𝑎 The steady state condition At steady state the rate of each reaction step, 𝑟 𝑘 , divided by its number of occurrences, 𝑛 𝑘 , must be equal to the overall reaction rate, 𝑟 𝑛𝑒𝑡 , to maintain mass balance. Using Faraday's law (Eq. 3b), the steady state condition can be used to link the current contributions of each step, 𝑖 𝑘 , to the overall current 𝑖 𝑛𝑒𝑡 (Eq. 7a), with 𝑧 𝑛𝑒𝑡 = ∑ 𝑛 𝑘 𝑧 𝑘 representing the total number of transferred electrons, and the subscript 𝑛𝑒𝑡 denoting properties of the overall reaction. Similarly, the sum of the standard Gibbs free energies ∆𝐺 𝑘 ∘ of the individual reaction steps (Eq. 7b, 7c), weighted by their occurrence numbers, constitutes the overall Gibbs free energy of the net reaction ∆𝐺 𝑛𝑒𝑡 ∘ (Eq. 7d). Finally, we obtain (see SI.M1c) an equation that links the standard potential of the overall reaction to the thermodynamic properties of its individual steps (Eq. 7e), with an example shown in Fig.