Ag-TiO_2光催化剂的直接化学合成及光催化性能研究

在醇水溶液体系中采用直接化学合成了Ag-TiO_2光催化剂,利用X射线衍射、红外光谱、氮气吸附-脱附和UV-Vis等方法对样品的结构及光学性能进行了表征。结果表明:Ag-TiO_2光催化剂为锐钛矿相TiO_2,Ag的掺杂不改变TiO_2的晶相并可以细化晶粒,晶粒尺寸平均约为10 nm,并可以扩展其可见光响应范围;Ag-TiO_2光催化剂为介孔结构,比表面积为248 m2/g,平均孔直径为7 nm;0.5%的Ag-TiO_2为最佳光催化剂,相比较TiO_2样品,其降解性能提高了135%,光催化性能提高了127%。     

掺银二氧化钛纳米带的制备及其光催化性能研究

TiO2纳米带作为一种纳米光催化剂用于污水处理中时,能克服TiO2纳米颗粒不易分离同收等困难,对其进行贵金属掺杂,可提高其光催化活性.本研究以价格低廉的钛白粉为原料,采用水热法制备了掺银的TiO2纳米带,并运用XRD,SEM和EDS等对所制备的样品进行表征,进行了光催化降解甲基橙反应,考察了纳米带中的掺银量,煅烧温度等条件对降解甲基橙反应的影响.结果表明,当TiO2纳米带掺银量为0.1%(质量分数,下同),焙烧温度为700℃,催化剂用量为0.05g,室温下用15W紫外灯光照180min时,掺银的TiO2纳米带对甲基橙的降解率可达98.51%,较掺杂前提高了22%左右.     

Modifying Electronic Structure of Cation-Exchanged Bimetallic Sulfide/Metal Oxide Heterostructure through In Situ Inclusion of Silver (Ag) Nanoparticles for Extrinsic Pseudocapacitor

The inferior electrical conductivity of conventional electrodes and their slow charge transport impose limitations on the electrochemical performance of supercapacitors (SCs) using those electrodes, necessitating strategies to overcome the limitations. An in situ Ag ion-incorporated cation-exchanged bimetallic sulfide/metal oxide heterostructure (Ag-Co_9-xFe_xS₈@α-Fe_xO_y) is synthesized using a two-step hydrothermal method. The coordination bond formation and Ag nanoparticle (NP) incorporation improve the electrical conductivity and adhesion of the heterostructure and reduce its interface resistance and volume expansion throughout the charge/discharge cycles. Density functional theory investigations indicate that the remarkable interlayer and interparticle conductivities of the heterostructure resulting from Ag doping have changed its electronic states, leading to an enhanced electrical conductivity. The optimized electrode has an excellent specific capacity (213.6 mA h g⁻¹ at 1 A g⁻¹) and can maintain 93.2% capacity retention with excellent Coulombic efficiency over 20 000 charge/discharge cycles. A flexible solid-state extrinsic pseudocapacitor (EPSC) is fabricated using Ag-Co_9-xFe_xS₈@α-Fe_xO_y and Ti₃C₂T_X electrodes. The EPSC has specific and volumetric capacitances of 259 F g⁻¹ and 2.7 F cm⁻³ at 0.7 A g⁻¹, respectively, an energy density of 80.9 Wh kg⁻¹ at 525 W kg⁻¹, and a capacity retention of 92.8% over 5000 charge/discharge cycles.     

溶胶-凝胶-微波法制备银掺杂TiO_2光催化剂及其光催化性能

用硝酸银和钛酸正丁酯为原料,采用溶胶-凝胶-微波辐射干燥法合成银掺杂TiO_2光催化剂TiO_2-Ag。为了提高催化剂的光催化活性和降解有机污染物的速率,用微波辅助Ti O2-Ag光催化剂降解有机污染物。通过扫描电子显微镜、红外光谱法、紫外可见光谱法和荧光光谱法对TiO_2-Ag催化剂进行测试和表征。以甲基橙为有机污染物,分别在太阳光照射和微波、紫外、紫外-微波条件下降解甲基橙以考察催化剂的光催化活性。结果表明,TiO_2-Ag光催化剂最佳制备条件为:银掺杂量n(Ag+)∶n(Ti~(4+))=0.003,离子液体用量3.0 m L,微波干燥功率210 W,微波干燥时间20 min,焙烧温度650℃,焙烧时间3 h,此条件下制备的TiO_2-Ag光催化剂在太阳光照射4 h下,紫外光照、微波辐射和紫外光照-微波辐射分别辐射55 min后,甲基橙降解率分别为98.70%、98.79%和99.05%。     

