掺硼浓度对金刚石薄膜电极电化学性能影响的研究

以不同掺硼浓度的金刚石薄膜作为电极材料,采用循环伏安法和交流阻抗法研究了电极的电化学性能,着重分析了掺硼浓度对金刚石电极电化学性能的影响.结果表明,随着掺硼浓度的增加,电极的电势窗口略微变小,背景电流也随之变大.在铁氰化钾电解液中,未掺杂金刚石薄膜的电极表面进行的不是可逆反应,而硼掺杂金刚石膜电极表面在反应过程中有着良好的活性和准可逆性;并且随着掺硼浓度的增加,其动力学过程主要受扩散过程控制.金刚石膜电极对苯酚模拟有机污染物的循环伏安实验表明,所考察的三个硼浓度不断增加的电极的氧化峰电流密度分别为0.8,1.9和5.1 mA(cm(2,说明在本实验范围内,金刚石膜电极对苯酚催化氧化作用随着掺硼浓度的增加而增强.     

卡马西平的电化学检测研究

利用滴涂法和简单的恒电位还原法制备性能稳定的电化学还原氧化石墨烯和多壁碳纳米管复合修饰电极（rGO/MWCNTs-GCE）,运用循环伏安法（CV）和差分脉冲伏安法（DPV）研究了卡马西平（CBZ）在所制备的修饰电极上的电化学行为,并对测定条件进行了优化。结果表明,CBZ在6.0×10^-6～2.0×10^-4 mol/L浓度范围内,氧化峰电流值与浓度呈明显的线性关系,检出限为1.0×10^-6 mol/L。优化实验条件后的电极呈现出良好的灵敏度、稳定性和重现性,可用于卡马西平的快速检测。     

基于铁氰化铈纳米膜修饰玻碳电极多巴胺的测定

采用电聚合法制备了铁氰化铈[CeFe(CN)6]纳米膜修饰玻碳电极。用循环伏安法研究了多巴胺(DA)在修饰电极上的电化学行为。实验结果表明,该修饰电极对于DA的氧化还原具有良好的电催化性能。相对于裸电极,DA在铁氰化铈纳米膜修饰玻碳电极上的氧化峰电流显著提高。利用差分脉冲伏安法测定DA,在0.0~1000.0 mol·L-1浓度范围内与氧化峰电流呈良好的线性关系,相关系数为0.994。信噪比为3时,DA检出限为6.0×10-8 mol·L-1。将该方法用于盐酸多巴胺针剂分析,回收率为95.8%~101.9%。     

对乙酰氨基酚在硼掺杂金刚石薄膜电极上的电化学行为及测定

硼掺杂金刚石(BDD)薄膜电极是用于电化学分析的理想电极材料。采用循环伏安法研究了BDD电极上对乙酰氨基酚的电化学行为。研究发现,对乙酰氨基酚的氧化反应为不可逆电氧化反应,氧化峰电流与扫描速率的平方根成正比,受扩散控制。通过优化循环伏安测试参数建立了BDD电极上对乙酰氨基酚的测定方法,优化后测试参数为扫描速率10 mV/s,电压扫描范围为-1.0².0 V(vs.Ag/AgCl),扫描1次,扫描步长2.44 mV,得到氧化峰电流值与对乙酰氨基酚浓度在10.02.0 V(vs.Ag/AgCl),扫描1次,扫描步长2.44 mV,得到氧化峰电流值与对乙酰氨基酚浓度在10.0⁵00.0 mg/L范围内呈线性关系,线性回归曲线为Y=1.279 34×10500.0 mg/L范围内呈线性关系,线性回归曲线为Y=1.279 34×10⁶X+5.696 73,r=0.999 79。对本测定方法进行了精密度、稳定性和回收率的方法学考察,测定结果令人满意。     

