2C ̇N → (CN) 2 ↑ Eq. 10 The proton thus formed can then be reduced at the HC adding to the enhanced H2 evolution observed in the over-charged full cell above 3.60 V in Figure . When the PW electrode potential is increased to 4.9 V vs Na + /Na, POF3 is additionally observed to evolve at >4.3 V vs Na + /Na (4.6 V vs. Li + /Li), which indicates that electrochemical oxidation of the electrolyte sets in at these potentials and induces the NaPF6 salt degradation.