Visible-Light-Active Plasmonic Ag-SrTiO3 Nanocomposites for the Degradation of NO in Air with High Selectivity

Investigating the Synergistic Effect of Decoration and Doping in Silver/Strontium Titanate for Air Remediation

Strontium titanate (STO) and its variants have emerged as leading materials in photocatalysis, particularly for degrading nitrogen oxides (NOx), due to their non-toxic nature, structural adaptability, and exceptional thermal stability. Although the one-pot sol-gel method leads to high-quality photocatalysts, areas remain for improvement. This study examines the impact of ethanol as a cosolvent in STO synthesis, focusing on optimizing the water-to-ethanol volume ratio. The findings reveal that a 1:3 ratio significantly enhances macropore formation and photocatalytic efficiency, achieving 42% NOx degradation under LED within three hours. Furthermore, incorporating 8.0 wt.% Ag into STO substantially improves visible light absorption and enables complete NOx elimination, thanks to enhanced charge separation and localized surface plasmon resonance. Even at high temperatures (1100 °C), the Ag-STO photocatalyst maintains partial activity, despite exceeding silver's melting point. These results highlight the potential of STO-based materials for industrial applications, positioning them as a promising solution for effective NOx mitigation.

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Silver-decorated SrTiO3 nanoparticles for high-performance supercapacitors and effective remediation of hazardous pollutants

SrTiO3/Ag nanocomposites were synthesized using a facile wet impregnation method, employing rigorous experimental techniques for comprehensive characterization. XRD, FTIR, UV, PL, FESEM, and HRTEM were meticulously utilized to elucidate their structural, functional, morphological, and optical properties. The electrochemical performance of the SrTiO3/Ag nanocomposite was rigorously assessed, revealing an impressive specific capacitance of 850 F/g at a current density of 1 A. Furthermore, the photocatalytic activity of the SrTiO3/Ag nanocomposite was rigorously examined using methylene blue (MB) dye, and the results were outstanding. After 120 min of UV irradiation, the nanocomposite exhibited an exceptional MB dye degradation efficiency exceeding 88%. The SrTiO3/Ag nanocomposite represents an exemplary catalyst in terms of efficiency, cost-effectiveness, environmental compatibility, and reusability. The electron and superoxide radicals play a chief role in the MB dye degradation process. The inclusion of Ag within the SrTiO3 matrix facilitated the formation of a conductive nano-network, ultimately resulting in superior capacitive and photocatalytic performance.

Tailoring defects in SrTiO3 by one step nanoarchitectonics for realizing photocatalytic nitrogen fixation in pure water

Surface contamination of materials by nitrogenous impurities is a major problem that can bias the quantification of ammonia in photocatalytic N₂ fixation reactions. In this work, SrTiO₃ nanocubes were prepared by using a nitrogenous precursor and engineered with Ti³⁺ sites and oxygen vacancy defects in a one-step solvothermal approach. It was observed that the synthesized materials were containing surface nitrogenous impurities and therefore a rigorous cleaning procedure was adopted to eliminate them to the best extent. The contribution of unavoidable surface impurities was deduced in the form of adventitious NH₃ by employing control experiments and a realistic photocatalytic NH₃ generation was achieved. It was found that pristine SrTiO₃ showed no photocatalytic activity, whereas one of the defected SrTiO₃ materials showed the highest NH₃ formation under natural sunlight in pure water, which was ascribed to the tuned defect sites, enhanced surface area and efficient separation of photogenerated charges. Based on the experimental results, a stringent protocol has been suggested for materials synthesis while working with nitrogenous precursors and for subsequent photocatalytic N₂ fixation experiments. Thus, the present study provides a simple and affordable procedure for catalyst synthesis for the studied application and expands the scope of perovskite oxide materials to fabricate efficient photocatalysts for sustainable NH₃ production.

