Spin-state regulated CoCe dual-atom catalyst triggers efficient 1O2 production for water cleanup

Abstract

Spin-state engineering of atomic active sites is pivotal in selective singlet oxygen (¹O₂) generation during Fenton-like catalysis. Dual-atom catalysts (DACs) offer flexibility in spin-state regulation, while precisely regulating spin states remains challenging. Here, a CoCe dual-atom catalyst (CoCe–N/C) with a moderate spin state was designed for efficient ¹O₂ generation in peroxymonosulfate (PMS) activation. The incorporation of Ce adjacent to Co–N₄ moieties distorted the symmetry of the ligand field and reduced the crystal field splitting energy (Δ), thus inducing spin crossover of the Co configuration from a low-spin state (LS Co³⁺: t⁶_2ge⁰_g) to a medium-spin state (MS Co³⁺: t⁵_2ge¹_g). The MS electron configurations of CoCe–N/C facilitated the orbital overlap with PMS and significantly reduced the ¹O₂ generation barrier, resulting in Rhodamine B (RhB) elimination kinetics 12.3 times higher than that of Co–N/C. Simultaneously, the electron buffer of neighbouring Ce enabled the conversion of Co³⁺/Co²⁺ via Ce⁴⁺/Ce³⁺ cycling to be stabilized and expedited, achieving strong anti-interference and dynamic-degradation capabilities in continuous-flow filtration systems for water purification. This study presents a novel strategy for spin-state modulation of DACs in ¹O₂-based Fenton-like reactions.