Scanning electrochemical microscopy imaging of rhodochrosite dissolution using gold amalgam microelectrodes

Abstract

Gold/mercury amalgam (Au/Hg) microelectrodes with a diameter of 25 microm were developed for the detection of environmentally relevant analytes such as manganese and iron by scanning electrochemical microscopy (SECM), and applied to investigate the controlled dissolution of manganese carbonate (MnCO(3); rhodochrosite) in acidic conditions. Characterization of the amalgam electrode geometry via approach curves recorded during SECM experiments revealed Au/Hg microelectrodes with sphere cap geometry. Quantitative determination of Mn(2+) has been achieved by calibration of the Au/Hg microelectrode in bulk solution experiments. Subsequent SECM imaging experiments confirm the applicability of amalgam microelectrodes for imaging of Mn(2+) production during dissolution of MnCO(3) at pH 3.9. This study confirms feasibility and provides the fundamental basis of SECM imaging with amalgam microelectrodes to address biogeochemically relevant questions.

Application of Sphere Cap Mercury Microelectrodes and Scanning Electrochemical Microscopy (SECM) for Heavy Metal Monitoring at Solid/Solution Interfaces

“…Moreover, a useful extension of the presented procedure would be the use of square wave anodic stripping voltammetry, which, in principle, would enable lower concentrations of metal ions to be monitored with less influence from dissolved oxygen [14,24,30].…”

Ex Situ Scanning Electrochemical Microscopy (SECM) Investigation of Bismuth‐ and Bismuth/Lead Alloy Film‐Modified Gold Electrodes in Alkaline Medium

“…In fact, the latter approach proved useful for sensitive and high-spatial resolution analysis of metal ions at a variety of solid/ solution interfaces [36,[45][46][47][48][49][50][51]. For these measurements the metal-coated gold substrates, once prepared in the alkaline solution as described above, were transferred in the SECM cell containing 0.1 mol L À1 acetate buffer (pH 4.5).…”

Advective and transient effects in combined AFM/SECM operation

“…The choice of scales determines the nondimensional form of Eqs. (2) and (8), as well as the numerical value of the resulting nondimensional parameters. A discussion of scaling is provided in detail in Appendix A.…”

“…A small electrode (diameter 25 lm or less) induces an electrochemical reaction, and the resulting Faradaic current (tip current) is proportional to the net flux of a redox species to the electrode surface. The SECM is used to spatially characterize surface kinetics, to provide high resolution imaging of the release of chemicals from a surface, and to electrochemically modify a surface [2][3][4]. One advantage of this technology is the ability to predict or interpret the response current based on a first principles theoretical description of the relevant phenomena.…”