Surface characterization of glassy carbon electrodes anodized in 1-alkanols by their wettability and capacitance

Abstract

The surface conditions of glassy carbon (GC) electrodes anodized in n-CnH2n+1OH (n=2, 4, 6, 8: electrodes 1-4), HO(CH2)nOH (n=2-5: electrodes 5-8), and HO(CH2CH2O)2CH2CH2OR (R=H, Me: electrodes 9 and 10) were explored by measuring the wettability and capacitance as well as the voltammetric response to Fe(CN)3-6; wetting properties were evaluated by the contact angle formed by a drop of water; the ratio between the values of capacitance obtained before and after the anodic modification was used instead of the capacitance itself. The data have revealed that LiClO4 is recommended rather than conc. H2SO4 as a supporting electrolyte to fix 1-alkanol molecules more effectively to GC electrode surfaces in the anodic modification. The surface conditions of electrodes 1-10 have reflected the identities of the modifier remarkably: electrodes 1-4 have surfaces with hydrophobicity and thickness correlated to the length of carbon chains of the modifiers; on the other hand, the surfaces of electrodes 5-10 are hydrophilic, which seemed to allow each of the modified electrodes, except for electrode 8, to have a double layer with a thickness similar to a bare GC electrode. The suppression in the electrode reaction of Fe(CN)3-6 was stronger at electrodes 6 and 8 than at electrodes 5 and 7, which can be explained by the invocation of an "odd-even" effect.