Metal-free ovalbumin-derived N-S-co-doped nanoporous carbon materials as efficient electrocatalysts for oxygen reduction reaction

Nanoporous carbon materials using bone char (BC) as a pore-inducer and dehydrated egg white as a precursor of carbon and heteroatoms were successfully obtained. They were synthesized in the presence of tetraethyl orthosilicate (TEOS) and BC (NSAC1), as well as in the absence of them (NSAC2, without TEOS; NSAC3, without BC). N2 gas porosimetry showed the effect of BC and TEOS on the surface area value of NSAC1 (345 m2 g−1), which was higher than that found for NSAC2 (280 m2 g−1) and NSAC3 (240 m2 g−1). X-ray diffraction patterns and Raman spectra showed a balance between the organized/non-organized structure, while SEM images showed some morphological modifications. FTIR spectra revealed the presence of heteroatoms in the carbon lattice, which were explored through XPS analysis. NSAC1 had higher contents of N (15.20%) and S (0.40%) than those found for NSAC2 (13.58% and 0.26%) and NSAC3 (15.14% and 0.18%), respectively. The electrocatalytic properties of the materials were investigated toward the oxygen reduction reaction (ORR), and the results were compared with those obtained for a commercial catalyst (Pt/C). The NSAC1 showed the best electrocatalytic activity for ORR, with an onset potential 110 mV more negative than that obtained for the Pt/C catalyst and an associated current density of 0.45 mA cm−2.