Abstract
•Carbon surfaces were modified by reaction of a Boc protected diazonium salt.•Upon removal of the Boc group, anthraquinone was coupled to the surface.•The modified surfaces catalyse the 2e reduction of O2 at pH 7.•The choice of GC, edge or basal HOPG surface does not affect the catalysis.
The oxygen reduction reaction was investigated at bare and anthraquinone modified glassy carbon and edge and basal plane highly oriented pyrolytic graphite electrodes. Anthraquinone was attached to the graphite electrodes through a –NHCH2C6H4– linker using electrochemical reduction of the corresponding Boc (Boc is tert-butyloxycarbonyl) protected diazonium salt, removal of the Boc protection and subsequent solid phase coupling to anthraquinone-2-carboxylic acid. In each case electrochemical reduction of the Boc protected diazonium salt leads to blocking of the surface. Following deprotection and coupling the apparent surface coverage of anthraquinone is found to be greatest on the edge plane electrode and lowest on the basal plane with the glassy carbon surface intermediate between the two. The immobilized anthraquinone is stable at the surface and catalyzes the reduction of oxygen to hydrogen peroxide.