Enhanced electrocatalytic reduction of oxygen with a molecule having multi-quinone moieties adsorbed in the nanofiber film

The electrochemical reduction of oxygen has been studied on two novel anthraquinone derivatives, 1,5-bis(2-anthraquinonyloxy)-3-oxapentane (AQ1), and 1,11-bis(2-anthraquinonyloxy)-3,6,9-oxaundecane (AQ2) having two quinone moieties with cyclic voltammetry (CV) and hydrodynamic voltammetry (HV). Anthraquinone derivative modified electrodes exhibited a well defined redox couple in an aqueous solution which is corresponding to (AQ/AQH2). The AQs adsorbed on the electrodes in the nanofiber network showed an electrocatalytic activity for the oxygen reduction with 620 mV positive potential shift and the current enhancement in a phosphate buffer solution (pH 7.0) as compared to a bare electrode. The compounds having two quinone moieties (AQ1, AQ2) showed the doubly increased catalytic current compared with that bearing a single quinine moiety (9,10-AQ). HVs with a rotating ring-disk electrode showed that the reduction of oxygen at the modified electrodes mostly occurs through the two-electron pathway to form H2O2 as a final product. The rate constant (k) for oxygen reduction with AQ1 and AQ2 modified electrodes was determined to be 2.4 × 105 and 2.7 × 105 M−1 s−1, respectively.