Surface-Plasmon-Resonance-Induced Photocatalysis by Core–Shell SiO2@Ag NCs@Ag3PO4 toward Water-Splitting and Phenol Oxidation Reactions

Visible Light-Driven Photocatalytic Degradation of Methylene Blue Dye Using a Highly Efficient Mg-Al LDH@g-C3N4@Ag3PO4 Nanocomposite

The issue of water resource pollution resulting from the discharge of dyes is a matter of great concern for the environment. In this investigation, a new ternary heterogeneous Mg-Al LDH@g-C3N4X@Ag3PO4Y (X = wt % of g-C3N4 with respect to Mg-Al layered double hydroxide (LDH) and Y = wt % of Ag3PO4 loaded on Mg-Al LDH@g-C3N430) nanocomposite was prepared with the aim of increasing charge carrier separation and enhancement of photocatalytic performance to degrade methylene blue (MB) dye. The prepared samples were subjected to characterization via Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, photoluminescence, and photoelectrochemical analysis. It was observed that in the presence of the composite of Mg-Al LDH and g-C3N4, the photocatalytic decomposition of MB under 150 W mercury lamp illumination increases significantly as opposed to Mg-Al LDH alone, and the Mg-Al LDH@g-C3N4 level with Ag3PO4 coating causes the complete degradation of MB to occur in less time. The outcomes show that the Mg-Al LDH@g-C3N430@Ag3PO45 nanocomposite demonstrated the highest photodegradation activity (99%). Scavenger tests showed that the two most effective agents in the photodegradation of MB are holes and hydroxyl radicals, respectively. Finally, a type II heterojunction photocatalytic degradation mechanism for MB by Mg-Al LDH@g-C3N430@Ag3PO45 was proposed.

Nanomaterials for Removal of Phenolic Derivatives from Water Systems: Progress and Future Outlooks

Environmental pollution remains one of the most challenging problems facing society worldwide. Much of the problem has been caused by human activities and increased usage of various useful chemical agents that inadvertently find their way into the environment. Triclosan (TCS) and related phenolic compounds and derivatives belong to one class of such chemical agents. In this work, we provide a mini review of these emerging pollutants and an outlook on the state-of-the-art in nanostructured adsorbents and photocatalysts, especially nanostructured materials, that are being developed to address the problems associated with these environmental pollutants worldwide. Of note, the unique properties, structures, and compositions of mesoporous nanomaterials for the removal and decontamination of phenolic compounds and derivatives are discussed. These materials have a great ability to scavenge, adsorb, and even photocatalyze the decomposition of these compounds to mitigate/prevent their possible harmful effects on the environment. By designing and synthesizing them using silica and titania, which are easier to produce, effective adsorbents and photocatalysts that can mitigate the problems caused by TCS and its related phenolic derivatives in the environment could be fabricated. These topics, along with the authors' remarks, are also discussed in this review.

Construction of Ag nanocluster-modified Ag3PO4 containing silver vacancies via in-situ reduction: With enhancing the photocatalytic degradation activity of sulfamethoxazole

Photocatalytic removal of sulfonamide antibiotics is an effective strategy to solve environmental pollution. Ag3PO4 is a promising anode material for photocatalytic material with photocatalytic degradation ability under ultraviolet light or natural light. Unfortunately, due to its instability, Ag+ could be reduced to Ag0 which loaded onto the surface of Ag3PO4 during the photocatalytic process, causing self-photocorrosion and resulting in the reduction of photocatalytic activity and stability. Herein, Ag3PO4 nanoparticles loaded with Ag nanoclusters containing Ag vacancies (Ag/Ag3PO4-VAg) were constructed by an in-situ reduction strategy to achieve effectively photocatalytic degradation behavior. The Ag nanoclusters loaded on the surface of Ag3PO4 can not only effectively inhibit the self-photocorrosion but also affords a localized surface plasmon resonance (LSPR) effect in the photocatalytic process, thus leading to the efficient generation and rapid transfer of photogenerated carriers behavior. In addition, the Ag vacancies in Ag3PO4 are crucial to increasing the adsorption energy of H2O for further enhancing the capture and accumulation of electrons. In detail, according to Zeta potential analysis, the strong adsorption sites of sulfamethoxazole (SMX) molecules are generated at the interface of Ag and Ag3PO4, which promote the activation of SMX molecules. A 100 ml of 20 mg/L SMX could be completely degraded within 15 min with an apparent rate constant (Kapp) of 0.306 min-1, which far exceeds the activity of most of the photocatalysts. This work may provide an attractive strategy to address the activity, stability of Ag3PO4 and and realizing the green remediation of SMX wastewater.

