掺硼金刚石电极质量和应用，以评估<em>原位</em>本地pH值通过水电改造
Summary
甲协议在原位 pH值代实验描述了硼掺杂的金刚石（BDD）电极和随后的应用程序的关键电化学参数的表征。
Abstract
硼掺杂的金刚石（BDD）的电极已经显示相当大的希望作为其中他们的许多报告性质如延长溶剂窗口，低背景电流，耐腐蚀等 ，从表面的催化惰性性质出现的电极材料。但是，如果在生长过程中，非金刚石碳（NDC）变得掺入到电极矩阵，电化学性能将随着表面变得更具有催化活性。因此，它是重要的electrochemist意识到的质量和所得到的在使用前的BDD电极的键电化学性能。本文介绍了一系列表征步骤，包括拉曼显微镜，电容，溶剂的窗口和氧化还原电化学，以确定BDD电极是否包含NDC可以忽略不计，即可以忽略不计的SP 2的碳。一个应用是强调了采取的催化惰性优势和NDC-自由表面的耐腐蚀的性质，即稳定的，可量化的地方质子和氢氧化生产，由于电解水在BDD电极。测量使用铱氧化物涂覆的BDD电极通过水电解诱导局部pH变化的方法进行详细描述的。
Introduction
电极材料的选择是非常重要在进行任何电化学研究时。在最近几年，sp 3键碳（金刚石）掺杂有足够硼呈现材料“金属样”已成为广泛的电分析应用的流行的选择由于其优异的电化学（和热和机械）性能1,2- 3。这些包括极端的解决方案，温度和压力条件4超宽溶剂窗户，低背景电流下的耐腐蚀性，并降低了结垢，相较于其他常用的电极材料5-7,3。但是，增加的非金刚石碳（NDC：藻2）的含量会导致降低的窗口溶剂，增加背景电流7,8，改变在两个不同的朝向内球的氧化还原物质的结构完整性和灵敏度，例如。氧气9-12。
请注意这样我的应用程序，NDC的存在被认为是有利的13。此外，如果材料不含有足够的硼它将表现为p型半导体，并显示氧化还原物种中的还原电位窗口，其中该材料被最耗尽电荷载体7的敏感性降低。最后，掺硼金刚石的表面化学（BDD）也可以起到在所观察到的电化学应答的作用。这是内球物种是敏感的表面化学和降低掺杂金刚石，其中氢（H – ） -尤其如此终止的表面可以使半导电BDD电极出现“金属状”7。
要利用的BDD的优异性能，它往往是必要的材料被充分掺杂且包含尽可能少的NDC越好。依赖于通过中生长的BDD的方法中，属性可以变化14,15。本文首先提出了一种材料和选rochemical表征协议指导，以评估在使用前BDD电极适用性（ 即充足的硼，最小的NDC），然后描述了基于局部改变pH值电化学使用的协议验证电极一个应用程序。这个过程需要NDC – 自由的BDD朝在施加施加极端电位（或电流），用于长时间腐蚀或溶解的表面韧性的优点。特别是使用一个BDD电极，以产生稳定的质子（H +）或氢氧化物（OH – ）通量由于水在靠近第二（传感器）电解（分别氧化或还原）16,17在这里被描述。
以这种方式，可以控制传感器的pH值环境中以系统的方式，例如，用于pH滴定实验，或以固定pH值在一个值，其中该电化学过程是最敏感的。后者为特别有用应用中的传感器被放置在源， 如河流，湖泊，海洋和体系的pH不是最佳为感兴趣的电化学测量。两个最近的例子包括：（i）产生的局部低pH，在pH值为中性溶液，用于电沉积和汞17的汽提;注意BDD是金属电沉积青睐的材料，由于扩展阴极窗口9,18,19。 （二）的硫化氢，本在高pH值，所述电化学检测形式的定量通过从中立到强碱性16局部增加的pH值。
Protocol
注：BDD电极使用化学气相沉积技术，附着到生长衬底最常用生长。它们离开生长室氢终止（疏水的）。如果种植足够厚的BDD可以从基底被删除，被称为独立。自由站立的BDD生长表面通常抛光以显著减少表面粗糙度。清洗BDD中酸的结果在氧（O）封端的表面。 1.酸洗BDD 放置浓硫酸的烧杯中（H 2 SO 4;约2ml或足够深，以覆盖金刚石）在热板上在RT并插入BDD。 添加硝酸?…
Representative Results
用于与不同的掺杂密度代表的BDD macrodisc电极获得拉曼光谱和电化学特性，并且两个显著和可以忽略的程度的NDC的，图1和2。 图1A和 B示出典型的拉曼数据为NDC-含有薄膜微晶BDD和较大的晶粒独立BDD，掺杂上述金属门限，分别为。 NDC的存在是可识别由之间1400 1600 -1标记的宽峰;不存在这样的峰在图1C，…
Discussion
