【作者】 高成耀；

【导师】 常明；

【作者基本信息】 天津大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 金刚石薄膜作为一种新型的电极材料有常规电极不可比拟的优势,具有高析氧电位、低背景电流、吸附惰性和高物理化学稳定的特点,因而成为电化学电极的优良之选,并且获得了在电合成、电化学催化、电分析方面的应用。本论文利用掺硼金刚石(BDD)薄膜电极较高过电势而能高效率产生强氧化性中间物种的优势,探讨了其在电催化降解有机物方面的应用,并成功将其应用于实际工业超高化学需氧量(COD)有机废水的处理。利用热丝(HFCVD)、微波等离子体(MPCVD)和直流等离子体喷射(DC plasma jet CVD)化学气相沉积方法制备不同特性的金刚石薄膜。除了在常规掺杂衬底Si上制备外,在相对高电导率的Ta、Ti、Nb等金属材料上亦沉积成功金刚石薄膜。在特定的工艺条件下,XRD、SEM和Raman测试表明沉积薄膜为良好的sp3键结构的多晶金刚石,非金刚石相成分较少。在成功制备金刚石薄膜的基础上探讨了沉积工艺条件如功率、气压和碳源量对成膜质量的影响。利用循环伏安、交流阻抗等测试方法对钽基金刚石电极(Ta/BDD)进行了电化学特性表征,并探讨了金刚石电极/溶液界面的电极过程。通过循环伏安法测试发现掺硼金刚石膜电极在Na2SO4体系中具有非常宽的电化学窗口,达到4.1 V(-1.8 V~+2.3 V (vs SCE)),而且具有较小的背景电流;通过与其它电极的对比实验发现金刚石薄膜电极较Pt、IrO2、RuO2电极具有更高的析氧电位。考察了溶液的酸碱性、CVD沉积过程碳源量及硼掺杂等因素对电极电势窗口的影响。用交流阻抗法研究了不同极化电压下的交流阻抗特性,并用等效电路进行了模拟。在金刚石电催化应用实验发现金刚石薄膜电极对典型难生物降解有机物苯酚和硝基酚都能进行有效电催化降解,在特定的时间内两种有毒物质去除率能达到100%,COD去除率接近100%,说明BDD电极是难降解有机物去除和COD电催化降解的优良电极。考察了电流密度、有机物初始浓度和不同电解质浓度对电催化过程的影响。与常规电催化电极PbO2进行电催化性能对比实验发现金刚石薄膜电极具有更高的电流效率。电极强化寿命实验发现Ta/BDD薄膜电极具有良好的电化学稳定性,XRD测试表明电极表面在长时间的电解过程中电极表面基本保持不变。将Ta/BDD电极用于超高COD降解实验并组装BDD电极电催化降解装置用于味精废水和橡胶废水的工业化处理。工业化降解过程中该装置表现出电流效率高、功耗小的特点,非常适合电催化降解超高COD有机废水。更多还原

【Abstract】 Diamond thin film is a new electrode material that has received great attention recently because it possesses several technologically important characteristics such as large overvoltage for the anodic oxygen evolution, low background currents, an inert surface with low adsorption properties, remarkable corrosion stability. Thanks to these properties, diamond film seems to be a promising electrode material than the traditional electrode and so, it has been studied with the goal of developing applications in electro-synthesis、electrochemical water treatment、electro-analysis technology. The high overpotential for oxygen transfer enables diamond electrode to produce hydroxyl radicals and short-lived species in the anodic oxidation reaction. In this dissertation, the application of boron-doped diamond electrodes for electro-catalytic degradation of organic matters is described and this kind of electrode material was successfully applied to actual industrial ultra-high chemical oxygen demand (COD) organic waste water treatment.Diamond film with different quality was prepared by hot filament chemical vapor deposition(HFCVD) , microwave plasma chemical vapor deposition (MPCVD)and DC plasma jet chemical vapor deposition (DC plasma jet CVD). Besides high doped Si, diamond was successfully deposited on metal substrates with relatively high conductivity such as Ta, Ti, Nb by CVD method. Raman spectroscopy, X-ray diffraction(XRD), and scanning electron microscopy(SEM)examinations demonstrated that the films had well-defined sp3 bond diamond features. Only very little non-diamond was found. The deposition conditions such as power, pressure and the concentration of carbon source effect on the quality of the diamond film were investigated.The electrochemical behaviors of Ta/BDD electrode were investigated using cyclic voltammetry and AC Impedance and electrode / solution model was proposed. It was found that characteristic voltammetry features of polycrystalline diamond electrodes deposited on Ta(Ta/BDD) in Na2SO4 solution were a wide potential range for water stability (4.1 V (-1.8 V~+2.3 V vs. Saturated calomel electrode)) and low background current. A much higher oxygen evolution potential of Ta/BDD electrode was obtained than the other electrode such as Pt、IrO2、RuO2. The effect of PH value and amount of carbon source in CVD deposition process to the BDD potential window were studied. Impedance characteristics of Ta/BDD under different polarization voltage were investigated by AC impedance measurement and equivalent circuit was used for the simulation.Electrochemical degradation of wastewater containing phenol and nitrophenol on Ta/BDD was studied. It was observed that both the two organic pollutant can be oxidation efficiently within a specified time, with pollutant and COD removal efficiency as high as 100%. The effect of current density、organic initial concentration、support solution and its concentration on the electrocatalytic degradation have been investigated. It was found that Ta/BDD anode provided a higher oxidation rate and higher current efficiency than conventional electro-catalytic electrodes PbO2 in the degradation of phenol. Good electrochemical stability of Ta/BDD electrode was obtained in the accelerated life test. XRD tests showed that electrode surface unchanged for a long time in the electrolysis process. According to the results, Ta/BDD anode were seen to be a unique electrode for the degradation of organic and COD simultaneously.BDD electrodes were assembled and used for ultra-high COD wastewater degradation. High-efficiency and low-power consumption were obtained in the catalytic degradation of monosodium glutamate and rubber industrial wastewater, proving BDD is an ideal electrode to electro-catalytic depredate of organic wastewater with ultra-high COD.更多还原