多壁碳纳米管/PEDOT复合修饰电极的制备及对苯二酚的测定

采用循环伏安法和悬凃法,在玻碳电极表面进行聚(3,4)-乙撑二氧噻吩(PEDOT)和多壁碳纳米管修饰,制备多壁碳纳米管-聚(3,4)-乙撑二氧噻吩复合修饰电极。通过扫描电镜观察复合电极的表面形貌,通过电化学阻抗谱(EIS)和循环伏安(CV)对复合电极进行电化学表征,用差分脉冲法(DPV)研究对苯二酚浓度与峰电流之间的线性关系。实验结果表明,制备的复合修饰电极对对苯二酚有明显的电催化作用,氧化还原峰电流明显增大;在p H为7.0的磷酸缓冲液(PBS)里,对苯二酚的峰电流最大。在1×10^-5～5×10^-4mol/L对苯二酚的浓度范围内,复合修饰电极的氧化峰电流值与浓度呈线性关系,其线性方程为y=47.95+0.097 9x,R²=0.961,检出限为1.9×10^-6mol/L。制备的复合修饰电极能够增强电化学信号,具有较好的稳定性。     

苯酚在硼掺杂金刚石薄膜电极上的电化学行为研究

对苯酚在硼掺杂金刚石(Boron-doped diamond,BDD)薄膜电极上的电化学行为进行了研究,采用三电极体系以BDD电极为工作电极,利用循环伏安法研究了苯酚在电极上的电化学氧化过程。研究发现,苯酚在电极上的氧化反应为完全不可逆的电氧化反应,受扩散控制,多次循环伏安扫描后苯酚在电极表面易发生聚合形成聚合物薄膜,导致氧化峰电流下降,但在高于水的分解电压条件下电解,该聚合物薄膜可以被氧化分解,电极恢复活性。     

硼掺杂金刚石膜电极电催化降解环己酮废水

采用循环伏安法、稳态极化法等对硼掺杂金刚石薄膜电极的电化学性能及电氧化降解含环己酮模拟废水的电极过程进行了研究,考察了电流密度、支持电解质浓度、起始环己酮浓度和pH值等因素对硼掺杂金刚石薄膜电极电氧化降解含环己酮模拟废水效果的影响。实验结果表明,硼掺杂金刚石薄膜电极能够对环己酮进行有效且稳定的降解,通过正交优化实验,得到较优工艺条件为阳极电流密度为5 mA·cm^-2,pH值为7,Na₂SO₄浓度为10 g·L^-1,起始环己酮浓度为20 mmol·L^-1,在该条件下COD去除率达92.95%,电流效率达80.81%,降解效果显著。     

Wood液态合金在NaOH溶液中的电化学反应及表面张力变化行为

通过改变液体金属在NaOH溶液中所处的环境介质,利用石墨电极对其施加电场,研究了液态金属的表面张力、界面电化学反应、氧化膜的产生、溶液中电润湿等动态过程。实验发现Wood合金液滴在阳极发生电化学反应产生的氧化膜会迅速减小表面张力并发生铺展,在阴极发生还原反应会使带氧化膜的金属在3 s内恢复到原状,电毛细作用力使氧化膜破裂,各氧化物与NaOH反应产生Sn（OH）₆^2-、SnO₃^2-、SnO₂^2-、PbO₃^2-、Cd（OH）₄^2-使溶液的颜色发生改变,溶液中生成Bi₂O₃-Bi（OH）₃白色共聚物。薄膜电介质层润湿和溶液中电润湿机理在本质上相同,表面张力随着电压的增大而减小并发生明显的电润湿铺展过程,但由于金属液滴通过电化学反应所能吸附的OH^-数量有限,润湿角存在饱和性。     

硼掺杂金刚石薄膜电极上水杨酸的电化学行为

硼掺杂金刚石(BDD)薄膜电极是用于电化学分析中的理想电极材料。以水杨酸(SA)为目标物,利用循环伏安法(CV)和电化学阻抗谱(EIS)对BDD电极上SA的电化学行为进行了研究。结果发现,SA的电化学过程有两个氧化峰,没有还原峰,氧化还原反应为不可逆反应。在低电势下出现的氧化峰电流正比于扫描速率的平方根,具有良好的线性关系,表明不可逆的氧化反应过程中扩散步骤为反应的控制步骤。电极/溶液界面的结构可以用R(QR)的等效电路拟合,当电极电位从开路电位(OCP)提高到2.5 V时,电荷转移电阻Rct从5.137×105Ω·cm2降低到4.171×102Ω·cm2,说明电极电位的增加能够加快氧化反应的进行,可以提高电催化反应速率大小。     

