Appreciable Enhancement of Photocatalytic Performance for N-doped SrMoO_(4) via the Vapor-thermal Method

A series of nitrogen-doped SrMoO_(4) with different Sr/N mole ratio (R=0,0.05,0.10,0.15,0.20,0.40,and 0.60) were synthesized using urea as the N source via the vapor-thermal method.The photocatalytic degradation ability of all samples was evaluated using methylene blue (MB) as a target contaminant.The band gaps of N-doped samples are all higher than that of pristine ones,which is only 3.12 eV.BET specific surface area S_(BET) and pore volume are increased due to the N doping.And the greater increase of S_(BET),the faster the photodegradation speed of methylene blue on SrMoO_(4).More specifically,the degradation efficiency of MB is improved up to 87%in 100 min.

Development strategies and improved photocatalytic CO_(2) reduction performance of metal halide perovskite nanocrystals

In recent years,photocatalytic CO_(2)reduction reaction(CRR) has attracted much scientific attention to overcome energy and environmental issues by converting CO_(2)into high-value-added chemicals utilizing solar energy.Metal halide perovskite(MHP) nanocrystals(NCs) are recognized as an ideal choice for CRR owing to their outstanding optoelectronic properties.Although great efforts have been devoted to designing more effective photocatalysts to optimize CRR performance,severe charge recombination,instability,and unsatisfactory activity have become major bottlenecks in developing perovskite-based photocatalysts.In this review,we mainly focus on the recent research progress in the areas of relevance.First,a brief insight into reaction mechanisms for CRR and structural features of MHPs are introduced.Second,efficient modification approaches for the improvement of the photocatalytic activity and stability of the perovskite-based catalysts are comprehensively reviewed.Third,the state-of-the-art achievements of perovskite-based photocatalysts for CRR are systematically summarized and discussed,which are focused on the modification approaches,structure design,and the mechanism of the CO_(2)reduction process.Lastly,the current challenges and future research perspectives in the design and application of perovskite materials are highlighted from our point of view to provide helpful insights for seeking breakthroughs in the field of CRR.This review may provide a guide for scientists interested in applying perovskite-based catalysts for solar-to-chemical energy conversion.

LDH-based nanomaterials for photocatalytic applications:A comprehensive review on the role of bi/trivalent cations, anions,morphology, defect engineering, memory effect, and heterojunction formation

Using sunlight to drive chemical reactions via photocatalysis is paramount for a sustainable future.Among several photocatalysts,employing layered double hydrides(LDH) for photocatalytic application is most straightforward and desirable owing to their distinctive two-dimensional(2D) lamellar structure and optical attributes.This article reviews the advancements in bimetallic/trimetallic LDHs and various strategies to achieve high efficiency toward an outstanding performing photocatalyst.Firstly,the tuning of LDH components that control the electro nic and structural properties is explained.The tu ning obtained through the adoption,combination,and incorporation of different cations and anions is also explained.The progress of modification methods,such as the adoption of different morphologies,delamination,and defect engineering towards enhanced photocatalytic activities,is discussed in the mainstream.The band engineering,structural characteristics,and redox tuning are further deliberated to maximize solar energy harvesting for different photocatalytic applications.Finally,the progress obtained in forming hierarchical heterostructures through hybridization with other semiconductors or conducting materials is systematically disclosed to get maximum photocatalytic performance.Moreover,the structural changes during the in-situ synthesis of LDH and the stability of LDH-based photocatalysts are deliberated.The review also summarizes the improvements in LDH properties obtained through modification tactics and discusses the prospects for future energy and environmental applications.

A Novel 3D Metal Coordination Polymer Based on Tetranuclear Cobalt Cluster Building Blocks:Synthesis,Crystal Structure and Photocatalytic Property

A novel 3D MCP,[Co;（μ;-OH）(btc)（bmip）];(1,H;btc=1,3,5-benzenetricarboxylate acid,bmip=1,3-bis（2-methylimidazolyl）propane),was synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction,powder XRD,FT-IR,TGA and elemental analysis techniques.MCP 1 features a 3D framework based on tetranuclear Co（Ⅱ）clusters where the four cobalt ions are coplanar,and shows an unusual binodal（3,10）-connected topology.Furthermore,the photocatalytic experiment result indicates the degradation ratios of rhodamine B（RhB）reach 78.2%when MCP 1 acts as catalyst.

