High selectivity and optimized mass transport equipped air-breathing cathode with efficient H2O2 generation for wastewater treatment

Catalyst selectivity and electrode interface species transport are key limitations in H₂O₂ synthesis via 2e⁻- oxygen reduction reaction. This study demonstrates increased catalyst selectivity and optimized mass transport of reactants (O₂) and products (H₂O₂) through a one-step acid-treated method applied to air-breathing cathodes. At lower current densities (20 mA cm⁻²), intrinsic catalyst selectivity domains H₂O₂ yield. The acid-oxidized catalyst exhibits an electron transfer number of 2.01 with exceptional H₂O₂ selectivity (99.11 %), attributed to increased carboxyl-group content, resulting in a 33.80 % improvement in H₂O₂ production (3614 mg L⁻¹ vs. 2701 mg L⁻¹ of untreated electrode). At higher current densities (40 mA cm⁻²), interfacial mass transport characteristics become the primary limiting factor. The electrode surface gains oxygen doping defect, oxygen vacancies, carbon edge defect sites, roughness, and hydrophobicity after acid treatment to form a oxygen-enriched microenvironment to facilitate O₂ and H₂O₂ mass transport. Maximum H₂O₂ production reaches 4258 mg/L, representing a 59.30 % enhancement. The acid-modified electrodes are used for Fenton-process degradation of dyeing wastewater. After 3h treatment, the chemical oxygen demand (COD) is reduced to 195 mg L⁻¹, with a removal efficiency of 83.42 %. This one-method dual-functional optimization strategy provides new insights for efficient H₂O₂ electrosynthesis, while demonstrates an extended application in wastewater treatment.