Improved Photocatalytic Activity and Stability of Nano‐sized Ag/Ag2CO3 Plasmonic Photocatalyst by Surface Modification of Fe(III) Nanocluster

The surface modification of Ag/Ag₂CO₃ with Fe(III) ions has been achieved through simply photoreduction‐impregnation method. The obtained products were characterized by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and UV‐vis absorption spectroscopy. Under visible‐light irradiation (γ>420 nm), the Fe(III)/Ag/Ag₂CO₃ sample displays a higher photocatalytic activity and stability than pure Ag₂CO₃ and Ag/Ag₂CO₃ samples for the degradation of methyl orange (MO). The improved photocatalytic activity and stability of this ternary system could be ascribed to the synergetic effect between Ag nanoparticles and Fe(III) nanocluster. The metallic Ag nanoparticles cause an obviously enhanced visible‐light absorption to produce more photogenerated charges, while the Fe(III) works as an active site for the following oxygen reduction to reduce the recombination rate of photogenerated electrons and holes.     

Ultrathin zinc selenide nanosheet-based intercalation hybrid coupled with CdSe quantum dots showing enhanced photocatalytic CO_2 reduction

Fabrication of well-designed heterojunctions is an extraordinarily attractive pathway for boosting the photocatalytic activity toward CO_2 photoreduction.Herein,a novel kind of na nosheet-based intercalation hybrid coupled with CdSe quantum dots(QDs) was successfully fabricated by a facile solvothermal method and served as photocatalyst for full-spectrum-light-driven CO_2 reduction.Ultra-small CdSe QDs were rationally in-situ introduced and coupled with lamellar ZnSe-intercalation hybrid nanosheet,resulting in the formation of CdSe Q.Ds/ZnSe hybrid heterojunction.Significantly,the concentration of Cd~(2+) could change directly the crystallinity and micromorphology of ZnSe intercalation hybrid,which in turn would impact on the photocatalysis activity.The optimized CdSe QDs/ZnSe hybrid-5 composite demonstrated a considerable CO yield rate of the 25.6 μmol g~(-1) h~(-1) without any additional cocatalysts or sacrificial agents assisting,making it one of the best reported performance toward CO_2 photoreduction under full-spectrum light.The elevated CO_2 photoreduction activity could be attributed to the special surface heterojunction,leading to improving the ability of light absorption and promoting the separation/transfer of photogenerated carriers.This present study developed a new strategy for designing inorganic-organic heterojunctions with enhanced photocatalyst for CO_2 photoreduction and provided an available way to simultaneously mitigate the greenhouse effect and alleviate energy shortage pressure.     

Plasmonic Ag/AgCl‐modified bismuth subcarbonate with enhanced visible light photocatalytic activity

Plasmonic Ag/AgCl‐modified bismuth subcarbonate (Bi₂O₂CO₃) composites were prepared by a multistep process with hydrothermal, deposition, and photoreduction in the absence of organic capping agents. The properties of the obtained Ag/AgCl/Bi₂O₂CO₃ samples were characterized using X‐ray diffraction, field emission scanning electron microscopy and X‐ray photoelectron, UV–visible diffuse reflectance, and photoluminescence spectroscopies. The results reveal that Ag/AgCl nanoparticles are dispersed on the Bi₂O₂CO₃ surface to achieve plasmonic Ag/AgCl/Bi₂O₂CO₃. The Ag/AgCl/Bi₂O₂CO₃ nanocomposites show improved rhodamine B (RhB) adsorption capacity and photocatalytic activity compared with pure Bi₂O₂CO₃ and Ag/AgCl. In addition, the Ag/AgCl/Bi₂O₂CO₃ composite with 20 wt% Ag/AgCl exhibits the highest photocatalytic activity and remains stable for the photodegradation of RhB under visible light. The enhanced photocatalytic activity of Ag/AgCl/Bi₂O₂CO₃ may be attributed to the surface plasmon resonance effect of in situ generated Ag nanoparticles and synergistic effect of Ag/AgCl and Bi₂O₂CO₃, which increase the separation efficiency of photogenerated electron–hole pairs under visible light irradiation.     

