Standard electrochemical behavior of high-quality, boron-doped polycrystalline diamond thin-film electrodes
Standard electrochemical behavior of high-quality, boron-doped polycrystalline diamond thin-film electrodes
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DOI：
10.1021/ac0000675
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发表时间：
2000-08-15
影响因子：
7.4
通讯作者：
Swain, GM
中科院分区：
文献类型：
--
作者：
Granger, MC;Witek, M;Swain, GM
高品质，硼掺杂的金刚石薄膜电极的标准电化学数据。来自两个不同来源的膜进行了比较（NRL和USU），两者都是高导电性的，氢终止的，和多晶的，膜酸洗和氢等离子体处理之前使用，以去除非金刚石碳杂质相和氢终止的表面。基于硼核反应分析，NRL膜的硼掺杂水平估计在10（19）B/cm（3）的中间范围内，并且USU膜的硼掺杂水平类似于5 × 10（20）B/cm（-3）。用Fe（CN）（6）（3-/4-）、Ru（NH3）（6）（3+/2+）、IrCl_（62-/3-）、甲基紫精、多巴胺、抗坏血酸、Fe ~（3 +/2+）和氯丙嗪等评价了电化学响应。在这些高质量的金刚石膜和速率常数在文献中报道的新鲜活化的玻璃碳观察。Ru（NH3）（6）（3+/2+）、IrCl 62-/3-、甲基紫精和氯丙嗪都涉及对金刚石表面微观结构和化学性质不敏感的电子转移，k（app）（o）在10（-2）-10（-1）cm/s范围内。速率常数主要受膜的电子性质的影响。Fe（CN）（6）（3-/4-）在氢封端的表面上经历对表面化学极其敏感的电子转移，其中k（app）（o）在10（-2）-10（-1）cm/s的范围内。氧表面终止严重抑制电子转移的速率。Fe ~（3+）/Fe ~（2+）在氢封端的表面进行缓慢的电子转移，k（app）（o）接近10 ~（-5）cm/s。已知sp ~（2）碳电极上的电子转移速率是由表面羰基官能团介导的;然而，由于氢封端，这种内层催化途径在金刚石上不存在。多巴胺，像其他儿茶酚和儿茶酚胺，经历缓慢的电子转移，k（app）（o）在10（-4）和10（-5）cm/s之间。将表面转化为氧终止对k（app）（o）几乎没有影响。缓慢的动力学可能与这些分析物在金刚石表面上的弱吸附有关。抗坏血酸的氧化是非常敏感的表面终止与最负的E-p（ox）观察在氢终止的表面。氧表面终止使E-p（ox）正移约250 mV或更多。提出了一个界面能图来解释电子转移，从而导致主要从硼掺杂水平和晶格氢的midgap态密度。另外，通过扫描电子显微镜和显微拉曼成像光谱的薄膜进行了表征。所提出的循环伏安法和动力学数据可以作为研究小组评估半金属（即，导电的）、氢封端的多晶金刚石。
Standard electrochemical data for high-quality, boron-doped diamond thin film electrodes are presented. Films from two different sources were compared (NRL and USU) and both were highly conductive, hydrogen-terminated, and polycrystalline, The films are acid washed and hydrogen plasma treated prior to use to remove nondiamond carbon impurity phases and to hydrogen terminate the surface. The boron-doping level of the NRL film was estimated to be in the mid 10(19) B/cm(3) range, and the boron-doping level of the USU films was similar to 5 x 10(20) B/cm(-3) based on boron nuclear reaction analysis. The electrochemical response was evaluated using Fe(CN)(6)(3-/4-), Ru(NH3)(6)(3+/2+), IrCl62-/3-, methyl viologen, dopamine, ascorbic acid, Fe3+/2+, and chlorpromazine, Comparisons are made between the apparent heterogeneous electron-transfer rate constants, k(app)(o), observed at these high-quality diamond films and the rate constants reported in the literature for freshly activated glassy carbon. Ru(NH3)(6)(3+/2+), IrCl62-/3-, methyl viologen, and chlorpromazine all involve electron transfer that is insensitive to the diamond surface microstructure and chemistry with k(app)(o) in the 10(-2)-10(-1) cm/s range. The rate constants are mainly influenced by the electronic properties of the films. Fe(CN)(6)(3-/4-) undergoes electron transfer that is extremely sensitive to the surface chemistry with k(app)(o) in the range of 10(-2)-10(-1) cm/s at the hydrogen-terminated surface. An oxygen surface termination severely inhibits the rate of electron transfer. Fe3+/2+ undergoes slow electron transfer at the hydrogen-terminated surface with k(app)(o) near 10(-5) cm/s, The rate of electron transfer at sp(2) carbon electrodes is known to be mediated by surface carbonyl functionalities; however, this inner-sphere, catalytic pathway is absent on diamond due to the hydrogen termination. Dopamine, like other catechol and catecholamines, undergoes sluggish electron transfer with k(app)(o) between 10(-4) and 10(-5) cm/s, Converting the surface to an oxygen termination has little effect on k(app)(o). The slow kinetics may be related to weak adsorption of these analytes on the diamond surface. Ascorbic acid oxidation is very sensitive to the surface termination with the most negative E-p(ox) observed at the hydrogen-terminated surface. An oxygen surface termination shifts E-p(ox) positive by some 250 mV or more. An interfacial energy diagram is proposed to explain the electron transfer whereby the midgap density of states results primarily from the boron doping level and the lattice hydrogen. The films were additionally characterized by scanning electron microscopy and micro-Raman imaging spectroscopy. The cyclic voltammetric and kinetic data presented can serve as a benchmark for research groups evaluating the electrochemical properties of semimetallic (i.e., conductive), hydrogen-terminated, polycrystalline diamond.