The electrocatalytic activity of T6[100] surface containing both sp(3) (C-1) and sp(2) (C-2) hybridized carbon atoms is explored using first-principles density functional theory based approach. The top layered C-1: atom of the surface is found to be more active towards the oxygen reduction reaction (ORR), as compared to that of C-2 atom. This is attributed to the presence of dangling a bond in the corresponding C-1 atom, leading to the high electron density near the Ferrmi level. Whereas, the pi electron in the top layered C-2 atom forms a weak out of plane network. As estimated from free energy profile, the overpotential is much lower when C-1 is considered as the active site and the final step i.e desorption of final OH-ion is found to be the potential determining step. We have also reported the effect of Si dopant on the catalytic activity of T6[100] surface and explained the origin of high overpotential value in this case. Thus in this report, we propose a new metal-free catalyst i.e T6[1001 surface, having both sp(2) (maintains the high metallicity needed to reduce ohmic loss) and sp(3) (helps in capturing the upcoming molecules) hybridized carbon atoms, as a potential candidate for ORR. (C) 2016 Elsevier B.V. All rights reserved.