Revealing the crystal facet effect on N2O formation during the NH3-SCR over α-MnO2 catalysts

The detailed atomic-level mechanism of the effect induced by engineering the crystal facet of α-MnO₂ catalysts on N₂O formation during ammonia-selective catalytic reduction (NH₃-SCR) was ascertained by combining density functional theory (DFT) calculations and thermodynamics/kinetic analysis. The surface energies of α-MnO₂ with specific (100), (110), and (310) exposed planes were calculated, and the adsorptions of NH₃, NO, and O₂ on three surfaces were analyzed. The adsorption energies showed that NH₃ and NO molecules could be strongly adsorbed on the surface of the α-MnO₂ catalyst, while the adsorption of O₂ was weak. Moreover, the key steps in the oxidative dehydrogenation of NH₃ and the formation of NH₂NO as well as dissociation of NH₂ were studied to evaluate the catalytic ability of NH₃-SCR reaction and N₂ selectivity. The results revealed that the α-MnO₂ catalyst exposed with the (310) plane exhibited the best NH₃-SCR catalytic performance and highest N₂ selectivity, mainly due to its low energy barriers in NH₃ dehydrogenation and NH₂NO generation, and difficulty in NH₂ dissociation. This study deepens the comprehension of the facet-engineering of α-MnO₂ on inhibiting N₂O formation during the NH₃-SCR, and points out a strategy to improve their catalytic ability and N₂ selectivity for the low-temperature NH₃-SCR process.

Z-Scheme CuOx/Ag/TiO2 Heterojunction as Promising Photoinduced Anticorrosion and Antifouling Integrated Coating in Seawater

In the marine environment, steel materials usually encounter serious problems with chemical or electrochemical corrosion and fouling by proteins, bacteria, and other marine organisms. In this work, a green bifunctional Z-scheme CuO_x/Ag/P25 heterostructure coating material was designed to achieve the coordination of corrosion prevention and antifouling by matching the redox potential of the reactive oxygen species and the corrosion potential of 304SS. When CuO_x/Ag/P25 heterostructure was coupled with the protected metal, the open circuit potential under illumination negatively shifted about 240 mV (vs. Ag/AgCl) and the photoinduced current density reached 16.6 μA cm^-2. At the same time, more reactive oxygen species were produced by the Z-shape structure, and then the photocatalytic sterilization effect was stronger. Combined with the chemical sterilization of Ag and the oxide of Cu, the bacterial survival rate of CuO_x/Ag/P25 was low (0.006%) compared with the blank sample. This design provides a strategy for developing green dual-functional coating materials with photoelectrochemical anticorrosion and antifouling properties.

Effect of CuO Loading on the Photocatalytic Activity of SrTiO3/MWCNTs Nanocomposites for Dye Degradation under Visible Light

In this study, we report on the preparation of copper oxide/strontium titanate/multi-walled carbon nanotube (CuO/STO/MWCNTs) nanocomposites and their photocatalytic activity for degradation of dye under visible light. The crystalline structures of the nanocomposites were investigated by an X-ray diffraction (XRD) technique, which explored the successful fabrication of CuO/STO/MWCNTs nanocomposites, and the cubic STO phase was formed in all samples. For the morphological study, the transmission electron microscope (TEM) technique was used, which had proved the successful preparation of CuO and STO nanoparticles. The energy dispersive X-ray spectroscopy (EDX), dark field scanning transmission electron microscope (DF-STEM-EDX mapping), and X-ray photoelectron spectra (XPS) analysis were performed to evidence the elemental composition of CuO/STO/MWCNTs nanocomposites. The optical characteristics were explored via UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) techniques. These studies clearly indicate the effect of the presence of CuO and MWCNTs on the visible absorption of the CuO/STO/MWCNTs nanocomposites. The photocatalytic activity of CuO/STO/MWCNTs nanocomposites was evaluated by the degradation of methylene blue (MB) dye under visible light irradiation, following first-order kinetics. Among the different x% CuO/STO/MWCNTs nanocomposites, the 5 wt.% CuO/STO/MWCNTs nanocomposites showed the highest photocatalytic efficiency for the degradation of MB dye. Moreover, the 5% CuO/STO/MWCNTs showed good stability and recyclability after three consecutive photocatalytic cycles. These results verified that the optimized nanocomposites can be used for photocatalytic applications, especially for dye degradation under visible light.

