LAUSR

Abstract Amorphous carbon (a-C) based catalysts having higher activity and stability for oxygen reduction reaction (ORR) were achieved by introducing quinone and carboxy groups onto a-C surfaces. The surface-bonded quinone groups increased the rate of ORR to hydrogen peroxide. The surface carboxy groups promoted the activity toward electrochemical peroxide reduction. However, few studies have reported on their contribution. ORR activity was controlled by varying density of quinone and carboxy groups on the a-C surfaces. The ORR activity was proceeded by 2 + 2 electron mechanism through H2O2 that acted as an intermediate. The number of electrons transferred per O2 molecule reached 4.08 at a maximum. The catalytic activity of the catalyst was stable in long term measurements (150 times in 20 h) because a-C inherently has high corrosion resistance and oxygen-contained surface functionalities are stable in aqueous solution. Consequently, the a-C catalysts possessed high ORR reproducibility.