Figure (b)depicts the electric potential profile from the bulk metal to the bulk solution. At the metal surface exists a large potential drop due to the metal electron tail, denoted χ M = 𝜙 M -𝜓 M . There are three potential differences in the space between the metal and the IHP, including one due to the firstlayer water molecules, one due to partially charged chemisorbates, and one due to the surface charge.