Breaking Trade-Off between Selectivity and Activity of 2e^- ORR to Boost Hydrogen Peroxide Production and In Situ...

The electrochemical 2e^- oxygen reduction reaction (ORR) offers a promising pathway for on-site hydrogen peroxide (H₂O₂) production as an alternative to the anthraquinone process. However, challenges remain for low selectivity and a trade-off between selectivity and activity (TOSA). This study develops a novel thermodynamic regulation strategy to improve the selectivity toward 2e^- ORR by suppressing competitive 4e^- ORR. With the decoupled decisive factors, the selectivity and activity of 2e^- ORR can be independently tuned to boost H₂O₂ production aiming to break the TOSA. Based on density functional theory predictions and experimental validations, a vanadium single atom electrocatalyst with an axially coordinated -NO₂ ligand exhibits 98.06% selectivity toward 2e^- ORR while the activity approaches the theoretical limit. The H₂O₂ yield rate reaches up to 7.47 mol g_cat^-1 h^-1 in a neutral electrolyte at 0.30 V vs RHE in a flow cell. Moreover, on-site production and in situ utilization of H₂O₂ for degrading typical recalcitrant organic pollutants are demonstrated in a dual-cathode electron-Fenton system. Tetracycline and phenol (20 mg L^-1) can be degraded with an efficiency up to 100% in 120 min. This study provides a proof-of-concept demonstration of a thermodynamic regulation strategy to promote H₂O₂ production by addressing low selectivity and TOSA of 2e^- ORR, and on-site production and in situ utilization of H₂O₂ have broader implications in environmental scenarios.