Potassium‐Ion‐Assisted Regeneration of Active Cyano Groups in Carbon Nitride Nanoribbons: Visible‐Light‐Driven Photocatalytic Nitrogen Reduction

As a metal‐free nitrogen reduction reaction (NRR) photocatalyst, g‐C₃N₄ is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g‐C₃N₄‐based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g‐C₃N₄ photocatalyst modified with cyano groups and intercalated K⁺ (mCNN), possessing extended visible‐light harvesting capacity and superior photocatalytic NRR activity (NH₃ yield: 3.42 mmol g^?1 h^?1). Experimental and theoretical studies suggest that the ‐C≡N in mCNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K⁺. The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst.     

CoxP/Hollow Porous C3N4 as Highly Efficient Schottky Contact Photocatalyst for H2 Evolution from Water Splitting

Photocatalytic water splitting to obtain hydrogen energy can transform low-density solar to high density, new and clean energy in a clean way, which is one of the ideal ways to solve the energy crisis and environmental pollution. In this paper, The Co_xP/hollow porous C₃N₄ composite photocatalytic material was synthesized by simple methods. The photocatalytic hydrogen production rate of Co_xP/hollow porous C₃N₄ reaches 1602 μmol g⁻¹ h⁻¹, which is 151 times of that of pure C₃N₄. The reasons for the high photocatalytic H₂ evolution activity of Co_xP/hollow porous C₃N₄ could be summarized as follows: (1) the hollow and porous structure of C₃N₄ shows higher light capture efficiency, larger specific surface area and more surface active sites. (2) metalloid Co_xP loaded forms the Schottky contact with C₃N₄, which improves the photogenerated charges separation efficiency of C₃N₄, prolongs the photogenerated charges lifetime and improves the photocatalytic H₂ evolution activity of C₃N₄. (3) The higher conductivity of metalloid Co_xP and the lower overpotential of hydrogen production are other reasons for the higher activity of photocatalytic hydrogen production of Co_xP/hollow porous C₃N₄. This work provides an important role for the design of efficient, stable, and efficient construction of photocatalysts for solar energy conversion.     

Graphitic C3N4 Decorated with CoP Co‐catalyst: Enhanced and Stable Photocatalytic H2 Evolution Activity from Water under Visible‐light Irradiation

In this work, graphitic C₃N₄ decorated with a CoP co‐catalyst (g‐C₃N₄/CoP) is reported for photocatalytic H₂ evolution reaction based on two‐step hydrothermal and phosphidation method. The structure of g‐C₃N₄/CoP is well confirmed by XRD, FTIR, TEM, XPS, and UV/Vis diffuse reflection spectra techniques. When the weight percentage of CoP loading is 3.4 wt % (g‐C₃N₄/CoP‐3.4 %), the highest H₂ evolution amount of 8.4×10² μmol g⁻¹ is obtained, which is 1.1×10³ times than that over pure g‐C₃N₄. This value also is comparable with that of g‐C₃N₄ loaded by the same amount of Pt. In cycling experiments, g‐C₃N₄/CoP‐3.4 % shows a stable photocatalytic activity. In addition, g‐C₃N₄/CoP‐3.4 % is an efficient photocatalyst for H₂ evolution under irradiation with natural solar light. Based on comparative photoluminescence emission spectra, photoelectrochemical I –t curves, EIS Nyquist plots, and polarization curves between g‐C₃N₄/CoP‐3.4 % and pure g‐C₃N₄, it is concluded that the presence of the CoP co‐catalyst accelerates the separation and transfer of photogenerated electrons of g‐C₃N₄, thus resulting in improved photocatalytic activity in the H₂ evolution reaction.     