Ionothermal Synthesis, Crystal Structure and Photocatalytic Property of a New Cobalt Coordination Polymer

The reaction of flexible bis（imidazole） ligand and 1,2-bis（imidazol-l＇-yl）methane （bimm） with Co（Ⅱ） salt under ionothermal method resulted in the formation of a new coordination polymer {[Co（bimm）3]·（PF6）2}n （1）. X-ray single-crystal diffraction determination reveals that 1 crystallizes in the triclinic Pi space group, with α = 8.647（6）, b = 12.092（9）, c = 14.967（1 l） A, α = 88.912（8）, β = 81.199（8）, ）, = 89.395（8）°, V= 1546 （2） A3, Z = 2, Mr = 793.39, Dc= 1.704 Mg/m3,μ = 0.768 mm-1 F（000） = 798, the final R = 0.0626 and wR = 0.1634 for 4319 observed reflections with I〉 2σ（I）. In compound 1, the Co（lI） ion is connected to another Co（ll） by two bimm ligands to form 1D double chains which are further linked by bimm ligands to form a 2D wavelike layer. Topologically, the structure of 1 represents a uninodal 2D 4-connected sq1/Shubnikov tetragonal plane net. Moreover, thermogravimetric analyses and photocatalytic property for 1 have also been investigated.

Synthesis and Photocatalytic Property of the ZrO_2/TiO_2 Pillared Laponite

The ZrO2/TiO2 pillared laponite （Ti-Zr-lap） photocatalysts were prepared with intercalation reaction by supercritical fluid drying （SCFD）,and characterized by XRD,TEM,SEM and BET surface area analysis,and the photocatalytic properties of Ti-Zr-lap were investigated by degradation of azo dye acid red B （ARB）.The results showed that the ZrO2/TiO2 pillared structures in laponite could be formed,with the mass fraction of （Zr4＋＋Ti4＋）/laponite （Xm） increasing,the basal spacing and the BET surface area of Ti-Zr-lap significantly increased.The Ti-Zr-lap used as photocatalyst had the advantages of stable and porous layered structure,large surface area with the anatase type TiO2.Compared with the Ti-Zr-lap dried by air drying,the Ti-Zr-lap dried by SCFD showed better photocatalytic property which was very close to that of P25 TiO2.Using the Ti-Zr-lap as photocatalyst with the optimum Xm of 0.16 and the calcination temperature of 500 ℃,under the conditions of the initial concentration of ARB 20 mg/L,photocatalyst concentration of 1.5 g/L and irradiation time 60 min,the decoloring rate of ARB could achieve 98.3%,indicating that the Ti-Zr-lap had excellent photocatalytic property.

Synthesis,Structure,Photoluminescence and Photocatalytic Properties of a New Cd(Ⅱ)Metal-organic Framework Based on 1,4-Di(2,6-dimethyl-3,5-dicarboxypyridyl)benzene

A new 3D coordination polymer, [Cd2（L）（bpb）2]n（1, H4L = 1,4-di（2,6-dimethyl-3,5-dicarboxypyridyl） benzene, bpb = 1,4-bis（4-pyridyl） benzene, has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, TGA, IR spectroscopy and UV-Vis spectrum. Complex 1 crystallizes in orthorhombic, space group C2221, with a = 10.9393（12）, b = 20.900（3）, c = 20.027（2） A, β = 90°, V = 4578.9（9） A^3, Dc = 41.668 Mg/cm^3, Mr = 1149.74, F（000） = 2312.0, μ = 0.996 mm^（–1）, Z = 4, the final R = 0.0316 and wR = 0.0786 for 4271 observed reflections with I 〉 2σ（I）. Structural analysis shows that 1 possesses a 3D network based on the 2D layer bridged by L^4-ligands, while the 2D layers are composed of the adjacent 1D chains joined by L^4-ligand. The photoluminescent investigation indicates that one broad emission band with the maximum of 445 nm can be observed in 1. Moreover, compound 1 has high photocatalytic degradation effects on methylene blue under UV irradiation.

