用于深海极端环境下的pH电极制备方法改进

潘依雯; 叶瑛; 韩沉花

用于深海极端环境下的pH电极制备方法改进

浙江大学海洋科学与工程学系,浙江杭州 310028

基金项目: 浙江省自然基金资助项目(Y5080084);国家自然科学基金重点项目(40637037);国家"八六三"项目(2006AA09Z216)。

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出版历程
- 收稿日期: 2009-06-11
- 修回日期: 2009-12-24

An improved approach of pH electrode preparation for application in the deep-sea environment

Department of Ocean science and Engineering, Zhejiang University, Hangzhou 310028,China

摘要

摘要: pH值是表征深海热液环境以及扩散流区域溶液化学性能的基本参数,因此原位精确获取溶液pH值是很多海洋科学研究者关注的问题。以前试制的电化学原位传感器IrO_x电极,在实际海试中虽然对海底异常信号有响应,但由于信号漂移问题,电极只能用于定性地发现异常。基于熔融碳酸锂氧化金属原理,提出了改进传统熔融碳酸锂法,并设计了强制空气对流和碳酸锂添加过氧化钠两种制备方法。通过实验室的性能测试以及相应的表面扫描电镜测试表明,用改进的方法制得的电极,校正曲线均符合能斯特定律。用强制空气对流和混合碳酸锂/过氧化钠法制得的电极,其性能均明显优于传统熔融碳酸锂法。可推断,在熔融碳酸锂氧化贵金属铱的过程中,氧含量的充分与否是影响IrO_x电极的性能和表面形态的重要因素,其中性能最优的是混合碳酸锂/过氧化钠法制得的电极。该类电极具有如下优点:重复性好;在大跨度pH溶液之间的响应快速稳定,长时间连续监测的漂移小于5 mV;同一批次所制备电极性能几乎相同;使用寿命长等。因此,该pH电极可用于深海的原位探测。该工作为进一步制备高性能的IrO_x电极奠定了坚实的基础。
- 深海探测 /
- 氧化铱电极 /
- pH测量 /
- 能斯特响应 /
- 电极稳定性
Abstract: pH is a fundamental parameter in understanding the chemical processes in deep-sea hydrothermal and diffuse flow areas. pH is also considered to be one of the important characteristics that influences the animal distribution within hydrothermal vent sites while pH is also affected by the metabolic processes of the organism. Hence, a accurate access for deep-sea in-situ pH is a common concern of both marine chemists and marine biologists. In the former application of sea trials, two phenomena have been found: one is that the electrode can respond to the chemical abnormality, the other is due to the drifting problem of the electrode. Data acquired by the electrode can only be used as a qualitative evidence for deep-sea research.Two novel approaches to the preparation of iridium oxide electrode are proposed based on the mechanics of molten alkali metal carbonate. Experiments and SEM surface analysis were carried out to characterize the different types of IrO_x electrodes. Including the electrodes prepared by the traditional approach, the results show that all three of them exhibit Nernst response. Comparing both the sensing characteristics and the SEM surface analysis of the three types of IrO_x electrodes, however, the IrO_x electrodes of advanced carbonate-melted methods exhibited better pH sensitivity and stability, and more solid surface. Therefore, it can be speculated that the oxygen contents during the preparation procedure is a key factor that affects the IrO_x film characteristics. Among the three types of IrO_x electrodes, the one prepared by molten mixed carbonate lithium and sodium peroxide showed the best sensing characteristics. It exhibited good reproducibility and sensitivity, small OCP (open circuit potential) drift (＜5 mV) of 7 d continuous pH measurements, long lifetime and remarkable agreement with respect to potential/pH slopes and apparent standard electrode potentials of individual electrodes prepared from the same batch. Although the aging effects caused the apparent standard electrode potential drop about 50 mV after 3 months, the problem could be eliminated by calibration. Therefore, the good performance of the IrO_x electrode prepared by molten mixed carbonate lithium and sodium peroxide may allow this type of IrO_x electrode be suitable for being applied to in-situ deep-sea measurement.
- deep-sea chemical measurement /
- IrO_x electrode /
- pH sensor /
- Nernst response /
- electrode stability

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