氰基修饰石墨相氮化碳构建高效的活性位点用于光催化还原CO2

作为影响光催化反应的关键因素,光催化剂的活性位点数量直接决定了光催化活性.传统石墨相氮化碳(g-C3N4)由于活性位点不足而表现出较弱的光催化活性.为了增加g-C3N4的活性位点数量,研究人员采取了各种策略,包括杂原子掺杂、表面改性和空位工程.其中,表面改性是增加催化剂活性位点的有效策略之一.氰基具有很强的吸电子能力,可在光催化反应中作为活性位点.然而,关于氰基作为CO2光还原活性位点的研究并不多,特别是对于氰基修饰增强g-C3N4活性的机理尚不清楚.构建多孔结构是暴露催化剂活性位点的有效措施之一.多孔结构可以有效改善纳米片的团聚,促进活性位点暴露,增大反应物与活性位点间的接触机会;并且相互连接的多孔网络可形成独特的传输通道,进一步促进载流子迁移.本文通过分子自组装和碱辅助策略合成了氰基改性的多孔g-C3N4纳米片(MCN-0.5).氰基由于具有良好的吸电子特性,促进了局部载流子分离,并充当了光催化反应的活性位点.受益于活性位点的影响,MCN-0.5表现出显著增强的光催化CO2还原活性.在不添加牺牲剂和助催化剂的条件下,MCN-0.5样品上CO和CH4产率达到13.7和0.6μmol·h–1·g–1,分别是传统煅烧法制备的g-C3N4(TCN)产生CO和CH4产率的2.5和2倍.通过盐酸处理MCN-0.5除去氰基,并没有破坏样品的形貌结构,但催化剂的光催化活性显著降低,证实了氰基活性位点的作用.光还原Pt纳米颗粒的实验结果表明,与对照样品相比,氰基修饰的样品上还原的Pt纳米颗粒更多,进一步证实了引入氰基为光还原反应提供了更多活性位点.CO2等温吸附测试结果表明,MCN-0.5对CO2的吸附能力不如对照样品,间接证明氰基能成为活性位点是由于其良好的吸电子能力促进了局部载流子分离.瞬态荧光光谱、光电化学表征结果表明,氰基修饰增强了载流子迁移和分离能力.根据理论计算和原位红外光谱提出了氰基修饰增强g-C3N4光催化还原CO2活性的作用机理.以三聚氰胺为前驱体接枝氰基的g-C3N4也表现出比体相g-C3N4明显增强的光催化还原CO2活性,这证明了氰基改性增强g-C3N4活性策略的通用性.本文通过在光催化剂材料中设计活性位点为太阳能高效转化提供了一个有效途径.     

Construction of a 2D Graphene‐Like MoS2/C3N4 Heterojunction with Enhanced Visible‐Light Photocatalytic Activity and Photoelectrochemical Activity

A novel graphene‐like MoS₂/C₃N₄ (GL‐MoS₂/C₃N₄) composite photocatalyst has been synthesized by a facile ethylene glycol (EG)‐assisted solvothermal method. The structure and morphology of this GL‐MoS₂/C₃N₄ photocatalyst have been investigated by a wide range of characterization methods. The results showed that GL‐MoS₂ was uniformly distributed on the surface of GL‐C₃N₄ forming a heterostructure. The obtained composite exhibited strong absorbing ability in the ultraviolet (UV) and visible regions. When irradiated with visible light, the composite photocatalyst showed high activity superior to those of the respective individual components GL‐MoS₂ and GL‐C₃N₄ in the degradation of methyl orange. The enhanced photocatalytic activity of the composite may be attributed to the efficient separation of electron–hole pairs as a result of the matching band potentials between GL‐MoS₂ and GL‐C₃N₄. Furthermore, a photocatalytic mechanism for the composite material has been proposed, and the photocatalytic reaction kinetics has been measured. Moreover, GL‐MoS₂/C₃N₄ could serve as a novel sensor for trace amounts of Cu²⁺ since it exhibited good selectivity for Cu²⁺ detection in water.     

