Sea urchin-like La-doped MnO₂ for electrocatalytic oxidation degradation of sulfonamide in water

A sea urchin-like La-doped α-MnO2 catalyst was successfully synthesized by a one-step hydrothermal method. The as-prepared material exhibits electrocatalytic activity for water oxidation, achieving an overpotential of 450 mV to reach a catalytic current density of 10 mA/cm2 in 1.0 M KOH solution. The urchin morphology and open tunneling structure can fully expose the rich active sites and facilitate mass transfer during electrochemical oxidation process. Moreover, the catalyst is also applied for sulfonamide degradation due to the generation of strong oxidizing •OH species during the process of water oxidation. The indirect oxidation of sulfonamide by •OH species was confirmed through radical quenching and capture studies. The catalyst degraded sulfonamide antibiotics with up to 40% efficiency within 2 h. The introduction of the heteroatom La3+ into MnO2 led to a redistribution of electrons around Mn, which altered the electron density of the metal sites, lowered the average valence state of Mn, facilitated the production of reactive MnIII species, and optimized the exposure density of the active sites. Therefore, the sea urchin-like La-doped MnO2 material shows potential for applications in electrochemical sustainability research.