Rational Design of Wide Spectral-Responsive Heterostructures of Au Nanorod Coupled Ag3PO4 with Enhanced Photocatalytic Performance

Cyclodextrin functionalization enhancement in a CA-β-CD/g-C3N4/Ag2CO3 Z-type heterojunction towards efficient photodegradation of organic pollutants

More free radicals can be produced quickly by CA-β-CD/CN/Ag2CO3, leading to more effective and stable photocatalytic activity. The interfacial charge separation has been improved by the CA-β-CD modified CN/Ag2CO3 heterojunction.

Anti-oil-fouling Au/BiOCl coating for visible light-driven photocatalytic inactivation of bacteria

In this work, gold/bismuth oxychloride (Au/BiOCl) nanocomposites with different morphologies were successfully prepared by simple solvothermal method and sodium borohydride reduction method, which exhibited significantly efficient visible-light-driven photocatalytic disinfection for Staphylococcus aureus (S.aureus). Particularly, the flower-like Au/BiOCl nanocomposite showed the highest photocatalytic bactericidal performance among the prepared Au/BiOCl samples. The radical trapping experiments revealed that the hole was the main reactive species responsible for the inactivation of S.aureus over Au/BiOCl composite. The enhanced photocatalytic bactericidal effect could be attributed to the enhanced adsorption intensity of visible light that originated from the surface plasmon resonance (SPR) effect of Au, rapid transfer and space transport of hot electrons caused by the hierarchical structure of BiOCl layered compound. Furthermore, the Au/BiOCl coating prepared on stainless steel wire mesh via in-situ synthesis method exhibited excellent superhydrophilic/underwater superoleophobic performance, which endowed the coating with anti-oil-fouling in water. More importantly, compared with Au/BiOCl powder catalyst, the prepared Au/BiOCl coating with anti-oil-fouling also possessed high photocatalytic bactericidal activity and stable recycling performance.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

The Surface Modification of Ag3PO4 using Tetrachloroaurate(III) and Metallic Au for Enhanced Photocatalytic Activity

The improvement of Ag3PO4 photocatalytic activity was successful by incorporating tetrachloroaurate(III) (AuCl4−)  and metallic Au on the surface of Ag3PO4. The photocatalysts were synthesized using the coprecipitation and chemisorption method. Coprecipitation of Ag3PO4 was carried out under ethanol-water solution using the starting material of AgNO3 and Na2HPO4.12H2O. AuCl4− ion and metallic Au were incorporated on the surface of Ag3PO4 using a chemisorption method under auric acid solution. The photocatalysts were characterized using XRD, DRS, SEM, and XPS. The AuCl4− ion and metallic Au were simultaneously incorporated on the Ag3PO4 surface. The high photocatalytic activity might be caused by increasing the separation of hole and electron due to capturing photogenerated electrons by metallic Au and Au(III) as electron acceptors. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Crystallinity-dependent photodegradation of metallic Bi in situ grown on perovskite Bi3TiNbO9 nanosheets toward antibiotic

Owing to its wide band gap of ~3.2 eV, perovskite Bi₃TiNbO₉ only absorbs the solar spectrum in the ultraviolet range, which restricts its use as an effective photocatalyst. Here, a controllable and facile reduction strategy was adopted to promote the in-situ growth of metallic Bi in perovskite Bi₃TiNbO₉ nanosheets. The in-situ growth of metallic Bi extended photoresponse to cover the whole visible region. Adsorption of tetracycline hydrochloride (TC-H) on the surface of Bi₃TiNbO₉ with in-situ growth of metallic Bi (BTNO_OV-Bi⁰) was dramatically enhanced, while BTNO_OV-Bi⁰ exhibited a superior photocatalytic performance for tetracycline hydrochloride (TC-H) degradation under visible light irradiation with the degradation rate of 5 times higher than that of pristine Bi₃TiNbO₉. Moreover, the degradation activity was strongly dependent on the crystallinity of metallic Bi phase in BTNO_OV-Bi⁰ samples. On the basis of experiment results, the visible-light driven catalytic mechanism of BTNO_OV-Bi⁰ was elucidated. Besides, the in-situ growth of metallic Bi was also introduced in perovskite Bi₅FeTi₃O₁₅, resulting in an enhanced photocatalytic activity, which indicated an enormous potential of this strategy in semiconductor structure tuning. Our study provides an effective approach to boost the performance of photocatalysts for solar-energy conversion.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