Efficient Electron Transfer by Plasmonic Silver in SrTiO3 for Low-Concentration Photocatalytic NO Oxidation

Photocatalysis presents a feasible option to control low-concentration NO emissions from industrial burning facilities, and increasing excitons in quantity and improving surface activity are the crucial issues to be solved. Plasmonic silver with the orientation of the (111) plane is uniformly distributed on the Ti-O termination of the SrTiO₃ (STO) (100) plane (major). The NO conversion rate has a sixfold increment compared to pristine STO. Meanwhile, the toxic NO₂ had a significant decline in the absence of water. This high performance could be attributed to the unique property of the localized surface plasmonic resonance of silver particles, which increases the optical response range of the catalyst. Meanwhile, the formation of a Schottky junction could promote the charge separation and enhance the lifetime of excitons via the electron transfer from silver particles to STO. More importantly, the Ag-O bond of the heterojunction increases the charge density of adjacent Ti, preferring to bond with the antibonding orbital electron of adsorbed molecules, which offers a favorable channel for the NO adsorption and activation of reactive oxidation species.

Exploring the photocatalytic conversion mechanism of gaseous formaldehyde degradation on TiO2-x-OV surface

To understand the conversion mechanism of photocatalytic gaseous formaldehyde (HCHO) degradation, strontium (Sr)-doped TiO_2-x-OV catalysts was designed and synthesized in this study, with comparable HCHO removal performance. Our results proved that foreign-element doping reduced Ti⁴⁺ to the lower oxidation state Ti^{(4- x)+}, and that the internal charge kinetics was largely facilitated by the unbalanced electron distribution. Oxygen vacancies (OVs) were developed spontaneously to realize an electron-localized phenomenon in TiO_2-x-OV, thereby boosting O₂ adsorption and activation for the enhanced generation of reactive oxygen species (ROS). At the chemisorption stage, in-situ DRIFTS spectra and density functional theory calculation results revealed that surface adsorbed O₂ (O_ads) and lattice O (O_lat) engaged in the isomerisation of HCHO to dioxymethylene (DOM) on TiO_2-x-OV and TiO₂, respectively. Time-resolved DRIFTS spectra under light irradiation revealed that the DOM was then converted to formate and thoroughly oxidized to CO₂ and H₂O in TiO_2-x-OV. While bicarbonate byproducts were detected from DOM hydroxylation or possible side conversion of CO₂ in TiO₂, owing to insufficient consumption of surface hydroxyl. Our study enhances the understanding on the photocatalytic oxidation of HCHO, thereby promoting the practical application in indoor air purification.

Developing sustainable, high-performance perovskites in photocatalysis: design strategies and applications

Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.

Ambient Air Purification by Nanotechnologies: From Theory to Application

Air pollution has been a recurring problem in northern Chinese cities, and high concentrations of PM2.5 in winter have been a particular cause for concern. Secondary aerosols converted from precursor gases (i.e., nitrogen oxides and volatile organic compounds) evidently account for a large fraction of the PM2.5. Conventional control methods, such as dust removal, desulfurization, and denitrification, help reduce emissions from stationary combustion sources, but these measures have not led to decreases in haze events. Recent advances in nanomaterials and nanotechnology provide new opportunities for removing fine particles and gaseous pollutants from ambient air and reducing the impacts on human health. This review begins with overviews of air pollution and traditional abatement technologies, and then advances in ambient air purification by nanotechnologies, including filtration, adsorption, photocatalysis, and ambient-temperature catalysis are presented—from fundamental principles to applications. Current state-of-the-art developments in the use of nanomaterials for particle removal, gas adsorption, and catalysis are summarized, and practical applications of catalysis-based techniques for air purification by nanomaterials in indoor, semi-enclosed, and open spaces are highlighted. Finally, we propose future directions for the development of novel disinfectant nanomaterials and the construction of advanced air purification devices.

