Mn–Ce Bicenter of a Dual Single-Atom Catalyst Synergistically Triggers Reactive Oxygen Species Generation for Efficient Ozonation of Emerging Contaminants

Abstract

The synergistic effect of multiple reactive oxygen species (ROS) facilitates the degradation and mineralization of recalcitrant contaminants. However, bottlenecks include the rational design of single-atom catalysts with multiple active sites to produce multiple ROS in heterogeneous catalytic ozonation (HCO) processes and the detailed interpretation of the generation mechanisms. In this study, we prepared a dual single-atom Mn–(N_x–C)–Ce catalyst with dual active sites via a simple and scalable one-pot method in which atomically dispersed active Mn–N₄ and Ce–N₄ sites synergistically promoted the generation of ^•OH. Moreover, density functional theory calculations and molecular dynamics simulations elucidated that Mn–N₄ sites on the catalyst surface preferred to generate ^•OH and ^•OH_ad, while Ce–N₄ sites preferred to generate other ROS (O₂^•–, ¹O₂, and *O_ad). The three main degradation pathways of N,N-diethyl-3-methylbenzamide (DEET) further revealed the synergistic effects of multiple ROS. Due to the ability for generation of multiple ROS, the Mn–(N_x–C)–Ce catalyst exhibited superior activity and excellent stability for the degradation of DEET and bezafibrate as well as advanced treatments of municipal sewage and coking wastewater. This study paves a new avenue for rationally designing a highly efficient and stabilized catalyst for ozone and provides an insight into the synergistic effect of Mn–Ce dual active sites in the HCO process.