Facile synthesis of TiO2/Ag3PO4 composites with co-exposed high-energy facets for efficient photodegradation of rhodamine B solution under visible light irradiation

In this study, TiO₂/Ag₃PO₄ composites based on anatase TiO₂ nanocrystals with co-exposed {101}, {010}/{100}, {001} and [111]-facets and Ag₃PO₄ microcrystals with irregular and cubic-like polyhedron morphologies were successfully synthesized by combining hydrothermal and ion-exchange methods. The anatase TiO₂ nanocrystals with different high-energy facets were controllably prepared via hydrothermal treatment of the exfoliated [Ti₄O₉]²⁻/[Ti₂O₅]²⁻ nanosheet solutions at desired pH values. The Ag₃PO₄ microcrystal with different morphologies was prepared via the ion-exchange method in the presence of AgNO₃ and NH₄H₂PO₄ at room temperature, which was used as a substrate to load the as-prepared anatase TiO₂ nanocrystals on its surface and to form TiO₂/Ag₃PO₄ heterostructures. The apparent rate constant of the pH 3.5-TiO₂/Ag₃PO₄ composite was the highest at 12.0 × 10⁻³ min⁻¹, which was approximately 1.1, 1.2, 1.4, 1.6, 13.3, and 24.0 fold higher than that of pH 0.5-TiO₂/Ag₃PO₄ (10.5 × 10⁻³ min⁻¹), pH 7.5-TiO₂/Ag₃PO₄ (10.2 × 10⁻³ min⁻¹), pH 11.5-TiO₂ (8.8 × 10⁻³ min⁻¹), Ag₃PO₄ (7.7 × 10⁻³ min⁻¹), blank sample (0.9 × 10⁻³ min⁻¹), and the commercial TiO₂ (0.5 × 10⁻³ min⁻¹), respectively. The pH 3.5-TiO₂/Ag₃PO₄ composite exhibited the highest visible-light photocatalytic activity which can be attributed to the synergistic effects of its heterostructure, relatively small crystal size, large specific surface area, good crystallinity, and co-exposed high-energy {001} and [111]-facets. The as-prepared TiO₂/Ag₃PO₄ composites still exhibited good photocatalytic activity after three successive experimental runs, indicating that they had remarkable stability. This study provides a new way for the preparation of TiO₂/Ag₃PO₄ composite semiconductor photocatalysts with high energy crystal surfaces and high photocatalytic activity.

TiO₂/Ag₃PO₄ composites with co-exposed {101}, {010}/{100}, {001} and [111]-facets were successfully synthesized by combining hydrothermal and ion-exchange methods.

Highly active WO3@anatase-SiO2 aerogel for solar-light-driven phenanthrene degradation: Mechanism insight and toxicity assessment

