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Electrochemistry Solutions

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Keithley's sensitive equipment for sourcing and measuring potential and current and measuring capacitance is widely used in a variety of electrochemistry applications, including cyclic voltammetry, amperometry, potentiometry, battery testing, sensors, electrodeposition, and electrical device characterization.

On this page, we describe nine key electrochemistry test methods that employ Keithley products and then follow with technical details of those products.

This table lists some of the test methods and applications that employ Keithley products.

 
 Methods and Measurement Capabilities Applications 
Cyclic Voltammetry Electrochemical Sensors
Linear Sweep Voltammetry Electrodeposition,
Electroplating
Open Circuit Voltage pH Measurements
Potentiometry Solar Cells
Resistivity Ion-Selective Electrodes
Current and Voltage Square Wave with Measure Battery Charge/Discharge
Pulsed I-V Semiconductor Device
Characterization
Capacitance-Voltage  Electrochemical Etching
Source and Sink Current and
Voltage
Corrosion Science
Measure DC Current and Voltage Nano-Device
Characterization 
 
Electrochemistry Test Methods 
Cyclic Voltammetry

Cyclic voltammetry (CV), a type of potential sweep method, is the most commonly used electrochemical measurement technique, which typically uses a 3-electrode cell.

Figure 1 illustrates a typical electrochemical measurement circuit made up of an electrochemical cell, an adjustable voltage source (VS), an ammeter (AM), and a voltmeter (VM). The three electrodes of the electrochemical cell are the working electrode (WE), the reference electrode (RE), and the counter electrode (CE). The voltage source (VS) for the potential scan is applied between the WE and CE. The potential (E) between the RE and WE is measured with the voltmeter, and the overall voltage (VS) is adjusted to maintain the desired potential at the WE with respect to the RE. The resulting current (i) flowing to or from the WE is measured with the ammeter (AM).

Cyclic Voltammetry Fig 1
Figure 1. Simplified measurement circuit for performing cyclic voltammetry.

Keithley SourceMeter® SMU instruments source voltage and measure current, which makes them well suited for cyclic voltammetry applications. Figure 2 illustrates how the instrument’s four terminals are connected to the 3-electrode electrochemical cell.

Cyclic voltammetry Fig 2
Figure 2. Connecting an Electrochemistry Lab System to an electrochemical cell for cyclic voltammetry.
When a SourceMeter SMU instrument is programmed to source voltage in the remote sense (4-wire) configuration, internal sensing provides a feedback voltage that is measured and compared to the programmed level. The voltage source is adjusted until the feedback voltage equals the programmed voltage level. Remote sensing compensates for the voltage drop in the test leads and analyte, ensuring the programmed voltage level is delivered to the working electrode.
Cyclic voltammetry Fig 3

The 2450-EC, 2460-EC, and 2461-EC Electrochemistry Lab Systems have a built-in display that can automatically plot a voltammogram using its cyclic voltammetry test script. Figure 3 shows a voltammogram generated by the instrument. The 2450, 2460, and 2461 instruments include a test script that performs cyclic voltammetry without a computer.

 

Figure 3. Voltammogram generated on 2450 graphical display.
Other electrochemistry test scripts that are included with the 2450-EC, 2460-EC, and 2461-EC Electrochemistry Lab Systems are open circuit potential measurements, potential pulse and square wave with current measurements, current pulse and square wave with potential measurements, chronoamperometry, and chronopotentiometry. These systems also include an electrochemistry translation cable with alligator clip set which enables the user to make easy connections between the instrument and an electrochemical cell.
This video demonstrates how to use the 2450-EC Electrochemistry Lab System as a potentiostat to perform cyclic voltammetry from 0 V to 0.6 V and back to 0 V using a 100 mV/s scan rate.  

  Learn more with our Cyclic Voltammetry Application Note:  Clclic Voltammetry Application Note  

 

Open Circuit Potential

The open circuit potential (OCP) of an electrochemical cell is a voltage measurement made between the reference and working electrodes. Measuring open circuit potential requires a voltmeter with high impedance to measure the voltage with no current or voltage applied to the cell. Because of their high input impedance, SourceMeter SMU instruments are well suited for OCP measurements when configured in a 4-wire configuration as shown in Figure 4. In this setup, the instrument is configured to measure voltage and source 0A. If OCP is measured before performing cyclic voltammetry, there is no need to rearrange any test leads manually between measurements because the instrument can automatically change functions internally. The 2450-EC, 2460-EC, and 2461-EC come with a test script for performing open circuit potential measurements.

