One‐Pot Fabrication of RGO–Ag3VO4 Nanocomposites by in situ Photoreduction using Different Sacrificial Agents: High Selectivity Toward Catechol Synthesis and Photodegradation Ability

Weak photon absorption and fast carrier kinetics in graphene restrict its applications in photosensitive reactions. Such restrictions/limitations can be overcome by covalent coupling of another photosensitive nanostructure to graphene, forming graphene‐semiconductor nanocomposites. Herein, we report one‐pot synthesis of RGO–Ag₃VO₄ nanocomposites using various sacrificial agents like ethanol, methanol, propanol and ethylene glycol (EG) under visible light illumination. The Raman spectral analysis and ¹³C MAS NMR suggest ethanol to be the best sacrificial agent among those studied. Thermal analysis studies, further, confirm the stability of the synthesized nanocomposite with ethanol as sacrificial agent. In view of this, the activity toward dye degradation was focused over the composites prepared via ethanol as sacrificial agent. It was observed and proved that cationic dyes could be degraded quantitatively and swiftly compared to anionic dyes (37.79%) in 1.5 h. This suggests that the surface of the nanocomposites is anionic as partial reduction takes place during synthesis process. In case of mixed dye degradation process, it was noticed that the presence of cationic dye doubles the degradation of anionic dye. The activity of these synthesized nanocomposites is more than five‐fold toward the phototransformation of phenol and photodegradation of textile dyes under visible light illumination.     

Preparation of high‐activity AgBr/Ag3PO4 photocatalyst based on hexadecyltrimethylammonium bromide and mechanism of photocatalytic enhancement

A high‐activity AgBr/Ag₃PO₄ heterojunction photocatalyst was synthesized based on hexadecyltrimethylammonium bromide. Its microspheres were characterized using X‐ray diffractometry, transmission electron microscopy and ultraviolet–visible diffuse reflectance spectroscopy. The new photocatalyst with high photocatalytic activity exceptionally outperforms pure Ag₃PO₄ and AgBr in methyl orange degradation. The enhancement of photocatalytic activity is attributed to the efficient separation of electron–hole pairs. In this photocatalytic reaction, h⁺ and ^?O^2? are the main reactive species that induce visible‐light‐driven degradation.     

Efficient solar photocatalyst based on Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/graphene nanosheets composite for photocatalytic decolorization of dye pollutants

Silver orthophosphate-graphene nanosheets composite (Ag₃PO₄-GNs) has been fabricated using a facile hydrothermal method. The Ag₃PO₄-GNs were characterized using XRD, UV–vis DRS and SEM. The photocatalytic activity of Ag₃PO₄-GNs was evaluated by photocatalytic decolorization of dye aqueous solutions under simulated solar light irradiation. It was observed that Ag₃PO₄ nanoparticles in Ag₃PO₄-GNs were attached on the surface of graphene nanosheets.The introduction of graphene nanosheets enhanced remarkably the visible light absorption region of Ag₃PO₄-GNs compared with bare Ag₃PO₄. The photocatalytic activity of Ag₃PO₄-GNs is nearly twice as high as that of the pure Ag₃PO₄. The removal efficiency can reach more than 90 % by Ag₃PO₄-GNs under simulated solar light irradiation within 25 min, which might mainly be attributed to high adsorption capacity, extended light absorption range and efficient charge separation. After irradiation for 60 min, 84.70 % TOC mineralization was achieved by Ag₃PO₄-GNs. Based on the results of detection of active species, the direct oxidization of dye pollutants in aqueous solution by holes takes a major role in the whole decolorization process by Ag₃PO₄-GNs. As a result, Ag₃PO₄-GNs with the high photocatalytic activity are proven to be an excellent light photocatalyst for potentially scalable removal of dyes in aqueous solutions and other environmental remediation under simulated solar light irradiation.     

BiPO4 photocatalyst employing synergistic action of Ag/Ag3PO4 nanostructure and graphene nanosheets