The global energy crisis and water pollution drive the researchers to develop highly effective and less energy intensive water purification technologies. In this study, a highly active WO₃@TiO₂-SiO₂ nanocomposite was synthesized and used for photocatalytic degradation of persistent organic pollutants under simulated solar light. The optimum WO₃@TiO₂-SiO₂ prepared with 2 wt% WO₃ loading and calcination at 800 °C exhibited higher photocatalytic activity, as the rate constant (k₁) for phenanthrene degradation was ∼7.1 times of that for the commercial TiO₂ (P25). The extremely large specific surface area (>400 m²/g) of WO₃@TiO₂-SiO₂ afforded it with enlarged pollutants adsorption performance and abundant active surface sites. The heterojunction of anatase with SiO₂ as well as loading of WO₃ decreased the band gap energy (E_g) of TiO₂, which extended the utilization spectrum of TiO₂ to visible region. Formation of Ti-O-Si band indicated the excess charges can cause Brønsted acidity due to the absorption of protons to compensate the charges. Moreover, the migration of photo-excited electrons from the conduction band of anatase to WO₃ and holes in the opposite direction restrained the electron-hole recombination. The photocatalytic degradation mechanism and pathway for phenanthrene degradation were proposed based on experimental analysis and density functional theory (DFT) calculation, and the toxicities of the degradation intermediates were evaluated by quantitative structure-activity relationship (QSAR) analysis. WO₃@TiO₂-SiO₂ also showed good separation (settling) performance and high stability. Our work is expected to offer new insight into the photocatalytic mechanism for WO₃, TiO₂ and SiO₂ based heterojunctions, and rational design and synthesis of highly efficient photocatalysts for environmental application.

Constructing a Z-scheme Heterojunction of Egg-Like Core@shell CdS@TiO₂ Photocatalyst via a Facile Reflux Method for Enhanced Photocatalytic Performance

A well designed and accurate method of control of different shell thickness and electronic transmission in a Z-scheme core@shell system is conducive to obtaining an optimum photocatalytic performance. Herein, the Z-scheme heterojunction of egg-like core@shell CdS@TiO₂photocatalysts with controlled shell thickness (13 nm, 15 nm, 17 nm, 22 nm) were synthesized by a facile reflux method, and the CdS@TiO₂ structure was proved by a series of characterizations. The photodegradation ratio on methylene blue and tetracycline hydrochloride over the 0.10CdS@TiO₂ composites with TiO₂ shell thickness of 17 nm reached 90% in 250 min and 91% in 5 min, respectively, which was almost 9.8 times and 2.6 times than that of TiO₂ and CdS on rhodamine B respectively under visible light. Besides, the higher total organic carbon removal ratio indicated that most of the pollutants were degraded to CO₂ and H₂O. The Z-scheme electronic transfer pathway was studied through radical species trapping experiments and electron spin resonance spectroscopy. Moreover, the relationship between shell thickness and photocatalytic activity demonstrated that different shell thickness affects the separation of the electron and holes, and therefore affected the photocatalytic performance. In addition, the effects of pollutants concentration, pH, and inorganic anions on photocatalytic performance were also investigated. This work can provide a novel idea for a well designed Z-scheme heterojunction of core@shell photocatalysts, and the study of photocatalytic performance under different factors has guiding significance for the treatment of actual wastewater.

Efficient decontamination of textile industry wastewater using a photochemically stable n-n type CdSe/Ag3PO4 heterostructured nanohybrid containing metallic Ag as a mediator

To address the environmental hazard posed by the discharge of textile industry wastewater, we combined n-type (CdSe) and n-type (Ag₃PO₄) visible-light-responsive semiconductors to produce a photochemically stable n-n type heterostructured nanohybrid comprising metallic Ag (CdSe/Ag/Ag₃PO₄, CAA) and employed this material as a catalyst for the decomposition of phenol and rhodamine B (RhB). The physicochemical properties of CAA and reference photocatalysts were investigated using instrumental techniques. Compared to individual Ag₃PO₄ and CdSe, CAA showed an elevated photocatalytic decomposition efficiency for both target pollutants, which was mainly attributed to increased charge separation efficiency and explained by the operation of the Z-scheme reaction mechanism. Moreover, we probed the effects of initial pollutant concentration, AgNO₃:NaH₂PO₄ molar ratio, and the CdSe:Ag₃PO₄ mass ratio of CAA on catalytic performance. Recycling tests revealed the high photochemical stability of CAA, which was ascribed to the prevention of Ag₃PO₄ photoreduction by electrons. Finally, a Z-scheme mechanism with vectorial charge transfer suggested for the visible-light-driven decomposition of pollutants over CAA nanohybrids was systematically discussed based on the results of scavenger tests and photoluminescence emission spectra analysis, and an explanation of the role of metallic Ag as a charge mediator was provided.

