Efficient degradation of chlorinated phenolic compounds by Fe@Cu materials with enhanced oxygen reduction reaction

Purification of wastewater that contains residual chlorinated phenolic compounds is important for water conservation. Fe@Cu bimetallic materials have the capability of degrading chlorinated phenolic pollutants, but the processes of electron transfer and active species generation have not been verified directly. In this work, the Fe@Cu bimetallic material, of which copper exhibits a special surface, obtained by a facile displacement reaction, was applied for 2,4-dichlorophenol (2,4-DCP) degradation. The degradation efficiency of 2,4-DCP, which is highly related to H2O2 generation and •OH production, can reach 100% at 30 min with an Fe@Cu dosage of 2 g/L in ambient atmosphere. The porous shell structure of Fe@Cu provides convenient channels for iron ion release and electron transport and transformation. According to DFT (density functional theory) calculations, Cu2O (1 1 1) on the surface of particles and Cu (1 1 1) with Fe doping possess higher selectivity and catalytic activity for H2O2 in situ generation through the 2e− oxygen reduction reaction (ORR) than Cu (1 1 1). The ⋅OH, which was the following product of *OOH and H2O2, was a strategic radical for 2,4-DCP degradation. The coexistence of •OH and •H in the Fe-Cu degradation system was directly proven. The intermediate products of 2,4-DCP degradation were identified, and the degradation intermediates revealed that the degradation function for 2,4-DCP mainly resulted from the synergistic action of ⋅H and ⋅OH. The highly efficient self-catalyst Fe@Cu can be a promising material for chlorinated phenolic compound removal in wastewater purification.