The amount of charge carried by the chemisorbates at the IHP is calculated as, -∑ 𝑁 ad 𝜃 𝑖 𝑒 0 𝜉 𝑖 𝑖 , where 𝑁 ad is the number density of adsorption sites, 𝜃 𝑖 and 𝜉 𝑖 are the coverage and net electron per chemisorbate of type i, 𝑒 0 is the elementary charge. Δ𝜙 ad is then calculated as the potential difference across an equivalent planar capacitor with charge amount of ∑ 𝑁 ad 𝜃 𝑖 𝑒 0 𝜉 𝑖 𝑖 on each side,