In situ electrodes

In situ electrodes to supply hydrogen as an electron donor to subsurface... 

The classical methods to determine substrate concentrations are off-line laboratory methods. This implies that samples are taken aseptically, pre-treated and transported to a suitable laboratory, where storage of these samples might be necessary before processing. The problems associated with these procedures are discussed below. There is only one general exception to this, namely, the gaseous substrate oxygen, for which in situ electrodes are generally used. 

Fig. 8-4 Correlation diagram for redox potential (pE) and oxygen saturation (note the log scale). In situ electrode measurements in a Dutch intertidal area. Reprinted with permission from the author.

Several of the artifacts noted above may be avoided through the use of in situ electrodes that can be inserted directly into sediment and measure activities of various solutes. Systems to measure oxygen and pH are often used. Very recently, new electrodes to measure pCOi, sulfide, iron, and manganese have been developed. By using microelectrodes, gradients over short distances can be resolved. 

Figure 16 A cell for in situ electrode surface studies by Raman spectroscopy. The working electrode (1) is embedded in an insulating piston that can be moved back and forth for the measurement and the electrochemical process (2) reference electrode, (3) counterelectrode (4) electrical contacts to the reference and counter electrodes, (6) glass cell, (7) Teflon cell holder, (8) Teflon tube for argon, (9) glass optical window, (10) Teflon piston, (11) base, (12) micrometer, (13) micrometer shaft, (14) electrical contacts to the working electrode, (15) solution entry (via septum), (16) mirror, (17) focusing lens, (18) detector.

Nishi T., SakkaT., Oguchi H., Fukami K., Ogata Y. H. In Situ Electrode Surface Analysis by Laser-Induced Breakdown Spectroscopy, J. Electrochem. Soc. 2008, 155, F237-F240. 

Dross, R. and Maynard, B. (2007) In-situ electrode testing for cathode carbon corrosion. ECS Trans., 11 (1), 1059-1068. 

Figure 19.13. SEM top view and TEM side view of a nan-equilibrium impregnation-reduction electrode. Deposition conditions 0.6 mM Pt(NH3)4Cl2,1 mM NaBHi, 40 minutes impregnation time, 2 hours reduction time, 50 C [3]. (Reprinted by permission of ECS— The Electrochemical Society, from Liu R, Her W-H, Fedkiw PS. In situ electrode formation on a Nafion membrane by chemical platinization.)...

Liu R, Her W-H, Fedkiw PS. In situ electrode formation on a Nafion membrane by chemical platinization. J Electrochem Soc 1992 139 15-23. 

Techniques which enable in situ electrode characterization (e.g., surface films can be identified while the electrode is in solution, under potential control), such as FTIR, RAMAN, XRD, EQCM, EXAFS, STM, AFM vs. ex situ methods that include XPS, SEM, and AES, SIMS and solid state NMR. 

Figure 3 shows a scheme of a suitable cell for in situ electrode surface studies by Raman spectroscopy. The working electrode is embedded in an... 

Room-Temperature Ionic Liquid-Based SEM/EDX Techniques for Biological Specimens and in situ Electrode Reaction... 

Fig. 17 a Cyclic voltammograms obtained for Si02/C/CoPc-in situ and Si02/C/CoPc-classic and Si02/C/Co electrodes in the presenee of 8.2 mg O2 b Cathodic currents for the Si02/ C/CoPe-in situ electrode vtisus O2 concentration. Reprinted with permission from [67]. Copyright (2013) Elsevier... 

Following the above review of the various spectroscopic techniques for in situ electrode/solution interface investigations, several points should be discussed. 

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