氰基修饰石墨相氮化碳构建高效的活性位点用于光催化还原CO2

作为影响光催化反应的关键因素,光催化剂的活性位点数量直接决定了光催化活性.传统石墨相氮化碳(g-C3N4)由于活性位点不足而表现出较弱的光催化活性.为了增加g-C3N4的活性位点数量,研究人员采取了各种策略,包括杂原子掺杂、表面改性和空位工程.其中,表面改性是增加催化剂活性位点的有效策略之一.氰基具有很强的吸电子能力,可在光催化反应中作为活性位点.然而,关于氰基作为CO2光还原活性位点的研究并不多,特别是对于氰基修饰增强g-C3N4活性的机理尚不清楚.构建多孔结构是暴露催化剂活性位点的有效措施之一.多孔结构可以有效改善纳米片的团聚,促进活性位点暴露,增大反应物与活性位点间的接触机会;并且相互连接的多孔网络可形成独特的传输通道,进一步促进载流子迁移.本文通过分子自组装和碱辅助策略合成了氰基改性的多孔g-C3N4纳米片(MCN-0.5).氰基由于具有良好的吸电子特性,促进了局部载流子分离,并充当了光催化反应的活性位点.受益于活性位点的影响,MCN-0.5表现出显著增强的光催化CO2还原活性.在不添加牺牲剂和助催化剂的条件下,MCN-0.5样品上CO和CH4产率达到13.7和0.6μmol·h–1·g–1,分别是传统煅烧法制备的g-C3N4(TCN)产生CO和CH4产率的2.5和2倍.通过盐酸处理MCN-0.5除去氰基,并没有破坏样品的形貌结构,但催化剂的光催化活性显著降低,证实了氰基活性位点的作用.光还原Pt纳米颗粒的实验结果表明,与对照样品相比,氰基修饰的样品上还原的Pt纳米颗粒更多,进一步证实了引入氰基为光还原反应提供了更多活性位点.CO2等温吸附测试结果表明,MCN-0.5对CO2的吸附能力不如对照样品,间接证明氰基能成为活性位点是由于其良好的吸电子能力促进了局部载流子分离.瞬态荧光光谱、光电化学表征结果表明,氰基修饰增强了载流子迁移和分离能力.根据理论计算和原位红外光谱提出了氰基修饰增强g-C3N4光催化还原CO2活性的作用机理.以三聚氰胺为前驱体接枝氰基的g-C3N4也表现出比体相g-C3N4明显增强的光催化还原CO2活性,这证明了氰基改性增强g-C3N4活性策略的通用性.本文通过在光催化剂材料中设计活性位点为太阳能高效转化提供了一个有效途径.     

Cost‐Efficient Graphitic Carbon Nitride as an Effective Photocatalyst for Antibiotic Degradation: An Insight into the Effects of Different Precursors and Coexisting Ions,and Photocatalytic Mechanism

In this study, the photocatalytic activity of graphitic carbon nitride (g‐C₃N₄) synthesized via different precursors (urea, thiourea, and dicyandiamide) is investigated in the degradation process of tetracycline. Owing to the efficient charge separation and transfer, prolonged radiative lifetime of charge, large surface area, and nanosheet morphology, the urea‐derived g‐C₃N₄ exhibits superior photocatalytic activity for tetracycline degradation under visible‐light irradiation. This performance can compare with that of most reported g‐C₃N₄‐based composite photocatalysts. Through the time‐circle degradation experiment, the urea‐derived g‐C₃N₄ is found to have an excellent photocatalytic stability. The presence of NO₃^?, CH₃COO^?, Cl^? and SO₄^2? ions with the concentration of 10 mm inhibits the photocatalytic activity of urea‐derived g‐C₃N₄, where this inhibitory effect is more obvious for Cl^? and SO₄^2? ions. For the coexisting Cu²⁺, Ca²⁺, and Zn²⁺ ions, the Cu²⁺ ion exhibits a significantly higher inhibitory effect than Ca²⁺ and Zn²⁺ ions for tetracycline degradation. However, both the inhibitory and facilitating effects are observed in the presence of Fe³⁺ ion with different concentration. The h⁺, ^.OH and ^.O₂^? radicals are confirmed as major oxidation species and a possible photocatalytic mechanism is proposed in a urea‐derived g‐C₃N₄ reaction system. This study is of important significance to promote the large‐scale application of g‐C₃N₄ photocatalysts in antibiotic wastewater purification.     

