Solid electrochemical potentiometric

It is typically on the order of several hundred nanometers. In practice the minimum thickness for polymeric membranes is 50gm or greater, which is far more than one would expect from (6.53). This is apparendy due to the fact that these membranes hydrate in the bulk, thus increasing the dielectric constant. They also form a hydrated layer at the solution/membrane interface (Li et al 1996) which affects their overall electrochemical properties and selectivities. Macroscopic ISEs use relatively thick membranes ( 500jU.m). In contrast, it is desirable to use thin membranes in the construction of asymmetric solid-state potentiometric ion sensors, in order to make their preparation compatible with the thin-layer preparation techniques. 

This anodic reaction provides sodium ions and electrons to the solid electrolyte and the inert Pt counter electrode, respectively, at the source side. Both the sodium ions and electrons will then travel through the solid electrochemical cell along previously-mentioned ionic and electronic paths to sustain the PEVD cathodic reaction for Na COj product formation at the sink side. Eurthermore, based on anodic reaction 60, the chemical potential of sodium is fixed by the vapor phase at the source side. Under open circuit conditions, this type of source can also serve as the reference electrode for a CO potentiometric sensor. 

The potential profiles in this PEVD system are illustrated in Figure 17. Although there is no driving force due to a difference in the chemical potential of sodium in the current PEVD system, the applied dc potential provides the thermodynamic driving force for the overall cell reaction (62). Consequently, electrical energy is transferred in this particular PEVD system to move Na COj from the anode to the cathode of the solid electrochemical cell by two half-cell electrochemical reactions. In short, this PEVD process can be used to deposit Na CO at the working electrode of a potentiometric CO sensor. 

Solid-State Electrochemical Potentiometric Sensors for Gas Analysis. . . 1105 H. -H. Mdbius... 

Solid-State Electrochemical Potentiometric Sensors for Gas Analysis... 

Mdbius HH (1991) Solid state electrochemical potentiometric sensors for gas analysis, hi Gopel W, Hesse J, Zemel JN (eds) Sensors a comprehensive survey. VCH, New YorkAVeinheim... 

Pasierb P, Rekas M (2(X)9) Solid-state potentiometric gas sensors-current status and future trends. J Solid State Electrochem 13(l) 3-25... 

Masked WC, Steele BCH (1986) Solid state potentiometric oxygen gas sensors. J Appl Electrochem 16(4) 475 89... 

Zhu J, Qin Y, Zhang Y (2009) Preparation of aU solid-state potentiometric ion sensors with polymer-CNT composites. Electrochem Commun 11(8) 1684-1687. doi 10.1016/i.elecom. 2009.06.025... 

In scanning electrochemical microscopy (SECM) a microelectrode probe (tip) is used to examine solid-liquid and liquid-liquid interfaces. SECM can provide information about the chemical nature, reactivity, and topography of phase boundaries. The earlier SECM experiments employed microdisk metal electrodes as amperometric probes [29]. This limited the applicability of the SECM to studies of processes involving electroactive (i.e., either oxidizable or reducible) species. One can apply SECM to studies of processes involving electroinactive species by using potentiometric tips [36]. However, potentio-metric tips are suitable only for collection mode measurements, whereas the amperometric feedback mode has been used for most quantitative SECM applications. 

In measurements of conductivity, no electrochemical reactions occur. Differences in conductivity are due to differences in the ionic strengths of solutions. An alternating potential is applied to the solution at a known potential. The current is measured and the conductivity in Siemens/cm calculated.16 In potentiometry, the analyte is presumed to undergo no electrochemical reaction. The potential at the electrode changes due to changes in potential across the surface of the membrane in a membrane electrode or at the electrode surface of a solid electrode. The most familiar example of a potentiometric electrode is the pH electrode. In amperometry, current does flow, due to reduction or oxidation of the substance being analyzed. 

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