Graphene-supported BiPO₄/Ag/Ag₃PO₄ photocatalyst has been fabricated by simple hydrothermal and impregnation reaction. In BiPO₄/Ag/Ag₃PO₄ based on Reduced Graphene Oxide (RGO), this network renders numerous pathways for rapid mass transport, strong adsorption and multireflection of incident light; meanwhile, the interface between BiPO₄/Ag/Ag₃PO₄ and RGO increases the active sites and electron transfer rate. BiPO₄/Ag/Ag₃PO₄ based on RGO noticeably exhibited high photocatalytic activity than that of BiPO₄/Ag/Ag₃PO₄ and P25 under visible light irradiation for cationic dye (Rhodamine B), anionic dye (methyl orange) and 4-chlorophenol (4-CP) as a neutral pollutant, which are usually difficult to be degraded over the other catalysts. This enhanced photocatalytic activity of Graphene-supported BiPO₄/Ag/Ag₃PO₄ for all pollutants could be mainly ascribed to the reinforced charge transfer from BiPO₄/Ag/Ag₃PO₄ to RGO, which suppresses the recombination of electron/hole pairs. Besides that, this photocatalyst can be used repetitively with a high photocatalytic activity and no apparent loss of activity occurs. The results reveal that the RGO nanosheets work as a photocatalyst promoter during the photocatalytic reaction, leading to an improved photocatalytic activity.     

Highly Efficient Photocatalytic Remediation of Simulated Polycyclic Aromatic Hydrocarbons (PAHs) Contaminated Wastewater under Visible Light Irradiation by Graphene Oxide Enwrapped Ag3PO4 Composite.

Effective removal of polycyclic aromatic hydrocarbons (PAHs) from wastewater before their discharge into the environment is an ever pressing requirement. In this study, for the first time, simulated PAHs contaminated wastewater was photocatalytically remediated with graphene oxide (GO) enwrapped silver phosphate as visible light‐driven photocatalysts. The GO/Ag₃PO₄ photocatalysts exhibited superior photocatalytic activity and stability compared with pure Ag₃PO₄, g‐C₃N₄ and TiO₂ (P25). The degradation efficiency of naphthalene, phenanthrene and pyrene could reach 49.7%, 100.0% and 77.9%, rspectively within 5 min irradiation. The apparent rate constants of photocatalytic degradation of 3 wt% GO/Ag₃PO₄ composite photocatalyst were 0.14, 1.21 and 2.46 min⁻¹ for naphthalene, phenanthrene and pyrene, respectively. They were about 1.8, 1.5 and 2.0 times higher than that of pure Ag₃PO₄, and much higher than that of g‐C₃N₄ and TiO₂. Meanwhile, the efficiencies of 44.6%, 95.2% and 83.8% were achieved for naphthalene, phenanthrene and pyrene degradation even after 5 times of recycling in the GO/Ag₃PO₄‐PAHs photocatalysis system. Reactive species of ∙O₂⁻ and h⁺ were considered as the main participants for oxidizing naphthalene, phenanthrene and pyrene.     

Enhanced Ethylene Photodegradation Performance of g‐C3N4–Ag3PO4 Composites with Direct Z‐Scheme Configuration

Photocatalytic oxidation of ethylene continues to be a challenge at the frontier of chemistry. In a previous report, a simple Ag₃PO₄ semiconductor material was shown to have strong photooxidative properties and efficiently oxidised water and decomposed organics in aqueous solution under visible‐light illumination. Herein, its effects on the photo‐oxidation of gaseous C₂H₄ were investigated by fabricating graphitic C₃N₄–Ag₃PO₄ composite semiconductors with direct Z‐scheme configuration. It was found that both the ethylene photo‐oxidative activity and the stability of Ag₃PO₄ are considerably improved by fabrication of Z‐scheme composites. Moreover, stable C₂H₄ photo‐oxidation activity could be obtained by treating the composite at 450 °C for 3 h after long‐term operation. From the point of view of environmental pollutant cleanup, the present technique avoids the side reaction of oxidising water and will be valuable for further investigations on both Ag₃PO₄ and CH degradation.     

Ag3PO4/BiVO4复合光催化剂的制备及可见光催化降解染料

结合回流法和原位沉淀法成功制备磷酸银/矾酸铋(Ag₃PO₄/BiVO₄)复合光催化剂. 通过X 射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、能量色散X射线光谱(EDS)、紫外-可见漫反射光谱(UV-Vis DRS)及光致发光(PL)光谱对制备样品进行表征. XRD和FESEM结果表明成功制备Ag₃PO₄/BiVO₄复合光催化剂. 采用节能发光二极管灯(LED)作为可见光光源, 在低消耗光催化系统中评价制备样品可见光催化降解染料的活性.当Ag₃PO₄和BiVO₄的组成摩尔比为1:3 时, 复合Ag₃PO₄/BiVO₄光催化剂呈现出高于纯相Ag₃PO₄的催化活性,可减少Ag₃PO₄的使用量. Ag₃PO₄/BiVO₄复合光催化剂在中性溶液中表现出高活性, 同时证实其对阳离子染料的光催化降解效果强于阴离子染料. 在Ag₃PO₄/BiVO₄系统中, 超氧自由基和空穴是主要的活性物种. 经过三次循环利用, Ag₃PO₄/BiVO₄复合催化剂的可见光催化活性表现出不同程度的降低, 归因于降解过程中产生金属银.     

