Highly efficient activation of peroxymonosulfate by MOF-derived CoP/CoOx heterostructured nanoparticles for the degradation of tetracycline

Both introducing oxygen vacancies (OVs) and enhancing charge transfer efficiency (CTE) have been proved to be effective strategies to improve the capability of the catalyst to activate peroxymonosulfate (PMS). The OVs on catalysts can promote the CTE of the catalyst/PMS oxidation system. However, current OVs introduction methods can only lead to very limited CTE enhancement. Here, the synthesis of CoP/CoOx heterostructured nanoparticles with abundant OVs and dramatically enhanced CTE through a reliable partial phosphidation method using ZIF-67 as a precursor was reported. The excellent CTE of the CoP/CoOx/PMS oxidation system was the result of the synergy of increased OVs and introduced CoP with high conductivity. When served as Fenton-like catalyst for tetracycline (TC) degradation via activating PMS, due to the synergy between abundant OVs and high CTE, CoP/CoOx exhibited superior performance for TC removal, with the pseudo-second-order kinetic rate constant ∼ 10.3 and 77.4 times that of CoPx and Co3O4, respectively. Moreover, the cobalt leakage (0.06 mg/L) was only about 1/2 and 1/3 of that of CoPx and Co3O4, respectively. The mechanism study suggested that SO4•−, •OH and O2•− played an important role in TC degradation. The excellent catalytic performance of CoP/CoOx was attributed to its abundant OVs and high CTE to generate more active oxygen species. This work provides new insights for designing and developing efficient catalysts for wastewater treatment via Fenton-like process.