Improved H₂O₂ Electrosynthesis on S-doped Co-N-C through Cooperation of Co-S and Thiophene S

Co-N-C based catalysts have emerged as a prospective alternative for H₂O₂ electrosynthesis via a selective 2e^- oxygen reduction reaction (ORR). However, conventional Co-N-C with Co-N₄ configurations usually exhibits low selectivity toward 2e^- ORR for H₂O₂ production. In this study, the S-doped Co-N-C (Co-N-C@S) catalysts were designed and synthesized for enhancing the electrosynthesis of H₂O₂, and their S doping levels and species were tuned to investigate their relationship with the H₂O₂ yield. The results showed that the S doping greatly enhanced the activity and selectivity of Co-N-C@S for H₂O₂ production. The optimal Co-N-C@S(12) displayed a high H₂O₂ production rate of 395 mmol g_cat^-1 h^-1, H₂O₂ selectivity of 76.06%, and Faraday efficiency of 91.66% at 0.2 V, which were obviously better than those of Co-N-C (H₂O₂ production rate of 44 mmol g_cat^-1 h^-1, H₂O₂ selectivity of 26.63%, and Faraday efficiency of 17.37%). Moreover, the Co-N-C@S(12) based electron-Fenton system displayed effective rhodamine B (RhB) removal, significantly outperforming the Co-N-C-based system. Experimental results combined with density functional theory unveiled that the enhanced performance of Co-N-C@S(12) stemmed from the combined effect of Co-S and thiophene S, which jointly enhanced electron density of the Co center, reduced the desorption energy of the *OOH intermediate, and then promoted the production of H₂O₂.