Synthesis and photocatalytic properties of InVO_4 sol containing nanocrystals by mild hydrothermal processing

The precursor precipitation of InVO4 was synthesized by co-precipitation using indium trichloride (InCl3), ammonium metavanadate (NH4VO3) and ammonia (NH3·H2O) as raw materials. The InVO4 sols with orthorhombic phase were obtained by hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). The precursor and sol of InVO4 were characterized by X-ray diffraction (XRD), Fourier Transform Infra-red spectra (FT-IR), scanning electron microscopy (SEM) measurements. The XRD patterns indicate that the InVO4 precursor is amorphous phase, InVO4 sol contains orthorhombic InVO4 nanocrystals. The results also reveal that the pH value of the reaction mixture and reaction temperature play important roles to the target phase. InVO4-TiO2 thin films on glass slides were prepared by the dip-coating method from the composite sol. The photocatalytic properties of the InVO4-TiO2 thin films were investigated by the photocatalytic degradation of methyl orange solution. The results indicate that it has better photocatalytic activities than pure TiO2 thin films or pure InVO4 thin films with UV light.

Rare Earth Ion Yb^3+ Doping of Bi2WO6 with Excellent Visible-light Photocatalytic Activity

The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.

Regulating Electron-Hole Separation to Promote the Photocatalytic Property of BiOBr_1−xI_x/BiOBr Local Distorted Hierarchical Microspheres

In this work, hierarchical BiOBr1−xIx/BiOBr heterojunction photocatalyst with a microsphere morphology was synthesized by a facile solvothermal process. It demonstrated that the local structure of the photocatalysts was highly distorted due to the substitution of bromide ions by iodine ions. The photocatalytic properties were evaluated by the photodecomposition of aqueous phenol solution under visible-light irradiation. The results indicated that all the composite photocatalysts exhibited high photocatalytic activity. In particularly, the BiOBr1−xIx/BiOBr (x = 0.25) sample exhibited over 92% degradation efficiency of phenol within 150 min, which is 24.6 and 3.08 fold enhancement in the photocatalytic activity over the pure phased BiOBr and BiOI, respectively. Moreover, this excellent photocatalytic property can be expanded to other colorless organic contaminants, verifying the common applicability of BiOBr1−xIx/BiOBr (x = 0.25) as an excellent visible-light photocatalyst for organics decomposition. The significant improvement in the photocatalytic activity can be explained by the high efficiency of charge separation due to the enhancement in the internal electric fields and band match that comes from the local structure distortion. This work provides valuable information for the design of highly active photocatalysts toward the environmental remediation.

Anisotropy of Photocatalytic Properties in Nanostructured Photocatalysts

Energy band engineering and the nature of surface/interface of a semiconductor play a significant role in searching high efficiency photocatalysts. Actually, the active facets, morphology controlling, especially the exposed facets modulation of photocatalysts during preparation are very desirable. In order to achieve high photocatalytic performance, intrinsic mechanism of such anisotropic properties should be fully considered. In this review, we mainly emphasis on the latest research developments of several extensively investigated photocatalysts and their anisotropic photocatalytic properties, as well as the correlation between effective masses anisotropy and photocatalytic properties. It will be helpful to understand the photocatalytic mechanism and promote rational development of photocatalyst for wide applications.

Characteristics and Photocatalytics Activities of Ce-Doped ZnO Nanoparticles

Ce-doped ZnO nanoparticles with various doping concentrations of cerium ion were prepared by the co-precipitation method. All prepared nanoparticles were characterized by electron spin resonance (ESR), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectroscopy. All nanoparticles show X-ray diffraction pattern that matched with ZnO in its wurzite structure and average grain size was in the range of 13 - 16 nm. UV-Vis measurements indicated a red shift of the photophysical response of ZnO after doping that was exhibited in reflection spectra in the visible region between 300 - 800 nm. In addition, it has been found from electron spin resonance measurements that defects, which are likely to be oxygen vacancy and an electron trapped at cerium site are formed in our Ce-doped ZnO particles. Photocatalytic activities of Ce-doped ZnO were evaluated by irradiating the nanoparticles solution to ultraviolet light by taking methyl orange as organic dye. The experiment demonstrated that the photodegradation increased as doping concentrations increased at first and then decreased when the doping concentra- tion exceeded 9 at%. It is proposed that the photocatalytic activity is strongly dependent on the formation of oxygen vacancy and an electron trapped at cerium site.