Open Circuit Potential Fig 4
Figure 4. Using an Electrochemistry Lab System to measure the open circuit potential of an electrochemical cell.

 

Resistivity

Electrical resistivity is a basic material property that quantifies a material’s opposition to current flow. The best technique for determining the resistivity of a material will vary depending upon the type of material involved, the magnitude of the resistance, and the geometry of the sample.

Conductors and Semiconductors – Source Current and Measure Voltage
The resistivity of conductors or semiconductors is usually determined by sourcing current and measuring the potential across the sample in a 4-wire configuration. The 4-wire configuration minimizes the lead and contact resistance to reduce their effect on measurement accuracy. In this configuration (Figure 5), two leads are used to source the current and another set of leads are used to measure the voltage drop across a conductive sample. The voltage drop across the sample will be very small, so a Keithley 2182A nanovoltmeter is used to make the measurement. Resistivity Fig 5
Figure 5. Using a current source and nanovoltmeter to measure a conductive sample.
Insulators – Apply Potential and Measure Leakage Current
An insulator’s resistivity is typically measured by applying a potential to the unknown resistance and measuring the resulting leakage current. This is a 2-terminal test. The volume resistivity is a measure of the leakage current directly through a material. The surface resistivity is defined as the electrical resistance of the surface of an insulator. Figure 6 shows circuit diagrams for both volume and surface resistivity. Resistivity Fig 6
Figure 6. Volume and surface resistivity measurement diagrams
These high resistance measurements require an instrument that can measure very low current and apply a potential. Both the 6517B Electrometer/Voltage Source and 6487 Picoammeter/Voltage Source are capable of measuring the resistivity of high resistance materials. These instruments can measure currents as low as tens or hundreds of femtoamps and have a built-in voltage source. When measuring very high resistances, it is important to shield the device and all cabling properly to avoid the effects of electrostatic interference.

 

Potentiometry

Potentiometry involves measuring the potential between two electrodes, typically a working electrode and a reference electrode. The potential difference is measured using a high impedance voltmeter or an electrometer, so that any current flow will be negligible (i=0). Potentiometry is used for applications such as pH measurements and voltage measurements made using ion selective electrodes. These potential meas urements are usually made using two electrodes and a high impedance voltmeter, such as a 6517B or 6514 Electrometer (Figure 7).

Potentiometry Fig 7
Figure 7. Electrometer measuring potential difference between two electrodes.

 

Electrochemical Sensors

Electrochemical sensors are used for many applications in diverse industries, including environmental and gas monitoring, medical applications like determining glucose concentration, as well as in the automotive and agricultural industries. Electrochemical sensors come in a wide range of differing designs; they may have two or three electrodes and could be potentiometric, amperometric, or voltammetric. Some sensors are based on organic electronic devices or nano-structures.

Choosing the optimum test equipment is crucial for electrochemical sensor R&D. For example, measuring the output of a potentiometric sensor may require a very high impedance voltmeter, such as a Keithley electrometer, which has high input impedance (>1016 ohm). Testing an amperometric gas sensor may demand the use of a very sensitive ammeter, such as a picoammeter, electrometer, or a SourceMeter SMU instrument.

Figure 8 shows a simple amperometric gas sensor. When a gas comes in contact with the working electrode (WE) a chemical reaction occurs, either oxidation or reduction, depending on the sensor. In an amperometric sensor, current flows between the counter electrode (CE) and the working electrode (WE). The current output, which is related to the gas concentration, is measured by a sensitive ammeter. If necessary, a third electrode, a reference electrode, can be added to the sensor to apply a potential.
Electrochemical Sensors Fig 8

Figure 8. A SourceMeter SMU instrument measuring the current
output of a 2-electrode amperometric gas sensor.

 

Solar Cells

To meet the increasing demand for clean energy, photovoltaic researchers are working to improve cell efficiency and reduce costs. Emerging technologies include dye-sensitized, organic, perovskite, and even 3D solar cells. Electrical characterization of solar cells is essential to determining how to make the cells as efficient as possible with minimal losses.

Some of the electrical tests commonly performed on solar cells involve measuring current and capacitance as a function of the applied DC voltage. Capacitance measurements are made as a function of frequency or AC voltage. Some tests require pulsed current-voltage measurements. These measurements are usually performed at various light intensities and temperatures. Important device parameters can be extracted from these measurements, including the output current, conversion efficiency, maximum power output, doping density, resistivity, etc.