Ultrathin g‐C3N4 Nanosheets Coupled with AgIO3 as Highly Efficient Heterostructured Photocatalysts for Enhanced Visible‐Light Photocatalytic Activity

The photocatalytic activity of graphite‐like carbon nitride (g‐C₃N₄) could be enhanced by heterojunction strategies through increasing the charge‐separation efficiency. As a surface‐based process, the heterogeneous photocatalytic process would become more efficient if a larger contact region existed in the heterojunction interface. In this work, ultrathin g‐C₃N₄ nanosheets (g‐C₃N₄‐NS) with much larger specific surface areas are employed instead of bulk g‐C₃N₄ (g‐C₃N₄‐B) to prepare AgIO₃/g‐C₃N₄‐NS nanocomposite photocatalysts. By taking advantage of this feature, the as‐prepared composites exhibit remarkable performances for photocatalytic wastewater treatment under visible‐light irradiation. Notably, the optimum photocatalytic activity of AgIO₃/g‐C₃N₄‐NS composites is almost 80.59 and 55.09 times higher than that of pure g‐C₃N₄‐B towards the degradation of rhodamine B and methyl orange pollutants, respectively. Finally, the stability and possible photocatalytic mechanism of the AgIO₃/g‐C₃N₄‐NS system are also investigated.     

Synergistic effects of sulfation and Fe-doping on the photocatalysis of titania

Fe-doped sulfated titania photocatalysts were prepared by one-step thermal hydrolysis of industrial titanyl sulfate and characterized using XRD, FT-IR, UV–Vis DRS, and N₂ adsorption–desorption techniques. The effects of the volume ratio of pre-adding water to TiOSO₄ on the structure of the titania photocatalysts were investigated. The photocatalytic activities of Fe-doped sulfated titania samples were evaluated using the photooxidation of methylene blue in aqueous solutions under UV light irradiation. The results indicate that Fe-doping induces the red shift of the absorption edge to the visible light range. Meanwhile, sulfur species in the form of sulfate are incorporated into the network of Ti–O–Ti and coordinated to titania in bidentate models, which can effectively promote the separation of the photogenerated electrons and holes. Synergistic effects of both are beneficial for improving the photocatalytic activity of the Fe-doped sulfated titania photocatalysts.     

Facile fabrication of g‐C3N4/MIL‐53(Al) composite with enhanced photocatalytic activities under visible‐light irradiation

A novel visible‐light‐driven g‐C₃N₄/MIL‐53(Al) composite photocatalyst was successfully prepared using a facile stirring method at room temperature. The g‐C₃N₄/MIL‐53(Al) composites were characterized and their effects on the photocatalytic activities for rhodamine B degradation were investigated. The g‐C₃N₄(20 wt%)/MIL‐53(Al) photocatalyst displayed optimal photocatalytic degradation efficiency, which was about five times higher than the photocatalytic activity of pure g‐C₃N₄. The improved photocatalytic performance of the g‐C₃N₄/MIL‐53(Al) photocatalyst was predominantly attributed to the efficient separation of electron–hole pairs and the low charge‐transfer resistance. g‐C₃N₄/MIL‐53(Al) also exhibited excellent stability and reusability. A proposed mechanism for the enhanced photocatalytic activity is also discussed based on the experimental results. Copyright © 2015 John Wiley & Sons, Ltd.     

A simple and rapid route for synthesizing the nanosized g-C3N4 materials with narrow bandgap and their photocatalytic activity

The graphitic carbon nitride (g-C₃N₄) materials with many intriguing properties have attracted much attention in photocatalysis. The photocatalytic activity of g-C₃N₄ is hindered by serious aggregation and limited exposed active sites. Herein is shown that nanosized g-C₃N₄ can be simply obtained by a superfast high-pressure homogenization approach. The high-pressure homogenization treatment can provide strong force to cut and/or to exfoliate the bulk g-C₃N₄ into nanosized g-C₃N₄ with good dispersion. Moreover, choosing different solvents during treatment can cause a different surface structure of as-prepared nanosized g-C₃N₄. In addition, the narrow bandgap properties, the high photogenerated charge carrier separation, and the transport abilities are achieved in as-prepared nanosized g-C₃N₄ because of the retaining conjugated C₃N₄ system. Specifically, the photocatalytic activities of as-prepared nanosized g-C₃N₄ have been significantly enhanced in terms of degradation of organic dye Rhodamine B (RhB) under visible light irradiation (10 times higher than that of bulk g-C₃N₄). These findings can provide a promising and simple approach to the exfoliation, nanonization, and surface functionalization of 2D layered materials.     

