Silica mesoporous nanosphere-loaded single-atom Cu as highly efficient peroxymonosulfate activator for phenazopyridine hydrochloride degradation at all pH values

Single-atom (SA) catalysts exhibited outstanding photocatalytic performance owing to atomically dispersed active sites, unique electronic structure, and high atomic utilization efficiency. Herein, single-atom catalyst was prepared with sodium copper chlorophyllin (SCc) by pyrolysis for achieving Cu atoms embedding on nitrogen-doped carbon silicon nanosphere (SA-Cu@NCSNs-3). Isolated Cu atoms was in a defined CuN₄ coordination structure. SA-Cu@NCSNs-3/PMS exhibited strong tolerance under a wider pH range. Notably, the degradation efficiency of PhH was highest at strong acid and alkali environment. The SA-Cu@NCSNs-3 generating h⁺, \({\text{O}}_2^{ \cdot - }\) ${\text{O}}_2^{·-}$ , and ¹O₂ by activating peroxymonosulfate (PMS) was confirmed by electron paramagnetic resonance (EPR) experiments. Besides, the transfer electron was proposed for phenazopyridine hydrochloride (PhH) degradation in SA-Cu@NCSNs-3/PMS system by electrochemical investigation. The effects of reaction condition on PhH photocatalytic degradation were investigated. 20 mg/L of PhH was decomposed within 12 min under UV–visible light irradiation at all pH values. Besides, the degradation efficiency of 10 organic pollutant was above 87% in different water matric. Furthermore, SA-Cu@NCSNs-3 exhibited an exceptional photocatalytic performance for several antibiotics and organic dyes mixture in different natural water. This work provides a facile and large-scale preparation methods to obtain SA-Cu.