Engineering Localized Alkalinity and Oxygen Enrichment for Efficient Acidic O2-to-H2O2 Electroreduction via Carbon-Based Triphase Interfaces

The sustainable production of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e⁻ ORR) on carbon-based catalysts offers a compelling alternative to the energy-intensive anthraquinone process. However, the slow kinetics of the 2e⁻ ORR in acidic media limits its efficiency. Herein, a novel strategy is introduced to overcome this limitation by engineering a needle-shaped hydrophobic carbon felt embedded with hard carbon as a natural air diffusion electrode (ADE). In situ and ex situ characterization show this design creates an oxygen-enriched, locally alkaline microenvironment at the triphase interface, which accelerates 2e⁻ ORR kinetics by confining oxygen enrichment within the hard carbon layer. Quantitatively, this oxygen-enriched hydrothermal carbon electrocatalyst achieves a remarkable H₂O₂ selectivity of 95.47% at near-zero overpotential and a high production rate of 487.82 mg L⁻¹ h⁻¹ at 200 mA cm⁻². Furthermore, density functional theory calculations reveal that the carboxyl and ether functional groups in hydrothermal hard carbon optimize O₂^* and OOH^* adsorption, promoting the desired 2e⁻ pathway. Importantly, this ADE design not only exhibits exceptional performance and long-term stability but also demonstrates a significantly reduced global warming potential compared to conventional methods, highlighting its potential to revolutionize industrial-scale H₂O₂ electrosynthesis by replacing commercial carbon black-based cathodes.