Visible/near-IR-light-driven TNFePc/BiOCl organic-inorganic heterostructures with enhanced photocatalytic activity

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

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

Photocatalytic Degradation of Tetracycline Hydrochloride Based on the Structure-Property Exploration of BiOCl

The correlation between structure and properties in the photodegradation reaction of bismuth oxychloride (BiOCl) was explored in this work. Three BiOCl samples with different sizes, morphological structures, and defects were prepared through a hydrothermal method with experimental manipulation. Their structural properties were comprehensively characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electron spin resonance, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, and photoluminescence. Taking the photodegradation of tetracycline hydrochloride (TC-HCl) as the probe reaction, we found that high activity could be achieved by decreasing their crystal size and thickness, introducing proper defects in the structure, and assembling the nanosheets to get microball structure. Combined with radical-scavenge experiments and electron spin resonance (ESR) spin-trap spectra, we conclude that ̇O2- was the dominant reactive oxygen species for the degradation reaction. The degradation detailed pathway of TC-HCl was further analyzed using liquid chromatography-mass spectrometry. This work explores the structure-property correlation of BiOCl and provides strategies for the rational design of active photocatalysts for water remediation.

Strategies based review on near-infrared light-driven bismuth nanocomposites for environmental pollutants degradation

Recently, solar energy has been considered the most vulnerable source to resolve environmental pollution and energy scarcity problems. Researchers have made intense research efforts to convert solar energy into chemical energy through photocatalysis processes as it is a green, clean and renewable energy source. Numerous discovered photocatalysts show absorption in the ultraviolet-visible (UV∼5% and visible ∼43%) region and are devoid of near-infrared (NIR ∼52%) light utilization. As infrared (IR) light contains a top portion of the solar spectrum; therefore, many alluring and attractive practical strategies have been explored to improve photocatalytic reactions and to harness full solar spectrum (including NIR light). Among those strategies, bandgap engineering, coupling with carbon quantum dots, heterostructure formation, mingling with plasmonic and upconversion (UC) NPs are more worthwhile. In different visible light-assisted photocatalysts, bismuth typically covers a distinctive, favorable, and earth-abundant group of freshly discovered innovative photocatalytic nanomaterials. Bi-based photocatalysts have suitable/good optoelectronic properties, crystalline geometric conformations, amendable electronic structure, and outstanding visible-light responsive range, helpful in environmental remediation and energy transformation. Due to the outstanding photo-oxidization/photodegradation capability of NIR-driven photocatalysts, bismuth-based nanomaterials have been considered suitable photocatalysts for inclusive solar energy utilization. Henceforth, keeping in mind the benefits of bismuth nanomaterials, the present review is focused on NIR-based modification strategies to upgrade solar light absorption of bismuth-based photocatalysts in the NIR region by making it NIR responsive photocatalyst. We have also discussed the photocatalytic applications of bismuth-based NIR responsive photocatalysts in pollutant degradation.

Bismuth Vacancy-Induced Efficient CO2 Photoreduction in BiOCl Directly from Natural Air: A Progressive Step toward Photosynthesis in Nature

Photocatalytic CO₂ conversion into carbonaceous fuels through artificial photosynthesis is beneficial to global warming mitigation and renewable resource generation. However, a high cost is always required by special CO₂-capturing devices for efficient artificial photosynthesis. For achieving highly efficient photocatalytic CO₂ reduction (PCR) directly from natural air, we report rose-like BiOCl that is rich in Bi vacancies (V_Bi) assembled by nanosheets with almost fully exposed active {001} facets. These rose-like BiOCl with V_Bi assemblies provide considerable adsorption and catalytic sites, which hoists the CO₂ capture and reduction capabilities, and thus expedites the PCR to a superior value of 21.99 μmol·g^-1·h^-1 CO generation under a 300 W Xe lamp within 5 h from natural air. The novel design and construction of a photocatalyst in this work could break through the conventional PCR system requiring compression and purification for CO₂, dramatically reduce expenses, and open up new possibilities for the practical application of artificial photosynthesis.

