Novel Z-Scheme ZnIn2S4-based photocatalysts for solar-driven environmental and energy applications:Progress and perspectives

Benefiting from strong redox ability,improved charge transport,and enhanced charge separation,Z-scheme heterostructures of ZnIn2S4 based photocatalysts have received considerable interest to tackle energy needs and environmental issues.The present review highlights the properties of ZnIn2S4 which make it a promising photocatalyst,and a suitable combination with oxidation photocatalyst to form Z-scheme,leading to improve their photocatalytic properties dramatically.As the central part of this review,various types of Z-scheme heterojunction developed recently based on ZnIn2S4 and their application in pollutant degradation,water splitting,CO2 reduction,and toxic metals remediation.Some analytical techniques to detect or trap the active radical and study the charge separation and lifetime of charge carriers in these Z-schemes are highlighted.This review offers its readers a broad optical window for the structural architecture of ZnIn2S4-based Z-schemes,photocatalytic activity,stability,and their tech-nological applications.Finally,we discuss the challenges and opportunities for further development on Z-Scheme ZnIn2S4-based photocatalysts toward energy and environmental applications based on the recent progress.     

Facile construction of highly efficient MOF-based Pd@UiO-66-NH2@ZnIn2S4 flower-like nanocomposites for visible-light-driven photocatalytic hydrogen production

Construction of metal-organic-frameworks-based composite photocatalysts has attracted much atten-tion for the reasonable band gap and high surface areas to improve the photocatalytic activity.In this study,the ternary heterojunction Pd@UiO-66-NH2@Znln2S4 nanocomposites were facilely prepared for the first time by a two-step method.The visible-light-promoted hydrogen production rate of 0.3％ Pd@UiO-66-NH2@Znln2S4 reaches up to 5.26 mmol g-1 h-1,which is evidently much higher than pure UiO-66-NH2,ZnIn2S4 and binary UiO-66-NH2/ZnIn2S4 composites.Such a huge improvement in the pho-tocatalytic performance is mainly attributed to the matched band gap of ZnIn2S4 and UiO-66-NH2,and the introduction of Pd NPs into photocatalysts that broaden spectral response range and promote the photon induced charge carrier separation.This work may provide a feasible approach for the design and construction of metal-organic-frameworks-based photocatalytic materials.     

Porous SnIn4S8 microspheres in a new polymorph that promotes dyes degradation under visible light irradiation

Porous SnIn(4)S(8) microspheres were initially synthesized through a facile solvothermal approach and were investigated as visible-light driven photocatalysts for dyes degradation in polluted water. The photocatalysts were characterized by XRD, SEM, TEM, N(2) adsorption-desorption, and UV-vis diffuse reflectance techniques. Results demonstrated that the as-synthesized SnIn(4)S(8) was of a new tetragonal polymorph, showing a band-gap of 2.5 eV, a specific surface area of 197 m(2) g(-1), and an accessible porous structure as well. The photocatalytic activity of the porous SnIn(4)S(8) was evaluated by decomposition of several typical organic dyes including methyl orange, rhodamine B, and methylene blue in aqueous solution under visible light irradiation. It is demonstrated that porous SnIn(4)S(8) was highly photoactive and stable for dyes degradation, showing photocatalytic activity much higher than binary constituent sulfides like In(2)S(3), SnS(2), or even ternary chalcogenide ZnIn(2)S(4) photocatalyst. The excellent photocatalytic performance of porous SnIn(4)S(8) is the consequence of its high surface area, well-defined porous texture, and large amount of hydroxyl radicals.     

Nanocrystalline zinc indium vanadate: a novel photocatalyst for hydrogen generation

Hydrogen is a future fuel and hence production of cheap hydrogen is an important area of research. Recently, the photocatalysts were used to generate hydrogen from water and hydrogen sulfide splitting under solar light. Hence, we designed Zinc Indium Vanadate, a novel visible light active photocatalyst and used for the generation of hydrogen by using solar light. We have demonstrated the synthesis of ZnIn2V2O9 (ZIV) catalyst by sonochemical route using NH4VO3, In (NO3)3 and Zn(CH3COO)2 as a precursors and PVP as a capping agent. The obtained product was further characterized by XRD, UV-DRS and FESEM. The XRD pattern reveals the existence of monoclinic crystal structure and broader peaks indicating the nanocrystalline nature of the material. The particle size was observed in the range of 50-70 nm. The optical study showed the absorption edge cut off at 520 nm with estimated band gap about 2.3 eV. Considering the band gap in visible range, ZnIn2V2O9 was used as a photocatalyst for photodecomposition of H2S under visible light irradiation to produce hydrogen. We observed excellent photocatalytic activity for the hydrogen generation by using this photocatalyst.     

