Accelerated C-F bond cleavage on sulfur vacancy-contained CoS2/MoS2 electrode featuring rich H*

Abstract

Carbon-fluorine (C-F) toxic groups in halogenated contaminants pose long-standing and significant threat to aquatic ecosystems and human health. In tackling the challenge of breaking C-F bond with low energy-consuming technique, this study reveals an enhanced electrochemical dehalogenation (ECHD) process using three-dimensional multilayer CoS₂/MoS₂ heterojunction cathode which possesses sulfur vacancies (S_v)-assisted modulation. It is found out that, when CoS₂ and MoS₂ grow together, S_v sites are constructed between MoS₂ and CoS₂ layers, fundamentally reversing the planar electronic inertness of MoS₂ and enhancing the coupling between H⁺ and reactive electrons, thereby generating substantial atomic hydrogen (H*). Meanwhile, the electronic interactions between S_v and neighboring S (S_n) enhance the adsorption of H* at S_n sites and suppressing the competitive H₂ evolution, constructing an H*-rich network. Accordingly, H* induces the substantial dechlorination of florfenicol (FLO), and the released free chloride ions indirectly optimized the C-F bond cleavage energy barrier, facilitating the cleavage of C-F bonds. With S_v-assisted modulated ECHD system and taking florfenicol as a representative, we accomplish near-total C-F bond removal with 100 % selectivity at －1.4 V_Ag/AgCl, marking a leap beyond current capabilities in efficiency, selectivity, environmental sustainability, and stability over 240-minute waste-free cycle.