Selective Photocatalytic Reduction of CO2 to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO₂) and water (H₂O) into fuels and value-added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C₃N₄ nanotubes (PCN) to form the photocatalyst Ag₁@PCN with Ag−N₃ coordination for CO₂ photoreduction using H₂O as the reductant. The as-synthesized Ag₁@PCN exhibits a high CO production rate of 0.32 μmol h⁻¹ (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal–support interactions (Ag−N₃) favor *CO₂ adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C₃N₄ and Ag single atoms, thereby accounting for the enhanced CO₂ photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal–support interactions in enhancing the photoactivity and CO selectivity of CO₂ photoreduction.     

Effects of the molar ratio on the photo-generated charge separation behaviors and photocatalytic activities of (BiO)2CO3-BiOBr composites

The molar ratio of two semiconductors will remarkably influence the photo-induced charge separation behaviors of the composites constructed, thus affecting the corresponding photocatalytic activity. Therefore, it is critical to reveal the relationship between the molar ratio of two semiconductors and the photo-induced charge separation; the information can shed light on the study of nature of surface catalysis. In this work, (BiO)₂CO₃-BiOBr composites were facilely fabricated in-situ through a pore impregnating approach using HBr aqueous solution. The samples were studied by BET, XRD, SEM, UV–Vis DRS and surface photovoltage spectroscopy (SPS). The photocatalytic activities of the samples were evaluated by the discoloration of methyl orange (MO) aqueous solution upon the simulated sunlight illumination. The results reveal that the (BiO)₂CO₃-BiOBr composite with 3/4 M ratio of (BiO)₂CO₃/BiOBr displays the highest photo-induced charge separation rate and photocatalytic activity, the results further manifest that no different electronic transfer property occurs after coupling (BiO)₂CO₃ with BiOBr.     

Synthesis and Study of Plasmon‐Induced Carrier Behavior at Ag/TiO2 Nanowires

Nanocomposites of Ag/TiO₂ nanowires with enhanced photoelectrochemical performance have been prepared by a facile solvothermal synthesis of TiO₂ nanowires and subsequent photoreduction of Ag⁺ ions to Ag nanoparticles (AgNPs) on the TiO₂ nanowires. The as‐prepared nanocomposites exhibited significantly improved cathodic photocurrent responses under visible‐light illumination, which is attributed to the local electric field enhancement of plasmon resonance effect near the TiO₂ surface rather than by the direct transfer of charge between the two materials. The visible‐light‐driven photocatalytic performance of these nanocomposites in the degradation of methylene blue dye was also studied, and the observed improvement in photocatalytic activity is associated with the extended light absorption range and efficient charge separation due to surface plasmon resonance effect of AgNPs.     

Novel organic/inorganic PDI-Urea/BiOBr S-scheme heterojunction for improved photocatalytic antibiotic degradation and H2O2 production

The matched energy band structure and efficient carrier separation efficiency are the keys to heterogeneous photocatalytic reactions. A novel organic/inorganic step scheme (S-scheme) heterojunction PDI-Urea/BiOBr composite photocatalyst was constructed by simple solvothermal reaction combined with in-situ growth strategy. The composite photocatalyst not only has high chemical stability, but also can generate and accumulate a large number of active species (h⁺, ^?O₂^?, ^?OH, H₂O₂). PDI-Urea/BiOBr showed higher photocatalytic activity for the degradation of antibiotic such as ofloxacin (OFLO), tetracycline (TC) and the production of H₂O₂ in the spectral range of 400–800 nm. The apparent rate constant of 15% PDI-Urea/BiOBr for photocatalytic degradation of TC (or OFLO) was 2.7 (or 2.5) times that of pure BiOBr and 1.7 (or 1.8) times that of pure PDI-Urea. The H₂O₂ evolution rate of 15% PDI-Urea/BiOBr was 2.5 times that of PDI-Urea and 1.5 times that of BiOBr, respectively. This work has formed a mature S-scheme heterojunction design thought and method, which offers new visions for the development of heterogeneous photocatalysts.     

Photo-induced carbon dioxide reduction on hexagonal tungsten oxide via an oxygen vacancies-involved process

Although converting the greenhouse gasses carbon dioxide (CO₂) into solar fuels is regarded as a convenient means of solar energy storage, the intrinsic mechanism on how the high chemical inertness linear CO₂ molecules is activated and converted on a semiconductor oxide is still elusive. Herein, by creating the oxygen vacancies on the typical hexagonal tungsten oxide (WO₃), we realize the continuous photo-induced CO₂ reduction to selectively produce CO under light irradiation, which was verified by isotope labeling experiment. Detailed oxygen vacancies evolution investigation indicates that light irradiation can simultaneously induce the in-situ formation of oxygen vacancies on hexagonal WO₃, and the oxygen vacancies promote the adsorption and activation of CO₂ molecules, leading to the CO₂ reduction to CO on the hexagonal WO₃ via an oxygen vacancies-involved process. Besides, the existence of water further promotes the formation of CO₂ reduction intermediate, further promote the CO₂ photoreduction. Our work provides insight on the mechanism for converting CO₂ into CO under light irradiation.     

