Potentiostat bipotentiostat

Makers of potentiostats, bipotentiostats, electrodes, and electrochemical cells are included. 

Electrochemical Equipment. Electrochemical experiments were performed using either a PAR Model 175 universal programmer and a PAR Model 363 potentiostat/galvanostat, or a Pine Instruments RDE-4 bipotentiostat, coupled with a Kipp and Zonen BD 91 X-y-y recorder. The current-time response for the chronoamperometry experiments was recorded with a Nicolet 4094 digital oscilloscope. All potentials were measured vs. a Ag/10"2 M Ag+ reference electrode. 

Apparatus Cyclic voltammetry and amperometric current-time curves were obtained with a Pine Instrument Inc., Model RDE4 bipotentiostat and Kipp Zonen BD 91 XYY recorder equipped with a time base module. All measurements were performed in a conventional single-compartment cell with a saturated calomel electrode as the reference electrode and a Pt mesh as the auxiliary electrode at room temperature. Chronoamperometry was made with EG G Princeton Applied Research potentiostat/galvanostat Model 273 equipped with Model 270 Electrochemical Analysis Software. 

Figure 1 shows a schematic diagram of the basic SECM instrument employing an amperometric microprobe. An UME tip is attached to a three-dimensional (3D) piezo positioner controlled by a computer, which is also used for data acquisition. A bipotentiostat (i.e., a four-electrode potentiostat) controls the potentials of the tip and/or the substrate versus the reference electrode and... 

Bipotentiostat — An instrument that can control the potential of two independent -> working electrodes. A - reference electrode and an -> auxiliary electrode are also needed therefore the cell is of the four-electrode type. Bipotentiostats are most often employed in electrochemical work with rotating ring-disk electrodes and scanning electrochemical microscopes. They are also needed for monitoring the electrode-reaction products with probe electrodes that are independently polarized. All major producers of electrochemical equipment offer this type of potentiostat. The instruments that can control the potential of more than two working electrodes are called multipotentiostats. 

A bipotentiostat is simply a potentiostatic circuit designed to allow simultaneous potential control of two working electrodes in an electrochemical cell. A simplified schematic of a bipotentiostat circuit is illustrated in Figure 4. Note that connections in this schematic are always indicated by a dot at the intersection, and crossing lines without a dot are not connected. Part of this circuit is identical to the potentiostat circuit, with the addition of am-... 

As an alternative to a bipotentiostat, two separate potentiostats can be used to control two working electrodes. For conventional potentiostats, both working electrodes would be held at circuit common, which requires that one of the potentiostats be operated in a floating mode. With potentiostats that allow a floating working electrode, the circuit common can be shared at the reference electrode and no isolation is required. Whether to use a single bipotentiostat or dual potentiostats in a SECM experiment is up to... 

Figure 9.4.2 Block diagram of RRDE apparatus, (a) Bipotentiostat. (b) Ordinary (three-electrode) potentiostat and voltage divider.

Instrumentation. A suitable microelectrode [119] or nanoelectrode [127] is attached to a piezo-driven micropositioner. It is connected as the working electrode with a potentiostat. A counter electrode and a reference electrode are wired in a three-electrode arrangement. Investigations with conducting substrates require the use of a bipotentiostat. The surface to be investigated is immersed into the electrochemical cell together with the other electrodes. The position of the microelectrode and the flowing current are controlled and monitored by a computer equipped with... 

The positioning system is comprised of micro- to nanoscale precision stepper motors and piezo elements with integrated encoders of a few nm resolution to facilitate precise positioning of the tip at x-, y-grid points at a veiy close distance above the sample surface. SECM instruments are equipped with a potentiostat if an electrochemical signal is to be applied or monitored at only the tip (WEI), or specifically, a bipotentiostat if a second electrochemical signal is to be applied or... 

The potentiostat described earlier is used to control the potential of the working electrode and to measure the corresponding current for an RDE. A bipotentiostat is... 

What sort of instrumentation would be needed for electrochemical experiments A potentiometry experiment requires little more than a pH meter. A potentiostat or galvanostat can be used for the controlling potential or current in an experiment. In a coulometric procedure, a device to integrate the current (i.e., a coulometer) would also be needed. A hydrodynamic voltammetry [e.g., a rotating disk electrode (RDE)] experiment would require an electrode rotor (to spin the electrode at a precisely known rotation speed), and the rotating ring-disk or RRDE refinement (see below) would necessitate the use of a bipotentiostat so that the disk and ring potentials can be independently controlled. An ac impedance measurement involves the use of a sine-wave oscillator and... 

The data acquisition system and bipotentiostat/galvanostat of the CH series 900 SECM are microprocessor based and communicate with the PC controller via a serial data link. The bipotentiostat/galvanostat is suitable for analytical voltammetry with tip and substrate potentials up to 10 V and a compliance voltage of 12 V and potentiostat rise time of 0.6 ps. The current measurement sensitivity is in the pA range (resolution <0.01 pA). Adjustable second-order Bessel filters provide noise reduction and prevent aliasing by the ADC, which has at least 16 bits of resolution. The software for the model series 900 SECM runs on the Windows operating system and provides... 

Using a split RDE, one may analyze two products simultaneously, i.e., the dissolution of Cu+ and Cu " or of Fe and Fe. These measurements require a tripotentiostat, which allows setting the electrode potentials for the disc and the two rings independently whereas an RRD electrode requires a bipotentiostat only. For these measurements, the electronic circuits require a common RE and a grounded CE. Differential amplifiers at the entrance of the three (or two) potentiostats uncouple the WEs (rings and disc) so that the whole circuit is grounded at one point. The related equipment and the procedure to produce electrodes for corrosion studies is described in the literature [45-47]. 

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