硼掺杂金刚石薄膜电极上水杨酸的电化学行为

硼掺杂金刚石(BDD)薄膜电极是用于电化学分析中的理想电极材料。以水杨酸(SA)为目标物,利用循环伏安法(CV)和电化学阻抗谱(EIS)对BDD电极上SA的电化学行为进行了研究。结果发现,SA的电化学过程有两个氧化峰,没有还原峰,氧化还原反应为不可逆反应。在低电势下出现的氧化峰电流正比于扫描速率的平方根,具有良好的线性关系,表明不可逆的氧化反应过程中扩散步骤为反应的控制步骤。电极/溶液界面的结构可以用R(QR)的等效电路拟合,当电极电位从开路电位(OCP)提高到2.5 V时,电荷转移电阻Rct从5.137×105Ω·cm2降低到4.171×102Ω·cm2,说明电极电位的增加能够加快氧化反应的进行,可以提高电催化反应速率大小。     

Vacuum-annealing induced band bending in phosphorus-doped (111) diamond

High-temperature annealing effects on hydrogen (H)-terminated phosphorus (P)-doped diamond (111) surfaces were investigated by X-ray photoelectron spectroscopy (XPS) and reflection high energy electron diffraction (RHEED) experiments. Thermally activated, surface band bending was observed, which is clearly attributed to surface structural changes and adsorbates dynamics. The XPS results are compared between boron (B)- and P-doped diamond surfaces and an energy band model has been introduced to the P-doped diamond surface. The annealing process induces downward band bending (to a maximum of 1.3 eV) in B-doped diamond whereas it reduces the internal barrier height (by about 1 eV) in P-doped diamond and finally, the surface bands are pinned in the middle of the band gap. The depletion layer widths are calculated for both diamond surfaces. The band bending imposed by the annealing process can be effective in tuning the surface barrier height.     

Potassium adsorption on hydrogen- and oxygen-terminated diamond(100) surfaces

The adsorption of K at 298 K is a route for the titration of surface groups like O and OH. The experiments were performed on a semi-conducting natural diamond (100) surface cleaned by a 480-W microwave hydrogen plasma at 750°C and a hydrogen pressure of 20 mbar, resulting in a very clean, ordered (2×1) surface. A second type of C(100) surface was prepared by ex situ oxidation, using a mixture of hydrochloric and nitric acids. The adsorption experiments were carried out in a UHV system equipped with facilities for photoelectron spectroscopy (XPS and UPS). K deposition was achieved using a dispenser source from the SAES Getters Company. The K uptake of H-terminated C(100) at room temperature is marginal, with a sticking coefficient of <0.03. The acid-treated C(100) surface shows the presence of a broad O 1s spectrum with different oxygen states (different binding energies) in the XPS region. The sticking coefficient for K adsorption at 298 K on this surface is nearly 1. The amount of K accommodated on the surface correlates with the oxygen coverage and a stoichiometry of nearly K/O=1 is reached for the saturated K coverage. In the O 1s spectrum, the high-energy state (534.2 eV) disappears, whereas the overall O 1s intensity is constant. Due to the K adsorption, the C 1s peak shifts by 0.5 eV to a higher binding energy. UPS He I spectra demonstrate a lowering of the work function by −1.9 eV.     

Structural investigation of nanocrystalline diamond/amorphous carbon composite films

