2.2.2- Primary product (electrons added)

According to Figure 4C, theoretical calculations show one of two extremes (i.e. all electrons added in second cell or no (minimal) electrons added in second cell) show the greatest efficiency with a given set of applied potentials. This varies as a result of the carbon to electron ratio as seen in equation (8). Hence there are multiple products mentioned in specific electron requirements, such as propanol/methanol for 0 additional electrons and formaldehyde/acetate for 8 additional electrons.
The case with hydrogen is  much more trivial in that the efficiency of the two-step fixation depends on whether or not the product of Faradaic efficiency and the applied potential in the primary fixation step is greater than that the product of the efficiencies associated with the second step and the potential applied. This is seen in Figure 4A, where for example the \(H_2\)-mediated fixation becomes more efficient with an additional bias applied of around 0.51V, the additional bias on top of 1.23V.