Visible‐Light Photocatalytic Activity and Deactivation Mechanism of Ag3PO4 Spherical Particles

Ag₃PO₄ spherical particles were synthesized by a facile precipitation method using silver nitrate and Na₂HPO₄ as precursors. The as‐prepared samples had a high photocatalytic activity toward Rhodamine B (RhB) degradation under visible‐light illumination. With increasing recycling times the photocatalytic activity first increased and then decreased. Based on systematic characterization of particles by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), a possible mechanism responsible for the improvement and subsequent decline of the photocatalytic performance of Ag₃PO₄ is proposed. Ag₃PO₄ spherical particles recycled for four times showed the highest photocatalytic activity because, according to our mechanism, Ag nanoparticles deposited on Ag₃PO₄ acted as electron trapping centers to prevent photogenerated electron‐hole pairs from recombination. A further increase in the recycle times decreases the photocatalytic activity owing to the shielding effect by Ag layers on the surface of Ag₃PO₄. The results presented herein shed new light on the photostability of Ag₃PO₄ spherical particles and are potentially applicable to other photocatalytically active composites.     

Ag3PO4-based nanocomposites and their applications in photodegradation of toxic organic dye contaminated wastewater: Review on material design to performance enhancement

Silver Orthophosphate (Ag₃PO₄) is a promising visible light driven photocatalyst. The morphology and structure of Ag₃PO₄ can be controlled by variety of synthetic methods for which it becomes the most extensively studied novel photocatalyst. Moreover, tailoring of Ag₃PO₄-based photocatalyst for performance enhancement attracts immense attention in recent times. The endeavour of this review paper to focus on the research progress of this material and the success gained so far by fabrication of Ag₃PO₄-based nanocomposite materials in photodegradation of selected toxic organic dyes. Some representative examples are discussed thoroughly. The underlying challenges and future perspectives are also brought into spotlight.     

Reduced Graphene‐Wrapped MnO2 Nanowires Self‐Inserted with Co3O4 Nanocages: Remarkable Enhanced Performances for Lithium‐Ion Anode Applications

A simple synthetic approach for graphene‐templated nanostructured MnO₂ nanowires self‐inserted with Co₃O₄ nanocages is proposed in this work. The Co₃O₄ nanocages were penetrated in situ by MnO₂ nanowires. As an anode, the as‐obtained MnO₂–Co₃O₄–RGO composite exhibits remarkable enhanced performance compared with the MnO₂–RGO and Co₃O₄–RGO samples. The MnO₂–Co₃O₄–RGO electrode delivers a reversible capacity of up to 577.4 mA h g^?1 after 400 cycles at 500 mA g^?1 and the Coulombic efficiency of MnO₂–Co₃O₄–RGO is about 96 %.     

Dispersion of Reduced Graphene Oxide in Multiple Solvents with an Imidazolium‐Modified Hexa‐peri‐hexabenzocoronene

An imidazolium‐modified hexa‐peri‐hexabenzocoronene derivative (HBC‐C₁₁‐MIM[Cl^?]) was designed and synthesized as a stabilizer to fabricate reduced graphene oxide (RGO). The resulting RGO/HBC‐C₁₁‐MIM[Cl^?] hybrid shows excellent dispersivity (5.0 mg mL^?1) and stability in water. RGO/HBC‐C₁₁‐MIM[Cl^?] was comprehensively characterized by using atomic force microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy, thus revealing that one HBC‐C₁₁‐MIM[Cl^?] group can stabilize about 178 carbon atoms on the graphene sheets. The obtained hybrid film exhibits a high conductivity of 286 S m^?1. Furthermore, the HBC‐C₁₁‐MIM[Cl^?]‐modified RGO sheets can be readily dispersed in polar organic solvents upon exchange of the hydrophilic Cl^? ions for hydrophobic bis(trifluoromethylsulfonyl) amide (NTf₂^?) ions.     

