Attachment of anthraquinone derivatives to glassy carbon and the electrocatalytic behavior of the modified electrodes toward oxygen reduction

The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with anthraquinones was studied using cyclic voltammetry (CV) and the rotating disk electrode (RDE) technique. Two methods were used in surface modification. The first method comprised immersion of the polished or anodically pretreated GC electrode in a solution containing 9,10-anthraquinone-2-carboxylic acid (AQ-2-COOH) or its anion (AQ-2-COO-) in dimethylsulfoxide ( DMSO) or 9,10-anthraquinone-2-ethanoic acid (AQ-2-CH2COOH) or its anion (AQ-2-CH2COO(-)) in N,N-dimethylformamide (DMF). Alternatively, the surface of the GC disk was modified by anodic oxidation of AQ-2-COOH or AQ-2-COO- in DMSO or AQ-2-CH2COOH in DMSO or DMF or AQ-2-CH2COO- in DMF. The modified electrodes showed electrocatalytic activity toward oxygen reduction in 0.1 M acetate buffer pH (4.8), 0.1 M phosphate buffer (pH 8) and 0.1 M NaOH. Atomic force microscopy (AFM) examination of the modified electrodes was carried out and the differences in surface morphology of various modifications were in evidence.