In the small substrate-tip gap, the electrochemical system can be defined by two electrodes, the tip and the sample, where a potential pulse at the tip will force an increase in the potential drop at the two solid-liquid interfaces. The required potential Vreq to enable local Faradaic currents is the change of the two solid-liquid potential drops from their rest potential to the potential of the respective halfreactions. This is illustrated in Figure , showing the evolution of the potential landscape in the tipsubstrate gap that are kept at some rest potential with respect to the solution (Vs1 and Vt1, solid line), as the interfaces are charged to the potential required for the electrochemical reactions (Vs2 and Vt2, dashed line) under influence of a pulse applied to the tip. It is worth noting that these potentials can be reached before the potential in the gap fully equilibrates, as illustrated here by the linear profile in the center . The required polarization is then taken as the sum 𝑉 𝑟𝑒𝑞 = |𝑉 𝑠1 -𝑉 𝑠2 | + |𝑉 𝑡1 + 𝑉 𝑡2 |. It should be noted that charging dynamics are expected to deviate from the ideal capacitor behavior at potentials above those required for the electrochemical reactions, as the interface may become (increasingly) non-polarizable once charge transfer is allowed. While this picture therefore illustrates the time required to reach sufficient polarization, it does not determine the (Faradaic) reaction rates.