Figure 9 shows several parameters that can be extracted from a typical forward bias I-V curve on a solar cell, including the maximum current (Imax), short circuit current (Isc), maximum power (Pmax), maximum voltage (Vmax), and open circuit voltage (Voc).  Solar Cells Fig 9
Figure 9. Typical forward bias I-V curve of a photovoltaic cell.

Instrumentation like the 4200A-SCS Parameter Analyzer can simplify testing and analysis when making these critical electrical measurements. The 4200A-SCS is an integrated system that includes instruments for making DC and ultra-fast I-V and C-V measurements, as well as control software, graphics, and mathematical analysis capability. The 4200A-SCS can make a wide range of solar cell measurements, including DC and pulsed current-voltage, capacitance-voltage, capacitance-frequency, drive level capacitance profiling (DLCP), and four-probe resistivity.

Figure 10 shows a solar cell connected to a 4200-SMU for I-V measurements. The four-wire connection eliminates lead resistance from the measurement circuit. Once the cell is connected to the output terminals, the 4200A-SCS’s interactive software makes it easy to set up voltage sweeps to generate I-V curves automatically, like the forward biased I-V curve of a photovoltaic cell shown in Figure 11.

 Solar Cells Fig 10 Solar Cells Fig 11
Figure 10. A solar cell connected to a 4200-SMU. Figure 11. Forward biased I-V characteristics of solar cell measured by 4200A-SCS Parameter Analyzer.

 

Rechargeable Battery Charge / Discharge

Keithley SourceMeter SMU instruments can simplify battery testing because they’re capable of sourcing and measuring both current and voltage. These instruments have the flexibility to source and sink current as well as measure voltage and current, making them perfect solutions for battery charge and discharge cycling.

For this test, the SourceMeter SMU instrument’s terminals are connected to the battery (Figure 12) with a 4-wire connection to eliminate the effects of lead resistance.  Rechargeable Battery Charge-Discharge Fig 12
Figure 12. Results of discharging battery shown on graphical display of 2460 SourceMeter SMU instrument.
For both charging and discharging cycles, the instrument is configured to source voltage and measure current. Even though the instrument is configured to source voltage, it will be in operating in a constant current mode. Figure 13 shows simplified circuit diagrams for both the charge and discharge cycles.

Rechargeable Battery Charge-Discharge Fig 13

Figure 13. Charge and discharge circuit diagrams.
A battery is usually charged using a constant current, so the SourceMeter SMU instrument is configured to set the voltage source to the voltage rating of the battery and the source limit to the desired charging current. At the beginning of the test, the battery voltage is less than the instrument’s voltage output setting. This voltage difference drives a current that is immediately limited to the user-defined current limit. When in current limit, the instrument operates as a constant current source until it reaches the programmed voltage level.

When discharging the battery, the SourceMeter SMU instrument operates as a sink because it is dissipating power rather than sourcing it. The instrument’s voltage source is set to a level lower than the battery voltage and the current limit sets the discharge rate. When the output is enabled, the current from the battery flows into the Hi terminal of the Instrument. As a result, the current readings will be negative. The results of measuring the discharge characteristics of a 2500 mAh battery are shown in Figure 14.

 
Rechargeable Battery Charge-Discharge Fig 14
Figure 14. Discharge characteristics of 2500 mAh D cell battery
using 2460.

 

Electrical Device Characterisation

SourceMeter SMU instruments and the 4200A-SCS Parameter Analyzer are ideal for electrical device characterization because they can source and measure current and voltage. In addition to containing multiple SMU instruments, a parameter analyzer can also include a capacitance-voltage unit or pulse-measure unit. The components that can be characterized can include carbon nanostructures and devices, sensors, solar cells, organic semiconductor devices, and other structures.

The number of SMU instruments needed for a particular application depends on the number of terminals on the device and the measurements required. In the organic FET (OFET) example shown in Figure 15, two SMU instruments are required to characterize the device. In this case, one instrument (SMU1) is connected to the Gate terminal and a second instrument (SMU2) is connected to the Drain terminal of the device. The Source terminal of the OFET is connected to common. The transfer characteristics of the OFET is determined by stepping the Gate voltage using SMU1 and sweeping the Drain voltage and measuring the Drain current using SMU2.  Electrical Device Characterisation Fig 15
Figure 15. 4200A-SCS parameter analyzer for organic FET I-V characterization.
The transfer characteristics of an OFET measured and graphed by the 4200A-SCS Parameter Analyzer are shown in Figure 16.  Electrical Device Characterisation Fig 16

Figure 16. Transfer characteristics of OFET measured by 4200A-SCS Parameter Analyzer. Note: OFET courtesy of Kent State University.