Design of Pd-Decorated SrTiO3/BiOBr Heterojunction Materials for Enhanced Visible-Light-Based Photocatalytic Reactivity

The development of photocatalytic materials that exploit visible light is imperative for their sustainable application in environmental remediation. While a variety of approaches have been attempted, facile routes to achieve such structures remain limited. In this contribution, a direct route for the production of a SrTiO₃/BiOBr/Pd heterojunction is presented that employs a low temperature, sustainable production method. The materials were produced in a two-step process wherein BiOBr nanoplates are fabricated in the presence of the SrTiO₃ nanospheres, generating a highly integrated composite material. Pd nanoparticle surface decoration was subsequently employed to facilitate and enhance charge separation lifetimes to optimize reactivity. The structures were fully characterized via a suite of approaches to confirm the final material composition and arrangement. Their reactivity was explored for the degradation of both colored and colorless model environmental pollutants, where the SrTiO₃/BiOBr/Pd demonstrated significant reactivity using visible light, leading to substrate degradation in <10 min in some cases. The enhanced reactivity was attributed to the significant integration between materials, facilitating electron transfer. Such studies provide key information for the development of new materials with optimized visible-light-driven photocatalytic reactivity for sustainable environmental remediation.

Universal strategy using environment-friendly inorganic compounds for the preparation of porous carbon nitride for efficient photocatalytic hydrogen production and environmental remediation

In this work, a facile strategy is proposed for the preparation of efficient porous CN for photocatalytic hydrogen production and environmental remediation.

Construction of novel polyethylenimine-g-C3N4/BiOCl heterojunctions for the efficient photocatalytic degradation of nitro explosives

Novel polyethylenimine-g-C₃N₄/BiOCl (PEI-CN/BC) heterojunctions displayed excellent photocatalytic activity on the degradation of nitro explosives.

Effect of SrTiO3 Nanoparticles in Conductive Polymer on the Thermoelectric Performance for Efficient Thermoelectrics

We present hybrid organic inorganic materials, namely, SrTiO₃/polyaniline (PANI) composites, with high thermoelectric performance; samples with various SrTiO₃ contents (10, 20, 30, and 50 wt.%) were prepared. The PANI component was obtained through the polymerization of aniline monomers, followed by camphosulfonic acid-doping to enhance its electrical conductivity. SrTiO₃, with a high Seebeck coefficient, was used as the N-type inorganic componenet; it was synthesized via a one-pot solvothermal methods and, then, dispersed into the conductive PANI matrix. The SrTiO₃ content influenced the Seebeck coefficient and electrical conductivity of the resulting composites. The variations in the thermoelectric properties of the SrTiO₃/PANI composites consequently changed their power factor; at room temperature, the highest value was ~49.6 μW·m/K², which is 17 times larger than that of pure PANI.

Improved in Situ Synthesis of Heterostructured 2D/2D BiOCl/g-C3N4 with Enhanced Dye Photodegradation under Visible-Light Illumination

A simple, in situ, and one-pot hydrothermal strategy was applied for the successful manufacturing of heterostructured 2D/2D BiOCl/g-C3N4 photocatalysts, and outstanding photodegradation of Rhodamine B in the condition of visible-light irradiation over the composites emerged. The investigation of various BiOCl/g-C3N4 ratios influencing the activity implied that the optimized B2C1 (mole ratio of BiOCl/g-C3N4 with 2:1) exhibited the higher degradation efficiency than that of the rest of the composites, even higher than that of pure BiOCl and pure g-C3N4, which yielded over 90% in the initial 30 min and reached almost 100% during the whole 70 min irradiation process. Kinds of characterizations demonstrated that the enhancement of photodegradation performance was caused by the intimate contact between BiOCl and g-C3N4 to form the heterostructure, which could benefit the generation of abundant visible-light photoinduced carriers and help enhance their separation and then promote their transportation to the surface.