Ni(bipy)2Ni(CN)4, a new type of one‐dimensional square tetra­cyano complex

The one‐dimensional structure of catena‐poly­[[bis(2,2′‐bi­pyri­dyl‐1κ²N,N′)‐μ‐cyano‐1:2κ²N:C‐di­cyano‐2κ²C‐di­nickel(II)]‐μ‐cyano‐C:N], [Ni₂(CN)₄(C₁₀H₈N₂)₂]_n, consists of infinite zigzag chains running parallel to the c axis. The chains are composed of paramagnetic [Ni(bipy)₂]²⁺ cations (bricks; nickel on a twofold axis) linked by diamagnetic [Ni(CN)₄]^2? anions (mortar; nickel on an inversion center) via bridging cyano groups. The bridging cyano groups occupy cis positions in the cation and trans positions in the anion, giving rise to a new previously unknown CT‐type chain (i.e. cis–trans‐type) among square tetra­cyano complexes. The coordination polyhedron of the paramagnetic Ni atom (twofold symmetry) is a slightly deformed octahedron with the two Ni—N(bipy) bonds in cis positions being somewhat longer [2.112 (3) Å] than the remaining four Ni—N bonds with a mean value of 2.065 (6) Å. The bond distances and angles in the anion have typical values.     

Preparation of Er3+:YAlO3/Fe-doped ZnO composite and investigation on solar light photocatalytic degradation of organic dyes

The Er³⁺:YAlO₃/Fe-doped ZnO composite, a new photocatalyst which could effectively utilize visible light, was prepared. In succession, the Er³⁺:YAlO₃/Fe-doped ZnO was characterized by XRD and SEM, respectively. Acid Red B dyes, was degraded under solar light irradiation to evaluate the photocatalytic activity of the Er³⁺:YAlO₃/Fe-doped ZnO. In addition, the effects of Er³⁺:YAlO₃ content, heat-treatment temperature and time on the photocatalytic activity of Er³⁺:YAlO₃/Fe-doped ZnO were reviewed. Otherwise, the effect of initial dye concentration, Er³⁺:YAlO₃/Fe-doped ZnO amount and solar light irradiation time on the photocatalytic degradation of Acid Red B were also investigated. It was found that the photocatalytic activity of Er³⁺:YAlO₃/Fe-doped ZnO is much higher than that of Fe-doped ZnO and pure ZnO for the similar system. Perhaps, the use of the Er³⁺:YAlO₃/Fe-doped ZnO may provide a new way to take advantage of ZnO in sewage treatment aspects using solar energy.     

3‐Cyano‐6‐hydroxy‐4‐methyl‐2‐pyridone: two new pseudopolymorphs and two cocrystals with products of an in situ nucleophilic aromatic substitution

Four crystal structures of 3‐cyano‐6‐hydroxy‐4‐methyl‐2‐pyridone (CMP), viz. the dimethyl sulfoxide monosolvate, C₇H₆N₂O₂·C₂H₆OS, (1), the N,N‐dimethylacetamide monosolvate, C₇H₆N₂O₂·C₄H₉NO, (2), a cocrystal with 2‐amino‐4‐dimethylamino‐6‐methylpyrimidine (as the salt 2‐amino‐4‐dimethylamino‐6‐methylpyrimidin‐1‐ium 5‐cyano‐4‐methyl‐6‐oxo‐1,6‐dihydropyridin‐2‐olate), C₇H₁₃N₄⁺·C₇H₅N₂O₂⁻, (3), and a cocrystal with N,N‐dimethylacetamide and 4,6‐diamino‐2‐dimethylamino‐1,3,5‐triazine [as the solvated salt 2,6‐diamino‐4‐dimethylamino‐1,3,5‐triazin‐1‐ium 5‐cyano‐4‐methyl‐6‐oxo‐1,6‐dihydropyridin‐2‐olate–N,N‐dimethylacetamide (1/1)], C₅H₁₁N₆⁺·C₇H₅N₂O₂⁻·C₄H₉NO, (4), are reported. Solvates (1) and (2) both contain the hydroxy group in a para position with respect to the cyano group of CMP, acting as a hydrogen‐bond donor and leading to rather similar packing motifs. In cocrystals (3) and (4), hydrolysis of the solvent molecules occurs and an in situ nucleophilic aromatic substitution of a Cl atom with a dimethylamino group has taken place. Within all four structures, an R₂²(8) N—H...O hydrogen‐bonding pattern is observed, connecting the CMP molecules, but the pattern differs depending on which O atom participates in the motif, either the ortho or para O atom with respect to the cyano group. Solvents and coformers are attached to these arrangements via single‐point O—H...O interactions in (1) and (2) or by additional R₄⁴(16) hydrogen‐bonding patterns in (3) and (4). Since the in situ nucleophilic aromatic substitution of the coformers occurs, the possible Watson–Crick C–G base‐pair‐like arrangement is inhibited, yet the cyano group of the CMP molecules participates in hydrogen bonds with their coformers, influencing the crystal packing to form chains.     

