Dual-Path Hydroxylation on Ce Single-Atom Cluster Decorated MgO toward Efficient Remediation of As^III/Cd²⁺...

The co-contamination of water and soil by arsenic (As^III) and cadmium (Cd²⁺) poses a significant challenge for remediation due to their opposing chemical behaviors. Herein, we report the design of cerium single-atoms clusters anchored at the edges of MgO (Ce_SACs-MgO) via a gel-calcination strategy. In coexisting As^III/Cd²⁺ systems, Ce_SACs-MgO exhibits exceptional simultaneous decontamination, achieving adsorption capacities of 1868 mg g^-1 for As^III and 2140 mg g^-1 for Cd²⁺ through formation of stable (Mg/Ce/Cd)-O-As inner-sphere coordination network. Distinct from conventional defect engineering via oxygen vacancies, the Ce-O-Mg heterointerface at the Ce_SACs-MgO edges creates coordinatively unsaturated sites and activates inert lattice oxygen. This weakens the Mg-O bond, redistributes the electron density around Mg and Ce, and lowers the kinetic barrier for interfacial water adsorption and dissociation. Consequently, Ce_SACs-MgO achieves superior surface hydroxylation, generating abundant active sites for As^III and Cd²⁺ sequestration. Moreover, during adsorption, isomorphous substitution by Cd²⁺ induces local tensile strain within the Ce_SACs-MgO lattice, promoting electron transfer and interfacial charge redistribution. This substantially accelerates adsorption kinetics, boosting As^III uptake by 83.8-fold compared to pristine MgO. This work presents an atomic-scale interface engineering strategy for composite heavy metal decontamination, establishing a new design paradigm for water and soil remediation.