Solvothermal Synthesis and Characterization of Zinc Indium Sulfide Microspheres

ZnIn2S4 microspheres have been solvothermally prepared at 160℃ for 12 h with ZnCl2.2H2O,InCl3,and thiourea as the starting reagents in ethanol.The morphology,structure,and phase composition of the asprepared product were characterized by means of X-ray powder diffraction(XRD),field-emission scanning electron microscopy(FE-SEM),X-ray photoelectron spectra(XPS),transmission electron microscopy(TEM),high-resolution TEM(HRTEM),and selected area electron diffraction(SAED).Results revealed that the prepared ZnIn2S4 microspheres were composed of sheetlike nanocrystals.The average diameter of the microspheres and the thickness of the nanosheets are about 1-6 μm and 10-50 nm,respectively.A possible growth mechanism of the ZnIn2S4 nanosheet-built microspheres was proposed and briefly discussed.     

Recent Progress in Metal‐Free Covalent Organic Frameworks as Heterogeneous Catalysts

Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with conventional porous materials such as inorganic zeolite, active carbon, and metal‐organic frameworks, COFs are a new type of porous materials with well‐designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal‐free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF‐based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.     

具有近红外吸收的二维/三维ZnIn2S4/氮掺杂石墨烯光催化剂的制备及其高效CO2捕获和光催化还原性能（英文）

具有宽光谱太阳能利用的分等级异质结光催化剂,正成为一种新兴的先进光催化材料,被应用于太阳能驱动二氧化碳转化为高附加值的化学原料.本工作通过水热法使二维硫化铟锌纳米墙垂直生长于三维氮掺杂石墨烯泡沫上,形成分等级异质结光催化剂.该催化剂展现出优异的光热转换效率、选择性捕获CO2和光催化还原CO2的能力.在273 K和1个大气压条件下,负载1 wt%氮掺杂石墨烯泡沫的复合催化剂表现出最优异的性能,其中对CO2和N2的吸附选择性为30.1,并且对CO2的等量吸附热为48.2 kJ mol^-1.在无助催化剂和牺牲剂的条件下,负载1 wt%氮掺杂石墨烯泡沫的复合催化剂,其光催化转化CO2为CH4、CO和CH3OH的效率分别是纯的硫化铟锌的9.1、3.5和5.9倍.该增强效应得益于三维石墨烯泡沫高度开放的网状结构,良好的CO2吸附能力和两种组份之间的强相互作用.此外,利用原位照射X射线光电子能谱仪和开尔文探针技术分析了电荷转移的方向,本工作为设计高效太阳能转化分等级异质结光催化剂开辟了新的思路.     

用于光催化的金属氧化物多孔材料的研究进展

金属氧化物材料的多孔化制备受到越来越多的关注,由于其大的比表面积、较多的活性位点、便于物质传输的双连续结构等特点,在环境保护、能源、精细化工等各个领域得到广泛的应用。本文综述了几种多孔金属氧化物材料(二氧化钛、铋系半导体、氧化锌、氧化亚铜等)在光催化领域的最新研究进展,分析了多孔氧化物的制备工艺、生长机理、光催化性能,最后对多孔氧化物材料的制备、改性及光催化性能进行了总结,并对未来的发展方向进行了展望。     

Phosphorene-Based Heterostructured Photocatalysts

Semiconductor photocatalysis is a potential pathway to solve the problems of global energy shortage and environmental pollution. Black phosphorus (BP) has been widely used in the field of photocatalysis owing to its features of high hole mobility, adjustable bandgap, and wide optical absorption range. Nevertheless, pristine BP still exhibits unsatisfactory photocatalytic activity due to the low separation efficiency of photoinduced charge carriers. In recent years, the construction of heterostructured photocatalysts based on BP has become a research hotspot in photocatalysis with the remarkable improvement of photoexcited charge-separation efficiency. Herein, progress on the design, synthesis, properties, and applications of BP and its corresponding heterostructured photocatalysts is summarized. Furthermore, the photocatalytic applications of BP-based heterostructured photocatalysts in water splitting, pollutant degradation, carbon dioxide reduction, nitrogen fixation, bacterial disinfection, and organic synthesis are reviewed. Opportunities and challenges for the exploration of advanced BP-based heterostructured photocatalysts are presented. This review will promote the development and applications of BP-based heterostructured photocatalysts in energy conversion and environmental remediation.     