Nanoparticle/Microsphere TiO_(2)/Bi_(2)WO_(6) Z-scheme Heterojunction with Excellent Visiblelight Photocatalytic Performance

Flower-like BiOBr/Bi_(2)WO_(6) Z-scheme heterojunction was prepared by a twostep solvothermal method.BiOBr microspheres were firstly synthesized through solvothermal method.Then the out part of the BiOBr microspheres was designed to react with Na2WO4 forming Bi_(2)WO_(6) nanosheets through ion exchange process.The BiOBr/Bi_(2)WO_(6) heterojunction has a larger BET surface area,smaller energy band gap,faster transfer of charge carriers and a much better visible-light photocatalytic performance than that of BiOBr and Bi_(2)WO_(6).It also has a better cycling stability than that of the BiOBr.Possible photocatalytic mechanism of the BiOBr/Bi_(2)WO_(6) heterojunction is proposed.

A Heterometallic Cu(Ⅰ)-Sr(Ⅱ) Coordination Polymer Based on Isonicotinic Acid Ligand: Synthesis, Crystal Structure, Luminescence and Photocatalytic Performance for Methylene Blue Degradation

Presented here is a new heterometallic Cu(I)-Sr(Ⅱ) coordination polymer, [Cu(3)Sr_2(isonic)_5 Br_2(H_2O)_3]n·n(H_2O)(1, Hisonic = isonicotinic acid), has been synthesized via the hydrothermal reactions of CuBr, Sr(NO_3)_2 and isonicotinic acid. The crystal structure is of triclinic system, space group P1 with a = 7.111(2), b = 14.934(4), c = 18.0255(11) ?, α = 83.137(15), β = 87.155(15), γ = 79.75(2)°, V = 1869.4(8) ?~3, C_(30)H_(29)Br_2Cu(3)N_5O_(14)Sr_2, Mr = 1209.27, Z = 2, Dc = 2.148 g/cm^3, F(000) = 1178, μ = 6.725 mm^(-1), R = 0.0500 and wR = 0.1008 for 4688 observed reflections(I > 2s(I)). Single-crystal X-ray diffraction analysis revealed that compound 1 features a 3 D heterometallic framework stabilized by bifunctional isonic ligands. In addition, the luminescent and photocatalytic properties of compound 1 were also investigated at room temperature.

Construction of a Photocatalytic Cobalt(Ⅱ) Coordination Polymer with 4-Connected Diamond Topology

A novel cobalt（Ⅱ） coordination polymer, [Co（tdc）（bpmp）（H2O）]n（1）, was hydrothermally synthesized using 2,5-thiophenedicarboxylate（tdc） and bis（4-pyridylmethyl）piperazine（bpmp） ligand as the organic linkers. X-ray single-crystal diffraction determination reveals that 1 crystallizes in the monoclinic Cc space group, with a = 18.836（2）, b = 5.9540（7）, c = 20.414（2） A, β = 97.4300（10）°, V = 2270.1（5） A3, Z = 4, Mr = 515.44, Dc = 1.508 Mg/m^3, μ = 0.890 mm-1, F（000） = 1068, the final R = 0.0263 and w R = 0.0665 for 3714 observed reflections with I 2σ（I）. In compound 1, the Co（Ⅱ） ions are connected by tdc2- anions to form a 1D double chain, and such chains are further linked by bpmp ligands to form a three-dimensional（3D） structure. Topologically, the structure of 1 represents a uninodal 3D dia（6^6） topology. What＇s more, powder X-ray diffraction patterns and photocatalytic property for 1 have also been investigated.

