Trace Mn decorating nitrogen-doped carbon electrocatalysts for self-powered bio-electro-fenton cells toward simulated wastewater treatment

Abstract

The in situ Fenton reaction utilizing H₂O₂ has gained significant attention due to its effectiveness in the oxidation of persistent organic pollutants. In this study, we have successfully developed an efficient 2-electron oxygen reduction reaction (2e⁻ ORR) electrocatalyst, Mn-PDA/CNT-2, which exhibits a high H₂O₂ selectivity of up to 96% within the potential range of 0.65 to 0.85 V vs. RHE in a 0.1 M KOH solution. Moreover, particular emphasis is given to the preparation of an air diffusion floating electrode (ADFE) by incorporating Mn-PDA/CNT-2 onto carbon felt (CF), which enables oxygen in the air to self-drive into the solid state interface of ADFE for the 2e⁻ ORR in bioelectrochemical systems (BESs). Remarkably, the self-aeration ADFE in microbial electrolysis cells (MECs) achieves an impressive maximum current efficiency of 93% for H₂O₂ production, and the cumulative production of H₂O₂ reaches a significant amount of 325.18 mg L⁻¹ within a 24 hour period. Additionally, an in situ bio-electro-Fenton system is employed for the degradation of Rhodamine B (RhB). The self-aeration ADFE-MECs system with a Hydraulic Retention Time (HRT) of 6 h demonstrate an effective RhB (6.5 M, pH ≈ 11) degradation rate nearly 90%, accompanied by reduced toxicity in the resulting degradation products.