Biphase Co@C core-shell catalysts for efficient Fenton-like catalysis

Despite the vital roles of Co nanoparticles catalytic oxidation in the Fenton-like system for eliminating pollutants, contributions of Co phases are typically overlooked. Herein, a biphase Co@C core-shell catalyst was synthesized by the electrochemical co-reduction of CaCO3 and Co3O4 in molten carbonate. Unlike the traditional pyrolysis method that is performed over 700 °C, the electrolysis was deployed at 450 °C, at which biphase structures, i.e., face-centered cubic (FCC) and hexagonal close-packed (HCP) structures, can be obtained. The biphase Co@C shows excellent catalytic oxidation performance of diethyl phthalate (DEP) with a high turnover frequency value (TOF, 28.14 min-1) and low catalyst dosage (4 mg L-1). Furthermore, density functional theory (DFT) calculations confirm that the synergistic catalytic effect of biphase Co@C is the enhancement for the breaking of the peroxide O-O bond and the charge transfer from catalysts to PMS molecule for the activation. Moreover, the results of radicals quenching experiments and electron paramagnetic resonance (EPR) tests confirm that SO4•-, •OH, O2•-, and 1O2 co-degrade DEP. Remarkably, 100% removals of three model contaminants, including DEP, sulfamethoxazole (SMX) and 2,4-dichlorophen (2,4-DCP), were achieved, either in pure water or actual river water. This paper provides an electrochemical pathway to leverage the phase of catalysts and thereby mediate their catalytic capability for remediating refractory organic contaminants.