One-step hydrothermal synthesis of Sn-doped α-Fe_(2)O_(3) nanoparticles for enhanced photocatalytic degradation of Congo red

We report on the synthesis of Sn-doped hematite nanoparticles(Sn-α-Fe_(2)O_(3) NPs)by the hydrothermal method.The prepared Sn-α-Fe_(2)O_(3) NPs had a highly pure and well crystalline rhombohedral phase with an average particle size of 41.4 nm.The optical properties of as-synthesizedα-Fe_(2)O_(3) NPs show a higher bandgap energy(2.40-2.57 eV)than that of pure bulkα-Fe_(2)O_(3)(2.1 eV).By doping Sn intoα-Fe_(2)O_(3) NPs,the Sn-doped hematite was observed a redshift toward a long wavelength with in-creasing Sn concentration from 0%to 4.0%.The photocatalytic activity of Sn-dopedα-Fe_(2)O_(3) NPs was evaluated by Congo red(CR)dye degradation.The degradation efficiency of CR dye using Sn-α-Fe_(2)O_(3) NPs catalyst is higher than that of pureα-Fe_(2)O_(3) NPs.The highest degradation efficiency of CR dye was 97.8%using 2.5%Sn-dopedα-Fe_(2)O_(3) NPs catalyst under visible-light irradi-ation.These results suggest that the synthesized Sn-dopedα-Fe_(2)O_(3) nanoparticles might be a suitable approach to develop a photocatalytic degradation of toxic inorganic dye in wastewater.

Study of Photocatalytic Activity of a Nanostructured Composite of ZnS and Carbon Dots

Environmental pollution jeopardizes our existence. For this purpose, research is moving more and more towards the search for economic means and green chemistry to curb this phenomenon. In this context, the photocatalytic activity of zinc sulfide nanoparticles (ZnS NPs) and nanostructured composite ZnS/carbon dots (ZnS/CDs) was evaluated after their synthesis. The results of X-ray diffraction (XRD) analysis indicate that the crystal structure of ZnS/CDs is identical to that of the cubic phase structure of ZnS, revealing that the cubic phase structure of ZnS was not altered in the presence of CDs. Indeed, there is no additional peak in the crystal structure of ZnS/CDs, revealing that the crystalline structure of ZnS is not responsible for the difference in photocatalytic activity between ZnS/CDs and ZnS NPs. Moreover, analysis performed by transmission electron microscopy (TEM) shows aggregation of the synthesized ZnS and ZnS/CDs nanoparticles with an average size estimated around 10 nm and 12 nm, respectively. In addition, the reflectance study in the visible range shows a reduction in the sunlight reflection intensity using ZnS/CDs compared to the capability of ZnS NPs. Photocatalytic degradation tests reveal that ZnS/CDs have the best methylene blue (MB) degradation rate. Indeed, under the optimal conditions, the photocatalytic activity can reach 100% efficiency within 100 min and 240 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnS/CDs and ZnS, respectively. This improvement in photocatalytic activity of ZnS/CDs may be due to the presence of CDs which can permit to undergo a reduction of reflection properties of ZnS NPs in the visible range. These results show that CDs can play a key role in enhancing the photocatalytic activity of ZnS, and suggest that ZnS/CDs could be used as eco-friendly composite materials for the degradation of organic pollutants of similar structures in the aquatic environment under solar irradiation.

Photoelectrocatalytic principles for meaningfully studying photocatalyst properties and photocatalysis processes:From fundamental theory to environmental applications

Photocatalysis is critically important for environmental remediation and renewable energy technologies.The ability to objectively characterize photocatalyst properties and photocatalysis processes is paramount for meaningful performance evaluation and fundamental studies to guide the design and development of high-performance photocatalysts and photocatalysis systems.Photocatalysis is essentially an electron transfer process,and photoelectrocatalysis(PEC)principles can be used to directly quantify transferred electrons to determine the intrinsic properties of photocatalysts and photocatalysis processes in isolation,without interference from counter reactions due to physically separated oxidation and reduction half-reactions.In this review,we discuss emphatically the PEC-based principles for characterizing intrinsic properties of photocatalysts and important processes of photocatalysis,with a particular focus on their environmental applications in the degradation of pollutants,disinfection,and detection of chemical oxygen demand(COD).An outlook towards the potential applications of PEC technique is given.