Peroxymonosulfate activation by oxygen vacancies-enriched MXene nano-CoO co-catalyst for efficient degradation of refractory organic matter: Efficiency, mechanism, and stability.

Cobalt-based catalysts have been widely explored in the degradation of organic pollutants based on peroxymonosulfate (PMS) activation. Herein, we report an MXene nano-CoO co-catalyst enriched with oxygen vacancies (O) and steadily fixed in nickel foam (NF) plates, which is used as an efficient and stable PMS activator for the removal of 1,4-dioxane (1,4-D). Ti originating from MXene was doped into the CoO crystal, generating large amounts of O, which could provide more active sites to enhance PMS activation and facilitate the transformation of Co and Co, causing a high stability. As a result, the 1,4-D removal efficiency of the NF/MXene-CoO/PMS system (k: 2.41 min) was about four times higher than that of the NF/CoO/PMS system (k: 0.62 min). In addition, singlet oxygen was the predominant reactive oxygen species. Notably, the 1,4-D removal of the NF/MXene-CoO/PMS system was over 95% after 20 h operation in the single-pass filtration mode with only 3.72% accumulative Co leaching, showing excellent stability and reusability of NF/MXene-CoO. This work provides a defect engineering strategy to design a robust and stable catalytic system for water treatment, which expands the application of MXene in the field of environmental remediation.