Porous Molybdenum‐Based Hybrid Catalysts for Highly Efficient Hydrogen Evolution

We have synthesized a porous Mo‐based composite obtained from a polyoxometalate‐based metal–organic framework and graphene oxide (POMOFs/GO) using a simple one‐pot method. The MoO₂@PC‐RGO hybrid material derived from the POMOFs/GO composite is prepared at a relatively low carbonization temperature, which presents a superior activity for the hydrogen‐evolution reaction (HER) in acidic media owing to the synergistic effects among highly dispersive MoO₂ particles, phosphorus‐doped porous carbon, and RGO substrates. MoO₂@PC‐RGO exhibits a very positive onset potential close to that of 20 % Pt/C, low Tafel slope of 41 mV dec^?1, high exchange current density of 4.8×10^?4 A cm^?2, and remarkable long‐term cycle stability. It is one of the best high‐performance catalysts among the reported nonprecious metal catalysts for HER to date.     

Construction of Er3+:YAlO3/RGO/TiO2 Hybrid Electrode with Enhanced Photoelectrocatalytic Performance in Methylene Blue Degradation Under Visible Light

Much attention has been paid on doping TiO₂ to narrow its band gap to promote the absorption of visible light and restrain the recombination of electron–hole pairs to improve its efficiency in photoelectrocatalysis (PEC) under visible‐light irradiation. However, the oxidation potential energy of photo‐induced holes for the modified catalysts by visible‐light excitation is lower than that without modification by UV excitation. In this work, we synthesized a co‐coupled TiO₂ electrode (denoted ERT) with the Er³⁺:YAlO₃ and reduced graphene oxide (RGO), achieving the synergetic effect of visible‐light‐to‐UV up‐conversion and response and great electron transfer ability. The effects of external bias voltage, electrolyte concentration and pH on the PEC activity were studied with the methylene blue (MB) as the target pollutant. The results indicated that PEC by the ERT electrode showed the highest MB removal compared with those by the electrodes coupled with RGO or Er³⁺:YAlO₃ alone. In addition, the kinetic rate constant of the PEC process using the ERT electrode was higher than the sum of those of the photocatalytic and electrocatalytic processes. The optimal conditions for PEC by the ERT electrode were an external bias voltage of 1.0 V, 0.1 mol L^?1 Na₂SO₄ and pH = 10.     

可见光驱动Ag3PO4催化降解罗丹明B和甲基橙

采用简易离子交换法制备可见光驱动Ag3PO4光催化剂.通过X射线衍射、场发射扫描电子显微镜、N2吸附-脱附、紫外-可见漫反射光谱及傅里叶变换红外光谱对所制备的Ag3PO4催化剂进行表征.结果表明,在可见光照射下,Ag3PO4催化剂对罗丹明B降解表现出优越的光催化活性,但对甲基橙的降解活性低,这归因于Ag3PO4催化剂对甲基橙分子吸附量低.可见光照Ag3PO4反应体系中,空穴和超氧自由基共同发挥作用导致罗丹明B和甲基橙光催化降解.在罗丹明B的协助作用下,Ag3PO4催化剂对甲基橙的可见光催化降解活性大大增强,这是由于罗丹明B的存在可产生更多的超氧自由基,从而使甲基橙进一步降解.     

Preparation of Photocatalytic Au–Ag2Te Nanomaterials

A facile approach has been developed for the preparation of various morphologies of Au–Ag₂Te nanomaterials (NMs) that exhibit strong photocatalytic activity. Te NMs (nanowires, nanopencils, and nanorice) were prepared from TeO₂ in the presence of various concentrations (16, 8, and 4 M ) of a reducing agent (N₂H₄) at different temperatures (25 and 60 °C). These three Te NMs were then used to prepare Au–Ag₂Te NMs by spontaneous redox reactions with Au³⁺ and Ag⁺ ions sequentially. The Au–Ag₂Te nanopencils exhibit the highest activity toward degradation of methylene blue and formation of active hydroxyl radicals on solar irradiation, mainly because they absorb light in the visible region most strongly. All three differently shaped Au–Ag₂Te NMs (10 μg mL^?1) provide a death rate of Escherichia coli greater than 80 % within 60 min, which is higher than that of 51 % for commercial TiO₂ nanoparticles (100 μg mL^?1). Under light irradiation, the Au NPs in Au–Ag₂Te NMs enhance the overall photo‐oxidation ability of Ag₂Te NMs through faster charge separation because of good contact between Ag₂Te and Au segments. With high antibacterial activity and low toxicity toward normal cells, the Au–Ag₂Te NMs hold great potential for use as efficient antibacterial agents.     

