SU983780A1 - Method of electrochemical activation of converter electrodes - Google Patents

Description

(5) METHOD OF ELECTROCHEMICAL ACTIVATION OF ELECTRODES OF CONVERTERS For example, the device relates to instrumentation, structure, in particular, restoration and stabilization of the performance characteristics of molecular electronics converters, which use a reversible iodide-iodide redox system with platinum-like templates, I-ideas, I would like, I would like, I would like, I would like, I would like, I would like, I would like, I would like to do that. for registration of mechanical effects (speed, acceleration, soil displacement, atmospheric pressure differential, etc.). The known method of anodic activation of a platinum electrode in a solution of sulfuric acid 1, the disadvantage of this method is the need to disassemble the transducer and replace iodine-iodide | systems on sulfuric acid solution. The known method of electrochemical activation of electrodes by electrochemical deposition of the active layer on the electrode surface and its subsequent removal by current of reverse polarity. The deposition and stripping process is repeated until the t23 activity of the electrodes is obtained. The disadvantage of this method is its inapplicability to effect an effective cleaning of the electrode surface from surfactant impurities, since the potential of the electrode, which determines the oxidation (reduction) and desn impurities from the surface of the electrode, during the electrochemical process. these active substances remain uncontrollable and do not reach the effective value of P (t stationary-diffusive currents, which are used in this method. The closest to the technical essence and achievable The result is an electrochemical activation method consisting in cyclic processing of the working electrode by cathode-anode current with continuous 3 9 control of the activation potential and periodic control of sensitivity, and the cycle is repeated until stable sensitivity of the converter is obtained. 33. The disadvantage of the known method is The duration of the activation process is due to insufficiently high activation activation currents and a short residence time of the electrode during the oxidation potential (reduction and desorption RIMES in every cycle (a cycle at the end of seconds) than at the anode cycle activation potential of the electrode does not reach high values because the concentration of CKI. The aim of the invention is to intensify the process of activation of the electrodes of the transducers. This goal is achieved by applying a voltage equal to the maximum permissible cathode potential to the working electrode for a time of 3-5 seconds, then a voltage equal to the maximum permissible anodic potential for the same period of time is applied to the electrode, while during the activation process subjected to mechanical stress. In FIG. Figure 1 shows the dependence of the activation current on time with the application of the maximum permissible value of the cathode 0.3 V (curve 1) and the anodic potential of 1.0 V (curve 2) on the electrode; in fig. 2 - cathode (curve 1) and anodic (curve 2J polarization characteristics of the activated electrode of the converter in a 0.1 n In + C iodide electrolyte, 0 n KI; Fig. 3 shows an electrical circuit for switching on the converter, allowing the proposed activation method The circuit includes a potentiostat, an output signal recorder, a voltmeter, and a diffusion sensor.Diffusion sensor consists of a housing 1, bounded from the front sides by membranes 2, made of inert material to the electrolyte material (for example, fluoroplastic a or pentone), divided into two compartments by a partition containing a narrow channel 3, in which there is a flow converter into an electrical signal consisting of four electrodes of two anodes (counter electrodes) 1 and two cathodes (working electrodes) 5 The internal cavity of the converter is filled with electrolyte 6, forming together with the converter electrodes a reversible redox redox system. The working electrodes 5, which are subject to activation, are connected to the potentiostat terminal, the working electrode, and one of Electrode 2 - auxiliary electrode to the terminal. A second nonpractable electrode k is used as the reference electrode, which is connected to the terminal of the potentiostat of the reference electrode. The value of the activation potentials is set by potentiometers U-j and U, located on the block 7 of the reference voltages. The potential at the working electrode is monitored with a voltmeter. The value of the activation current is monitored by a recorder connected to the recorder's potentiostat terminal. At the moment of application of the potential, the activation current rushes up and then decreases (Fig. 1). The maximum current is 20 to 25 times the activation current that is used in a known method. In order to obtain higher activation currents, the converter undergoes perturbation during the activation process (mechanical effects, for example, acceleration, vibration, etc.), as a result of which the activated electrode is washed by the flow of the working electrolyte, which accelerates the supply of electrolyte II to the electrode (during cathode activation) and electro-oxidizing G (with anodic activation) particles and removal of reaction products. After 3-5 s, the activation current decreases by 80-90, approaching a steady-state value (area of the limiting current), which is comparable to the activation current in the known method. Therefore, activation (anodic or cathodic) is completed when the current falls to a stationary value. The decay time of the current determines the duration of cathodic (anodic) activation. Example. 1. A diffusion transformer connects to a potentiostat as a three-electrode electrochemical cell: the working electrode of the transducer to the terminal is the working electrode, the counter electrode to the auxiliary electrode terminal and the second counter electrode to the comparison electrode terminal (Fig. 3J.

