金属钾和碳酸钠高压合成金刚石

以金属钾和碳酸钠为反应原料, 在压力为2 GPa, 温度为500 ℃的密封白金坩埚中反应18 h, 所得产物通过粉末X射线衍射和显微拉曼分析进行了表征, 证实合成出了微米级的金刚石. 对金刚石的合成机理进行了研究, 推测其反应过程为碳酸钠在铂和钾的作用下分解出CO2, CO2与钾反应得到金刚石. 研究结果表明金刚石可以在温和的条件下合成.     

电化学还原预处理对BiVO_4薄膜电极光电化学氧化水性能的提高

在酸性水溶液中(pH=2.0),采用电化学还原(ER)方法对BiVO4薄膜电极进行预处理,并探讨了其对薄膜电极光电化学氧化水性能的影响.结果表明,这种预处理可显著提高电极的光电化学氧化水的性能,且具有良好的光电化学稳定性.利用扫描电子显微镜、X射线衍射、拉曼光谱、光电子能谱、紫外-可见漫反射光谱、荧光光谱、电化学阻抗谱及Mott-Schottky等方法对ER处理前后的电极进行了表征.结果表明,ER预处理使电极粗糙度增大,表面积增大约1.4倍;电极材料的晶型无明显变化,但V—O对称伸缩振动略有红移;表面Bi,V和O结合能变小,Bi3+部分被还原,Bi/V原子比增大;ER处理导致电极平带电位负移,光生载流子在薄膜电极/溶液界面转移速率加快,表面复合速率降低.这些变化和表面积增加是BiVO4电极光电化学性能提高的主要原因.     

电极制作方法对电解二氧化锰循环伏安行为的影响

采用压制泡沫镍、石墨棒模具、粉末微电极三种电极制作方法研究电解二氧化锰在硫酸镁溶液中的循环伏安行为,并用X射线衍射法分析电解二氧化锰放电/充电后结构形态的变化。结果表明:用粉末微电极制作的研究电极在循环伏安扫描过程中反应灵敏、解析度好,所得循环伏安谱图中还原、氧化峰的变化与X射线衍射谱图中衍射峰的变化具有较好的对应关系,能更真实地反映电解二氧化锰的电化学性质。     

溶剂热电化学还原氯仿制备类金刚石碳膜的研究

报道了采用溶剂热电化学法还原氯仿制备类金刚石碳膜(DLC)的新体系. 实验在－1.2或－1.6 V (vs. Ag/AgCl/Cl^－)下, 对溶解在以Bu₄NCl作为支持电解质的碳酸丙烯酯(PC)溶液中的氯仿进行电化学还原. 研究了温度、氯仿/PC比例和电极材料对沉积的影响. 采用拉曼光谱, SEM, FTIR, XPS等方法对产物进行表征. 结果表明,在100 ℃,氯仿/PC比例为1∶3, Pt电极上沉积的DLC膜含有较高的sp³杂化态碳. 论文还提出了电化学还原氯仿沉积DLC薄膜的机理.     

基于超微电极的原位电化学拉曼光谱

原位电化学拉曼光谱是一种重要的光谱电化学技术.基于超微电极的原位电化学拉曼光谱将拉曼光谱反映的结构信息与电极表面的电化学过程从实验上严格对应和关联,为深刻理解电化学反应机理提供依据.本文综述了采用超微电极作为工作电极的原位电化学拉曼光谱的研究方法和应用进展,总结了应用超微电极作为工作电极开展电化学拉曼光谱实验的方法和具有表面增强拉曼活性的超微电极制备方法,展示了如何利用在超微电极表面获得的拉曼光谱与界面电化学过程的严格关联研究单个锌颗粒电化学氧化过程、吡啶分子在Au电极表面的电化学吸附过程,以及如何利用该技术能以高的信噪比和灵敏度同时测量光电流与分子反应这一特性研究对巯基苯胺选择性光氧化反应.采用超微电极作为工作电极的原位电化学拉曼光谱技术极大拓展了拉曼光谱技术的研究范围,有望成为探索(光)电化学反应的有力工具.     

暂态电化学表面增强拉曼光谱研究对硝基苯硫酚分子的电化学还原过程

对硝基苯硫酚是表面增强拉曼光谱研究中最常用的探针分子之一,对硝基苯硫酚在电极表面电化学还原反应的研究有助于对芳香族硝基化合物还原机理的认识. 本文应用暂态电化学-表面增强拉曼光谱技术,研究了对硝基苯硫酚在循环伏安和计时电流法过程中的表面增强拉曼光谱. 结果表明,实验实现了完全与电化学检测时间分辨率同步的表面增强拉曼光谱检测,以最快5毫秒的时间分辨率研究了对硝基苯硫酚分子在金电极表面的还原过程. 结果分析推测其此反应过程极快,在5毫秒的时间分辨率下仍难以捕获其中间物种. 本研究为人们更深层次研究和认识硝基苯类化合物电化学还原过程提供了参考和方向.     

