This reaction cannot be dismissed, as all necessary educts and products have been detected experimentally or theoretically. We, therefore, replicated our approach for the PO formation mechanism on sodium with the surface oxidation process. We found the initial surface oxidation step to be endothermic on all considered sodium surfaces (Tab. 4). The reaction schematic for the surface oxidation pathway is depicted in Fig. , and the PO formation reaction along this path would require over 2 eV in total. The direct surface oxidation is energetically unfavorable compared to our proposed carbonate formation, supporting the initial claim that carbonate formation is the driving force behind the first step of the PO formation mechanism. Further, a reaction of PC into PO resulting in CO 2 formation has been proposed . Similarly to the direct oxidation reaction of propene, we dismiss this reaction due to the absence of CO 2 in our measurements.