Photocatalytic Reduction of Cr (VI) over g-C3N4 Photocatalysts Synthesized by Different Precursors

Graphitic carbon nitride (g-C₃N₄) photocatalysts were synthesized via a one-step pyrolysis process using melamine, dicyandiamide, thiourea, and urea as precursors. The obtained g-C₃N₄ materials exhibited a significantly different performance for the photocatalytic reduction of Cr(VI) under white light irradiation, which is attributed to the altered structure and occupancies surface groups. The urea-derived g-C₃N₄ with nanosheet morphology, large specific surface area, and high occupancies of surface amine groups exhibited superior photocatalytic activity. The nanosheet morphology and large surface area facilitated the separation and transmission of charge, while the high occupancies of surface amine groups promoted the formation of hydrogen adsorption atomic centers which were beneficial to Cr(VI) reduction. Moreover, the possible reduction pathway of Cr(VI) to Cr(III) over the urea-derived g-C₃N₄ was proposed and the reduction process was mainly initiated by a direct reduction of photogenerated electrons.     

Covalent Triazine Framework Nanosheets for Efficient Energy Storage and Conversion

Two-dimensional crystalline covalent triazine frameworks(CTFs) have received much attention because of their unique triazine structure, which endows CTFs with high thermal and chemical stability, high proportion of nitrogen and permanent porosity. Based on this unique structure characteristic, CTFs have shown great potential in energy storage and conversion due to the intrinsically strong conjugated structure, delocalized electron and rich active sites. However, charge carrier(electron, hole or ion) transport can't reach the deep active sites and charge diffusion was impeded by defects in bulk CTFs. Hence, to break through this barrier, increasing attention has been paid to get few layered CTFs or CTFs nanosheets in order to shorten the pathways of charge diffusion and expose more active sites. This review summarizes the synthetic methodologies of CTFs nanosheets and the potential application in photocatalytic and electrochemical energy storage and conversion.     

鳞状BiOBr/Bi2WO6的合成及其吸附性能

采用一步水热法成功制备鳞状形貌的BiOBr/Bi₂WO₆复合物,通过X射线衍射（XRD）仪、扫描电子显微镜（SEM）、N2吸附/解吸附比表面测定仪（BET）、傅里叶变换红外（FT-IR）光谱等对复合物进行了表征。对比Bi₂WO₆与BiOBr的SEM照片,结合KBr的浓度实验,提出了BiOBr/Bi₂WO₆的鳞状形貌的形成机理。选取有机染料为吸附质,BiOBr/Bi₂WO₆为吸附剂进行了复合物吸附性能测试。结果表明,BiOBr/Bi₂WO₆对阳离子染料表现出优越的吸附性能,10 min对次甲基蓝（MB）的吸附率高达99%,优于常规的活性炭吸附剂。此外,BiOBr/Bi₂WO₆对有机染料的吸附行为符合准二级反应速率方程和Freundlich等温吸附模型。     

多孔柿饼状BiOBr光催化剂的简易溶剂热法合成（英文）

以硝酸铋和十六烷基三甲基溴化铵(CTAB)为Bi和Br源,采用聚乙烯吡咯烷酮(PVP)辅助溶剂热法首次成功制备了多孔纳米片聚结的柿饼状溴氧化铋(BiOBr)。通过多种分析技术对分级微米结构BiOBr材料的物化性质进行了表征,并对其在可见光照射下降解亚甲基蓝(MB)的光催化活性进行了评价。结果表明,溶剂热时间和PVP的加入量对产物的颗粒形貌和结晶度有显著影响。当加入0.7 g PVP时,120℃溶剂热处理12 h,可得到多孔纳米片聚结的柿饼状BiOBr样品。多孔柿饼状BiOBr样品的比表面积为4 m2·g^-1,带隙能为2.64 eV,在可见光区具有较强的光吸收性能,具有良好的可见光驱动降解MB的光催化活性和稳定性。我们推断,多孔纳米片聚结的柿饼状BiOBr样品具有优良的可见光催化性能,这与该样品的较高比表面积、多孔结构、低带隙能以及独特的颗粒形貌有关。     

Template Based Synthesis of Porous Graphdiyne Nanosheet for Reversible and Fast NO2 Detection by UV Irradiation

Two-dimensional graphdiyne (GDY) formed by sp and sp² hybridized carbon has been found to be an efficient toxic gas sensing material by density functional theory (DFT). However, little experimental research concerning its gas sensing capability has been reported owing to the complex preparation process and harsh experimental conditions. Herein, porous GDY nanosheets are successfully synthesized through a facile solvothermal synthesis technique by using CuO microspheres (MSs) as both template and source of catalyst. The porous GDY nanosheets exhibit a broadband optical absorption, rendering it suitable for the light-driven optoelectronic gas sensing applications. The GDY-based gas sensor was demonstrated to have excellent reversible to NO₂ behaviors at 25 °C for the first time. More importantly, higher response value and faster response-recovery time once exposed to NO₂ gas molecules are achieved by the illumination of UV light. In this way, our work paves the way for the exploration of GDY-based gas detection experimentally.     