Fabrication of interlayer β-CD/g-C3N4@MoS2 for highly enhanced photodegradation of glyphosate under simulated sunlight irradiation

Graphitic carbon nitride (g-C₃N₄) has been considered to be a promising metal-free photocatalyst, although the high recombination rate of charge carriers and poor absorption of visible light have limited its applications. In order to overcome these problems, an interlayer composite photocatalyst that comprised β-cyclodextrin (β-CD), oxygen-doped C₃N₄ (O-C₃N₄) and molybdenum disulfide (MoS₂) was successfully constructed for the highly enhanced photodegradation of glyphosate in this study. The structure and morphology, optical properties, and photoelectrochemical properties of the prepared photocatalyst were characterized via a series of characterization techniques. The average fluorescence lifetime of the composite photocatalyst was extended from 6.67 ns to 7.30 ns in comparison with that of g-C₃N₄, which indicated that the composite photocatalyst enhanced the absorption of visible light and also inhibited the recombination of electron–hole pairs. The mass ratio of MoS₂ that corresponded to O-C₃N₄/MoS₂-5 enabled the highest removal rate under simulated sunlight irradiation, which was almost twice that achieved using pure g-C₃N₄. Relative species scavenging experiments revealed that ·O₂⁻ was the main species during the process of photodegradation. Besides, a toxicity test indicated that glyphosate became less toxic or non-toxic after photodegradation. This study provided an effective, feasible and stable photocatalyst driven by simulated sunlight irradiation for the highly enhanced photodegradation of glyphosate.

The fabrication of an interlayer β-CD/g-C₃N₄@MoS₂ composite photocatalyst for highly enhanced photodegradation of glyphosate and a toxicity test.

(111) Facets-Oriented Au-Decorated Carbon Nitride Nanoplatelets for Visible-Light-Driven Overall Water Splitting

Development of a simple and stable photocatalyst for overall water splitting is a promising avenue for solar energy conversion. Here, carbon nitride (CN) nanosheet panels decorated with in situ-formed (111) facets-oriented Au nanoparticles (AuNPs) have been prepared by vapor-deposition polymerization followed by an easy immersion technique. Benefiting from the enhanced visible light absorption, the surface plasmon resonance effect of AuNPs, rapid transportation and separation of charge carriers, as well as better-aligned valence band levels, the as-obtained photocatalyst shows effective overall water splitting with stoichiometric H₂ and O₂ evolution even without any sacrificial agent, distinct from the half-reaction of Pt-decorated CN. This work opens up a brand-new route for facet self-selective growth of metal on two-dimensional conjugated carbon nitride materials, which has been demonstrated to be effective for artificial photosynthesis applications.

Challenges and prospects of advanced oxidation water treatment processes using catalytic nanomaterials

Centralized water treatment has dominated in developed urban areas over the past century, although increasing challenges with this model demand a shift to a more decentralized approach wherein advanced oxidation processes (AOPs) can be appealing treatment options. Efforts to overcome the fundamental obstacles that have thus far limited the practical use of traditional AOPs, such as reducing their chemical and energy input demands, target the utilization of heterogeneous catalysts. Specifically, recent advances in nanotechnology have stimulated extensive research investigating engineered nanomaterial (ENM) applications to AOPs. In this Perspective, we critically evaluate previously studied ENM catalysts and the next-generation treatment technologies they seek to enable. Opportunities for improvement exist at the intersection of materials science and treatment process engineering, as future research should aim to enhance catalyst properties while considering the unique roadblocks to practical ENM implementation in water treatment.