g-C3N4基异质耦合光催化剂制备及在环境污染物去除领域的研究进展

石墨相氮化碳(g-C₃N₄)作为一种可见光响应型半导体材料,具有稳定性高、廉价、结构与性能可调控性高等优点。随着绿色环保、无二次污染的光催化技术的不断发展,g-C₃N₄光催化剂逐渐成为环境与能源科学领域的研究热点。而单一的g-C₃N₄存在光激发电子-空穴复合过快、可见光的利用率低等缺陷导致其光催化效率较低。在众多的改性方法中,异质耦合被认为是提高g-C₃N₄光催化性能的有效方法。近年来,研究者通过将不同的无机半导体、贵金属、碳材料等与g-C₃N₄进行异质耦合,提高了光电子在光催化体系中的转移效率,拓宽了g-C₃N₄基光催化剂对可见光的吸收范围,并且增强了g-C₃N₄催化剂稳定性与结构的可调控。本文总结了异质耦合光催化剂的催化机理,综述了以g-C₃N₄为基础的异质耦合光催化体系的构建,探讨了g-C₃N₄基异质结在处理环境污染物中的研究进展。最后,对如何设计性能优异的g-C₃N₄基光催化剂及在光催化降解染料、有机污染物以及有毒重金属等研究方向的发展提出展望。     

Graphene in Photocatalysis: A Review

In recent years, heterogeneous photocatalysis has received much research interest because of its powerful potential applications in tackling many important energy and environmental challenges at a global level in an economically sustainable manner. Due to their unique optical, electrical, and physicochemical properties, various 2D graphene nanosheets‐supported semiconductor composite photocatalysts have been widely constructed and applied in different photocatalytic fields. In this review, fundamental mechanisms of heterogeneous photocatalysis, including thermodynamic and kinetics requirements, are first systematically summarized. Then, the photocatalysis‐related properties of graphene and its derivatives, and design rules and synthesis methods of graphene‐based composites are highlighted. Importantly, different design strategies, including doping and sensitization of semiconductors by graphene, improving electrical conductivity of graphene, increasing eloectrocatalytic active sites on graphene, strengthening interface coupling between semiconductors and graphene, fabricating micro/nano architectures, constructing multi‐junction nanocomposites, enhancing photostability of semiconductors, and utilizing the synergistic effect of various modification strategies, are thoroughly summarized. The important applications including photocatalytic pollutant degradation, H₂ production, and CO₂ reduction are also addressed. Through reviewing the significant advances on this topic, it may provide new opportunities for designing highly efficient 2D graphene‐based photocatalysts for various applications in photocatalysis and other fields, such as solar cells, thermal catalysis, separation, and purification.     

纳米异质结光催化材料制取太阳能燃料研究进展

光催化制取太阳能燃料主要包括光催化分解H₂O制取H₂及光催化还原CO₂制取碳氢化合物, 是应对能源危机最具前景的方法之一。目前, 太阳能燃料的最高转化效率为5%, 无法满足商业化要求(≥10%)。纳米异质结由于能展现出单组分纳米材料或体相异质结所不具备的独特性质, 更能促进光生电子和空穴快速转移, 提供更多的光生电子或使光生电子具有更强的还原性, 因而能显著提高光催化活性。本文主要综述了几种纳米异质结(I-型、II-型、p-n型及Z-型)的光催化原理及其在制取太阳能燃料方面的研究进展, 并展望了研究发展方向。     

离子掺杂改性TiO2光催化剂的理论研究进展

光催化技术是一种治理环境污染的新技术,但由于存在2个瓶颈问题(光催化活性需要紫外光激发及量子转换效率低)而制约了其推广应用。围绕上述问题,国内外开展了大量的改性研究并取得了一定的成果,尤其是近年来开始重视该方面的理论研究,这对推动光催化技术的发展起到了重要作用。介绍了本课题组及文献报道的对离子掺杂锐钛矿相TiO2光催化材料理论研究方面取得的主要结果,总结了不同离子掺杂及共掺杂对TiO2晶体结构、电子结构、光学性质和光催化性能的影响规律,提出了如何选择合适的掺杂离子以便有效地提高TiO2光催化性能的方法。     

Strategies for Improving the Photocatalytic Hydrogen Evolution Reaction of Carbon Nitride-Based Catalysts

Due to the depletion of fossil fuels and their-related environmental issues, sustainable, clean, and renewable energy is urgently needed to replace fossil fuel as the primary energy resource. Hydrogen is considered as one of the cleanest energies. Among the approaches to hydrogen production, photocatalysis is the most sustainable and renewable solar energy technique. Considering the low cost of fabrication, earth abundance, appropriate bandgap, and high performance, carbon nitride has attracted extensive attention as the catalyst for photocatalytic hydrogen production in the last two decades. In this review, the carbon nitride-based photocatalytic hydrogen production system, including the catalytic mechanism and the strategies for improving the photocatalytic performance is discussed. According to the photocatalytic processes, the strengthened mechanism of carbon nitride-based catalysts is particularly described in terms of boosting the excitation of electrons and holes, suppressing carriers recombination, and enhancing the utilization efficiency of photon-excited electron–hole. Finally, the current trends related to the screening design of superior photocatalytic hydrogen production systems are outlined, and the development direction of carbon nitride for hydrogen production is clarified.     