Facile one‐step synthesis of broken case‐like carbon‐doped g‐C3N4 for photocatalytic degradation of benzene

Herein, a novel broken case‐like carbon‐doped g‐C₃N₄ photocatalyst was obtained via a facile one‐pot pyrolysis and cost‐effective method using glyoxal‐modified melamine as a precursor. The obtained carbon/g‐C₃N₄ photocatalyst showed remarkable enhanced photocatalytic activity in the degradation of gaseous benzene compared with that of pristine g‐C₃N₄ under visible light. The pseudo‐first‐order rate constant for gaseous benzene degradation on carbon/g‐C₃N₄ was 0.186 hr^?1, 5.81 times as large as that of pristine g‐C₃N₄. Furthermore, a possible photocatalytic mechanism for the improved photocatalytic performance over carbon/g‐C₃N₄ nanocomposites was proposed.     

多级Ag/Bi/氮空位g-C3N4/Ti3C2Tx肖特基结的构筑及其全光谱催化性能

采用原位溶剂热反应制备多级 Ag/Bi/Nv-g-C₃N₄(氮空位-g-C₃N₄)/Ti₃C₂T_x肖特基结, 并对其物相组成和晶体结构、微观形貌和孔结构、表面元素组成和化学态、光学和光电化学性质进行了表征。由于 Ag、Bi和 Ti₃C₂T_x协同的表面等离激元共振效应,Ag/Bi/Nv-g-C₃N₄/Ti₃C₂T_x表现出全光谱吸收特性。由载流子浓度差驱动的界面极化电荷转移诱导形成的肖特基结, 显著提高了光生载流子(包括热电子和热空穴)的分离效率和利用率。因此, 与 Nv-g-C₃N₄、Ti₃C₂T_x、Ag/Nv-g-C₃N₄、Bi/Nv-g-C₃N₄和 Ag/Bi/Nv-g-C₃N₄相比, Ag/Bi/Nv-g-C₃N₄/Ti₃C₂T_x表现出显著增强的全光谱催化活性, 其在可见光和近红外光照射下光催化降解四环素的反应速率常数分别为 0.033和 0.008 6 min^-1, 为对比样品的 10~2.1倍和 8.6~1.8倍。     

多级Ag/Bi/氮空位g-C3N4/Ti3C2Tx肖特基结的构筑及其全光谱催化性能

采用原位溶剂热反应制备多级Ag/Bi/Nv-g-C₃N₄(氮空位-g-C₃N₄)/Ti₃C₂T_x肖特基结,并对其物相组成和晶体结构、微观形貌和孔结构、表面元素组成和化学态、光学和光电化学性质进行了表征。由于Ag、Bi和Ti₃C₂T_x协同的表面等离激元共振效应,Ag/Bi/Nv-g-C₃N₄/Ti₃C₂T_x表现出全光谱吸收特性。由载流子浓度差驱动的界面极化电荷转移诱导形成的肖特基结,显著提高了光生载流子(包括热电子和热空穴)的分离效率和利用率。因此,与Nv-g-C₃N₄、Ti₃C₂T_x、Ag/Nv-g-C₃N₄、Bi/Nv-g-C₃N₄和Ag/Bi/Nv-g-C₃N₄相比,Ag/Bi/Nv-g-C₃N₄/Ti₃C₂T_x表现出显著增强的全光谱催化活性,其在可见光和近红外光照射下光催化降解四环素的反应速率常数分别为0.033和0.008 6 min^-1,为对比样品的10~2.1倍和8.6~1.8倍。     

