Efficient activation of peroxymonosulfate by Mn single-atom: Critical role of Mn-N4 coordination for generating singlet oxygen

Single-atom catalysts with high catalytic efficiency and simple preparation methods are critical for activation of peroxymonosulfate (PMS) to degrade emerging contaminants in aqueous solution. Herein, manganese single-atom nitrogen-doped carbon catalyst (SA-Mn-NC) was synthesized by precisely controlled catalytic carbonization using small-molecule organic compounds as precursors, and Mn was uniformly dispersed in a single-atom state and existed in the ligand structure of Mn-N4. Thus, the SA-Mn-NC had considerable catalytic activity and can realize 100% bisphenol A degradation within 3 min with kobs of 1.56 min−1, which was 4.7 and 9.2 times higher than that of NC (0.33 min−1) and Mn-NC (0.17 min−1). Moreover, SA-Mn-NC has excellent environmental adaptability, negligible metal leaching concentration, good cycling stability, and selectivity to electron-rich compounds. EPR tests, quenching experiments, electrochemical measurements, and selective degradation results together confirmed that singlet oxygen (1O2) was the main active species in the SA-Mn-NC/PMS system. The coupled N-active sites of Mn-N4 contribute to the efficient activation of PMS to generate 1O2 and achieve high catalytic turnover frequency. This work provides a simple strategy for the preparation of single-atom catalysts with considerable PMS catalytic efficiency and negligible metal leaching toxicity, which is of guiding importance for the design of single-atom catalysts for high-efficiency water treatment.