Low-temperature synthesis of nitrogen doped carbon nanotubes as promising catalyst support for methanol oxidation

The electrochemical methanol oxidation reaction(MOR) is of paramount importance for direct methanol fuel cell(DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms,through catalyst-support interaction.

Hydrothermal synthesis and enhanced photocatalytic activity of hierarchical flower-like Fe-doped BiVO_4

Fe-doped BiVO4with hierarchical flower-like structure was prepared via a hydrothermal method using sodium dodecylbenzene sulfonate(SDBS)as structure directing agent.X-ray diffraction(XRD),scanning electron microscope(SEM),transmissionelectron microscope(TEM),high resolution transmission electron microscope(HRTEM),X-ray photoelectron spectroscopy(XPS)and UV-Vis were applied for characterization of the as-prepared samples.The formation mechanism of flower-like structure wasproposed based on the evolution of morphology as a function of hydrothermal time.Fe-doped into substitutional sites of BiVO4effectively improved the migration and separation of photogenerated carrier and enhanced the utilization of visible light.Flower-likeFe-doped BiVO4showed much higher visible-light-driven photocatalytic efficiency for degradation of methyl blue compared withthe pristine BiVO4.And the sample with a Fe/Bi mole ratio of2.5%showed the highest photocatalytic efficiency.

N-doped NaTaO3 synthesized from a hydrothermal method for photocatalytic water splitting under visible light irradiation

NaTaONcatalysts were synthesized by a hydrothermal（H） and a solid-state（S） methods in this study.The H-and S-NaTaONsamples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, UV–visible（UV–vis） diffuse reflectance spectroscopy, and photoluminescence（PL） spectroscopy. The XRD patterns of the H-and S-samples showed peaks indexed to the pure phase of perovskite NaTaOand minor peaks assignable to TaNat various synthesis temperatures. Substitution of oxygen by nitrogen ions causes the light absorption of the H-and S-NaTaONsamples to be extended to the 600–650 nm region, thus making the samples visible-light active. The NaTaONsamples exhibited photocatalytic activity for Hand Oevolution from aqueous methanol and silver nitrate solutions under visible-light irradiation. The UV–vis and PL spectra of the Hand S-catalysts revealed the presence of cationic vacancies and reduced metallic species, which acted as recombination centers. These results demonstrated that the preparation method plays a critical role in the formation of defect states, thereby governing the photocatalytic activity of the NaTaONcatalysts.

In-situ hydrothermal synthesized γ-Al_2O_3/O-g-C_3N_4 heterojunctions with enhanced visible-light photocatalytic activity in water splitting for hydrogen

In this work, γ-Al2O3and hydrogen peroxide treated g-C3N4(O-g-C3N4) were combined through a novel in-situ hydrothermal method to form heterojunction structured photocatalysts. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL). FT-IR results indicate that oxygen functional groups can be grafted on the surface of O-g-C3N4by hydrogen peroxide treatment. The visible light photocatalytic hydrogen evolution rate was investigated in 10 vol% TEOA aqueous solution. The optimal Al2O3mass content is set to be 20 wt% and the corresponding hydrogen evolution rate is 1288 µmol/h/g which is approximately 6, 3 folds that of pristine g-C3N4and O-g-C3N4respectively and 1.6 folds that of mechanical mixed composite with the same Al2O3mass content. The photocurrent density–time curves were carried out under visible light illumination for four on–off cycles. The electrochemical impedance spectroscopy (EIS) measurements verified the enhanced separation efficiency of electron–hole pairs. This work raised a new method to form the heterojunction structured photocatalysts and achieved a remarkable improvement of the photocatalytic activity in water splitting for hydrogen under visible light irradiation. © 2016

Double layered,one-pot hydrothermal synthesis of M-TiO_2(M=Fe^(3+),Ni^(2+),Cu^(2+)and Co^(2+)) and their application in photocatalysis

