Regulating B-Site Metals in Delafossite to Reach Efficient and Selective Peroxymonosulfate Activation for Water Remediation
Ying Zhao, Dan Song, Xiangyu Zhang, Shuo Wang, Zhiqiang Sun, Caihong Liu, Jun Ma, Yueming Ren
Abstract
Transition metals (TMs) are excellent active sites to activate peroxymonosulfate (PMS) for water remediation; however, the factors determining the efficiency and selectivity of PMS activation over different TMs remain blurred. Herein, delafossite with different B-site metals (denoted as CuBO 2, B = Mn, Fe, Co, Cr) was synthesized to activate PMS for Orange I (OI) degradation. Their catalytic activity order followed CuCrO 2 (91.5%) ≈ CuCoO 2 (91.2%) > CuMnO 2 (46.9%) > CuFeO 2 (27.9%); especially the degradation rate ( k ) of CuCrO 2 (CuCoO 2 ) was 14.0 (12.6)-fold and 30.0 (27.1)-fold higher than that of CuMnO 2 > CuFeO 2, respectively. Mechanism analysis showed that sulfate radical (SO 4 •– ) was the main oxidant responsible for OI degradation in the CuCoO 2 /PMS system, while CuCrO 2 interacted with PMS to execute an electron transfer pathway (ETP) for degrading OI. Experimental and density functional theory calculation results deciphered that the d-band centers of CuCoO 2 ( E d = −1.22 eV) and CuCrO 2 ( E d = 0.62 eV) were closest to the Fermi level ( E F ), thereby facilitating the interfacial electron transfer process and enhancing the PMS activation efficiency. Moreover, it was important to note that the E d value of CuCoO 2 was located below the E F, which led CuCoO 2 to easily lose electrons to PMS, thereby generating sulfate radicals SO 4 •– . On the other hand, the E d value of CuCrO 2 was situated above the E F, which facilitated the catalyst to obtain electrons, acting as electron shuttles and driving a nonradical ETP. Finally, the established CuBO 2 -activated PMS systems also exhibited excellent stability and robust resistance against coexisting substances. These findings provided an alternative perspective to understanding the inherent nature of TM-based catalysts for regulating the efficiency and selectivity of PMS activation in water remediation.