The 4200A-SCS Parameter Analyzer offers many advantages for characterizing devices electrically. This configurable test system can simplify sensitive electrical measurements because it integrates multiple instruments into one system that includes interactive software, graphics, and analysis capabilities.

 

Electrodeposition, Electroplating

Electrodeposition is the process of applying a thin film of metal to a conductive surface. This process has many applications including decorative coatings, corrosion prevention, and even nanowire and nanostructure fabrication. Traditionally, this process involved a current source connected between two electrodes, an anode and a cathode. The current drives the metal ions from the anode to the cathode as shown in Figure 17. In this simple example, a 6220 Current Source causes the Ag+ ions from the anode to be drawn to the cathode.

 Electrodeposition, Electroplating Fig 17
Figure 17. Electroplating circuit using a constant current source.
Electrodeposition may require using a constant DC current or voltage, or it may require a pulsed or stepped signal with controlled deposition time. In addition to sourcing a current or voltage, the specific application may require monitoring current or voltage. A Series 2400 or Series 2600B SourceMeter SMU instrument can control the parameters of the source automatically, as well as monitor the resulting current or potential in the circuit. Four-wire control from the instrument to the 2-electrode configuration can be used to eliminate the effects of lead resistance.

Keithley Products for Electrochemical Applications
Keithley Potentiosats
High accuracy, lower cost alternatives for electrochemistry lab instrumentation

The 2450-EC, 2460-EC, and 2461-EC Potentiostats are flexible, low-cost, and ideal for research and development in fundamental electrochemical lab research, characterizing next generation materials and electrolytes, new energy storage devices, and faster, smaller sensors. The potentiostats include everything you need for electrochemistry testing, including cyclic, squarewave, or galvanic voltammetry, chronoamperometry, and chronopotentiometry.  

Keithley SMU Potentiostat EC Solutions
Features Benefits
Perform cyclic, squarewave, or galvanic voltammetry, chronoamperometry, and chronopotentiometry Lower cost alternative to potentiostats
Simplified user interface Accelerates test setup by as much as 50%
Real-time plotting of voltammograms on the front panel Expedites test analysis and time to answer
Analytical graph cursors Allow immediate analysis of results without a computer
Built-in scripting language Create libraries of reusable, customizable experimental software
Screen capture function Supports copying test results from the display to reports
10nV and 10fA measurement sensitivity Enables low voltage and low current measurements with confidence
Front panel input banana jacks; rear panel input triaxial connections Convenient; saves money on additional adapter accessories
Context-sensitive help function Minimizes the learning curve
Front-panel USB 2.0 memory I/O port Facilitates transferring data, test scripts, or tests
Models
Model
Touch
 Screen 

 Channels 

Max Current Source/Measure Range
Max Voltage Source/Measure Range
Measurement Resolution (Current/Voltage)
 Power 


 

2450-EC

Yes
1
1A
200V
10fA / 10nV 20 W Datasheet_buttonTek_Vivid_Blue

2460-EC

Yes  1
7A
100V
1pA / 100nV 100 W Datasheet_buttonTek_Vivid_Blue

2461-EC

Yes 1 10A 100V 50pA / 5nV

100 W

Datasheet_buttonTek_Vivid_Blue

 


Keithley High Resistance/Low Current Electrometers
Our most sensitive current and charge measurement instruments

Choose from three sensitive options for precision high resistance and low current measurements. The 5½-digit Model 6514 and Model 6517B Electrometers offer 1fA sensitivity, >200Tohms input impedance on voltage measurements, and charge measurements down to 10fC. The 6½-digit Model 6430 Sub-Femtoamp Remote SourceMeter SMU Instrument can measure current with 1aA sensitivity. Its low noise and drift performance make it ideal for research on single electron devices, highly resistive nanowires and nanotubes, polymers, and electrochemical applications.