Novel Au/La-Bi5O7I Microspheres with Efficient Visible-Light Photocatalytic Activity for NO Removal: Synergistic Effect of Au Nanoparticles, La Doping, and Oxygen Vacancy

Sphere-like Bi₅O₇I (BOI) doped with La (L-BOI) samples were prepared by a solvothermal method followed by calcination at 450 °C for 2 h. Au nanoparticles were loaded on 6% La-doped Bi₅O₇I (2%A-6%L-BOI) microspheres by a room-temperature chemical reduction method. The UV-vis absorption spectra show that the L-BOI and 2%A-6%L-BOI samples have a strong visible-light absorption in comparison with the pure BOI. The electron paramagnetic resonance results indicate that the number of oxygen vacancies in L-BOI samples is increased with an increasing amount of the La dopant. The band structure of the prepared photocatalysts is investigated by confirming the positions of the valence band (VB) measured by XPS-VB and the Fermi level computed by density functional theory, respectively. NO is selected as a target gaseous pollutant to confirm the influence of La doping and the plasmonic effect of Au nanoparticles on the photocatalytic activity of BOI microspheres. The 2%A-6%L-BOI sample exhibits an enhanced photocatalytic performance compared to BOI, L-BOI, and A-BOI photocatalysts under visible-light irradiation. Interestingly, the 2%A-6%L-BOI sample also can reduce the amount of intermediate NO₂ during the NO removal process. The enhanced photocatalytic efficiency of the 2%A-6%L-BOI photocatalyst is profited from the synergy of La-ion doping, oxygen vacancy, and the surface plasmon resonance effect of Au nanoparticles. Based on the results of trapping experiments and electron spin resonance spectroscopy tests, h⁺, e^-, and ^•O₂^- were involved in the NO oxidative removal.

Synergetic Effects of Pd0 Metal Nanoparticles and Pd2+ Ions on Enhanced Photocatalytic Activity of ZnWO4 Nanorods for Nitric Oxide Removal

Doping and novel metallic nanoparticles loading on the photocatalyst are two effective means to enhance its photocatalytic activity. In our study, Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods were fabricated by a two-step hydrothermal process and room-temperature reduction method. The performance of the as-prepared samples was evaluated through the photocatalytic nitric oxide (NO_x) removal under simulated solar and visible-light irradiation. Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods present a significantly enhanced photocatalytic activity for NO_x removal compared with Pd⁰-loaded or Pd²⁺-doped ZnWO₄ under simulated sunlight irradiation owing to a narrower band gap of Pd²⁺ doping compared with that of pure ZnWO₄. The role of Pd⁰ nanoparticles is to act as an electron reservoir to restrain the recombination of e^-/h⁺ pairs. According to the trapping measurements, the photoinduced holes and electrons play critical roles during the photocatalytic process. In addition, electron spin resonance (ESR) results further confirm that ^•O₂^- and ^•OH radicals are present and assist in the photocatalysis under simulated solar light irradiation. Stability test demonstrated that 1.5% Pd⁰/0.5% Pd²⁺-co-modified ZnWO₄ nanorods as photocatalyst have high photocatalytic stability in NO_x removal. This work proved that Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods can be considered as an efficient photocatalyst for NO_x removal.

Perovskite Structure Associated with Precious Metals: Influence on Heterogenous Catalytic Process

The use of perovskite-based materials and their derivatives can have an important role in the heterogeneous catalytic field based on photochemical processes. Photochemical reactions have a great potential to solve environmental damage issues. The presence of precious metals in the perovskite structure (i.e., Ag, Au, or Pt) may improve its efficiency significantly. The precious metal may comprise the perovskite lattice as well as form a heterostructure with it. The efficiency of catalytic materials is directly related to processing conditions. Based on this, this review will address the use of perovskite materials combined with precious metal as well as their processing methods for the use in catalyzed reactions.

