The Standard Hydrogen Electrode (SHE) requires a platinum electrode due to platinum's excellent catalytic properties, which facilitate fast reactions and ensure that potential changes are not influenced by reaction kinetics. The electrode is dipped in hydrochloric acid (HCl) because chloride ions (Cl-) serve as an effective, inert counter anion with a high diffusion coefficient, minimizing solution resistance. Other metals and acids are not suitable as they do not provide the same level of catalytic efficiency or stability, which is crucial for accurate electrochemical measurements. Additionally, the use of platinum black enhances the surface area of the electrode, further promoting rapid reactions.