Keithley Electrometer EC Solutions
Features Benefits
Extremely low noise (0.4fAp-p for 6430, <1fA for 6517B and 6514) Ensures more accurate measurements of the extremely low currents common in device and materials research.
Resistance measurements up to 1016ohm (6517B) Measures resistance on ultra-high resistance materials and insulators accurately.
Remote PreAmp can be located at the signal source (6430) Allows making a direct or very short connection to the signal source, minimizing noise sources such as cable noise.
Low burden voltage Eliminates errors that affect the accuracy of low current measurements.
Built-in ±1kV voltage source with sweep capability (6517B) Simplifies performing leakage, breakdown, and resistance testing, as well as volume (ohm-cm) and surface resistivity (ohms/square) measurements on high resistivity materials.
Optional Model 8009 Resistivity Chamber for measuring volume and surface resistivities of sample materials (6517B) Protects you from contact with potentially hazardous voltages —opening the lid of the chamber automatically turns off the instrument’s voltage source.
High measurement speeds even on low-level signals Allows faster low-level component testing.
Programmable digital I/O and built-in interfaces Simplifies building automated component test systems.
Models
Model

 Current 

Voltage
Resistance
Charge
 Source 


 

6514

100aA - 20mA
10µV - 200V
10mohm - 200Gohm
110fC - 20μC - Datasheet_buttonTek_Vivid_Blue

6517B

100aA - 20mA
10µV - 200V
100ohm - 10Pohm
10fC - 2μC 0 - ±1000V Datasheet_buttonTek_Vivid_Blue

6430

10aA - 100mA 1µV - 200V 1µohm - >20Tohm -

0 - ±200V 0 - ±100mA

Datasheet_buttonTek_Vivid_Blue

 


Keithley 4200-SCS Parameter Analyser
A fully integrated solution to characterise materials, processes and semiconductor devices

Accelerate research, reliability and failure analysis studies of semiconductor devices, materials and process development with the 4200A-SCS. The highest performance parameter analyzer, it delivers synchronizing current-voltage (I-V), capacitance-voltage (C-V) and ultra-fast pulsed I-V measurements.

Visit our 4200-SCS page here ->

Keithley 4200-SCS 

Keithley Ultra-low Resistance Configurations
Measure resistance down to microohms with controlled resistance sourcing

When connected, the Model 2182A and Model 6220 or 6221 can be operated like a single instrument. The 2182A/622X combination is ideal for resistance measurements, pulsed I-V measurements, and differential conductance measurements, providing significant advantages over other solutions. The 2182A/622X combination is also well suited for many nanotechnology applications because it can measure resistance without dissipating much power in the device under test (DUT), which would otherwise invalidate results or even destroy the DUT.

Keithley Ultra-low Resistance EC Solutions
Features Benefits
Measure resistances from 10nohm to 100Mohm Covers an extremely wide measurement range and specializes in ultra-low resistance measurements for characterizing high conductivity materials, nanomaterials, and superconducting materials.
Synchronized current-pulsed source and measurement times as short as 50µs Limits power dissipation in components such as nanodevices and nanomaterials that can be easily destroyed unless tested at very low power levels.
Delta mode current reversal, resistance measurement technique Makes accurate ultra-low resistance measurements by eliminating the effects of thermal offsets and reduces noise down to 30nV p-p noise (typical) for one reading. Multiple readings can be averaged for greater noise reduction.
Differential conductance measurement Offers speeds ten times faster and lower noise than other conductance measurement techniques. Good measurements are made without the need to average the results of multiple sweeps.
Nanovoltmeter and current source interface to work together seamlessly Both instruments can be operated like a single instrument when making differential conductance and resistance measurements.
Delta, differential conductance, and pulse modes generate minimal current transients Allows characterizing devices that can be easily disrupted by current spikes.
Models
Model
Voltage
Resistance
 Source 
PC Interface


 

2182A

100nV - 100V
10nohm - 100Mohm
DC: ±10fA – 100mA RS-232, GPIB Datasheet_buttonTek_Vivid_Blue

6220

100nV - 100V
10nohm - 100Mohm

DC: ±10fA – 100mA
AC: 4pAp-p – 200mAp-p

RS-232, GPIB, LAN Datasheet_buttonTek_Vivid_Blue

6221

100nV - 100V

DC: ±10fA – 100mA
AC: 4pAp-p – 200mAp-p

0 - ±200V 0 - ±100mA

RS-232, GPIB, LAN Datasheet_buttonTek_Vivid_Blue