To find the relationship between the peak separation and the rate constant, we need to know the H-upd coverage at the peak potential, which we can obtain through solving the differential equation in Eq. 45b. For this we define the overpotential 𝜂 as the potential difference to the equilibrium peak potential (Eq. 45a) and make use of the dimensionless scan rate (Eq. 44b) to arrive at Eq. 45c.