Hard template derived N, S dual heteroatom doped ordered mesoporous carbon as an efficient electrocatalyst for oxygen reduction reaction

Abstract

At present, a low-cost and efficient electrocatalyst is vital to conquering the sluggish oxygen reduction reaction (ORR) in fuel cells. In particular, N and S dual heteroatom doped mesoporous carbon (NSMC) catalysts are believed to be one of the best ORR catalyst options due to the distribution of nitrogen, sulfur sites. In this work, for NSMC synthesis we employed 2D Santa barbara amorphous (SBA-15) silica as support material and L-cysteine as N and S dual precursor. The optimal loading of NSMC-0.4, reveals the high concentration of defect sites (ID/IG = 0.99), pyridinic (21.41 at. %), graphitic-N (50.27 at. %), thiophene-S (77.16 at. %) sites on MC surface resulting in an improved ORR performance. The NSMC-0.4 showed more positive onset potential of 0.78 V vs. RHE, half-wave potential of 0.68 V, current density of 2.8 mA/cm2, peroxide production of 81%, followed by two-electron reduction process and lower Rct of 10 Ω/cm2 in an alkaline electrolyte solution. However, NSMC-0.6 demonstrated the higher amount of peroxide selectivity (150%) due to the presence of a large quantity of pyrrolic-N sites. In addition, our work provide an excellent guide for the synthesis and design of NSMC for efficient peroxide production via an electrochemical synthesis route.