Hydrogen dissolution, anodic limiting currents

The dissolution reaction is Pt - Pt2+ + 2e and the value of its reversible thermodynamic potential is 1.2 V on the normal hydrogen scale. The evolution of O2 in acid solution at a current density of, say, 100 mA cm, needs an overpotential on platinum of nearly 1.0 V, i.e., the electrode potential would be >2.0 V. It follows feat at these very anodic potentials platinum would tend to dissolve, although its dissolution would be slowed down by fee fact feat it forms an oxide film at fee potentials concerned. Nevertheless, fee facts stated show feat fee alleged stability of Pt may be more limited than is often thought. This is an important practical conclusion because dissolved Pt from an anode may deposit on fee cathode of fee cell, and instead of having fee surface one started wife as fee cathode, it becomes in fact what is on its surface, platinum. 

Limitations include current attenuation in long sections of wire. Uneven current distribution results in premature localized anode degradation, especially near the connection to a single current feed point. Multiple feed points improve the current distribution and provide system redundancy in the event of excess local anode dissolution. Current ripple effects, especially at low frequencies, should be avoided. The substrate materials are at risk to hydrogen damage if these anodes assume a cathodic character outside of their normal operational fimction (for example, if the system is de-energized). 

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