Electrochemistry's Signature Technique
Cyclic voltammetry is arguably the most widely used electroanalytical method. By sweeping the electrode potential back and forth while measuring current, it produces a characteristic voltammogram that encodes a wealth of information about redox processes, reaction kinetics, and diffusion behavior. Electrochemists often say: 'When in doubt, run a CV first.'
Anatomy of a Voltammogram
The forward sweep oxidizes (or reduces) the analyte at the electrode surface. Current rises as the potential approaches the formal potential E°′, reaches a peak when the surface concentration is momentarily depleted, then falls as the diffusion layer thickens. The reverse sweep reverses the reaction, producing a mirror-image peak. The positions, heights, and shapes of these peaks reveal the thermodynamics and kinetics of the redox process.
Reversibility and Scan Rate
A fully reversible redox couple shows a peak separation of exactly 59/n mV at 25°C, independent of scan rate. As the scan rate increases, sluggish electron transfer causes the peaks to spread apart — the system transitions from reversible to quasi-reversible to irreversible. Plotting peak separation versus scan rate is a standard diagnostic for measuring electron transfer rate constants.
Applications Across Science
CV is used everywhere: characterizing battery electrode materials, studying enzyme redox centers, detecting heavy metals in water, investigating corrosion mechanisms, and screening electrocatalysts for fuel cells and CO₂ reduction. Its simplicity, speed, and richness of information make it indispensable in research and quality control alike.