Insight into Self-Assembly Broccoli-Like N-Doped Cobalt Nickel Spinel Based Peroxydisulfate Activation for Highly Effective Organic Pollutants Degradation: Performance and Degradation Mechanism

A series of N-doped MCo2O4 (N@MCo2O4, M = Ni, Mg, Co, and Cu) were fabricated via one-pot hydrothermal method, and the catalysts were applied for Rhodamine B (RhB) degradation. Note that quick RhB removal (98.2% removal in 10 min with 0.2 g L-1 N@NiCo2O4 and 1 g L-1 PDS dosage) was observed without pH adjustment (pH = 6.2) with a highest reaction rate of 0.145 min-1, which was 10.08, 1.23, and 1.58 times over that N-doped of MgCo2O4 (0.014 min-1), Co3O4 (0.118 min-1), CuCo2O4 (0.092 min-1), respectively. DFT calculations found that the lowest PDS adsorption energy (-4.91 eV) of N@NiCo2O4 among N@NiCo2O4 (M = Ni, Mg, Co, and Cu) was the major reason of the greatest catalytic performance. Quenching experiments, radical quantification, and electron paramagnetic resonance (EPR) revealed directly that the singlet oxygen (1O2) was the dominant reactive oxygen species (ROS) for RhB degradation via non-radical pathway.