Answer:
To increase surface area of the platinum electrode which results in superior quality and action of the electrodes as opposed to normal platinum electrodes.
Step-by-step explanation:
Platinization of Platinum is the process of covering platinum electrode with a layer of platinum black. Platinum black is a finally divided form of platinum, optimized for catalysing the addition of hydrogen to unsaturated organic compound. This increases the surface area of the platinum electrodes and therefore exhibits action superior to that of normal electrodes.