Zero-Valent Iron Inside Carbon Nanocube as an Efficient Peroxymonosulfate Activator toward Catalytic Oxidation of Organic Pollutants

The agglomeration tendency of nano zero-valent iron (Fe⁰) limits its practical applications toward catalytic oxidation of organic pollutants. Herein, an in situ encapsulation of polydopamine on the surface of Prussian blue (PB) nanocubes followed by a confined reduction treatment strategy was presented to confine the zero-valent iron nanoparticles (Fe⁰) inside hollow carbon nanocube (Fe⁰@C) as an efficient peroxymonosulfate (PMS) activator toward catalytic oxidation of toxic organic contaminants. The catalytic results showed that 100% degradation of bisphenol A (BPA) could be completed within 5 min with Fe⁰@C nanocube as a catalyst to activate PMS. This delicately designed Fe⁰@C nanocube displayed a superior kinetic rate constant compared with the pure Fe⁰ nanoparticles (4.2-fold). Experimental evidence revealed that the generation of multiple reactive oxygen species in the nanocubes played a vital role for the significantly enhanced catalytic efficiency for organic contaminants. Both SO₄^•-, •O₂^-, and •OH dominated radical processes, and nonradical pathways involving ¹O₂ were accounted for PMS activation and organic contaminant degradation. The superior catalytic performance was attributed to a carbon layer with large specific surface area and highly dispersed Fe⁰ nanoparticles to provide abundant active sites, distinct nanocube structure to concentrate the reactant molecules within a confined space, and an excellent electron/mass transport property.