A double layered, one-pot hydrothermal method was adopted in this work to prepare transition metal ions （Fe3＋, Ni2＋, Cu2＋ and Co2＋） doped TiO〉 The morphology and chemical properties of TiO2 and the status of metal ions were characterized with XRD, TEM, BET, UV-Vis and XPS analysis. TEM images show that the obtained TiO2 was very uniform with an average particle size of 10.4 nm. XPS, TEM and XRD results show that transitional metals were doped onto TiO2 in the form of ions. Photocatalytic decomposition of oxalic acid under UV illumination and methylene blue degradation under visible light on these materials were conducted, respectively. The results reveal that Cu2＋-TiO2 and C02＋-TiO2 showed a highest activity under UV and visible light illumination, respectively, and they were both more active than commercial P25 TiO2. With this special design of double layers, the hydrolysis of titanium precursor in the system with water can be easily controlled and metal ions are simply doped. This strategy can be further applied to synthesize metal ion doped TiO2 using various metal precursors with controllable amounts, and thus lead to better optimization of highly active photocatalyst.

Nitrogen-Doped Carbon Nanotube-Supported Pd Catalyst for Improved Electrocatalytic Performance toward Ethanol Electrooxidation

In this study, hydrothermal carbonization(HTC)was applied for surface functionalization of carbon nanotubes(CNTs) in the presence of glucose and urea. The HTC process allowed the deposition of thin nitrogen-doped carbon layers on the surface of the CNTs. By controlling the ratio of glucose to urea, nitrogen contents of up to 1.7 wt%were achieved. The nitrogen-doped carbon nanotube-supported Pd catalysts exhibited superior electrochemical activity for ethanol oxidation relative to the pristine CNTs.Importantly, a 1.5-fold increase in the specific activity was observed for the Pd/HTC-N1.67%CNTs relative to the catalyst without nitrogen doping(Pd/HTC-CNTs). Furtherexperiments indicated that the introduction of nitrogen species on the surface of the CNTs improved the Pd(0)loading and increased the binding energy.

Microstructure and optical properties of nitrogen-doped ZnO film

The nitrogen doping of ZnO film deposited by the magnetron sputtering method is subsequently realized by the hydrothermal synthesis method.The nitrogen-doped ZnO film is preferably（002） oriented.With the increase of hexamethylenetetramine（HMT） solution concentration,the average grain size of the film along the 002 direction almost immediately decreases and then monotonously increases,conversely,the lattice strain first increases and then decreases.The structural evolution of the film surface from compact and even to sparse and rough is attributed to the enhanced nitrogen doping content in the hydrothermal process.The transmission and photoluminescence properties of the film are closely related to grain size,lattice strain,and nitrogen-related defect arising from the enhanced nitrogen doping content with HMT concentration increasing.

Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10^(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.

Synthesis and Characterization of Novel N-doped TiO2 Photocatalyst with Visible Light Active

A novel N-doped TiO2 （N1-N2-TiO2） with substitutional and interstitial N impurities simultaneously was successfully synthesized. The catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, photoluminescence, and electron paramagnetic resonance. The results demonstrated that the nitrogen was substituted for the lattice oxygen atoms, and was also interstitially doped into the TiO2 lattice. The photocatalytic tests indicated that the N1-N2-TiO2 showed the highest photocatalytic activities of all the N-doped TiO2 under visible light, attributing to the synergetic effect of substitutional and interstitial nitrogen of N-doped TiO2.

Preparation and Characterization of Silver Doped ZnO Nanostructures

ZnO was prepared by hydrothermal method. The result of scanning electron microscopy showed that the materials had nano rod structures. Ag-doped ZnO was prepared by UV-photoreduction. Crystalline phases and optical absorption of the prepared Ag-doped ZnO samples were determined by X-ray diffraction, Raman spectrum, UV-visible, and UV- photoreduction spectrophotometer. X-ray analyses revealed that Ag was doped ZnO crystallizes in hexagonal wurtzite structure. The incorporation of Ag+ in the site of Zn2+ provoked an increase in the size of nanocrystals as compared to pure ZnO. The photocatalytic and photoluminescence properties of materials were considered.