Photocatalytic degradation of organic dyes by Er<Superscript>3+</Superscript>: YAlO<Subscript>3</Subscript>/Co- and Fe-doped ZnO coated composites under solar irradiation

In this work, the Er³⁺: YAlO₃/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er³⁺: YAlO₃/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er³⁺: YAlO₃). Besides, the photocatalytic activity of Er³⁺: YAlO₃/Fe-doped ZnO is better than that of Er³⁺: YAlO₃/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er³⁺: YAlO₃, heat-treatment temperature and time on the photocatalytic activity of the Er³⁺: YAlO₃/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er³⁺: YAlO₃/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er³⁺: YAlO₃/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.     

Acid‐treated g‐C3N4‐Cu2O composite catalyst with enhanced photocatalytic activity under visible‐light irradiation

Acid‐treated g‐C₃N₄‐Cu₂O was prepared by hydrothermal reduction followed by high temperature calcination and acid exfoliation. The structures and properties of as‐synthesized samples were characterized using a range of techniques, such as X‐ray photoelectron spectroscopy, scanning electron microscopy, Photoluminescence Spectroscopy and the Brunauer–Emmett–Teller (BET) theory. The photocatalytic activity was evaluated by measuring the photodegradation of methyl orange under visible‐light irradiation. Based on the results of TEM, XPS, EPR and other techniques, it was verified that a heterojunction was formed. The acid treatment process can increase the specific surface area to form abundant heterojunction interfaces as channels for photo‐generated carrier separation, thereby enhancing its light utilization and quantum efficiency. Results indicate that acid‐treated g‐C₃N₄‐Cu₂O possesses a large specific surface area, which provides plentiful activated sites for heterojunctions to form; in addition, it showed a high visible light effect and the minimum charge‐transfer resistance. Furthermore, the g‐C₃N₄‐Cu₂O material exhibits high levels of effectiveness and stability. Electron paramagnetic resonance and a series of radical trapping experiments demonstrate that the holes and ?O₂^? could be the main active species in methyl orange photodegradation. This work could provide new insights into the fabrication of composite materials as high‐performance photocatalysts, and facilitate their application in addressing environmental protection issues.     

Cu2(dien)2Ag5(CN)9 containing the one‐dimensional polymeric cation [Cu(dien)Ag(CN)2]nn+ and the unusual [Ag2(CN)3]− anion (dien is diethylenetriamine)

From the 1:1 system of [Cu(dien)₂](NO₃)₂ and K[Ag(CN)₂] in water (dien is diethyl­enetri­amine, C₄H₁₃N₃), the novel compound catena‐poly­[bis­[[μ‐cyano‐1:2κ²C:N‐diethyl­enetri­amine‐2κ³N‐copper(II)silver(I)]‐μ‐cyano‐1:2′κ²C:N] di­cyano­silver(I) tri­cyanodisilver(I)], [CuAg(CN)₂(dien)]₂[Ag(CN)₂][Ag₂(CN)₃], has been isolated. The structure is formed from positively charged [–Cu(dien)–NC–Ag–CN–]_nⁿ⁺ chains and two isolated centrosymmetric [Ag(CN)₂]^? and [Ag₂(CN)₃]^? anions. In the cationic chains, the Cu atoms are linked by bridging di­cyano­argentate groups, and the deformed square‐pyramidal coordination polyhedron of the Cu^II cation is formed from a tridentate chelate‐like bonded dien ligand and two N‐bonded bridging cyano groups. One of the bridging cyano groups occupies the apical (ap) position [mean Cu—­N_eq = 2.02 (2) Å, and Cu—N_ap = 2.170 (3) Å; eq is equatorial]. Short argentophilic interactions in the range 3.16–­3.30 Å are present in the crystal structure.