Au电极上CO_2电还原过程中电极失活原因

在水溶液中,电还原CO_2制取CO时,电极易中毒失活,采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)对反应前后的电极材料进行检测,研究CO_2在KHCO_3水溶液中发生电化学还原反应时,Au电极失活原因及电极材料活性降低对反应过程的影响。结果表明,电极表面吸附了一层黑色有害物质。这层黑色有害物质大部分是石墨碳,并有微量的铁和锌。采用塔菲尔曲线、电化学阻抗(EIS)、线性扫描曲线、恒电位电解和气相色谱法等研究了有害物质对CO_2电还原反应动力学过程的影响,发现随着反应的进行,生成CO的平衡电位负移,电荷转移电阻增大,交换电流密度变小,产物CO的电流效率迅速降低。说明电极表面附着的有害物质使电极材料活性降低,阻碍了CO_2电还原反应的进行。     

Au和Ag电极上CO2电还原反应的动力学特征对比

采用循环伏安和塔菲尔曲线、恒电位电解、气相色谱方法,研究了CO2在Au, Ag电极上发生电还原反应的动力学特征. 结果表明,在0.1 mol/L KHCO3水溶液中,CO2可在Au, Ag电极上发生电还原反应生成CO, CO2在Au和Ag电极上被电还原为CO的平衡电位分别为-0.720和-0.934 V,交换电流密度为0.4014和0.3011 mA/cm2,传递系数为0.33和0.35,电荷转移电阻为31.98和42.64 W×cm2,最高电流效率为82%和65%. 表明Au电极的催化活性高于Ag电极.     

阴极极化对微生物在电极表面附着的影响

以天然海水作为电解质,利用荧光显微镜、扫描电镜等表征方法和开路电位、恒电位极化等电化学测试手段研究了生物膜附着与电极表面电位的相互影响。结果表明：（1）生物膜在电极表面的附着导致了开路电位正移;（2）阴极极化能有效抑制微生物附着,并且阴极氧还原反应是阴极极化抑制微生物附着的主要原因;（3）搅拌等能促进阴极反应、增大阴极极化电流密度的措施都会在一定程度上利于阴极极化对微生物附着的抑制作用。     

电解CO_2储存可再生电能的N-甲基吡咯烷酮/四丁基高氯酸铵电解液研究

将CO_2转化为甲醇,用作燃料或基础化工原料,是实现CO_2资源化利用的重要途径之一。研究设计了一种新型双室隔膜电解池,能够在N-甲基吡咯烷酮(NMP)/四丁基高氯酸铵(TBAP)溶液中,以可再生电能为能源,用电化学催化还原的方法将CO_2转化为CO,然后用工业制甲醇的传统方法将CO氢化还原为甲醇。循环伏安测试结果表明,CO_2在Au电极上发生了电还原反应;恒电位电解测试结果表明,阴极电流密度最高可达6.6 m A×cm~(-2);气相色谱检测结果表明,阴极气相反应产物主要为CO,生成CO的电流效率最高可达93%。由于CO_2电还原反应自身有H_2O生成,阴极表面有H2析出。扫描电镜(SEM)检测表明,Au电极表面没有附着物生成。在N-甲基吡咯烷酮/四丁基高氯酸铵溶液中电还原CO_2,具有电解液性质稳定、电极不中毒的优点,因而具有潜在的工业化应用前景。     

硫化黑2BR 200%在石墨镀银电极上的电催化还原

采用涂附法制备了石墨镀银电极。用配有EDS的扫描电子显微镜(FE-SEM)对石墨镀银电极表面结构进行了表征,以石墨镀银电极和石墨电极为工作电极,采用线性扫描法研究了硫化黑在NaOH溶液中的电化学还原行为,探讨了溶液pH值对硫化黑2BR 200%电还原反应的影响。实验结果表明：用涂附法制备得到的石墨镀银电极表面分布了大量金属银颗粒,该石墨镀银电极对硫化黑2BR 200%的还原反应显示了很高的电催化活性,其电催化活性高于石墨电极;电解液的pH值越大,硫化黑的电还原反应就越容易。在恒电流电解中,以镀银石墨电极为阴极,电流密度为6.25 mA•cm^-2,反应温度为(27±2)℃时,硫化黑的电解实验的电流效率可达92.2%。     

