N-doped ordered mesoporous carbons prepared by a two-step nanocasting strategy as highly active and selective electrocatalysts for the reduction of O2 to H2O2

Abstract

A new, two-step nanocasting method was developed to prepare N-doped ordered mesoporous carbon (NOMC) electrocatalysts for the reduction of O2 to H2O2. Our strategy involves the sequential pyrolysis of two inexpensive and readily available N and C precursors, i.e. aniline and dihydroxynaphthalene (DHN), inside the pores of a SBA-15 hard silica template to obtain N-doped graphitic carbon materials with well-ordered pores and high surface areas (764 and 877m2g−1). By tuning the ratio of carbon sources to silica template, it was possible to achieve an optimal filling of the pores of the SBA-15 silica and to minimise carbon species outside the pores. These NOMC materials displayed outstanding electrocatalytic activity in the oxygen reduction reaction, achieving a remarkably enhanced kinetic current density compared to state-of-the-art N-doped carbon materials (−16.7mAcm−2 at −0.35V vs. Ag/AgCl in a 0.1M KOH solution as electrolyte). The NOMC electrocatalysts showed high selectivity toward the two-electron reduction of oxygen to hydrogen peroxide and excellent long-term stability.