Electrochemical research stretches across many different fields (as is evidenced by the numerous applications listed here). While many areas are distinct, there is often a great deal of overlap, especially in terms of some experimental techniques. â€œPhysical Electrochemistryâ€ is a bit of a catch-all term that actually covers many areas that are more fundamental in their research goals.
Physical electrochemistry includes theoretical and experimental aspects of double-layer structure, kinetic and mechanistic studies of heterogeneous electron transfer at electrode-electrolyte interfaces, electrocatalysis, and the application of spectroscopic and other techniques to the study of electrochemical interfaces and processes.
Ideally, researchers would take a full semester course on physical electrochemistry. If that isn't possible, knowledge of a few basics can assist you in your research. The principal experimental technique in physical electrochemistry is cyclic voltammetry (CV). CV is a linear scan of potential “out and back” with the measured current plotted vs potential. Scan rates can run from below 1 mV/s to more than 1000 V/s. At first glance, a CV gives a measure of the thermodynamics of an electron transfer (E0). It can be used analytically to solve for an unknown (diffusion coefficient, concentration, electrode area). More detailed analysis can lend insight into the kinetics, adsorbed/bound species, and can even yield mechanistic information.
Note that digital instruments approximate a linear sweep with a staircase, which is fine for diffusing species. Current resulting from bound species and capacitance, however, can be lost—though Gamry has a “Surface Mode” option that preserves/records all current passing through the electrode.
CV analysis, which has long been a combination of art and science, is best done today using simulation. Accurate models and a good simulation program are much better for studying complex systems. Basic information is available without simulation, but detailed information including rate parameters, adsorption isotherms, and chemical equilibria are not easily accessed outside of simulation.
Other techniques commonly used for research electrochemistry include pulse voltammetry, electrochemical impedance spectroscopy, chronoamperometry, chronocoulometry, and chronopotentiometry.
Electroanalytical chemistry is an expanding niche of physical electrochemistry. Traditional analytical electrochemistry was based around a wide range of pulse techniques. These techniques include differential pulse, square wave, normal pulse, various stripping techniques, and more. They can be incredibly sensitive, and are often better than cyclic voltammetry for getting analytical solutions.
Improvements in materials development are leading to greater interest in electrochemistry as a tool for sensing, particularly in life sciences. Here electroanalytical chemistry is meeting biochemistry with some impressive results. The most common electrochemical sensors around—glucose sensors—are used by millions of people everyday. Smaller electrodes, electrode arrays, more sensitive and faster potentiostats and electrochemical techniques like fast scan CV and EIS are continuing to revolutionize what is possible with electrochemistry.
A basic setup from Gamry for doing physical electrochemistry would consist of any Gamry potentiostat, Physical Electrochemistry (PHE200) and Pulse Voltammetry (PV220) software, a VistaShield Faraday Cage (likely with Stir-Purge), and a Dr. Bob’s Cell Kit (jacketed for temperature control).
DigiElch electrochemical simulation software is a necessity for any researcher making use of cyclic voltammetry for anything more complex than grabbing ipeak and E½. DigiElch is also an excellent tool for teaching.
The lower cost Series G’s (300 and 750) are good for measurements down to low nA/high pA, and for scan rates up to 10 V/s (faster is possible but not recommended). Researchers who need sensitivity down to a few pA and below, or who want to run fast CV’s up to over 1000 V/s will need a Reference instrument (600 or 3000). Generally, for electrodes below 100 μm in diameter, it is wise to go with a Reference family. For macro-electrodes (generally a few mm in diameter) a Series G will perform very well.
Scientists wanting to do experiments involving adsorbed species, or studying dynamics of the double layer, will need a Reference family instrument (600 or 3000) to do Surface Mode CV tests, and are very likely to benefit from electrochemical impedance spectroscopy (EIS300) and a quartz crystal microbalance (eQCM 10M).
A bipotentiostat setup could be useful for researchers doing rotated ring-disk electrodes (RRDE) or other collector-generator type experiments like with thin layer cells or scanning electrochemical microscopy. Rotating electrodes are best served by a EuroCell, with a kit setup for doing such work.
Gamry employs several PhD electrochemists whose various and extensive backgrounds provide insight into your research, beyond simple understanding of Gamry systems.
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