Construction of Hierarchical Hollow Co9S8/ZnIn2S4 Tubular Heterostructures for Highly Efficient Solar Energy Conversion and Environmental Remediation

Visible‐light‐responsive hierarchical Co₉S₈/ZnIn₂S₄ tubular heterostructures are fabricated by growing 2D ZnIn₂S₄ nanosheets on 1D hollow Co₉S₈ nanotubes. This design combines two photoresponsive sulfide semiconductors in a stable heterojunction with a hierarchical hollow tubular structure, improving visible‐light absorption, yielding a large surface area, exposing sufficient catalytically active sites, and promoting the separation and migration of photogenerated charges. The hierarchical nanotubes exhibit excellent photocatalytic H₂ evolution and Cr^VI reduction efficiency. Under visible‐light illumination, the optimized Co₉S₈/ZnIn₂S₄ heterostructure provides a remarkable H₂ generation rate of 9039 μmol h^?1 g^?1 without the use of any co‐catalysts and Cr^VI is completely reduced in 45 min. The Co₉S₈/ZnIn₂S₄ heterostructure is stable after multiple photocatalytic cycles.     

Efficient Visible‐Light‐Driven Carbon Dioxide Reduction by a Single‐Atom Implanted Metal–Organic Framework

Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and photoreduce CO₂ with high efficiency under visible‐light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long‐lived electrons for the reduction of CO₂ molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO₂, which is equivalent to a 3.13‐fold improvement in CO evolution rate (200.6 μmol g^?1 h^?1) and a 5.93‐fold enhancement in CH₄ generation rate (36.67 μmol g^?1 h^?1) compared to the parent MOF.     

Electromagnetic properties of Fe3O4‐functionalized graphene and its composites with a conducting polymer

Hybrid materials of Fe₃O₄‐decorated reduced graphene oxide (Fe₃O₄‐RGO) and poly(3,4‐ethylenedioxythiophene) (PEDOT) were prepared by poly(ionic liquid)‐mediated hybridization. In this hybrid material, poly(ionic liquid) was found to perform multiple roles for: (1) stabilizing Fe₃O₄‐RGO against aggregation in the reaction medium, (2) transferring Fe₃O₄‐RGO nanomaterials from aqueous into organic phase, and (3) associating Fe₃O₄‐RGO nanomaterials with PEDOT. The hybrid materials of Fe₃O₄‐RGO with PEDOT showed the lowest surface resistivity of 80 Ω sq^?1 at an RGO‐Fe₃O₄ loading of 1 wt %, and exhibited superparamagnetic behavior with an electromagnetic interference shielding effectiveness of 22 dB. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Enhanced photocatalytic activity of Ag3PO4 via Fullerene C60 modification

Fullerene‐C₆₀‐modified Ag₃PO₄ photocatalysts (C₆₀/Ag₃PO₄) were prepared via facile chemical precipitation. The structures, morphology and photocatalytic properties of C₆₀/Ag₃PO₄ were characterized by X‐ray diffractometry (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectrometry, and ultraviolet–visible (UV–vis) absorption spectrometry. C₆₀/Ag₃PO₄ exhibits considerably higher photocatalytic activity for degradation of Methyl Orange. The degradation conversion reached 93% after 8 min of light irradiation. Besides, the enhancement of photocatalytic activity could be attributed to the active species ?OH_, which can be ascribed to strong synergistic effect between Fullerene C₆₀ and Ag₃PO₄.     

Facile Synthesis of Ag/Ag3PO4 Composites with Highly Efficient and Stable Photocatalytic Performance under Visible Light

The Ag/Ag₃PO₄ composites with various shapes (spheres, polyhedral, and microcubes) were synthesized by a facile precipitation method and a subsequent light‐reduction route at room temperature. The as‐prepared Ag/Ag₃PO₄ composites were characterized in detail by X‐ray diffraction, Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, scanning electron microscopy, UV–vis diffuse reflection, and photoluminescence spectroscopy. The growth processes of different morphologies Ag/Ag₃PO₄ composites are also discussed. The decomposition test of rhodamine B (RhB) indicated that the Ag/Ag₃PO₄ composites enhanced the photocatalytic performance compared with pure Ag₃PO₄, which was attributed to the surface plasmon resonance (SPR) of Ag nanoparticles and the stability of the photocatalysts. Moreover, uniform cubes of Ag/Ag₃PO₄ showed the highest photocatalytic activity and could completely degrade RhB in 7 min, which could be primarily ascribed to the cubic structure of Ag/Ag₃PO₄ with strong visible‐light absorption and efficient separation of the photo‐generated electrons and holes. Furthermore, the possible photocatalytic mechanism is also discussed.