基于量子化学计算优化的氮掺杂碳量子点缓蚀剂制备及其缓蚀性能

[目的]氮掺杂碳量子点(N-CQDs)作为一种绿色高效的新型缓蚀剂,在腐蚀控制领域具有巨大的应用潜力。但由于其结构无法精确调控,很难对制备N-CQDs的众多前驱体进行筛选。[方法]依据密度泛函理论(DFT),通过Fukui指数计算各前驱体分子的优先反应活性位点,确定前驱体分子间一步脱水缩合反应产物的分子结构,并进行全局参量和局部参量的计算,分析了采用柠檬酸分别与乙二胺、尿素和氨基胍盐酸盐作为前驱体所合成的3种N-CQDs的缓蚀性能,再通过称重法对水热法合成的3种N-CQDs的缓蚀性能进行验证,优选出缓蚀性能最佳的缓蚀剂。采用紫外可见吸收光谱、荧光光谱和高分辨率场发射透射电镜表征优选缓蚀剂的荧光性能和表面形貌,并以电化学方法和表面分析方法研究此缓蚀剂对Q235碳钢在0.5 mol/L硫酸溶液中的缓蚀机理。[结果]以柠檬酸和氨基胍盐酸盐为前驱体制备的N-CQDs-3缓蚀性能最佳,且试验结果和理论计算结果一致。N-CQDs-3在紫外激发光下显示蓝绿光,平均粒径为(2.5±0.8)nm。该缓蚀剂是一种混合型缓蚀剂,主要通过物理和化学吸附同时抑制金属在酸溶液中腐蚀反应的发生,其对Q235碳钢在0.5 mol/L硫酸溶液中的缓蚀效率最高可达95.3%。[结论]通过量子化学计算方法对制备N-CQDs所用的前驱体进行筛选,提前预测其缓蚀性能,可提高试验效率。

氮掺杂的硫化镉锌光催化降解水中抗生素

以N,N-二甲基甲酰胺(DMF)为氮源,通过水热法制备了氮掺杂的硫化镉锌(N-Zn_(0.67)Cd_(0.33)S).利用TEM､XRD､XPS等表征手段对N-Zn_(0.67)Cd_(0.33)S进行了物相鉴定,证明了N元素的成功引入.在模拟可见光条件下,考察了N-Zn_(0.67)Cd_(0.33)S对四环素(TC)及环丙沙星(CIP)的光催化降解性能.结果表明,DMF用量为13mL的催化剂(NZCS-13)在30min内对两种抗生素的降解率分别为99.9%和86.9%,降解速率分别为0.2397和0.0676min^(-1),是纯相Zn_(0.67)Cd_(0.33)S(ZCS)的2.33和2.57倍.自由基捕获实验和电子自旋共振测试结果表明,超氧自由基(·O_(2)^(-))是主要的活性物种.PL､UV-Vis DRS､电化学等测试结果表明N掺杂材料性能的提升主要源于光生电荷的有效分离.此外,所得催化剂在连续5次降解实验中表现出良好的循环稳定性.

铝氮共掺杂溴氧化铋光催化性能的研究

【目的】为解决有机染料行业所造成的水污染问题,降解有害物质罗丹明B(RhB),对铝氮共掺杂的溴氧化铋基光催化剂开展研究。【方法】采用水热合成法合成了一系列掺杂不同含量铝或氮或铝氮共掺杂的溴氧化铋(BiOBr)样品,并采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和紫外-可见光分光光度计(UV-vis)对其进行表征。在可见光照射下,光催化降解罗丹明B。【结果】结果表明,铝和氮单独掺杂或共掺杂均能提升BiOBr的光催化性能,且铝氮共掺杂时对光催化的提升效果基本介于铝和氮单独掺杂之间。【结论】铝和氮之间对光催化性能的提升并不是简单叠加,而是存在相互作用的关系,并据此推测掺杂氮元素可以减弱掺杂铝元素对BiOBr晶格的破坏作用。

用于尿素氧化的介孔Ni-NiO@NC电极构造

电催化尿素氧化反应(UOR)可作为直接尿素燃料电池(DUFC)的阳极反应。采用水热联合热解的方法,在介孔含氮碳基体(NC)上构建了锚定Ni和NiO晶体异质结的UOR电催化剂。在1.67 V时,优化工艺合成的Ni-NiO@NC-500复合材料的碱性介质UOR阳极峰值电流密度为237 mA/cm2,在10 mA/cm2的UOR的电势为1.38 V(vs RHE)。12 h的CA循环电流密度>80%。Ni-NiO@NC-500良好的电催化活性关键在于Ni和NiO之间形成了异质结,界面处存在协同作用,Ni/NiO异质结不仅提供了更多的UOR活性位点,而且有利于尿素吸附和气体产物解吸。此外,N掺杂调节了复合材料的电子密度,加快了UOR过程中的电子传递,其介孔结构有利于电解质的渗透和电子转移,其NC提高了催化剂的稳定性。Ni-NiO@NC-500材料将有望成为一种高效、低成本的UOR电催化剂。

