Novel lignin-based single atom catalysts as peroxymonosulfate activator for pollutants degradation: Role of single cobalt and electron transfer pathway

In this work, a facile one-pot pyrolytic strategy was employed to fabricate a nitrogen coordinated Co single-atom catalyst (SA Co-N/C catalyst) by using lignin as carbon sources. The HAADF-STEM images and X-ray absorption spectra (XAS) analysis showed the isolated Co atoms less than 2 A throughout the entire SA Co-N/C architecture. Results showed that the single-atom Co sites served as the main active sites for naproxen (NPX) degradation via peroxymonosulfate (PMS) activation. This was confirmed by the high positive correlation (R-2 = 0.9675) between the rate constants and Co amounts in all SA Co-N/C catalysts. In particular, the as-prepared SA Co-N/C catalyst with a very small Co loading (2.45 wt.%) exhibited exceptional high turnover frequency (TOF) value for NPX (4.82 min(-1)), which is promising for the potential application prospect. Electron transfer was induced by the single-atom Co sites, which was the dominated mechanism for the NPX degradation.