Dual-functional Mn-single atom catalysts for synergistic H2O2 generation and activation: Toward efficient refractory organic wastewater treatment

Electro-oxidation is a promising technology for treating refractory organic pollutants in landfill leachate but faces challenges of high energy consumption and inefficient degradation of complex organics. This study introduces a manganese single-atom catalyst (MnSAC) doped on carbon nanotubes (CNTs) within a gas-diffusion electrode to enhance electro-oxidation performance. The bifunctional catalyst simultaneously promotes 2e oxygen reduction reaction for H 2 O 2 generation and in-situ activation of H 2 O 2 to produce reactive oxygen species, primarily hydroxyl radicals ( • OH). In a system employing a Ni-Sb-SnO 2 anode and operating under the operation conditions (initial chemical oxygen demand: 478   mg   L 1 ; electrolyte: 0.1   mol   L 1 Na 2 SO 4 , current density: 10   mA   cm 2 , volume: 100   mL), a 90% removal rate (reduced to 49   mg   L 1 ) was achieved. The core innovation lies in the unique N-coordinated MnSAC (Mn-N 4 ) sites on CNTs, identified via Density Functional Theory calculations to exhibit ΔG of −3.46   eV for H 2 O 2 activation and organic adsorption. The Mn-N-C structure modulates the d-band center to optimize electron/charge distribution and transfer. This synergistic design: 1) enhances H 2 O 2 activation and radical generation, 2) accelerates organic pollutant adsorption/degradation, and 3) improves reaction kinetics. The catalyst addresses critical issues like metal leaching and energy inefficiency, offering a robust, sustainable solution for refractory organic wastewater treatment.