In situ photoreduction of Ag+-ions by TiO2 nanoparticles deposited on cotton and cotton/PET fabrics

The possibility of in situ photoreduction of Ag⁺-ions using TiO₂ nanoparticles deposited on cotton and cotton/PET fabrics in the presence of amino acid alanine and methyl alcohol has been discussed. The possible interaction between TiO₂, alanine and Ag⁺-ions was evaluated by FTIR analysis. The fabrication of TiO₂/Ag nanoparticles on both fabrics was confirmed by SEM, EDX, XRD, XPS and AAS analyses. Cotton and cotton/PET fabrics impregnated with TiO₂/Ag nanoparticles provided maximum reduction of Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. Although excellent antibacterial activity was preserved after ten washing cycles, a significant amount of silver leached out from the fabrics into the washing bath. The perspiration fastness assessment revealed that smaller amounts of silver were also released from the fabrics into artificial sweat at pH 5.50 and 8.00. In addition, deposited TiO₂/Ag nanoparticles imparted maximum UV protection to fabrics.     

Enhanced photocatalytic activity and stability of AgBr/BiOBr/graphene heterojunction for phenol degradation under visible light

In this work, we have reported synthesis of AgBr/BiOBr photocatalyst supported on graphene (Gr) using facile precipitation method. AgBr/BiOBr/Gr was characterized using various spectral techniques like FESEM, TEM, XRD, FTIR, XPS, Raman and PL analyses. AgBr/BiOBr/Gr had improved visible light absorption. PL studies indicated the reduction in recombination of photogenerated electron hole pair of AGBr/BiOBr/Gr. AFM analysis confirmed the thickness of AGBr/BiOBr/Gr was less than 8.0 nm. The higher dispersibility of photocatalyst was ascertained by Tyndall effect. AgBr/BiOBr/Gr photocatalyst was effectively used for the photodegradation of phenol from simulated water. The phenol degradation process was remarkably influenced by adsorption process. The concurrent adsorption and photocatalytic was effective for degradation of phenol. The phenol was completely mineralized into CO₂ and H₂O in 6 h. The degradation process followed pseudo first order kinetics. The results confirmed that integration of AgBr/BiOBr with graphene caused an increase in photocatalytic activity due to reduced recombination of photogenerated electron hole pair and electron sink behavior of graphene for photogenerated electrons of BiOBr. AgBr/BiOBr/Gr photocatalyst displayed significant stability and recyclability for ten catalytic cycles.     

The effects of local environment towards yield and selectivity on photocatalytic CO2 reduction catalyzed by metal-organic framework

The CO₂ photoconversion is sensitive to the local reaction environment, of which activity and selectivity can be regulated by the change of reaction systems. This paper focuses on investigating the photocatalytic CO₂ reduction behaviors of MOFs with the involvement of water under different reaction modes, including gas-solid and liquid-solid systems. The CO₂ photoreduction in a liquid-solid system shows high performance in generating HCOOH with the selectivity of 100%. In contrast, the gas-solid system referring to the synergistic interaction of MOFs and H₂O vapor benefits to the formation of gas-phase products, such as CO and CH₄. The possible mechanisms of photocatalytic CO₂ reaction in two modes were investigated by in-situ Fourier-transform infrared spectroscopy, which indicates that the distinction in reaction consequence may result from the difference in CO₂ chemisorbed modes and the proton provision. The choice of reaction system plays an important role in the achievement of high efficiency and selectivity for photocatalytic CO₂ reduction, which is of great practical value in real-world applications.     

Ternary BiOBr/TiO2/Ti3C2Tx MXene nanocomposites with heterojunction structure and improved photocatalysis performance

The rational design and construction of heterojunction structure is an effective strategy to improve the photocatalytic performance. Herein, a series of BiOBr nanosheets-immobilized TiO₂/Ti₃C₂T_x MXene hybrid materials with heterojunction structure were synthesized by a facial one-step hydrothermal method. The ternary composites show outstanding performance as photocatalysts for the degradation of rhodamine B due to the optimized synergetic effects of BiOBr, TiO₂ and Ti₃C₂T_x. The improved photocatalytic performance is remarkably attributed to the construction of a heterojunction between TiO₂ and BiOBr due to their well-matching of energy band position, which can enhance the absorption for visible light and promote the transfer of photo-generated charge carriers. Moreover, Ti₃C₂T_x acts as an electron trap to further accelerate the separation of photo-generated electrons and holes.     