甲酸在Aucore@Ptshell/Pt电极上电催化氧化的原位SERS

用化学还原法合成了Aucore@Ptshell纳米粒子, 并用扫描电子显微镜(SEM)及X射线衍射(XRD)等技术对纳米粒子进行表征; 采用电化学原位表面增强拉曼光谱(SERS)技术对甲酸的电催化氧化过程进行了研究, 成功地获得了甲酸在Aucore@Ptshell/Pt电极上解离吸附的原位SERS. 结果显示, 在开路电位时, 甲酸能在Aucore@Ptshell/Pt电极表面自发氧化, 解离生成强吸附中间体COad和弱吸附中间体HCOOad, 在电位为+0.10 V时检测到氧化产物CO2的谱峰. 研究结果表明, Aucore@Ptshell/Pt电极对甲酸的氧化具有较高的催化活性和较强的SERS效应, 甲酸在Aucore@Ptshell/Pt电极上的电催化氧化过程遵循双途径机理.     

基于天然产物的新型铁氮共掺杂碳电催化剂的制备及氧还原性能

以廉价天然植物果实红枣作为唯一碳源,采用牺牲模板法制备了一种具有层状多孔结构的铁氮共掺杂碳材料(Fe-N-CM).采用X射线粉末衍射、X射线光电子能谱、透射电子显微镜、氮气吸-脱附仪和拉曼光谱对Fe-N-CM样品的形貌和结构进行了表征,用旋转圆盘电极及环盘电极对Fe-N-CM催化剂的氧还原反应(ORR)性能进行了研究.结果表明,所制备的层状多孔Fe-N-CM材料比表面积达到429.8 m~2/g,铁颗粒在材料表面均匀分散,铁和氮的协同作用使Fe-N-CM具有良好的氧还原催化活性,其对氧还原反应的催化稳定性和抗甲醇性能优于商业Pt/C催化剂.     

n型金刚石薄膜催化生长碳纳米管

研究了n型金刚石薄膜作为催化剂生长碳纳米管的方法.首先采用丙酮裂解化学气相沉积(CVD)法制备均匀的n型金刚石薄膜,然后采用乙醇为碳源的CVD法,在850、900和950℃下,分别在n型金刚石薄膜上制备了碳球、竹节状碳管和多壁碳纳米管.所得产物用扫描电子显微镜、透射电子显微镜、拉曼光谱和X射线光电子能谱表征.实验结果表明产物的形貌与反应温度有关.我们还提出了与金刚石催化生长碳纳米管结果相符的实验机理.     

纳米SnO2/TiO2电极的制备及其电催化降解间-硝基苯酚

用电化学方法在乙二醇溶液中制备锡、钛醇盐配合物Sn0.75Ti(OCH2CH2OH)(7-x),将电解液水解、干燥后在400℃煅烧2 h,得到纳米级SnO2/TiO2粉体。通过红外光谱(FT-IR)和拉曼光谱(Raman)对电解产物进行测试,纳米SnO2/TiO2粉体通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)进行表征。实验表明,在有机体系电解得到的纳米SnO2/TiO2粉体颗粒分散较理想,粒径在100～200 nm。再通过溶胶-凝胶法在钛丝表面得到纳米SnO2/TiO2电极,采用循环伏安法研究电极在酸性溶液和间-硝基苯酚溶液中的氧化还原行为和电催化活性。结果表明,纳米TiO2掺杂SnO2电极的氧化峰电流达到143×10-3A/cm2,氧化还原峰电位差明显减小,催化降解间-硝基苯酚的COD去除率达到86.1%,具有较高的电催化活性。     

不同结构及氮掺杂NiO/rGO氧还原催化剂的制备与性能研究

本文以还原氧化石墨烯（rGO）为载体制备了片状NiO/rGO和球形NiO/N-rGO结构的氧还原催化剂. 通过X-射线衍射（XRD）、Raman（拉曼）测试、X-射线光电子能谱（XPS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等方法表征了两种催化剂的结构和形貌. 采用循环伏安法（CV）、Tafel曲线、线性扫描伏安法（LSV）、旋转圆盘电极（RDE）和旋转环盘电极（RRDE）等技术测试研究了两种催化剂的电化学催化氧还原性能. 研究结果表明,球形NiO/N-rGO催化剂催化氧还原的峰电流密度和起始电位（0.89 V vs. RHE）与商业化的Pt/C（20%）催化剂相近. 旋转圆盘电极（RDE）和旋转环盘电极（RRDE）测试证明,在碱性电解液中NiO/rGO和NiO/N-rGO催化的氧还原反应均主要通过4?鄄电子途径反应途径发生,球形NiO/N-rGO催化剂展现出替代Pt/C基催化剂的潜力.     

