reveal non-uniform morphologies and less aggregation of the particles in the doped sample. Raman spectra ensure the phase purity of the samples and a blue shift on Cr doping. X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The room temperature magnetic studies reveal a significant variation in the magnetic parameters on Cr doping in TiO2 . The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance is studied for the degradation of methylene blue (MB) dye under visible-light irradiation. A higher photocatalytic efficiency is found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. In the present study, nanoparticles of TiO2 and Cr doped TiO2 by a cost-effective acid-modified sol-gel process. The effect of Cr doping on the microstructure, thermal, magnetic and photocatalytic properties of TiO2 were explored in detail. The transmission electron microscopy (TEM) images exhibit the presence of elongated nanoparticles with an average size of 10 nm. Field emission scanning electron microscopy (FESEM) was used to study the surface morphology of the synthesized materials, which revealed non-uniform morphologies and less aggregation of the particles in the Cr-doped sample. Energy dispersive x-ray spectroscopy (EDS) confirms the elemental compositions with the appropriate stoichiometry of the elements. Raman spectra ensure the phase purity of the materials and also a blue shift with the incorporation of Cr ions in TiO2 . X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The magnetic nature of all the synthesized samples was examined through the vibrating sample magnetometer (VSM) and revealed weak ferromagnetic behavior of the samples. These results signify that the oxygen vacancies and defects play a crucial role in developing the ferromagnetic nature of oxide semiconductors. The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance of the prepared samples was studied for the degradation of methylene blue (MB) dye under irradiation of visible light. A higher photocatalytic efficiency was found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. This article is protected by copyright. All rights reserved.

Constructing AgBr/BiOBr@silkworm cocoons photocatalytic degradation and antibacterial material: Based on the excellent adsorption properties of silkworm cocoons

The silkworm cocoon (SC) possesses excellent adsorption performance due to the specific composite structure. Silk fibroin, the main component of SC, possesses lots of functional groups which are suitable for attachment of ligands, it plays an important role in the adsorption and chelation of metal ions, thus making SC a meaningful carrier. As a result, SC exhibits the best adsorption effect on Malachite green (MG), reaching 86.8% within 3 h in the present work. Additionally, AgBr/[email protected] visible light-driven (VLD) photocatalyst was successfully fabricated by ultrasound-assisted impregnation method with AgBr/BiOBr as a model and SC as a support. AgBr/[email protected] showed a remarkable photocatalytic degradation rate for Rhodamine B (Rh B, 98.52%), MG (80.08%) and Tetracycline (TC, 70.92%) under 120 min irradiation. Besides, it displayed superior activity in Staphylococcus aureus (S. aureus) disinfection, and the antibacterial efficiency above 99% upon 20 min of visible-light irradiation. The outstanding photocatalytic and antibacterial properties were mainly attributed to intimate contact and matched energy band positions between AgBr and BiOBr, which efficiently produce more active e--h+ pairs, and availably restrict the recombination of photogenerated carriers. This work could arouse an increasing interest in designing more SC-based photocatalysts for wastewater treatment.

Two-dimensional g-GeC/PtSe2 van der Waals heterostructure: a visible light-driven direct Z-scheme photocatalyst for overall water splitting

The vertical stacking of different two-dimensional materials to construct van der Waals heterostructures (vdWHs) opens up a promising platform for designing high-efficiency photocatalysts. Direct Z-scheme heterostructures for photocatalytic dissociation have received much attention in recent years, in which charge carriers migrate directly between two semiconductors without redox mediators. Here, the electronic and optical properties as well as the solar-to-hydrogen conversion efficiency of g-GeC/ PtSe2 vdWHs are systematically investigated, especially for their high-efficiency visible-light water splitting catalyst features. Calculations show that the g-GeC/ PtSe2 vdWH is a semiconductor with an indirect band gap of 1.356 eV, featuring a type-II band alignment. The built-in electric field E int and band bending at the interface lead to a direct Z-scheme photocatalytic structure, and photocatalytic water splitting can be realized in the pH range of 0–14. In particular, with biaxial tensile strain ϵ= 4% applied, the g-GeC/PtSe2 vdWH possesses a smaller band gap, wider visible light response range and very high STH conversion efficiency (η STH) up to 49.07%, entirely satisfying the optimal photocatalytic water splitting conditions. This work provides a new perspective for designing promising direct Z-scheme visible light water splitting catalysts with a high-efficiency solar energy conversion, beneficially to the development of clean energy.

Mutually supportive growth strategy to engineer a hollow biochar sphere-supported TiO2 composite with improved interfacial compatibility for efficient visible light-driven photocatalysis

Improving the interfacial compatibility between active components and support is significant and challenging. Herein, a mutually supportive growth strategy was created to engineer a Fe-Cu-doped hollow biochar sphere (HBS)-supported TiO2 (TiO2/Fe-Cu-HBS) composite with strong interfacial interaction via simultaneous growth of crystalline TiO2 and epitaxial carbonization of mechanical activation-treated starch-FeCl3-CuCl2. The TiO2/Fe-Cu-HBS composite with highly dispersed distribution and embedding of spherical TiO2 particles on the Fe-Cu-HBS shell had a narrow bandgap, favorable visible light capture and absorption capability, high separation efficiency of electron–hole pairs, and high transfer efficiency of photogenerated carriers. The superior photogenerated electron transport, high specific surface area, and enriched surface oxygen vacancies led to the generation of abundant reactive radicals on TiO2/Fe-Cu-HBS under visible light stimulation, contributing to efficient photocatalytic degradation of tetracycline hydrochloride (removal rate of 95.4% within 120 min; mineralization rate of 75.3% within 180 min), rhodamine B (removal rate of 99.2% within 100 min), and carbamazepine (removal rate of 67.5% within 120 min). Moreover, TiO2/Fe-Cu-HBS maintained high photocatalytic degradation efficiency after five cycles ascribed to its favorable structural stability. A mechanism of photocatalytic degradation of tetracycline hydrochloride and possible degradation pathways were proposed. This work provides a new growth strategy for constructing highly active and stable visible light-driven TiO2-based composite photocatalysts for effectively treating organic pollutants.

Bone powder decorated TiO2 and ZnO nanoparticles: The first investigation of NOx degradation by solar light and visible light-driven photocatalyst

This study performed the transformation of food waste and resin into the valuable photocatalyst which was applied in the NOx decomposition. Bone waste was used as the agricultural waste because of its high CaCO3 compositions. In this study, heterojunction composites were synthesized by calcination ZnO and TiO2 with chicken bone and pork bone (ZnO@Pb, ZnO@Cb, TiO2@Pb and TiO2@Cb). The degradation of NOx can be obtained from 63.30% to 81% under solar light irradiation from the concentration of NOx at 550 ppb. TiO2 decorated with pork bone under visible light gives the best NOx removal efficiency at 70%, with the concentration of NOx at 1800 ppb (1.8 ppm). Furthermore, the trapping experiments confirm that h+ and e− have an impact on the degradation of NOx. The addition of bone waste also shortened the band gap of TiO2/ZnO from 0.649 to 1.266 eV with the microcube formation. This study provides important information on cost-less catalysts for degrading nitrogen oxide (NOx) under solar light and visible light.