Highly efficient electrocatalysis of oxygen to hydroxyl radical by FeN2O2 single-atom catalyst for refractory organic pollutant removal

The heterogeneous electro-Fenton (Hetero-EF) provides an effective and environmentally friendly method for refractory pollutants removal by strongly oxidative •OH. However, the •OH generation shows an insufficient activity in activating H2O2 to •OH due to the too strong H2O2 binding on the catalytic site. Here, an iron single-atom FeN2O2 catalyst anchored on hollow spherical porous carbon (FeN2O2-HPC) was designed to enhance •OH production by modulating the H2O2 binding. The FeN2O2-HPC Hetero-EF system showed a •OH production rate of 25.0 μmol h−1 and kinetic rate constant of 2.06 h-1 for phenol removal, which exceeded the FeN4 catalyst (the most reported iron single-atom). Density function theory calculations revealed that FeN2O2 could lower the H2O2 adsorption energy and energy barrier of H2O2 activation to •OH compared with FeN4, thus enhancing •OH production. This work gives a new insight into the •OH generation enhancement of Hetero-EF by modulating single-atom coordination environment for refractory pollutants removal.