Enhanced electrocatalytic degradation of acid orange 7 by using double perovskite La2CoxNi1-xMnO6/nickel foam as the electro-Fenton cathodes

Abstract

Adequate generation of hydrogen peroxide and its subsequent activation into reactive oxygen species (ROS) play a crucial role in the catalytic efficiency of heterogeneous electro-Fenton for the degradation of contaminants. Herein, a series of La2NiMnO6 double perovskite with Co doping (La2CoxNi1-xMnO6) were prepared by a facile sol-gel technique and applied as catalysts in heterogeneous electro-Fenton system to removal acid orange 7 (AO7). Nickel foam was chosen as the supporting substrate for the catalyst owing to its excellent physical properties to accelerate the conversion of O2 to H2O2. La2Co0.5Ni0.5MnO6 achieved 90.22 % of AO7 decomposition rate at 120 min via the heterogeneous electro-Fenton system, which was a significant improvement over the catalytic efficiency of both only NF and La2NiMnO6 electrodes. Further studies have shown that the introduction of Co could heighten the efficient redox recycling of Ni2+/Ni3+ and Mn3+/Mn4+ on the electrode surface, synergically facilitating the conversion of H2O2 to OH. Meanwhile, the three redox pairs (Ni2+/Ni3+, Mn3+/Mn4+ and Co2+/Co3+) also stimulated the production of superoxide radicals (O2−), which was also not negligible in enhancing degradation. Finally, the possible pathway and mechanism of the degradation of AO7 were proposed. This work demonstrates that La2CoxNi1-xMnO6/NF has the potential to be a satisfactory electrode for decomposition of organic dyes in aqueous solution.