Trioctylphosphine Oxide (TOPO)-Assisted Facile Fabrication of Phosphorus-Incorporated Nanostructured Carbon Nitride Toward Photoelectrochemical Water Splitting with Enhanced Activity

Designing nanostructured arrays of two-dimensional surfaces and interfaces is a versatile approach to increasing their photoelectrochemical activity. Here, phosphorus (P)-incorporated nanostructured carbon nitride (h-PCN) with an enlarged surface area is fabricated by employing trioctylphosphine oxide (TOPO) as a dopant precursor for visible-light-driven photoelectrochemical water splitting to produce hydrogen. The structural, morphological, and electronic properties of the photocatalyst have been characterized through various physicochemical techniques. We show that the incorporation of P into the g-C₃N₄ framework enhances light absorption over broad regimes, charge separation, and migration, as well as the specific surface area, showing excellent photocurrent enhancement (5.4 folds) in the cathodic direction as compared to bulk g-C₃N₄. Moreover, the photocathode shows 3.3-fold enhancement in current at zero biased potential. Without using any cocatalyst, the photoelectrodes produced 27 μmol h^-1 of H₂ and 13 μmol h^-1of O₂ with 95% faradic efficiency. The excellent photoelectrochemical behavior toward water-splitting reactions by the photoelectrode is attributed to the synergistic effect of P incorporation and active sites emerging from the nanostructured architecture of the material. This work demonstrates the facile fabrication of nanostructured P-incorporated g-C₃N₄ toward water-splitting reactions to produce hydrogen without using a cocatalyst in a simple and cost-effective way.

Prominence of Cu in a plasmonic Cu-Ag alloy decorated SiO2@S-doped C3N4 core-shell nanostructured photocatalyst towards enhanced visible light activity

A series of Cu-Ag bimetal alloys decorated on SiO₂ and the fabrication of few-layer S-doped graphitic carbon nitride (SC) warped over it to form a core-shell nanostructured morphology have been demonstrated and well characterized through various physiochemical techniques. HRTEM data confirmed the formation of a compact nanojunction between the SiO₂ and SC, where Cu-Ag is embedded uniformly with an average particle size of 1.3 nm. The Ag : Cu (1 : 3) between SiO₂ and SC produces 1730 μmol h^-1 g^-1 of H₂ under visible light illumination. Moreover, 6.2-fold current enhancement in the case of Ag : Cu (1 : 3) as compared to the Ag-loaded core-shell nanostructured photocatalyst indicates higher electron-hole-pair separation. The excellent activity was due to the synergistic alloying and plasmonic effect of Ag and Cu. DFT studies reveal that the Cu atom in the Cu-Ag bimetal alloy plays a pivotal role in the generation of H₂, and the reaction proceeds via a 4-membered transition state. The mechanistic insight proceeds from the generation of hot electrons due to the LSPR effect and their transfer to the SC layer via a compact nanojunction.

