Transformation of worst weed into N-, S-, and P-tridoped carbon nanorings as metal-free electrocatalysts for the oxygen reduction reactionElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta04809e

Substituting sustainable/cost-effective catalysts for scarce and costly metal ones is currently among the major targets of sustainable chemistry. Herein, we report the synthesis of N-, S-, and P-tridoped worst-weed-derived carbon nanorings (WWCNRs) that can serve as a metal-free and selective electrocatalyst for the oxygen reduction reaction (ORR). The WWCNRs are synthesized via activation-free polymerization of worst weed, Eclipta prostrata , and then removal of the metallic residues by using HCl. The WWCNRs exhibit good catalytic activity towards the 4 electron-transfer ORR with a low onset potential and high kinetic limiting current density, along with high selectivity (introducing CO, the sample loses only