锐钛矿型TiO2（101）面掺杂Ag的第一性原理研究

采用基于密度泛函理论的第一性原理方法和周期性平板模型相结合的方法,对Ag原子掺杂TiO2(101)面进行了理论计算。结果表明Ag原子有向表面富集的趋势,其中银原子在TiO2(101)表面最外层能量最低,结构最为稳定。Mulliken电荷布居分析结果表明,掺杂过程中电子由Ag原子向周围原子移动。能带结构和态密度分析表明掺杂银原子后,TiO2(101)面禁带中间出现了明显的由银4d轨道构成的杂质能级,该能级的出现导致了TiO2(101)面的吸收光谱向长波方向移动,产生的红移现象,有利于光催化性能的提高。     

Enhanced photoelectrochemical response of reduced-graphene oxide/Zn1−xAgxO nanocomposite in visible-light region

Graphene based nanocomposites have the potential to work as efficiently, multifunctional materials for energy conversion & storage. These composites may exhibit better photocatalytic properties by the improvement of their electronic and structural properties than pure photocatalysts. In the present work, reduced graphene oxide (rGO) & ZnO nanocomposite with 0–5 atom% Ag doping was prepared by electrodeposition method and characterized by XRD, Raman spectroscopy, FE-SEM, EDX, UV–Vis spectroscopy and final photoelectrochemical activity was assessed under 1.5 AM solar simulator in 1 M NaOH as electrolyte. Significant changes in the Raman spectrum for the nanocomposite suggest the possible electronic interaction between rGO and ZnO nanocomposite and its successful fabrication, which improves the charge separation and enhanced photoelectrochemical activity in the nanocomposite. We find a red-shift of 0.35 eV in the UV–vis spectrum and therefore an enhanced photoelectrochemical activity in the visible range on Ag doping in rGO/ZnO nanocomposite. Nanocomposite with 1 atom% Ag doping showed the highest photocurrent density of 2.48 mA/cm² at 0.8 V vs Ag/AgCl over other samples, which was almost five times higher than that for undoped rGO/ZnO composite. Calculated Flat-band potential and donor densities using Mott–Schottky data also supported the better photoelectrochemical response for Ag doping in nanocomposite.     

XPS,TDS, and AFM studies of surface chemistry and morphology of Ag-covered L-CVD SnO2 nanolayers

This is well known that the selectivity and sensitivity of tin dioxide (SnO₂) thin film sensors for the detection of low concentration of volatile sulfides such as H₂S in air can be improved by small amount of Ag additives. In this paper we present the results of comparative X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS), and atomic force microscopy (AFM) studies of the surface chemistry and morphology of SnO₂ nanolayers obtained by laser-enhanced chemical vapor deposition (L-CVD) additionally covered with 1 monolayer (ML) of Ag. For as deposited SnO₂ nanolayers, a mixture of tin oxide (SnO) and tin dioxide (SnO₂) with the [C]/[Sn] ratio of approximately 1.3 was observed. After dry air exposure, the [O]/[Sn] ratio slightly increased to approximately 1.55. Moreover, an evident increasing of C contamination was observed with [C]/[Sn] ratio of approximately 3.5. After TDS experiment, the [O]/[Sn] ratio goes back to 1.3, whereas C contamination evidently decreases (by factor of 3). Simultaneously, the Ag concentration after air exposure and TDS experiment subsequently decreased (finally by factor of approximately 2), which was caused by the diffusion of Ag atoms into the subsurface layers related to the grain-type surface morphology of Ag-covered L-CVD SnO₂ nanolayers, as confirmed by XPS ion depth profiling studies. The variation of surface chemistry of the Ag-covered L-CVD SnO₂ after air exposure observed by XPS was in a good correlation with the desorption of residual gases from these nanolayers observed in TDS experiments.