电解液组成对CO_2电化学还原效率的影响

为了考察电解液组成(溶剂和支持电解质)对CO_2电还原效率的影响,以金属银为工作电极,在三电极电解槽中进行了恒电位电解及循环伏安扫描实验。结果表明:相比于二甲基甲酰胺(DMF)和甲醇,用乙腈作溶剂时产物CO法拉第效率最高;强酸作为阳极液支持电解质可以降低CO_2还原过电位并提高CO部分电流密度;离子液体作为阴极液支持电解质可以全面提高CO_2还原效率。研究不同离子液体的催化行为,发现离子液体中阳离子部分对CO部分电流密度的影响比阴离子的影响更明显,进一步证实了咪唑阳离子对还原CO_2起主要催化作用。     

CO_2在离子液体/有机溶剂/水复合电解液中电催化还原

在1-丁基3-甲基咪唑三氟甲基磺酸盐([Bmim][CF3SO3])/碳酸丙烯酯(PC)溶液中,研究了CO2在金电极上的电还原反应,分析了水对有机电解液导电率、黏度和阴极反应动力学过程的影响。结果表明:当含水量(质量分数)较低时,水的存在有利于CO的生成,为2%时,生成CO的电流效率达到最高值96.5%。当含水量进一步增加时,生成CO的电流效率降低,生成H2的电流效率升高。CO2电还原气相产物可用于替代天然气生产甲醇,阴极电解液的最佳含水量为0—10%。     

对硝基苯酚在铜电极上的电化学还原过程研究

采用循环伏安法研究了不同pH溶液中对硝基苯酚在铜电极上的电化学还原行为,选定了不同的电位利用计时电流法电解对硝基苯酚。研究了对硝基苯酚电解还原过程中pH、电位和电解时间对去除效率的影响,并对反应机理进行了探讨。结果表明,对硝基苯酚在铜电极上能发生还原反应,并且随着pH的升高,还原电位负移。     

用膜—电极组合或气体扩散电极电化学转化无水卤化氢为卤气

用膜－电极组合,或膜和电极分开的装置如带膜的气体扩散电极使无水卤化氢电化学转化为卤气,介绍了所用的电槽和工艺。该电槽中装配有离子传递膜,膜的一侧与阳极接触,另一侧与阴极接触。该工艺包括：将无水卤化氢通入电解槽,在两极间施以1．0－2．0V的电压（阳极电位高于阴极电位）在槽压206．7－757．9kPa、温度为40－120℃、电流密度5．8－12kA/m^2的条件下进行电解,无水卤化氢在阳极上被氧化成无水卤气和质子,该质子通过离子交换后在阴极被还原;在膜的阴极侧通水且与含氧的气体接触。     

电化学还原CO2阴极材料研究进展

CO2的电化学转化具有环境、资源和经济效益等多重意义。本文综述了电化学方法还原CO2阴极材料的发展现状,分别对水基溶剂、有机溶剂和离子液体中电极材料的研究情况进行了阐述,并指出了其各自的优缺点。水基溶剂中,CO2加氢具有充足的H+来源且反应过程相对较为简单,但产物燃料化特性不明显;有机溶剂中反应效率较高,但反应路径较为复杂;离子液体是较新的研究领域,生成CO2的反应过电位大大降低,但产物较为复杂且分离有难度。最后对电化学还原CO2阴极材料的发展趋势进行了展望,认为还需在复合材料、反应界面开展更深入的探索。     

Vibrational Spectroscopy in Assessment of Early Osteoarthritis—A Narrative Review

