Precisely Engineered Co–O–Mn/Co Sites in Cobalt Single-Atom Catalysts for Highly Sensitive Detection of As(III) in Water

Arsenic contamination in groundwater, primarily as As(III), poses a critical global health risk, impacting hundreds of millions of people. Yet, the rapid and accurate in-situ detection of dissolved As(III) remains a major technical challenge. In this study, we developed a Co single-atom catalyst (Co SAC) by anchoring atomically dispersed Co onto oxygen-vacancy-enriched α-Mn₂O₃ nanowires, establishing a strong electronic metal-support interaction (EMSI) that modulates the local electronic structure. Integration of this catalyst into the electrode enabled the construction of a highly sensitive electrochemical sensor with enhanced As(III) detection. The Co₁/α-Mn₂O₃-V_O-modified electrode demonstrated excellent sensitivity (5.37 μA·ppb^-1·cm^-2), a wide linear detection range (0.5-750 ppb), and an ultralow detection limit (0.13 ppb). It also showed robust performance in real groundwater samples, confirming its practical applicability in complex environments. Mechanistic studies revealed that EMSI promoted the formation of Co-O-Mn/Co active sites. These sites facilitated the formation of Co-O-As intermediates, enabling efficient electron transfer from Co to As and lowering the activation energy for As(III) reduction by 43%. This work successfully constructs a highly efficient electrochemical sensing platform for trace As(III) detection. It not only systematically elucidates the pivotal role of single-atom catalysts (SACs) in modulating the interfacial electronic structure and facilitating As(III) recognition but also provides fundamental insights into the catalytic transformation mechanism. These findings offer strategic guidance for the rational design of advanced catalytic materials and advance the development of portable environmental monitoring technologies.