硫粉为硫源,多元醇辅助合成硫化钼纳米片

MoS₂ nanosheets are prepared with sulfur powder and Na₂MoO₄ by a one-pot two-phase method at 170-200 ℃ for 8 h. In addition, a three-step growth mechanism based on the aggregation and coalescence model is proposed. The reassembly of sulfur powder ensures the transformation from sulfur powder to H₂S to reduce Na₂MoO₄ and plays a key role in the successful preparation of MoS₂ nanosheets. The as-prepared MoS₂ nanosheets are rich in unsaturated sulfur atoms, probably resulting from the dislocation cores of the MoS₂ nanosheets, which have been found to be beneficial for hydrogen evolution reaction catalysis. The method and growth mechanism adopted in this study may be applied to other transition metal dichalogenides for similar structures. The facile and green method provides an alternative for the preparation of MoS₂ nanosheets.     

原位溶剂热聚合法制备金属有机骨架/碳化氮纳米片涂覆的固相微萃取纤维用于红茶中农药残留的高灵敏检测

有机氯(OCPs)和拟除虫菊酯(PYs)是两类广泛使用的农药,对自然环境和人类健康具有极大危害。在本研究中,通过原位溶剂热聚合法制备了金属有机骨架/碳化氮纳米片(UiO-66/HOCN)复合材料涂覆的固相微萃取(SPME)纤维,该纤维拥有良好的稳定性,并对OCPs和PYs具有高效的萃取性能。将其与气相色谱-质谱(GC-MS)相结合,建立了用于OCPs和PYs检测的高灵敏分析方法。该方法对9种农药目标物表现出了令人满意的回收率和重现性,具有检出限低(0.03～0.30 ng/L)、线性范围宽(0.1～800.0 ng/L)和线性相关系数良好(≥0.997 8)等优点。将所建立的方法用于实际红茶样品中农药残留的检测,成功地在实际样品中检测出了艾试剂(6.6 ng/L)、α-硫丹(54.7 ng/L)和联苯菊酯(185.8 ng/L)。实验结果表明,所建立的分析方法适用于复杂基质中农药残留的分析和监测。     

Sb2S3纳米粒子修饰ZnO纳米片微纳分级结构的光电化学性能

采用恒电位方法,选择氯化钾和乙二胺(EDA)为添加剂,在氧化铟锡(ITO)导电玻璃上制备了高度有序的ZnO纳米片阵列,通过二次电沉积得到了ZnO纳米片上生长纳米棒的微纳分级结构.利用化学浴沉积法在ZnO基底上沉积Sb₂S₃纳米粒子制备出了Sb₂S₃/ZnO纳米片壳核结构和Sb₂S₃/ZnO微纳分级壳核结构.利用扫描电子显微镜(SEM)、X射线衍射(XRD)、紫外-可见(UV-Vis)吸收光谱、瞬态光电流等对其形貌、结构组成和光电化学性能进行了表征和分析.结果表明, Sb₂S₃/ZnO纳米片上生长纳米棒分级壳核结构的光电流明显高于Sb₂S₃/ZnO纳米片壳核结构.在Sb₂S₃/ZnO纳米片壳核结构和Sb₂S₃/ZnO微纳分级壳核结构的基础上旋涂一层P3HT薄膜形成P3HT/Sb₂S₃/ZnO复合结构,以上述复合结构薄膜为光活性层组装成杂化太阳电池,其中, P3HT/Sb₂S₃/ZnO分级壳核结构杂化太阳电池的能量转换效率最高,达到了0.81%.     

N掺杂富含(001)晶面TiO_2纳米片的制备及N掺杂浓度对可见光催化活性的影响(英文)

采用水热法制备了富含(001)晶面的锐钛矿型TiO2纳米片,并通过改变热处理过程中NH3流速制备不同N掺杂浓度的TiO2纳米片.运用X射线衍射、场发射扫描电镜、高分辨率透射电子显微镜、紫外-可见漫反射光谱、X射线光电子能谱和荧光光谱对光催化剂进行了结构和性能表征,并以罗丹明B为目标降解物,考察了N掺杂浓度对TiO2纳米片可见光催化活性的影响.结果表明,NH3流速为40ml/min时制备的N掺杂TiO2纳米片具有最低的光生电子-空穴复合速率,最高的OH产生能力并表现出最高的光催化活性.同时,讨论了N掺杂浓度对TiO纳米片可见光催化活性影响的机理.     

SnO_2/石墨纳米片复合电极及其在超级电容器中的应用

在电场的作用下对石墨棒进行电化学剥离,使其表面形成相互平行排列,且垂直于石墨棒基底的二维(2D)石墨纳米片阵列(GNSA).然后通过阴极还原电沉积法制备Sn O2/石墨纳米片阵列(Sn O2/GNSA)复合电极.采用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)和傅里叶变换红外(FT-IR)光谱对其形貌和结构进行了表征.电化学测试表明该复合电极具有优异的超电容性能,在0.5 mol·L-1Li NO3电解质中,扫描速率为5 m V·s-1,电位窗口为1.4 V时,比电容达4015 F·m-2.由Sn O2/GNSA复合电极和相同电解质组装成的对称型超级电容器,在扫描速率为5 m V·s-1时,其电位窗口可增至1.8 V,能量密度达到0.41 Wh·m-2,循环5000圈后其比电容仍保持为初始比电容的81%.