Nitrogen doped mesoporous carbon aerogels and implications for electrocatalytic oxygen reduction reactions

Mesoporous carbon aerogels with 0-4% nitrogen content were prepared from 3D resorcinol (R) - melamine (M) - formaldehyde (F) aerogels by tuning the M/R ratio during the polymerization process. The carbon matrix obtained has a complex porosity. Although the surface area and pore volume are maintained, the pore volume from N-2 adsorption decreases with increasing N content. Increasing the M/R ratio increases not only the N but also the O content of RMF based carbon samples. The O and N containing functional groups are less abundant on the surface than in the bulk. N occurs at the surface predominantly in form N-6 and N-Q With increasing heteroatom concentration the carbon surface becomes less hydrophobic, but high amounts seem to reduce accessibility to the pores. The effect of N content on the catalytic performance in oxygen reduction reactions (ORR) was measured by cyclic voltammetry (CV). The onset potential approaches that of a PAN derived carbon in the sample with the highest N content. The strong correlation between the cathode current density and the BET surface area reveals the role of the accessibility of the N species in the electrocatalytic process. (C) 2016 Elsevier Inc. All rights reserved.