Nanocrystalline diamond/amorphous carbon (NCD/a-C) composite films have been prepared by microwave plasma chemical vapor deposition (MWCVD) from methane/nitrogen mixtures. The complex nature of the coatings required the application of a variety of complementary analytical techniques in order to elucidate their structure. The crystallinity of the samples was studied by selected-area electron diffraction (SAED). The diffraction patterns revealed the presence of diamond crystallites within the films. From the images taken by transmission electron microscopy (TEM) the crystallite size was determined to be on the order of 3–5 nm. The results were confirmed by X-ray diffraction (XRD) measurements exhibiting broad (111) and (220) peaks of diamond from which the average size of the crystallites was calculated. The grain boundary width is 1–1.5 nm as observed by TEM images which corresponds to a matrix volume fraction of about 40–50%. This correlates very well with the crystalline phase content of about 50% in the films estimated from their density (2.75 g/cm³ as determined by X-ray reflectivity). The bonding structure of the composite films was studied by electron energy loss spectroscopy (EELS) in the region of carbon core level. The spectra were dominated by a peak at 292 eV indicating the diamond nature of the investigated films. In addition, the spectra of NCD/a-C films possessed a shoulder at 284 eV due to the presence of a small sp² bonded fraction. This phase was identified also by X-ray photoelectron spectroscopy (XPS). The sp²/sp³ ratio was on the order of 10% as determined by deconvolution of the C1s XPS peak.     

Boron doped diamond (BDD)-layers on titanium substrates as electrodes in applied electrochemistry

The composite diamond/titanium electrode which has been investigated here is characterized by a multilayer structure. Termination of the diamond surface in aqueous electrolytes by CH₂ and C=O is supported by electrochemical measurements. A TiC-layer is formed at the phase boundary between the diamond and the titanium. The electrode shows high overvoltages in aqueous electrolytes (η between 1 and 2 V) for cathodic H₂ and anodic O₂ and Cl₂ evolution. This corresponds to the large band gap of diamond, ΔE=5.45 eV. Redox reactions and electrosynthesis at these novel electrodes are briefly reviewed.     

Fabrication of conducting polymer-gold nanoparticles film on electrodes using monolayer protected gold nanoparticles and its electrocatalytic application

We wish to report a simple and new strategy for the fabrication of gold nanoparticles-conducting polymer film on glassy carbon (GC) and indium tin oxide (ITO) surfaces using 5-amino-2-mercapto-1,3,4-thiadiazole capped gold nanoparticles (AMT-AuNPs) in 0.01 M H₂SO₄ by electropolymerization. The presence of amine groups on the surface of the AuNPs was responsible for the deposition of the AMT-AuNPs film on the electrode surface. The atomic force microscopy (AFM) studies reveal that the fabricated p-AMT-AuNPs film showed homogeneously distributed AuNPs with a spherical shape of ∼8 nm diameter. The XPS spectrum shows the binding energies at 83.8 and 87.5 eV in the Au 4f region corresponding to 4f_7/2 and 4f_5/2, respectively. The position and difference between these two peaks (3.7 eV) exactly match the value reported for Au⁰. The N1s XPS showed three binding energies at 396.7, 399.6 and 403.3 eV, corresponding to the NH, –NH– and –N⁺H–, respectively, confirming that the electropolymerization proceeded through the oxidation of –NH₂ groups present on the periphery of the AMT-AuNPs. The application of the present p-AMT-AuNPs modified electrode was demonstrated by studying the electro reduction of oxygen at pH 7.2. The p-AMT-AuNPs film enhanced the oxygen reduction current more than three times than that of p-AMT film prepared under identical conditions.     

Electronic surface barrier properties of boron-doped diamond oxidized by plasma treatment

The electronic surface barrier characteristics of single-crystal and nanocrystalline boron-doped diamond in electrolytes are evaluated. Two cases are compared: Oxidation by RF oxygen plasma treatment and oxidation by anodic polarization in alkaline electrolyte. It is shown that the plasma treatment reduces the surface barrier to about 1.0 eV compared to 1.7 eV when subjected to anodic oxidation. For single-crystalline diamond, the oxygen evolution reaction in 0.1 M H₂SO₄ electrolyte is almost insensitive to the oxidation method while the plasma-treated nanocrystalline diamond electrode shows an enhanced activity of grain boundary defects at anodic potentials. X-ray photoemission spectroscopy measurements reveal that the plasma oxidation induces a higher content of carbonyl surface groups than anodic oxidation as well as a small amount of non-sp³ contents.     