Mineralization of carcinogenic anthracene and phenanthrene by sunlight active bimetallic oxides nanocomposites

Polycyclic aromatic hydrocarbons (PAHs) are causing environmental concerns due to their persistent nature and carcinogenicity. Hence, their removal through advanced nanomaterials with characteristics of low-cost and high efficiency is essential. In view of this, bimetallic oxides (BMOs) nanocomposites of NiO-ZnO, ZnCo₂O_4, MnCo₂O₄ and CoFe₂O₄ were synthesized via green route using leaf extract of Aegle marmelos. Subsequently, these BMOs were investigated for photocatalytic removal of selected PAHs like anthracene (ANTH) and phenanthrene (PHEN) from water. Nanospheres of NiO-ZnO, ZnCo₂O_4, and CoFe₂O₄ and nanosheets of MnCo₂O₄ with particle size range of 10-30 nm were confirmed by transmission electron microscopy. At neutral pH, nanocomposites showed excellent ability in degrading 2 mg L^-1 of PAHs (ANTH: 98%; PHEN: 93%) within 12 h under the exposure of sunlight. Among the synthesized BMOs, NiO-ZnO was found best followed by ZnCo₂O_4, MnCo₂O₄ and CoFe₂O_4. This fact is attributed to the highest surface area (129 m² g^-1) and particles stability (zeta potential: -30 eV) of NiO-ZnO. Photodegradation of PAHs by nanocomposites followed first order kinetics and fitted in Langmuir model for adsorption. Higher degradation under sunlight and lower removal efficiency with scavenger confirmed the photodegradation activity of nanocomposites. Overall, reusable (n = 10) nanocomposites with no loss of activity have high photocatalytic potential in the removal of carcinogenic PAHs.

Investigation on Photocatalytic Removal of NO under Visible Light over Cr-Doped ZnO Nanoparticles

Removal of nitrogen oxide pollution has attracted much attention, and photocatalysis is considered as an effective method to treat polluted gas. Currently, modified semiconductors with approximate band gap are used as visible-light-driven photocatalysts. Herein, this is the first investigation of photocatalytic removal of NO under visible light over Cr-doped ZnO nanoparticles (Cr-ZnO NPs). Furthermore, the trapping species experiment and electron spin resonance measurement were conducted to identify the primary reactive factor of the photocatalytic reaction. In this study, Cr-ZnO NPs were synthesized by the sol-gel method with a narrow band gap, enhanced NO photocatalytic degradation performance, low NO2 conversion yield, and high stability under visible light.

Photocatalytic Nitrogen Oxide Removal Activity Improved Step-by-Step through Serial Multistep Cu Modifications

Previous research has evidenced the insufficient efficiency in a one-step modified photocatalyst for NO removal. In this article, a serial multistep modification was explored to improve the NO removal activity of g-C₃N₄. In the experiment, a g-C₃N₄ photocatalyst has been successfully modified by Cu elements three times on one continuous process. Meanwhile, results showed that the serial multistep modifications could improve NO removal activity by g-C₃N₄ step by step. The main active species in the g-C₃N₄ system were h⁺ and ^•O₂^- but they were h⁺ and ^•OH in the three-modified g-C₃N₄ systems. Moreover, different mechanisms of activity improvement caused by the modified Cu in the serial-modified samples were identified. In the first modified sample, Cu²⁺ can decompose H₂O₂ molecules into ^•OH via a Fenton-like reaction. In the second modified sample, the H₂O₂ molecule is activated by Cu⁰ and decomposed into ^•OH by the generated photoelectrons. After the third modification, the synergistic effects of the N vacancy and Cu⁰ were identified, which significantly enhanced the photocatalytic NO removal activity of g-C₃N₄. This study proposed that the serial multistep modification can be a promising method to improve the NO removal activity of g-C₃N₄ stage-by-stage.

