In Situ Li⁺ Intercalation into Nanosized Chevrel Phase Mo₆S₈ toward Efficient Electrochemical Nitroarene Reduction

Electrochemical nitroarene reduction enables the green production of anilines at ambient conditions thanks to the manipulated transfer of multiple electrons and protons via controlling potentials and currents, but challenges remain in pH-neutral electrolysis using nonprecious catalysts. Here, Chevrel phase Mo₆S₈ with high conductivity and insertable frameworks is proposed for the first time as a cost-efficient candidate with prominent performance and, more importantly, as a new platform to unravel cation effects on nitroarene electroreduction. Nanosized Mo₆S₈ derived from polymer-confined sulfidation affords a high yield (∼95%) and Faradaic efficiency (∼99%) for reducing 4-nitrostyrene to 4-aminostyrene at -0.45 V (vs RHE) in 0.1 M LiClO₄, outperforming a series of counterparts of metal sulfides and even noble metals. The combination of experimental and theoretical analyses identifies an intercalation-correlated cation effect, expanding the current knowledge limited to the outer Helmholtz plane of electrodes. In situ Li⁺ intercalation into Mo₆S₈ cavities during electrolysis ameliorates the electronic configurations and thereby promotes the adsorption of the nitro group on low-coordinated Mo sites for hydrogenation via a proton-coupled electron transfer mechanism. Furthermore, the efficient electrosynthesis of aniline derivatives with conserved reducing groups from a wide range of substrates highlights the promise of Mo₆S₈ for electrochemical refinery.