A platinum electrode is a crucial component in electrochemistry. Let’s delve into its fascinating properties and applications:

1. Stability and Resistance to Corrosion:

   • Platinum (Pt) is a noble metal known for its exceptional stability and resistance to corrosion.
   • Similar to gold (Au), Pt is often used in jewelry due to its durability and lustrous appearance.

2. Electrode Function:

   • As an electrode, Pt serves various purposes:
     • Oxidation of Organics: It can oxidize organic compounds.
     • Hydrogen Generation: Pt electrodes are employed to generate hydrogen gas.
     • Oxygen Reduction: Pt can reduce oxygen.
   • Pt electrodes come in different forms, such as wires of varying diameters or foils with different thicknesses.

3. Composition and Structure:

   • Pt electrodes are typically polycrystalline (not single crystals), lacking a well-defined crystalline structure.
   • Some Pt electrodes contain a small amount of rhodium to enhance rigidity, especially when the electrode is thin foil.
   • Figure 1 shows a cyclic voltammogram of a smooth Pt electrode in 0.5 M H₂SO₄.
     • In the potential range of 0.4 to 0.8 V (vs. NHE), the Pt surface remains “clean,” and the current charges the double layer.
     • As the potential becomes more positive, the current corresponds to the formation of adsorbed oxygen or platinum oxide.
     • The point labeled “2” marks the start of bulk oxygen evolution.
     • Upon reversing the potential, the cathodic current involves the reduction of surface platinum oxide.
     • If dissolved oxygen is present, it will also be reduced concurrently with platinum oxide reduction.
     • Peaks due to adsorbed hydrogen atoms appear in the double layer region, their shape and number influenced by the Pt surface’s crystal faces.
     • Bulk hydrogen evolution begins at point “1.”
     • These surface processes are pH-dependent, with the cyclic voltammogram shifting by approximately -60 mV per unit pH.