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO₂ under mild condition is of great importance because these reactions involving CO₂ can not only produce value-added chemicals from abundant and inexpensive CO₂ feedstock but also close the carbon cycle. However, the chemical inertness of CO₂ requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO₂. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO₂ at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO₂ conversion to value-added chemicals under mild condition.     

Novel Bi/BiOBr/AgBr composite microspheres: Ion exchange synthesis and photocatalytic performance

Novel Bi/BiOBr/AgBr composite microspheres were prepared by a rational in situ ion exchange reaction between Bi/BiOBr microspheres and AgNO₃. The characteristic of the as-obtained ternary microspheres was tested by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL). Under visible light irradiation, Bi/BiOBr/AgBr microspheres exhibited an excellent photocatalytic efficiency for rhodamine B (RhB) degradation, which was about 1.4 and 4.9 times as high as that of Bi/BiOBr and BiOBr/AgBr, demonstrating that the highest separation efficiency of charge carriers in the heterostructured Bi/BiOBr/AgBr. The photocatalytic activity of Bi/BiOBr/AgBr microspheres just exhibited a slight decrease after three consecutive cycles. The photocatalytic mechanism investigation confirmed that the superoxide radicals (O₂^•−) were the dominant reactive oxygen species for RhB degradation in Bi/BiOBr/AgBr suspension.     

Protein-mediated synthesis of antibacterial silver nanoparticles deposited on titanium dioxide nanotube arrays

We report on an effective route to decorate titanium nanotube arrays (TiNT) with silver nanoparticles (AgNPs). In this method, surface-adsorbed antibody molecules serve as templates to bind silver ions by electrostatic interaction. The photocatalytic activity of the TiNT under UV irradiation causes the photoreduction of AgNPs to occur, and the biological template is decomposed simultaneously. This route also was successfuly applied to gold nanoparticles (starting from negatively charged metallic precursor ions). Compared to undecorated samples, the AgNPs/TiNT samples under visible light display a much higher antibacterial activity against Escherichia coli.

Synthesis and photocatalytic properties of sunlight-responsive BiOBr–CoWO4 heterostructured nanocomposites

Efficient sunlight-responsive BiOBr–CoWO₄ heterostructured nanocomposite photocatalysts were prepared via a chemical precipitation route at 100°C in 4 hours. The prepared BiOBr–CoWO₄ heterostructures were characterized for phase identification, chemical composition, surface morphology, optical properties and surface area using various techniques. The X-ray diffraction pattern of the BiOBr–CoWO₄ nanocomposite was composed of diffraction peaks equivalent to both the tetragonal phase of BiOBr and the monoclinic phase of CoWO₄ nanoparticles. X-ray photoelectron spectral study of the BiOBr–CoWO₄ nanocomposite revealed orbitals of both BiOBr and CoWO₄ compounds. Transmission electron microscopy images revealed that spherical particles of CoWO₄ (20–25 nm) were dispersed on the surface of BiOBr. UV–visible–near-infrared spectral study of the BiOBr–CoWO₄ nanocomposite showed good visible-light absorption. Among the manufactured materials, BiOBr–CoWO₄-2 nanocomposite showed better charge carrier separation efficiency, as demonstrated by photoluminescence and time-resolved fluorescence. To study the practical utility of the prepared materials, their photocatalytic capability was examined for the degradation of rhodamine B (RhB) aqueous solution under sunlight irradiation. The photodegradation results showed that BiOBr–CoWO₄-2 nanocomposite degraded 98.69% RhB solution and the degradation constant was 0.067 min⁻¹, which was 5.6 and 22.5 times larger than that of pure BiOBr and CoWO₄ nanoparticles, respectively, after 60 minutes of sunlight irradiation. The superior photoactivity was facilitated by electron–hole pair separation and transfer driven by the heterostructure interface between BiOBr particles and CoWO₄ nanoparticles. The removal of RhB was initiated by photogenerated h⁺, O₂^{• −} and ^•OH reactive species based on the scavenger effect.     