2. The converter is subjected to a perturbation (acceleration, vibration) with the help of a special device, in which electrolyte flow with volumetric flow flows through the channel of the working electrode

. 3. Remove the cathode and anodic polarization characteristics of the working electrode relative to the equilibrium non-polarizable (second) counter-electrode (Fig. 2J, which determine the maximum allowable value of the cathode (-0.9 V) and anodic (1.0 V) potentials corresponding to a sharp increase in current on polarization curves, due to the onset of electrolyte decomposition and the evolution of gases, hydrogen during cathodic polarization, and oxygen at anodic. k. The dependence of the activation current on time is removed (Fig. 1) when applied to the electrode This maximum allowable value of the cathode -0.9 V (curve 1J and anodic 1.0 8 (curve 2) potential and determine the duration of the cathodic (SC 3 s and anode CLQ k s) activation, where t is the time for which the current activation decreases from the moment the potential is applied by about 90, approaching a stationary value (current limit site),

5. The activation potentials are set on the reference voltage locus 7: on the first reference voltage source U, the value is 0.9 V, a

on the second and the value of +1.0 V.

6. Set the dial to U position, which corresponds to the value of the potential at the working electrode -0.9 V.

7. After 3 s, the Ui-U2 switch is switched to the UQ position, which corresponds to the potential at the working electrode + 1.0 V, and maintains the electrode at this potential for 4 s.

8. The indicated cycle of anodic cathodic activation is repeated 4-5 times, after which the sensitivity of the converter electrodes is monitored. For this purpose, I apply a potential of - 5 V to the working electrode and subject the converter to a calibrated perturbation over the entire operating range and measure the sensor response (as a measurement of diffusion current) to this using a KSP-U current recorder.

disturbance. Sensor sensitivity is defined as the ratio of the change in current magnitude to the magnitude of the calibration disturbance.

9. The activation process, followed by monitoring the sensitivity of the converter, is repeated until the maximum sensitivity is obtained, which does not change with further cycling of the activation potential (current).

The intensification of the activation process consists in reducing the activation time (number of cycles) and is achieved due to the following factors:

higher activation currents, in which a large number of active centers takes part in the electrochemical reaction of iodine discharge ionization;

longer electrode stay at activation potential by maintaining a constant potential value during the entire period of cathodic or anodic activation

by creating a flow of the working electrolyte in the measuring channel, which contributes to increasing the activation currents and effectively removing from the channel the products of oxidation (reduction) of impurities of surface-active substances desorbed from the electrode surface.

The invention makes it possible to shorten the full activation time by kO-SO times, without having to switch off the sensors from the measuring system, which leads to savings in working time.

Claims (3)

1. Damaskin BB and others. Introduction to electrochemical kinetics. M., Higher School, 1975. 361. 9837808 2. USSR author's certificate No. 508812, cl. H 01 G 9/22, 197. 3. USSR author's certificate of pr. Application. IP .97b, cl. H 01, 29.01.81 (prototype). 1