带有O形端的表面开始提倡，因为氢终止表面是电化学不稳定的，尤其是在高的阳极电位7,40,41。改变表面终止可能影响范围内的夫妇，如电解水（这里用来改变当地溶液的pH值）的电子转移反应动力学。此外，如果包含的BDD显著NDC在晶界也有可能是在施加极端阳极的/阴极电位主张本文用于pH代，蚀刻可能发生在这些弱点。这将导致该膜腐蚀和薄膜，最终剥离，这表现在一种不稳定的PH值产?…
Declarações
The authors have nothing to disclose.
Acknowledgements
我们要感谢乔纳森·纽兰博士在图4B的照片，处理光学显微镜图像，视频，珍妮弗小姐韦伯对接触角测量的建议和视觉效果，吴诗贤谭为溶剂的窗口，如图2B数据，马克西姆约瑟夫博士的建议拉曼光谱，和华威电化学和接口组的成员也谁帮助开发这里所描述的协议。我们还要感谢约瑟夫·马克斯，Lingcong猛，佐伊·艾尔斯和罗伊Meyler他们参与拍摄的协议。
Materials
| Pt Wire | Counter Electrode | ||
| Saturated Calomel Electrode | IJ Cambria Scientific Ltd. | 2056 | Reference Electrode (alternatively use Ag|AgCl) |
| BDD Electrode | Working Electrode | ||
| Iridium Tetrachloride | VWR International Ltd | 12184.01 | |
| Hydrogen Peroxide | Sigma-Aldrich | H1009 | (30% w/w) Corrosive |
| Oxalic Acid | Sigma-Aldrich | 241172 | Harmful, Irritant |
| Anhydrous Potassium Chloride | Sigma-Aldrich | 451029 | |
| Sulphuric Acid | VWR International Ltd | 102765G | (98%) Corrosive |
| Potassium Nitrate | Sigma-Aldrich | 221295 | |
| Hexaamine Ruthenium Chloride | Strem Chemicals Inc. | 44-0620 | Irritant |
| Perchloric Acid | Sigma-Aldrich | 311421 | Oxidising, Corrosive |
| 2-Propanol | Sigma-Aldrich | 24137 | Flammable |
| Nitric Acid | Sigma-Aldrich | 695033 | Oxidising, Corrosive |
| Sputter/ Evapourator | With Ti & Au targets | ||
| Raman | 514.5 nm laser | ||
| Annealing Oven | Capable of 400°C | ||
| Ag paste | Sigma-Aldrich | 735825 | or other conductive paint |
| Potentiostat | |||
| pH Buffer solutions | Sigma-Aldrich | 38740-38752 | Fixanal buffer concentrates |
| Phenolphthalein Indicator | VWR International Ltd | 210893Q | |
| Methyl Red Indicator | Sigma-Aldrich | 32654 |
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Citar este artigo
Read, T. L., Macpherson, J. V. Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis. J. Vis. Exp. (107), e53484, doi:10.3791/53484 (2016).