Fabrication of dual Z-scheme photocatalyst via coupling of BiOBr/Ag/AgCl heterojunction with P and S co-doped g-C3N4 for efficient phenol degradation

Advances in noble metal mediated Z-scheme photocatalytic system have ushered in a climax on environmental remediation. Herein, graphitic carbon nitride (GCN) and phosphorus sulphur co-doped graphitic carbon nitride (PSCN) were synthesized via calcination process. GCN, PSCN and Z-scheme visible light driven (VLD) ternary BiOBr/PSCN/Ag/AgCl nanophotocatalyst were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–visible diffuse reflectance spectra (UV–vis DRS). BiOBr/PSCN/Ag/AgCl nanocomposite exhibited superior visible light driven photocatalytic ability as compared to pristine PSCN, AgCl and BiOBr towards degradation of phenol. The results explicated promising photocatalytic activity along with space separation of photocarriers caused via formation of BiOBr/PSCN/Ag/AgCl Z-scheme heterojunction. The visible light absorption efficacy of BiOBr/PSCN/Ag/AgCl photocatalyst was confirmed by photoluminescence (PL) spectra. Finally, recycling experiments were explored for the mechanistic detailing of phenol photodegradation employing BiOBr/PSCN/Ag/AgCl photocatalyst. After seven successive cycles photodegradation efficacy of photocatalyst was reduced to 90% from 98%. Proposed mechanism of BiOBr/PSCN/Ag/AgCl nanophotocatalyst for degradation of phenol was discussed. OH and O₂⁻ radicals were main reactive species responsible for photocatalytic phenol degradation.     

光催化合成金属Ag纳米颗粒的生长机制——晶核密度控制的生长模式转换

利用AgNO3水溶液,通过严格控制TiO2薄膜的化学活性,系统研究了在TiO2表面光催化合成金属Ag纳米颗粒的生长行为。研究发现,光催化合成金属Ag纳米颗粒存在着两个完全不同的生长机制,分别对应着金属Ag纳米颗粒的各向同性和各向异性生长。当溶液浓度较低时,Ostwald熟化(OR)机制主导着金属Ag纳米颗粒的长大过程;当溶液浓度较高时,取向附生(OA)机制决定着金属Ag纳米颗粒长大成纳米片。原位消光光谱分析表明,OR机制和OA机制生长的前期具有相近消光特征,决定金属Ag纳米颗粒生长模式的关键是AgNO3溶液的浓度,更准确地说是金属Ag初级晶核的局域密度。在此基础上提出了有关光催化合成金属Ag纳米颗粒的生长模型。     

Enhancing the Photocatalytic Activity of Anatase TiO2 by Improving the Specific Facet‐Induced Spontaneous Separation of Photogenerated Electrons and Holes

Recently, it has been proven that directional flow of photogenerated charge carriers occurs on specific facets of TiO₂ nanocrystals. Herein, we demonstrate that the photocatalytic activity of anatase TiO₂ nanocrystals in both photoreduction and photooxidation processes can be enhanced by selectively depositing Pt nanoparticles on the {101} facets, which strengthens spontaneously surface‐induced separation between photogenerated electrons and holes in the photocatalysis process. An optimal ratio of the oxidative {001} facets to the reductive {101} facets exists with regard to the photocatalysis of the faceted TiO₂ nanocrystals, and this is crucial for balancing the recombination and redox reaction rates of photogenerated electrons and holes. The present work might help us gain deeper insight into the relation between the specific surface of semiconductor photocatalysts and their photocatalytic activities and provides us with a new route to design photocatalysts with high photocatalytic activity.     

Different Atomic Terminations Affect the Photocatalytic Nitrogen Fixation of Bismuth Oxybromide: A First Principles Study

We have systematically investigated the electronic structures and activation capacities of BiOBr {001} facets with different atomic terminations by means of DFT methods. Our calculations reveal that oxygen vacancies (OVs) give a significant boost in band edges of the O‐terminated BiOBr {001} facets, and excess electrons induced by OVs could exceed the reduction potentials of high‐energy N₂ intermediates. Interestingly, the Bi‐terminated BiOBr {001} facets may be good candidates for photocatalytic nitrogen fixation due to the stronger activation ability of N₂ molecules comparing with O‐terminated BiOBr {001} facets with OVs. Moreover, the Bi‐terminated BiOBr {001} facets may tend to yield NH₃ instead of N₂H₄.