Hairy silica nanosphere supported metal nanoparticles for reductive degradation of dye pollutants

Hairy materials can act as a sort of scaffold for the fabrication of functional hybrid composites. In this work, silica nanospheres modified with covalently grafted poly(4-vinylpyridine) (P4VP) brushes, namely, "hairy" silica spheres, were utilized as a support for the anchorage of metal nanoparticles (MNPs), thus resulting in the hierarchical SiO₂@P4VP/MNP structure. In this triple-phase boundary heteronanostructure, the SiO₂-supported MNPs are well stabilized by the P4VP matrix to avoid aggregation and leaching. These SiO₂@P4VP/MNP nanocomposites exhibit good catalytic activity in the reductive degradation of organic dyes, i.e., 4-nitrophenol and rhodamine B and possess excellent stability and recyclability for five successive cycles.

Growth of macroporous TiO2 on B-doped g-C3N4 nanosheets: a Z-scheme photocatalyst for H2O2 production and phenol oxidation under visible light

BCN/TiO₂ heterostructured photocatalyst was demonstrated towards H₂O₂ production and phenol oxidation under visible light, based on Z-scheme and p–n heterojunction mechanism.

Cu-Ag Bimetal Alloy Decorated SiO2@TiO2 Hybrid Photocatalyst for Enhanced H2 Evolution and Phenol Oxidation under Visible Light

With a broader objective to replace visible light driven Pt-based photoelectrochemical/catalytic hydrogen evolution, a series of cost-effective bimetallic nanoalloys of Cu-Ag have been deposited on core-shell nanostructured SiO₂@TiO₂ through a facile reduction route. The physicochemical properties, i.e. crystal structure, morphology, chemical environment, and optical properties of Cu-Ag bimetal alloy decorated SiO₂@TiO₂ hybrid photocatalyst, have been thoroughly investigated through X-ray diffraction, high resolution transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy, respectively. TEM study confirms the coating of an ultrathin layer of TiO₂ shell on 100 nm sized SiO₂ core, and about 4.5 nm of Ag-Cu nanoalloys are uniformly distributed on the core-shell nanostructure. The higher light absorption throughout the visible range and better separation of charge carrier by Ag-Cu (1:3) deposited SiO₂@TiO₂ hybrid compared to other counterparts is confirmed from UV-vis, diffuse reflectance spectroscopy, photoluminescence, and electrochemical impedance studies. Eightfold higher photocurrent enhancements, threefold enhanced photocatalytic hydrogen generation, and twofold higher phenol oxidation activities of Ag-Cu (1:3) deposited SiO₂@TiO₂ hybrid compared to those of the monometallic plasmonic catalyst may be attributed to the synergetic effect of enriched light harvesting and surface plasmon induced hot electron transfer from the nanoalloy to the TiO₂ interface, resulting in efficient charge transfer.

Use of silica-based homogeneously distributed gold nickel nanohybrid as a stable nanocatalyst for the hydrogen production from the dimethylamine borane

In this study, the effects of silica-based gold-nickel (AuNi@SiO2) nanohybrid to the production of hydrogen from dimethylamine borane (DMAB) were investigated. AuNi@SiO2 nanohybrid constructs were prepared as nanocatalysts for the dimethylamine borane dehydrogenation. The prepared nanohybrid structures were exhibited high catalytic activity and a stable form. The resulting nanohybrid, AuNi@SiO2 as a nanocatalyst, was tested in the hydrogen evolution from DMAB at room temperature. The synthesized nanohybrids were characterized using some analytical techniques. According to the results of the characterization, it was observed that the catalyst was in nanoscale and the gold-nickel alloys showed a homogenous distribution on the SiO2 surface. After characterization, the turn over frequency (TOF) of nanohybrid prepared for the production of hydrogen from dimethylamine was calculated (546.9 h-1). Also, the prepared nanohybrid can be used non-observed a significant decrease in activity even after the fifth use, in the same reaction. In addition, the activation energy (Ea) of the reaction of DMAB catalyzed AuNi@SiO2 nanohybrid was found to be 16.653 ± 1 kJmol-1 that facilitated the catalytic reaction. Furthermore, DFT-B3LYP calculations were used on the AuNi@SiO2 cluster to investigate catalyst activity. Computational results based on DFT obtained in the theoretical part of the study support the experimental data.