Electron transfer-mediated enhancement of superoxide radical generation in fenton-like process: Key role of oxygen vacancy-regulated local electron density of cobalt sites

Designing metal oxides with oxygen vacancy (OV) is a prospective strategy for boosted Fenton-like process. However, what OV is, whether OV enhancement increases the catalytic performance, OV-related H2O2 activation, and relationship between OV and ROS or non-radical pathways have not been fully understood. Herein, yolk-shell Co3O4 nanospheres with various OV were fabricated to overcome the above contentious problems and establish a relationship between OV, ROS, and electron transfer in sulfadiazine (SDZ) degradation via H2O2 activation. The results showed that the delocalized electron-rich Co sites around OV with increasing OV allowed the improved conductivity, thereby leading to stronger adsorption and activation of H2O2 to generate more (OH)-O-center dot as evidenced by the attenuated adsorption energy and prolonged O-O bond. The subsequent rapid depletion of (OH)-O-center dot coupled with the increase in O-2(center dot-) over time and the emergence of electron transfer from SDZ explored a pathway enhancing O-2(center dot-) generation for SDZ degradation.