Enhancing Electrode Surface Area

Platinum electrodes make use of a specialized surface treatment the results in a very high surface area electrode. Electrodeposition of platinum black from chloroplatinic acid produces a surface covered with platinum black – a from of very finely divided, porous platinum. These platinized platinum electrodes have a BET surface area 400-500 times their macroscopic geometrical area¹⁾, and can have three orders of magnitude greater capacitance than shiny platinum electrodes²⁾.

Studies³⁾ of activation methods of platinum electrodes show that CPE-P⁴⁾ values increase with increasing salt concentration in the electrolyte. Capacitance also increases with increasing salt concentration, roughly as the log of concentration. Effective electrodes require activation, consisting of 50 cycles of cyclic voltametry with a platinum counter electrode, each cycle between appx. +/- 1.2V, and about 1/2 hour per cycle. CV curves stabilized only after many cycles. There is significant drift in capacitance over time, requiring periodic (perhaps weekly) reactivation.

The frequency dependence of capacitance on solid electrodes is due to the interaction of atomic scale inhomogeneities with the electrolyte rather than to the geometry aspect of roughness⁵⁾.

The following photo shows the two paraxial graphite electrodes discussed on the page, Cell Constant of Parallel Wire Electrodes.

A close-up view of one of the electrodes shows deep grooves and high surface irregularity in the extruded polymer-graphite-carbon rods (1pixel =0.75 μm):

Glassy carbon is used in electrochemistry owing to its high electrical conductivity, immunity to surface contamination, and very good corrosion resistance.

Glassy carbon has no open porosity – so it probably has much lower surface area than graphite.

Glassy carbon can be oxidatively activated to increase its surface area three to five orders of magnitude, as measured by an increase in capacitance⁶⁾ and BET surface area⁷⁾.

• Fine extruded graphite rod
• Carbon and graphite electrodes
• Tokai glassy carbon
• Tokai graphite electrodes
• Pine Intsturments carbon screen printed electrodes
• Pine Intsturments Glassy carbon electrodes
• Pine Intsturments Pyrolytic carbon electrodes
• Glassy carbon narrow rods
• High purity graphite rods

About glassy carbon electrodes:

• Activated by polishing with sub-micron alumina
• Care and feeding
• Material properties

Type 304 stainless steel electrodes may provide electrodes of sufficient surface area, particularly if their microscopic area is enhanced by treatment with abrasives or electrolytic etching.

Here is a photo of a 0.050" (1.27mm) 304 stainless steel tube, closed on the end, and a close-up photo of the same tube, showing about ¼ of the diameter (1pixel =0.75 μm).