一步水热法制备锰氮掺杂TiO_(2)及光催化降解室内甲醛

采用一步水热法,以四水氯化锰为锰源,尿素为氮源,制备了锰掺杂、氮掺杂以及锰氮共掺杂TiO_(2)光催化剂。采用X射线衍射仪、紫外可见漫反射光谱仪、透射电镜及X射线光电子能谱仪等对样品进行表征;以氙灯模拟太阳光照条件,以气态甲醛为目标污染物,测试了样品的光催化性能。研究结果表明:各掺杂样品均为锐钛矿相结构,吸收均出现不同程度红移,禁带宽度变窄;Mn/Ti掺杂最佳摩尔比为0.10%,N/Ti掺杂最佳摩尔比为50%,各最优掺杂比例样品光催化性能从高到低为Mn-N-TiO_(2)-50,N-TiO_(2)-50,Mn-TiO_(2)-0.10和纯TiO_(2),12 h内的甲醛降解率分别为81.67%,72.02%,62.39%,46.78%,共掺杂样品的光催化性能优于单掺杂样品与纯TiO_(2)样品,表现出明显的协同作用;5次循环后,Mn-N-TiO_(2)-50的甲醛降解率仍有73.82%,表现出良好的稳定性。

氮掺杂碳点的制备及其在Hg^(2+)测定中的应用研究

以柠檬酸为碳源,尿素、邻菲罗啉、氨水、硫脲、精氨酸为氮源,通过水热法合成了5种氮掺杂荧光碳点。对合成的碳点进行荧光性能表征,测定了每种碳点的最佳激发和发射波长,在最佳发射波长下,利用荧光猝灭对Hg^(2+)进行检测。结果表明,以精氨酸为氮源制备的碳点对Hg^(2+)检测具有较灵敏的响应,其线性范围为0.25~1.5μmol/L。

氮硫共掺杂中空纳米炭瓶的可控合成

杂原子掺杂碳材料因优异的电化学性能日益受到重视。以生物质基化合物(果糖)为碳源,油酸钠和三段共聚物为软模板,结合水热碳化法,原位可控合成瓶状结构的氮硫共掺杂中空纳米碳材料。分析碳材料的微观形貌、元素组成和元素结合形态等特性。碳纳米颗粒具有中空瓶状结构,并掺杂了N/S元素。基于微观形貌,推测材料从中空瓶状结构生长成实心花生状结构的演变机理。在6 mol/L KOH溶液中,该材料制得的电极以1 A/g电流在0~1 V循环,比电容为133.2 F/g,以10 A/g电流循环1 000次,电容保持率为90%。

水热法制备掺杂铁离子的TiO_2纳米粒子及其光催化反应研究

以 Ti Cl4为前驱体 ,采用水热法制备了掺杂铁离子的 Ti O2 纳米粒子 ,利用 XRD对不同条件下制备的产物进行了表征 ,探讨了反应温度、胶体溶液 p H值和反应时间对水热反应的影响 .考察了所制备的 Fe3 +-Ti O2 纳米粒子光催化降解罗丹明 B的催化性能 ,实验发现 ,制备的掺杂 0 .1 % Fe3 +-Ti O2 纳米粒子与纯 Ti O2相比 ,具有更好的催化活性 .

水热法制备N掺杂纳米TiO_2及其光催化活性研究

以钛酸四丁酯和氨水为前驱物,采用水热法制备N掺杂TiO2纳米微粒,利用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UVVisDRS)等技术对不同条件下制备的产物进行了表征.探讨了不同体积比的前驱物、水热温度、水热时间及煅烧温度对水热产物的影响;考察了N掺杂催化剂在紫外线和可见光下光催化降解甲基橙和苯酚的催化性能.