Dataset Information

Electrochemistry in Micro- and Nanochannels Controlled by Streaming Potentials.

ABSTRACT: Fluid and charge transport in micro- and nanoscale fluidic systems are intrinsically coupled via electrokinetic phenomena. While electroosmotic flows and streaming potentials are well understood for externally imposed stimuli, charge injection at electrodes localized inside fluidic systems via electrochemical processes remains to a large degree unexplored. Here, we employ ultramicroelectrodes and nanogap electrodes to study the subtle interplay between ohmic drops, streaming currents, and faradaic processes in miniaturized channels at low concentrations of supporting electrolyte. We show that electroosmosis can, under favorable circumstances, counteract the effect of ohmic losses and shift the apparent formal potential of redox reactions. This interplay can be described by simple circuit models, such that the results described here can be adapted to other micro- and nanofluidic electrochemical systems.

SUBMITTER: Kostiuchenko ZA

PROVIDER: S-EPMC6996092 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Electrochemistry in Micro- and Nanochannels Controlled by Streaming Potentials.

Kostiuchenko Zinaida A ZA Cui Jin Z JZ Lemay Serge G SG

The journal of physical chemistry. C, Nanomaterials and interfaces 20200109 4

Fluid and charge transport in micro- and nanoscale fluidic systems are intrinsically coupled via electrokinetic phenomena. While electroosmotic flows and streaming potentials are well understood for externally imposed stimuli, charge injection at electrodes localized inside fluidic systems via electrochemical processes remains to a large degree unexplored. Here, we employ ultramicroelectrodes and nanogap electrodes to study the subtle interplay between ohmic drops, streaming currents, and farada ...[more]

PMID: 32030113

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Project description:A large number (1253) of high-quality streaming potential coefficient ( Csp) measurements have been carried out on Berea, Boise, Fontainebleau, and Lochaline sandstones (the latter two including both detrital and authigenic overgrowth forms), as a function of pore fluid salinity ( Cf) and rock microstructure. All samples were saturated with fully equilibrated aqueous solutions of NaCl (10 -5 and 4.5 mol/dm 3) upon which accurate measurements of their electrical conductivity and pH were taken. These Csp measurements represent about a fivefold increase in streaming potential data available in the literature, are consistent with the pre-existing 266 measurements, and have lower experimental uncertainties. The Csp measurements follow a pH-sensitive power law behaviour with respect to Cf at medium salinities ( Csp=-1.44×10-9Cf-1.127 , units: V/Pa and mol/dm 3) and show the effect of rock microstructure on the low salinity Csp clearly, producing a smaller decrease in Csp per decade reduction in Cf for samples with (i) lower porosity, (ii) larger cementation exponents, (iii) smaller grain sizes (and hence pore and pore throat sizes), and (iv) larger surface conduction. The Csp measurements include 313 made at Cf>1 mol/dm 3 , which confirm the limiting high salinity Csp behaviour noted by Vinogradov et al., which has been ascribed to the attainment of maximum charge density in the electrical double layer occurring when the Debye length approximates to the size of the hydrated metal ion. The zeta potential ( ζ ) was calculated from each Csp measurement. It was found that ζ is highly sensitive to pH but not sensitive to rock microstructure. It exhibits a pH-dependent logarithmic behaviour with respect to Cf at low to medium salinities ( ζ=0.01133log10Cf+0.003505 , units: V and mol/dm 3) and a limiting zeta potential (zeta potential offset) at high salinities of ζo=-17.36±5.11 mV in the pH range 6-8, which is also pH dependent. The sensitivity of both Csp and ζ to pH and of Csp to rock microstructure indicates that Csp and ζ measurements can only be interpreted together with accurate and equilibrated measurements of pore fluid conductivity and pH and supporting microstructural and surface conduction measurements for each sample.

Dataset Information

Electrochemistry in Micro- and Nanochannels Controlled by Streaming Potentials.

Publications

Electrochemistry in Micro- and Nanochannels Controlled by Streaming Potentials.

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