OH radical degradation of blocking aryl layers on glassy carbon and gold electrodes leads to film thinning on glassy carbon and pinhole films on gold

Aryl layers on glassy carbon and gold electrodes were degraded by hydroxyl radicals from UV photolysis of hydrogen peroxide. The electrode surfaces were modified via electrochemical reduction of two structurally different azobenzene diazonium derivatives. The degradation of the aryl films was studied by AFM, XPS and electrochemical measurements using [Fe(CN)6]4 − as solution probe. While the prepared aryl layers inhibited the electrochemical response of hexacyanoferrate, their degradation with OH radicals resulted in different electrochemical behaviours for glassy carbon and Au electrodes. The aryl layer on glassy carbon was thinned, indicated by the increasing reversibility of the [Fe(CN)6]4 − response, whereas the aryl film on Au showed pinhole formation, indicated by the microelectrode behaviour of the hexacyanoferrate response without retarded reversibility.

► Glassy carbon and gold electrodes were modified using the diazonium reduction method.
► Aryl films on GC and Au electrode surfaces were attacked by UV-induced OH radicals.
► CV response of the [Fe(CN)6]4 − probe was used to evaluate the aryl film degradation.
► Decreasing thickness of aryl layers on GC was in evidence after H2O2/UV treatment.
► Pinhole formation after OH radical attack on aryl-modified Au electrode was confirmed by AFM.