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 gcat–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 gcat–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.