Nitrogen-Doped Carbon Nanodots@Nanospheres as An Efficient Electrocatalyst for Oxygen Reduction Reaction

Abstract

In this work, nitrogen-doped carbon nanodots (N-CNDs) with sizes of 2–6 nm were successfully synthesized by hydrothermal treatment of natural biomass (e.g., fresh grass) at 180 °C for 10 h. The synthesized carbon nanodots were subsequently immobilized onto functionalized microporous carbon nanospheres (MCNSs) with an average diameter of ∼100 nm and a surface area of 241 m2 g−1 via a simple hydrothermal process to self-assembly form a carbon-based nanocomposite (N-CNDs@MCNSs) owing to the presence of oxygen (O)-containing surface functional groups. As electrocatalyst for oxygen reduction reaction (ORR) application, our experimental results demonstrated that sole N-CNDs could not form stable electrocatalyst film for ORR measurement owing to their high water dispersion property, while the N-CNDs@MCNSs exhibited high electrocatalytic activity with an onset potential of −0.08 V, superior durability and high resistance to methanol cross-over effect, comparable to commercially available Pt/C electrocatalyst.