不同基底BDD电极对模拟染料废水的降解脱色试验

在Si、Ta、SiC、Ti四种不同的基底上通过热丝化学气相沉积法分别生长了掺硼金刚石（BDD）薄膜。试验对BDD膜层的微观形貌、电极的电化学性能进行了研究。四种基底的BDD电极均具有较宽的电位窗口;Ta—BDD和SiC—BDD晶体形貌完整;Ta—BDD和Ti—BDD具有较好的膜基附着力,具有较长的寿命。试验表明,使用12h后,Ta—BDD与Ti—BDD仍具有良好的电解性能,微观形貌完整,而Si—BDD和SiC—BDD分别使用4h和6h后,膜层便开始脱落。试验测定了Ta—BDD电极对活性艳红X-3B模拟染料废水的降解脱色效果,考察了不同条件（槽电压、电解质浓度、电解质种类及pH）对脱色效果的影响。结果表明：在酸性介质中,当硫酸钠浓度为2．5s／L时,经过120min电解,模拟废水中的染料可脱除至1％以下。NaCl作为支持电解质时,相比于Na2SO4对废水色度的脱除具有更强的作用。     

Carbon and nitrogen 1s energy levels in amorphous carbon nitride systems: XPS interpretation using first-principles

A series of carbon nitride structures have been generated, by using a classical potential in a Metropolis Monte Carlo liquid quench procedure. The resulting structures are relaxed further using the density functional theory approach. Structures are generated with various mass densities and varying N/C ratios. X-ray photoelectron spectroscopy (XPS) calculations within the first-principles methodology are performed on the generated amorphous carbon nitride systems. Depending on the carbon bonding configuration, the carbon 1s energies are found to vary from 283 to 288 eV while those of nitrogen are found to range from 397 to 405 eV. Additional calculations on model crystalline systems like nitrogen substituted graphite (nitrogen in trigonal structure) and nitrogen substituted diamond support the finding that the C and N 1s energies are not only sensitive to the coordination number of the atom but also to the interatomic distances. Our calculations based on computer generated structures are a viable alternative for the analysis of XPS spectra and support the interpretation of the N 1s energy at 398.4 eV to correspond to two-coordinated N with at least one sp² C nearest neighbor.     

AFM and XPS studies of a homoepitaxial diamond (001) surface nitrided using 500-eV N2+ ion beam

A homoepitaxially grown p-type diamond (001) surface was nitrided by irradiation with a 500-eV N₂⁺ ion beam. X-Ray photoelectron spectra (XPS) were taken in situ during the nitridation. The C1s and N1s XPS spectra were divided into three (A, ∼284.7; B, ∼285.6; and C, ∼287.3 eV) and four (D, ∼398.4; E, ∼399.5; F, ∼401.0; and G, ∼403.3 eV) components, respectively. The A component of the C1s core level originated from the diamond substrate lying under the nitrogen penetration zone. The B and C components came from the nitrogen-diluted layer and from the carbon nitrides, respectively. The composition ratio of nitrogen/carbon in the C phase, N_D+F/C_C, was 0.71. The N_all/C_B+C ratio was 0.25. The morphology of the surface was also measured in air by atomic force microscope (AFM). It was found that grain-like material covered the surface after nitridation. A typical grain size was approximately 50 nm in diameter with a height of 5 nm. However, the grains themselves were not carbon nitrides. The crystallinity of the nitride was investigated using reflection high-energy electron diffraction (RHEED), but the formation of β-C₃N₄ could not be confirmed from the RHEED patterns, due to overlapping with the twin structures of diamond.     

Chemically immobilised carbon nanotubes on silicon: Stable surfaces for aqueous electrochemistry

Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (1 0 0) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. Electrochemical monitoring of the aminophenyl groups confirmed the formation of an amide linkage between the single-walled carbon nanotubes and the aminophenyl layer. The carbon nanotube electrode showed high stability and good electrochemical performance in aqueous solution. At moderate scan rates the Ru(NH₃)₆^+3/+2 couple exhibited quasi-reversible electron transfer kinetics with a standard heterogenous rate constant of 1.2 × 10⁻³ cm s⁻¹ at the covalently-linked carbon nanotube surface. The electrode thus combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, carbon nanotubes for desirable electrochemical properties, and stability in aqueous medium for future applications in environmental sensing.