and is thus known. However, Figure reveals how the fraction of the current carried by the direct mechanism depends on the remaining unknown kinetic parameters in the system while remaining agnostic about the values they should assume, namely the B(aq) B(org) partitioning rate constant 𝑘𝑘 𝑃𝑃ℎ𝑇𝑇,𝑓𝑓 , and the exchange current densities for the individual parallel pathways 𝑗𝑗 0,𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 and 𝑗𝑗 0,𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 . At an arbitrary overpotential 𝜂𝜂 = 50 mV, the current arising from the direct pathway was divided by the total current flowing through the interface at varying combinations of 𝑘𝑘 𝑃𝑃ℎ𝑇𝑇,𝑓𝑓 and 𝑗𝑗 0,𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 /𝑗𝑗 0,𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 (where 𝑗𝑗 0,𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 was set to be 30 mA/cm 2 to simulate quasireversible kinetic behavior in the system). Figure shows that if the kinetics of the direct and sequential electrochemical steps are equal (𝑗𝑗 0,𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 /𝑗𝑗 0,𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 = 1), then 𝑘𝑘 𝑃𝑃ℎ𝑇𝑇,𝑓𝑓 can assume a value between 1 to10 5 cm/s and the total current is still mostly carried by the interfacial-direct mechanism, with 𝑗𝑗 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 /𝑗𝑗 𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 ≈ 0.75 at the upper end of this range. This arises from the fact that 𝑘𝑘 𝑃𝑃ℎ𝑇𝑇,𝑓𝑓 effectively controls the maximum rate that current can flow through the sequential pathway and thus it can only support a small fraction of the total current drawn from the system when the current demand is high. The direct mechanism does not have such a limitation, so the remainer of the current flows through this pathway instead. It can be seen at the highest value of 𝑘𝑘 𝑃𝑃ℎ𝑇𝑇,𝑓𝑓 = 10 5 the sequential pathway can meet more of the current demands of the system and thus the fraction 𝑗𝑗 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 /𝑗𝑗 𝑠𝑠𝑑𝑑𝑠𝑠𝑠𝑠𝑑𝑑𝑠𝑠𝑑𝑑𝑑𝑑𝑠𝑠𝑠𝑠 is somewhat lower. We estimate that the upper bound of a rate constant for a partitioning process should be related to the average velocity of a molecule along its mean free path in solution, which in this case would be on the order of 10 3 cm/s for DPP in liquid water (S7). Thus, for a measured partition coefficient of 10 5 the current in a kinetic measurement should be representative of the interfacial direct mechanism, unless the intrinsic kinetics of the direct mechanism (𝑗𝑗 0,𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 ) is more than an order of magnitude lower than that of the sequential mechanism. Even in this case, the contribution of the sequential mechanism quickly decreases with increasing overpotential (Figure ) and the majority of the current potential response in a kinetic measurement would be reflective of the interfacial direct mechanism.