Magnesium lignosulfonate-derived N, S co-doped 3D flower-like hierarchically porous carbon as an advanced metal-free electrocatalyst towards oxygen reduction reaction.

The development of metal-free electrocatalytic materials that are economical, friendly to the environment, and efficiency towards the oxygen reduction reaction (ORR) is of significant interest. Hence, this paper synthesizes nitrogen and sulfur co-doped three-dimensional magnesium lignosulfonate (MLS-derived) flower-like hierarchical porous carbon (NSLPC) materials by a simple and green method. The synthesized NSLPC uses magnesium lignosulfonate as the sulfur source and carbon precursor, melamine as nitrogen source, MgO as hard template, and ZnCl 2 as the activator. We also investigated the effect of the ratio of MgO to ZnCl 2 on the catalyst performance. When the ratio of MgO to ZnCl 2 is 10:0.5, NSLPC-1005 possesses the highest ORR activity with an enormous surface area (1752.54 m2 g−1), abundant active sites, and a hierarchical porous network structure. In alkaline media, NSLPC-1005 has an initial potential of 0.97 V , as well as an excellent half-potential of 0.86 V (vs. Hg/HgO), and an ultimate current density of 5.35 mA cm−2. It exhibits attractive ORR performance as well as outstanding cyclic stability that are comparable to commercial Pt/C electrocatalysts. This research developed an effective approach to synthesize metal-free carbon materials with high activity and long-term durability as electrocatalysts, which have a promising application in sustainable energy conversion technology. [Display omitted] • NSLPC has a 3D flower-like structure facilitating contact of reactants and sites. • NSLPC are constructed of extremely thin carbon nanosheets of only about 10 nm. • Sulfur and nitrogen double doping produce numerous active carbon atoms. • N-doped carbon nanoparticles evenly distributed on NSLPC offering active sites. [ABSTRACT FROM AUTHOR]