This paper presents a method for improving the efficiency of the reduction of oxygen, which occurs by way of a four-electron transfer and is catalyzed by bilirubin oxidase (BOD), by adsorbing 2,2'-azinobis(3-ethylbenzothiazolin-6-sulfonate) (ABTS) on the surface of a MgO-templated carbon (MgOC) electrode. The ABTS molecules adsorbed on the surface of MgOC show very stable redox behavior without disproportionation, which would cause the degradation of these molecules. The maximum catalytic current increased two times in the presence of ABTS across a wide pH range. The pH-dependence of the oxygen reduction voltammogram revealed that the ABTS adsorbed on the electrode surface accelerated the direct and mediated electron transfer rates by improving the orientation of BOD on the carbon surface and/or by enhancing enzyme loading favorable for the electron transfer, and by mediating the electron transfer from the electrode to the electro-active site of BOD. (C) 2015 Elsevier Ltd. All rights reserved.