Nitrogen-doped carbon materials derived from acetonitrile and Mg-Co-Al layered double hydroxides as electrocatalysts for oxygen reduction reaction

Abstract

N-doped carbon materials of various morphologies (carbon platelets, carbon nanotubes) were prepared by simultaneous carbonization of CH3CN and decomposition of Mg-Co-Al layered double hydroxides (LDHs) at 600, 700 and 800°C followed by treatment with HCl.Several techniques including powder X-ray diffraction, thermogravimetric analysis, elemental analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen sorption were applied to describe their physicochemical features. The electrocatalytic performance of N-doped carbon materials for oxygen reduction reaction (ORR) was evaluated using rotating disk electrode (RDE) and cyclic voltammetry (CV) measurements in alkaline solution.The samples prepared at 600 and 700°C appear to be more active for ORR than that prepared at 800°C. Higher activity of C-600 and C-700 is associated with higher contribution of carbon platelets providing higher specific surface area and offering higher concentration of the active sites. The contribution of carbon tubular nanostructures in C-600, C-700 and C-800 increases with increasing synthesis temperature. The presence of carbon nanotubes seems to be not advantageous for ORR performance.The N-doped carbon materials are able to catalyze the oxygen reduction reaction by 2 and 4 electrons. The order of selectivity for 4-electron reduction is the following: C-800<C-700<C-600. Among studied samples, C-600 has the highest concentration of pyridinic nitrogen being responsible for 4-electron reduction and the lowest concentration of O-containing groups, in particular carbonyl and carboxyl, being responsible for 2-electron reduction.