Osteoarthritis (OA) is a degenerative disease, and there is currently no effective medicine to cure it. Early prevention and treatment can effectively reduce the pain of OA patients and save costs. Therefore, it is necessary to diagnose OA at an early stage. There are various diagnostic methods for OA, but the methods applied to early diagnosis are limited. Ordinary optical diagnosis is confined to the surface, while laboratory tests, such as rheumatoid factor inspection and physical arthritis checks, are too trivial or time-consuming. Evidently, there is an urgent need to develop a rapid nondestructive detection method for the early diagnosis of OA. Vibrational spectroscopy is a rapid and nondestructive technique that has attracted much attention. In this review, near-infrared (NIR), infrared, (IR) and Raman spectroscopy were introduced to show their potential in early OA diagnosis. The basic principles were discussed first, and then the research progress to date was discussed, as well as its limitations and the direction of development. Finally, all methods were compared, and vibrational spectroscopy was demonstrated that it could be used as a promising tool for early OA diagnosis. This review provides theoretical support for the application and development of vibrational spectroscopy technology in OA diagnosis, providing a new strategy for the nondestructive and rapid diagnosis of arthritis and promoting the development and clinical application of a component-based molecular spectrum detection technology.     

Monitoring of polymer content in an emulsion polymerization using spatially resolved spectroscopy in the near infrared region and Raman spectroscopy

The potential of spatially resolved spectroscopy (SRS) for in situ monitoring is evaluated in this work. SRS is based on near-infrared spectroscopy. It is well adapted to heterogeneous systems and collects information about both physical and chemical properties. In this work, the polymer content in emulsion copolymerization is predicted using SRS. The reaction was first carried out in batch mode for particle nucleation followed by semi-continuous monomer addition under starved conditions to allow particle growth. SRS and Raman spectroscopy are compared, and the advantages and disadvantages of both methods are highlighted, revealing that each method has its own benefits. Different operating conditions were varied, including the monomer ratio, the surfactant mass fraction, and the agitation speed. Regression models were developed using partial least square for both techniques.     

In-process vibrational spectroscopy and ultrasound measurements in polymer melt extrusion

Spectroscopic techniques have the potential to provide powerful, molecular-specific, non-invasive measurements on polymers during melt processing operations. An exploration is reported of the application and assessment of sensitivity of in-process vibrational spectroscopy—on-line mid-infrared (MIR), on-line near-infrared (NIR), in-line NIR and in-line Raman—for monitoring of single screw extrusion of high-density polyethylene and polypropylene blends. These vibrational spectroscopic techniques are compared with novel in-line ultrasound velocity measurements, which were acquired simultaneously, to assess the sensitivity of each method to changes in blend composition and to explore the suitability for their use in real time process monitoring and control.     

Characterisation of insoluble charcoal in Weipa bauxite

The role of charcoal like components (also referred to as char) in soil organic matter reactivity has become increasingly evident. Recently we have demonstrated the role of such material in bauxite. Sodium hydroxide is used at elevated temperatures to separate aluminium hydroxide from ferric oxide in bauxite in the Bayer process and charcoal like material may interfere with the precipitation of aluminium hydroxide. In this paper we study the solubility, structure and composition of charcoal in the feed stockpile of bauxite ore by solubility, laser Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and pyrolysis gas chromatography mass spectrometry (py-GC/MS). The charcoal was treated under simulated Bayer process conditions of 245 °C in 5 M sodium hydroxide. The alkaline digestion test showed that a large fraction of the charcoal was insoluble (∼90%). Surprisingly, the spectroscopic characterisation revealed not only typical polycyclic aromatic networks expected for charcoals (aromaticity f_a = 0.64), but also showed an aliphatic character and that the sample contained alkyl chains ranging from nC₁₀ to nC₂₃ carbon chain lengths. The role of this material in bauxite refineries is discussed.     

Electrical relaxation and conduction mechanisms in iron doped barium strontium titanate

Polycrystalline Ba_0.7Sr_0.3Ti_(1?x)Fe_xO₃ (x = 0.1) (BSTF) ceramics, synthesized via solid-state reaction route were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and complex impedance spectroscopy (CIS). The Rietveld refinement of the XRD data confirmed the presence of tetragonal and cubic phases in the prepared sample. The SEM image revealed that the sample has well distributed grains along with some degree of agglomerations. The electrical behaviour of the BSTF ceramic has been studied by complex impedance spectroscopy (CIS) as a function of frequency (1 Hz to 1 MHz) at different temperatures (RT to 700 K). Two semicircular arcs observed in the Cole-Cole plot confirm the contribution from the grain and grain boundary in overall impedance. Both the electrical as well as ac conduction phenomena take place via correlated barrier hopping (CBH) authenticated by detailed complex modulus analysis and ac fitted conductivity respectively. The values of activation energies calculated from electrical impedance, modulus, and conductivity data clearly reveal that the relaxation and conduction processes in BSTF ceramic are induced by doubly ionized oxygen vacancies.     