Straightforward Synthesis of SnO2/Bi2S3/BiOCl-Bi24O31Cl10 Composites for Drastically Enhancing Rhodamine B Photocatalytic Degradation under Visible Light

The pursuit of robust photocatalysts that can completely degrade organic contaminants with high performance as well as high energy efficiency, simplicity in preparation, and low cost is an appealing topic that potentially promotes photocatalysts for being used widely. Herein, we introduce a new and efficient SnO2/Bi2S3/BiOCl-Bi24O31Cl10 (SnO2/Bi2S3-Bi25) composite photocatalyst by taking advantage of the robust, simple, and potentially scalable one-pot synthesis, including the hydrothermal process followed by thermal decomposition. Interestingly, we observed the formation of BiOCl-Bi24O31Cl10 (abbreviated as Bi25) heterojunctions derived from reactions between Bi2S3 and SnCl4·5H2O precursor solutions under the hydrothermal condition and thermal decomposition of BiOCl. This Bi25 heterojunction acts as an interface to reduce the recombination of photogenerated electron-hole (e--h+) pairs as well as to massively enhance the visible light harvesting, thereby significantly enhancing the photocatalytic degradation performance of the as-prepared composite photocatalyst. In detail, the photocatalytic degradation of Rhodamine B (RhB) activated by visible light using 15% SnO2/Bi2S3-Bi25 shows the efficiency of 80.8%, which is superior compared to that of pure Bi2S3 (29.4%) and SnO2 (0.1%). The SnO2/Bi2S3-Bi25 composite photocatalyst also presents an excellent photostability and easy recovery from dye for recycling. The trapping test revealed that the photogenerated holes play a crucial factor during the photocatalytic process, whereas superoxide radicals are also formed but not involved in the photocatalytic process. Successful fabrication of SnO2/Bi2S3-Bi25 composite photocatalysts via a straightforward method with drastically enhanced photocatalytic performance under visible light activation would be useful for practical applications.

Deep Eutectic Solvent-Assisted Synthesis of Ternary Heterojunctions for the Oxygen Evolution Reaction and Photocatalysis

Hierarchical nano-/microstructured photocatalysts have drawn attention for enhanced photocatalytic performance. Deep eutectic solvents (DESs) have been used as a green sustainable media to act as both solvent and structure-inducing agent in the synthesis of hierarchical nanomaterials. In this work, the DESs-assisted synthesis of flower-structured BiOCl/BiVO₄ (BOC/BVO) with g-C₃ N₄ (BOC/BVO/g-CN) ternary heterojunctions was achieved by using a simple wet-chemical method, providing good acidic and alkaline oxygen evolution reaction (OER) catalysts. BOC/BVO/g-CN-15 achieved an enhanced photocatalytic activity for OER with an overpotential of 570 mV in 1 m H₂ SO₄ and 220 mV in 1 m KOH electrolyte at a current density of 10 mA cm^-2 with excellent stability and extraordinary durability of the catalyst. The ternary heterojunctions displayed extended lifetimes for photogenerated charges and enhanced the separation efficiency of photogenerated electron-hole pairs, which is helpful to enhance the photocatalytic OER. Furthermore, the photocatalytic performance of the ternary heterojunctions in aqueous solution was demonstrated through photocatalytic dye degradation of methyl orange (MO) as a model pollutant, resulting in 95 % degradation of 20 ppm of MO in 210 min under the irradiation of a 35 W Xe arc lamp. This work not only provides new insight into the design of catalysts by using green solvents but also into the design of highly efficient metal-free OER photocatalysts for applications in acidic and alkaline media.

Full-Spectrum Photocatalytic Activity of ZnO/CuO/ZnFe2O4 Nanocomposite as a PhotoFenton-Like Catalyst

Deriving photocatalysts by the calcination of hydrotalcite-like compounds has attracted growing interest for extending their photocatalytic activity to the visible and even near-infrared (NIR) light regions. Herein, we describe the acquisition of a ZnO/CuO/ZnFe2O4 nanocomposite with good photoFenton-like catalytic activity under UV, visible and near-infrared (NIR) light irradiation by optimizing the calcination temperature of the coprecipitation product of Zn2+, Cu2+ and Fe3+. The ZnO/CuO/ZnFe2O4 nanocomposite is composed of symbiotic crystals of ZnO, CuO and ZnFe2O4, which enable the nanocomposite to show absorption in the UV, visible and NIR light regions and to produce a transient photocurrent in the presence of H2O2 under NIR irradiation. The full-spectrum photoFenton-like catalyst shows improved performance for the degradation of methyl orange with an increasing amount of H2O2 and is very stable in the recycling process. We believe that the ZnO/CuO/ZnFe2O4 nanocomposite is a promising full-spectrum photoFenton-like catalyst for the degradation of organic pollutants.

