Isomerization and ionization of N2O4 on model ice and silica surfaces

► Isomerization and ionization of N2O4 on model ice and silica surfaces were studied computationally. ► MP2 and B3LYP methods were used. ► Asymmetric ONONO2 and separate ion pair NO+NO3− were found to be isoenergetic. ► Dangling surface -OH bonds were found to play a key role in the isomerization. ► Proposed mechanism may play a role in HONO production in the atmosphere.