硼硅酸盐玻璃浸出前后结构变化的研究

硼硅酸盐玻璃作为最具工业化应用前景的高放射性废物的固化基材,其中的放射性核素主要以浸出方式进入生物圈.本工作采用了MCC-1静态浸泡法对在90℃去离子水中浸泡28 d后的硼硅酸盐玻璃的浸出行为进行了研究.借助电感耦合等离子体发射光谱(ICP-OES)、傅里叶红外光谱(FTIR)、拉曼光谱(Raman)以及掠入射X射线衍...     

FTIR and Raman Spectroscopy of Carbon Nanoparticles in SiO2, ZnO and NiO Matrices

Coatings of carbon nanoparticles dispersed in SiO₂, ZnO and NiO matrices on aluminium substrates have been fabricated by a sol–gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite coatings with a view to apply these as selective solar absorber surfaces in solar thermal collectors. Cross-sectional high resolution transmission electron microscopy (X-HRTEM) was used to study the fine structure of the samples. Raman spectroscopy was used to estimate the grain size and crystallite size of the carbon clusters of the composite coatings. X-HRTEM studies revealed a nanometric grain size for all types of samples. The C–SiO₂, C–ZnO and C–NiO coatings contained amorphous carbon nanoparticles embedded in nanocrystalline SiO₂, ZnO and NiO matrices, respectively. Selected area electron diffraction (SAED) showed that a small amount of Ni grains of 30 nm diameter also existed in the NiO matrix. The thermal emittances of the samples were 10% for C–SiO₂, 6% for the C–ZnO and 4% for the C–NiO samples. The solar absorptances were 95%, 71% and 84% for the C–SiO₂, C–ZnO and C–NiO samples, respectively. Based on these results, C–NiO samples proved to have the best solar selectivity behaviour followed by the C–ZnO, and last were the C–SiO₂ samples. Raman spectroscopy studies revealed that both the C–ZnO and C–NiO samples have grain sizes for the carbon clusters in the range 55–62 nm and a crystallite size of 6 nm.     

Photodegradation of Azathioprine in the Presence of Sodium Thiosulfate

The effect of sodium thiosulfate (ST) on the photodegradation of azathioprine (AZA) was analyzed by UV-VIS spectroscopy, photoluminescence (PL), FTIR spectroscopy, Raman scattering, X-ray photoelectron (XPS) spectroscopy, thermogravimetry (TG) and mass spectrometry (MS). The PL studies highlighted that as the ST concentration increased from 25 wt.% to 75 wt.% in the AZA:ST mixture, the emission band of AZA gradual downshifted to 553, 542 and 530 nm. The photodegradation process of AZA:ST induced: (i) the emergence of a new band in the 320–400 nm range in the UV-VIS spectra of AZA and (ii) a change in the intensity ratio of the photoluminescence excitation (PLE) bands in the 280–335 and 335–430 nm spectral ranges. These changes suggest the emergence of new compounds during the photo-oxidation reaction of AZA with ST. The invoked photodegradation compounds were confirmed by studies of the Raman scattering, the FTIR spectroscopy and XPS spectroscopy through: (i) the downshift of the IR band of AZA from 1336 cm⁻¹ to 1331 cm⁻¹, attributed to N-C-N deformation in the purine ring; (ii) the change in the intensity ratio of the Raman lines peaking at 1305 cm⁻¹ and 1330 cm⁻¹ from 3.45 to 4.57, as the weight of ST in the AZA:ST mixture mass increased; and (iii) the emergence of a new band in the XPS O1s spectrum peaking at 531 eV, which was associated with the C=O bond. Through correlated studies of TG-MS, the main key fragments of ST-reacted AZA are reported.