Pentagonal defects enriched carbon fibers for enhanced H₂O₂ electrosynthesis

To achieve highly-efficient and energy-saving H2O2 production via two-electron oxygen reduction reaction (2e⁻ ORR), a pentagonal edge defects packaged carbon fiber catalyst (PED-CF) from Bi-MOF was developed. Controllable pentagonal defect densities were created by regulating the pyrolysis duration, as characterized by AC-TEM and Raman. The optimized PED-CF showed high performance toward 2e⁻ ORR, delivering an onset of potential of 0.76 V vs. RHE and a maximum 2e⁻ ORR selectivity of ~99 % in 0.1 M KOH, surpassing most recently reported state-of-the-art electrocatalysts. Impressively, a linear relationship between the pentagonal defects on the edge (ID1/IG) with ORR selectivity was revealed, implying the critical role of pentagonal edge defects in H2O2 production. Furthermore, in-situ ATR-SEIRAS and in-situ Raman demonstrated the interactions between *OOH intermediate and PED-CF, highlighting the significant role of pentagonal edge defects for 2e⁻ ORR. Combined with theoretical calculations, the synergism between zigzag edges and pentagons greatly optimized the adsorption energy of *OOH toward the 2e⁻ ORR pathway. A natural air diffusion electrode assembled with PEDCF achieved exceptional H2O2 production rates, reaching 8.12 and 6.72 mol gcat⁻¹ h⁻¹ at 100 mA cm− 2 in alkaline and neutral electrolytes, respectively. Furthermore, the sulfide oxidation reaction (SOR) as anode reaction coupled with 2e⁻ ORR realized 61.4 % energy-saving at 100 mA cm− 2 compared to the conventional 2e⁻ ORR system. This study opens a pathway for designing high-performance and energy-effective carbon electrocatalysts for sustainable H2O2 electrosynthesis.

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