Spin Coupled FeCo Dual-Atom Sites Direct Selective Ozone Activation for Hypersaline Wastewater Purification

Heterogeneous catalytic ozonation represents a powerful process for eliminating refractory organic contaminants from hypersaline wastewater, yet its application is restricted by two critical bottlenecks: inefficient ozone activation and lack of control over on-demand reactive oxygen species generation. In this study, we unravel that spin-coupling in a heteronuclear dual-atom catalyst (Fe₁Co₁-NC) can address both limitations. By replacing one metal center with an electronically matched but magnetically inert element (Fe₁Zn₁-NC and Ga₁Co₁-NC), we disentangle the long-conflated contributions of charge redistribution and spin coupling, and identify the latter as the decisive kinetic contributor. The spin-polarized channel across Fe-Co pairs synchronizes H₂O activation at the Fe site with ozone decomposition at the Co site, steering the reaction along a spin-compatible proton-coupled electron transfer pathway that selectively generates surface-bound hydroxyl radicals. Consequently, Fe₁Co₁-NC exhibits enhanced oxalic acid degradation in the presence of ozone, with a turnover frequency 21.5 times that of the spin-decoupled Fe₁Zn₁-NC. Coupling the catalyst with a gas-diffusion tri-phase reactor further overcomes salinity-induced ozone mass-transfer limitations and enables robust, sustainable mineralization of real hypersaline wastewater. This work identifies inter-site spin coupling as a kinetic descriptor for spin-sensitive ozone activation and provides a spin-decoupling strategy for the mechanistic design of dual-atom catalysts.