The predicted peak positions of the volcano plots are similar for both the PCET pathway and the composite mechanism at 0 V (ΦN*,peak = -0.53 and -0.61 eV, respectively), resulting in similar predictions of which materials lie near the peak of the volcano as well as a similar predicted ordering of materials based on NRR activity. The activity ordering of materials at 0 V therefore generally agrees with that of previous work. For example, both the PCET pathway and composite mechanism predict that Ru(111) is near the top of the NRR volcano due to its favorable scaling between intermediates, which agrees with previous modeling results on metals using PCET and CHE approaches. However, the consideration of multiple reaction pathways and the chemical NRR steps in the composite mechanism results in non-linear changes in Φmax on several surfaces as a function of applied bias. Consequently, the potential dependence of Φmax observed for the composite mechanism deviates substantially from the simpler PCET mechanism and previous studies for some materials. This non-linearity results in a large deviation of the peak positions between the PCET mechanism and composite mechanism at -0.5 V (ΦN*,peak = -0.82 and -0.22 eV, respectively), and a greater bias dependence of Φmax for some materials. This results in different ordering of surfaces based on NRR activity at different biases, as shown in Figure , which plots Φmax at each studied potential for a subset of surfaces using the composite mechanism.