太阳能光解水制H2催化剂研究进展

氢气是未来人类社会可持续发展的理想能源,光解水制H2的关键是具有高性能的光催化剂.论述了光解水的机理;综述了近年来有关TiO2、过渡金属氧化物、层状金属氧化物、光生物催化剂以及其它新的复合物在光解水方面的研究进展;讨论了提高其光催化反应活性的途径;对存在的问题和前景进行了展望.     

Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO2 Films

The nanocrystalline S doped titanium dioxide films were successfully prepared by the improved sol-gel process. Here TiO(C₄H₉O)₄ and CS(NH₂)₂ were used as precursors of titania and sulfur, respectively. The as-prepared specimens were characterized using x-ray diffraction (XRD), x-ray energy dispersive spectroscopy (EDS), high-resolution field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) surface area, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of organic dyes in aqueous solution. The results of XRD, FE-SEM, and BET analyses indicated that the TiO₂ films were composed of nanoparticles. S doping could obviously not only suppress the formation of brookite phase but also inhibit the transformation of anatase to rutile at high temperature. Compared with pure TiO₂ film, S doped TiO₂ film exhibited excellent photocatalytic activity. It is believed that the surface microstructure of the modified films is responsible for improving the photocatalytic activity.     

A Review of Phosphorus Structures as CO2 Reduction Photocatalysts

Effective photocatalytic carbon dioxide (CO₂) reduction into high-value-added chemicals is promising to mitigate current energy crisis and global warming issues. Finding effective photocatalysts is crucial for photocatalytic CO₂ reduction. Currently, metal-based semiconductors for photocatalytic CO₂ reduction have been well reviewed, while review of nonmetal-based semiconductors is almost limited to carbon nitrides. Phosphorus is a promising nonmetal photocatalysts with various allotropes and tunable band gaps, which has been demonstrated to be promising non-metallic photocatalysts. However, no systematic review about phosphorus structures for photocatalytic CO₂ reduction reactions has been reported. Herein, the progresses of phosphorus structures as photocatalysts for CO₂ reduction are reviewed. The fundamentals of photocatalytic CO₂ reduction, corresponding properties of phosphorus allotropes, photocatalysts with phosphorus doping or phosphorus-containing ligands, research progress of phosphorus allotropes as photocatalysts for CO₂ reduction have been reviewed in this paper. The future research and perspective of phosphorus structures for photocatalytic CO₂ reduction are also presented.     

TiO2光催化剂的研究与应用进展

为了解决日益严重的环境污染问题和能源问题,越来越多的研究者将精力投入到ZnO、CdS、TiO_2和BiVO_4等半导体材料的研究中。其中,TiO_2以优异的氧化能力、较强的化学稳定性、较低的价格以及无毒性吸引了广泛的目光。针对近年来TiO_2的光催化性能研究及其改性方法的研究进展,以及应用热点进行了综述,并对如何进一步提升其性能进行了展望。     

新型可见光催化剂BiVO4的制备方法

作为一种新型可见光催化剂,钒酸铋（BiVO₄）因为拥有较窄的禁带宽度（2.4eV）以及合适的导带和价带位置在可见光催化领域受到广泛关注,在水的光解以及有机污染物的降解等方面都有研究及应用。不同的制备方法对材料的形貌和结构都有较大的影响,进而影响到光催化剂的光催化性能。综述了国内外BiVO₄的制备方法,并在此基础上展望了该领域的发展方向。     

Hybridized 2D Nanomaterials Toward Highly Efficient Photocatalysis for Degrading Pollutants: Current Status and Future Perspectives

Organic pollutants including industrial dyes and chemicals and agricultural waste have become a major environmental issue in recent years. As an alternative to simple adsorption, photocatalytic decontamination is an efficient and energy‐saving technology to eliminate these pollutants from water environment, utilizing the energy of external light, and unique function of photocatalysts. Having a large specific surface area, numerous active sites, and varied band structures, 2D nanosheets have exhibited promising applications as an efficient photocatalyst for degrading organic pollutants, particularly hybridization with other functional components. The novel hybridization of 2D nanomaterials with various functional species is summarized systematically with emphasis on their enhanced photocatalytic activities and outstanding performances in environmental remediation. First, the mechanism of photocatalytic degradation is given for discussing the advantages/shortcomings of regular 2D materials and identifying the importance of constructing hybrid 2D photocatalysts. An overview of several types of intensively investigated 2D nanomaterials (i.e., graphene, g‐C₃N₄, MoS₂, WO₃, Bi₂O₃, and BiOX) is then given to indicate their hybridized methodologies, synergistic effect, and improved applications in decontamination of organic dyes and other pollutants. Finally, future research directions are rationally suggested based on the current challenges.