Fe/N-doped carbon magnetic nanocubes toward highly efficient selective decolorization of organic dyes under ultrasonic irradiation.

Fe/N-doped carbon magnetic nanocubes (Fe/N-C MNCs) were feasibly fabricated through in situ thermal transformations of Prussian blue nanocubes (PB NCs) in an inert atmosphere, and the resultant composite employed as the heterogeneous noble-metal-free catalyst possessed satisfactory catalytic performance in hydrogen peroxide activation. By examining the properties of Fe/N-C MNCs, we demonstrate for the first time that the catalyst could act in synergy with ultrasonic irradiation and accelerate the selectivity of the degradation reaction of dyes. The degradation efficiency of the organic positively charged dye (methylene blue) is significantly increased after ultrasonic irradiation addition, probably owing to charge matching between a positively charged dye and the Fe/N-C MNCs. Interestingly, organic pollution degradation mainly follows a non-radical pathway. Furthermore, singlet oxygen (O) is predominantly produced by Fe/N-C MNCs on HO activation, and it is the contributor to catalytic degradation instead of hydroxyl and/or superoxide anion radicals. Moreover, the Fe/N-C MNCs exhibit excellent stability and reusability. These findings offer interesting insights into the potential application of functional noble-metal-free materials in catalysis and wastewater remediation under ultrasonic radiation.