Easy fabrication of poly(butyl acrylate)/silicon dioxide core-shell composite microspheres through ultrasonically initiated encapsulation emulsion polymerization

In this study, instead of using the usual chemical methods, poly(butyl acrylate)/silicon dioxide (PBA/SiO₂) core-shell composite microspheres were prepared using a physical method-ultrasonically initiated encapsulation emulsion polymerization. The morphology and particle size of the PBA/SiO₂ microspheres were analysed using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The encapsulation state was determined using X-ray photoelectron spectroscopy (XPS). The composition and thermogravimetric behavior were characterized using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The TEM and DLS results show that monodisperse PBA/SiO₂ core-shell composite microspheres were successfully obtained. The diameter and shell thickness were 150 nm and 15 nm, respectively. The XPS and FTIR results show that there was no new chemical bond between the PBA shell and the SiO₂ core. They were just combined by physical adsorption. The encapsulation efficiency of SiO₂ microspheres by PBA is 8.2% through TGA. In addition, this article focuses on the formation mechanism of PBA/SiO₂ core-shell microspheres prepared through ultrasonically initiated encapsulation emulsion polymerization. Intuitive observation and the results of TEM and DLS, especially the change in zeta potential, clearly indicate an encapsulation process. Thereinto, a bilayer-structure space established by appropriate amount of cetyltrimethyl ammonium bromide (CTAB) molecules is the key to realize ultrasonically initiated encapsulation emulsion polymerization.

A full-spectrum photocatalyst with strong near-infrared photoactivity derived from synergy of nano-heterostructured Er3+-doped multi-phase oxides

The development of full-spectrum photocatalysts active in the near-infrared (NIR) region has gained increasing attention in the photodegradation of organic pollutants. Herein, we designed a full-spectrum photocatalyst with strong NIR photoactivity based on the synergy of Er³⁺-doped ZnO-CuO-ZnAl₂O₄ multi-phase oxides (Er³⁺-doped Zn/Cu/Al-MPO) via the formation of n-p-n double heterojunctions. The photocatalyst was prepared by synthesizing nanosheets of a Zn/Cu/Al/Er hydrotalcite-like compound (Zn/Cu/Al/Er-HLC) with a co-precipitation method followed by calcination of the nanosheets at 800 °C. The as-prepared Er³⁺-doped Zn/Cu/Al-MPO inherits the nanosheet morphology of Zn/Cu/Al/Er-HLC, and displays over-doubled photoactivity in the entire ultraviolet (UV), visible and NIR regions compared to undoped Zn/Cu/Al-MPO. The excellent photocatalytic activity of Er³⁺-doped Zn/Cu/Al-MPO, especially its strong NIR photoactivity, is ascribed to its Er³⁺-doped CuO-involved multi-crystalline phase heterostructure, i.e., n-p-n double heterojunctions, which does not only offer an enhanced NIR absorption but also promotes the separation of photogenerated charge carriers. Importantly, the synergy of all the parts of the n-p-n double heterojuctions plays an important role in interface band structure regulation for the enhancement of the photocatalytic properties of Er³⁺-doped Zn/Cu/Al-MPO. This work has demonstrated the feasibility of utilizing hydrotalcite-like precursors in the design of full-spectrum photocatalysts active in the NIR region.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

ZnO/ZnFe2O4 nanocomposite as a broad-spectrum photo-Fenton-like photocatalyst with near-infrared activity

ZnO/ZnFe₂O₄ nanocomposite/H₂O₂ shows NIR activity due to the absorption of NIR, electron–hole pair separation by p–n junction promoted charge transfer, and reaction of electrons with H₂O₂.