Identification of the diamond-like B-C phase by confocal Raman spectroscopy

The new diamond-like B-C phase was obtained from the graphite-like BC phase in a laser-heated diamond anvil cell at high temperature 2230+/-140 K and high pressure 45 GPa. Raman spectra of the new phase measured at ambient conditions revealed a peak at 1315 cm(-1), which was attributed to longitudinal-optical (LO) mode. The X-Y Raman mapping was used to investigate spatial distribution of the diamond-like phases and was shown to be a powerful tool in studying the sp(2)-to-sp(3) phase transformations occurring in the diamond cell under high temperature and high pressure.     

Effects of acid etching on the structure of PtNi catalyst and total exposed active sites

The integration technology of hydrogen preparation–hydrogen storage not only can utilize hydrogen energy efficiently but also can improve the selectivity of the electrode maximally. In the present work, the structure and composition of the PtNi catalyst was characterized by X-ray diffraction (XRD); and its electrochemical properties, morphology, and surface binding energy were analyzed by cyclic voltammetry (CV) and linear scanning voltammetry (LSV), scanning electron microscopy equipped with energy-dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The effects of different acid etching treatments (e.g., etching time, etchant concentration, and etching temperature) on the structure and surface active sites were investigated by the orthogonal experiment. The experimental results reveal that after etching with 0.5 mol/L of perchloric acid for 0.5 h at 60°C, the electrode weight loss of the PtNi catalyst is mainly attributed to the large loss of Ni atoms in film layer. This results in the reduced alloy phase in film layer and the appearance of Pt characteristic diffraction peak. The relative content of Pt on the surface of the film electrode increases significantly, and the total number of active sites also increases correspondingly. The binding energy of Pt4f_7/2 decreases by 0.19 eV, and the number of active sites involved in hydrogen release decreases, indicative of the reduced promotion effect of the PtNi catalyst on hydrogen release.     

Nonenzymatic amperometric sensor of hydrogen peroxide and glucose based on Pt nanoparticles/ordered mesoporous carbon nanocomposite

A simple and facile synthetic method to incorporate Pt nanoparticles inside the mesopores of ordered mesoporous carbons (OMCs) is reported. The Pt/OMCs nanocomposite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and nitrogen adsorption-desorption. The results show that the incorporation of Pt nanoparticles inside the pores of OMCs does not change the highly ordered two-dimensional hexagonal mesostructure of OMCs matrix. Nonenzymatic amperometric sensor of hydrogen peroxide and glucose based on the Pt/OMCs nanocomposite-modified glassy carbon (GC) electrode is developed. Compared with the original OMCs-modified electrode, the Pt/OMCs-modified electrode displays improved current response towards hydrogen peroxide and gives linear range from 2 to 4212 μM. At an applied potential of −0.08 V, the Pt/OMCs nanocomposite gives linearity in the range of 0.5-4.5 mM glucose in neutral buffered saline solution. This glucose sensor also exhibits good ability of anti-interference to electroactive molecules. The combination the unique properties of Pt nanoparticles and the ordered mesostructure of OMCs matrix guarantees the enhanced response for hydrogen peroxide and glucose.     

促进型PtMoSi/C催化剂的制备、表征及电催化活性

采用甲醛还原、H2还原、肼还原三种方法制备了添加硅钼酸的PtMoSi/C阳极催化剂, 并用XRD、XPS和TEM技术对催化剂进行了表征. XRD表明Pt粒子呈立方面心晶态结构, TEM显示PtMoSi/C催化剂粒径小(3−4 nm), 分布窄, 分散性好. XPS分析可知Pt主要以0价, Mo主要以6价, Si主要以4价形态存在于催化剂中. 同时通过循环伏安法和线性扫描法考察了制备方法和添加硅钼酸对催化剂电化学活性的影响. 结果表明, 甲醛还原法制备的PtMoSi/C催化剂(Pt、Mo的原子比为3:1)对甲醇氧化的电化学性能和抗中毒性能优于自制的PtRu/C和E-TEK PtRu/C催化剂, 可能是因为添加硅钼酸可以使活性组分的分散度提高, 从而提高了催化剂的活性和抗毒性能.     