SnO2/TiO2 nanotube heterojunction: The first investigation of NO degradation by visible light-driven photocatalysis

Titania (TiO₂) as a commercial photocatalyst has been continually struggling due to the limitation of ultraviolet light response and the high recombination rate of photoinduced carriers. The development of heterojunction nanostructures provides great promise to achieve the activation by visible light and suppress the photoinduced electron-hole pairs recombination. Herein, we synthesized a SnO₂ and TiO₂ nanotube heterojunction (SnO₂/TNT) via a one-step hydrothermal strategy and systematically investigated NO photocatalytic degradation over the SnO₂/TNTs heterojunction under visible light at the parts per billion level. Various physicochemical characterization techniques were conducted to verify the physical and chemical properties of the materials. For example, the morphology and lattice spacings of the materials were examined by high-resolution TEM (HR-TEM) images and selected area electron diffraction (SAED) pattern, X-ray photoelectron spectroscopy (XPS) was employed to study the oxidation states and propose the band alignment diagram of the SnO₂/TNTs heterojunction, and photoluminescence spectroscopy was employed for understanding of carrier's trapping, migration and transfer. The photocatalytic results show that the SnO₂/TNTs heterojunction exhibits the superior photocatalytic performance, and the photocatalytic degradation efficiency of NO can reach 60% under visible light with effective inhibition of NO₂ production. The excellent photocatalytic ability is due to the low recombination rate of the photoinduced electron-hole pairs. Furthermore, a trapping experiment was combined with electron spin resonance (ESR) and utilized to identify the involvement of reactive radicals in the photocatalysis process suggesting that and OH mediated pathways play a predominant role in NO removal.

The solvent-driven formation of multi-morphological Ag-CeO2 plasmonic photocatalysts with enhanced visible-light photocatalytic reduction of CO2

Ag-CeO2 plasmonic photocatalysts with multiple morphologies were synthesized via a simple solvent-driven method. The phase compositions, morphologies and optical properties of the samples were systematically investigated. A combination of noble metal Ag and semiconductor CeO2 in certain solvents (such as methanol and ethylene glycol) enhanced surface plasmon resonance (SPR), which was attributed to the good dispersion of Ag particles on CeO2 and high Ag0 ratios on the surface. The enhanced SPR effect boosted absorption of incident light and facilitated charge carrier separation and transport efficiency caused by the formation of Schottky barriers, thus promoting VLPCR performance. The optimum ACG sample (ethylene glycol was adopted as the solvent) exhibited the maximum VLPCR activity, achieving a CH4 yield of 100 μmol and a CH3OH yield of 35 μmol per gram of catalyst per hour during 6 h visible-light irradiation.

Plasmonic photocatalysis: complete degradation of bisphenol A by a gold nanoparticle-reduced graphene oxide composite under visible light

Bisphenol A is a well-known endocrine disruptor that comes from plastic/epoxy resin-based consumer products, pollutes our environment and is responsible for various human diseases. Thus, its removal from water/food/the environment is becoming a challenging issue. Here we report the visible light photocatalytic degradation of bisphenol A using a gold nanoparticle based composite with reduced graphene oxide. The nanocomposite captures visible light and produces hydroxyl radicals that oxidize bisphenol A into smaller organic fragments such as phenol derivatives and aliphatic aldehydes/ketones. The composition of the nanocomposite has been optimized for most efficient degradation of bisphenol A under visible light and the approach may be extended for the sunlight-based removal of bisphenol A from water/food/the environment.

Mesocrystalline anatase nanoparticles synthesized using a simple hydrothermal approach with enhanced light harvesting for gas-phase reaction

The most selective De-NO_x process reached by mesocrystalline anatase nanoparticles was associated with the developed mesoporosity, visible light photoactivity and mesocrystallinity.