Highly efficient and stable electrooxidation of methanol and ethanol on 3D Pt catalyst by thermal decomposition of In_2O_3 nanoshells

In this paper In_2O_3 nanoshells have been synthesized via a facile hydrothermal approach.The nanoshells can be completely cracked into pony-size nanocubes by annealing,which are then used as a support of Pt catalyst for methanol and ethanol electrocatalytic oxidation.The prepared In_2O_3 and supported Pt catalysts(Pt/In_2O_3) were characterized by X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),field effect scanning electron microscopy(FESEM),and transmission electron microscopy(TEM).Cyclic voltammetry(CV),linear sweep voltammetry(LSV),chronoamperometry and electrochemical impedance spectroscopy(EIS) were carried out,indicating the excellent catalytic performance for alcohol electrooxidation can be achieved on Pt/In_2O_3 nanocatalysts due to the multiple active sites,high conductivity and a mass of microchannels and micropores for reactant diffusions arising from 3D frame structures compared with that on the Pt/C catalysts.     

钴-聚吡咯-碳载PtNi燃料电池催化剂的制备及应用

采用脉冲微波辅助化学还原合成新型载体钴-聚吡咯-碳(Co-PPy-C)负载PtNi催化剂.利用透射电镜(TEM)和X射线衍射(XRD)研究了催化剂的结构和形貌,此外,利用循环伏安(CV)和线性扫描伏安(LSV)等方法测试了催化剂的电化学活性及耐久性. PtNi/Co-PPy-C催化剂的金属颗粒直径约为1.77 nm,催化剂在载体上分布均匀且粒径分布范围较窄. XRD结果显示, PtNi/Co-PPy-C中Pt(111)峰最强, Pt主要是面心立方晶格.CV结果显示,其电化学活性面积(ECSA)为72.5 m²·g^-1,明显高于商用催化剂Pt/C(JM)的56.9 m²·g^-1.为进一步考查催化剂耐久性,电化学加速5000圈耐久性测试后, PtNi/Co-PPy-C颗粒发生明显集聚, ECSA衰减率和0.9 V下比质量活性衰减率分别为38.2%和63.9%.此外,采用有效面积为50 cm²的单电池用于评价自制催化剂的性能,发现在70 ℃且背压为50 kPa时电池的性能最好,此时自制PtNi/Co-PPy-C催化剂制备膜电极(MEA)的最大功率密度达到523 mW·cm^-2.可见自制催化剂的电化学性能高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.     

Effect of pressure on the growth of boron and nitrogen doped HFCVD diamond films on WC–Co substrate

Boron and nitrogen compounds are added in the acetone/hydrogen gas mixture to deposit hot filament chemical vapor deposition (HFCVD) diamond films on the cobalt cemented tungsten carbide (WC–Co) substrate under the pressure of 1–4 kPa. The as‐deposited diamond films are characterized by field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), X‐ray diffraction (XRD) spectroscopy and Raman spectroscopy. The results reveal that the surface morphology, growth rate, structure and quality of the diamond films vary with the pressure and the type of the impurity addition. The diamond grains tend to develop into the nanometer scale with the decrease of the pressure. However, adding of boron or nitrogen impurities in the gas mixture will weaken the nanocrystallization effect by reducing the carbon supersaturation. Density functional theory (DFT) calculations indicate that co‐adsorption of B and N containing radicals can favor the adsorption of CH₃ on diamond (100) surface. Thus, at low pressure of 1 kPa, large grained cubic (100) facet diamond rather than typical nanometer diamond is produced for B–N co‐addition gas mixture. The present results appear to be useful to efficiently synthesize high quality doped diamonds with desirable properties for mechanical application. Copyright © 2015 John Wiley & Sons, Ltd.     

In situ electrodeposition of Pt nanoclusters on glassy carbon surface modified by monolayer choline film and their electrochemical applications

Pt nanoclusters attached to the monolayer choline (Ch) modified glassy carbon surface were successfully synthesized by use of in situ cyclic voltammetry (CV) method. Field emission scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS) were used to characterize the properties of this modified electrode. It was demonstrated that Ch was immobilized onto the carbon surface forming a covalently planted Ch monolayer, which could induce the formation of Pt nanoclusters. The preliminary study found that the homogeneous nanostructured Pt/Ch film exhibited remarkable electrocatalytic activity towards the oxidation of methanol and nitrite.