Engineering Proton‐Deficient Micro‐Environments on Co‐cluster/atom Ensembles for Efficient Cyclooctasulfur Electrosynthesis From Sulfur Dioxide

ABSTRACT Electrochemical cyclooctasulfur synthesis (S ₈ ) from SO ₂ in an acidic media is a promising strategy for mitigating SO ₂ emissions and enabling sustainable sulfur recycling. However, achieving high S ₈ selectivity is challenging due to the competing hydrogen evolution reaction (HER). Here, Co‐cluster/atom ensembles (Co _C/SA ‐NC) were designed and attempted for the first time to achieve highly selective electrocatalytic conversion of SO ₂ to S ₈ . Theoretical calculations have predicted that Co _C/SA ‐NC possesses stronger SO ₂ adsorption and enhances proton diffusion into SO ₂ for SO ₂ RR promotion. As expected, Co _C/SA ‐NC experimentally facilitated SO ₂ ‐to‐S ₈ conversion through efficient hydrogenation and polymerisation, and created a local proton‐deficient micro‐environment to suppress HER. Consequently, the Co _C/SA ‐NC ensembles attained a high Faradaic efficiency of 87% and a remarkable S ₈ yield of 2802.6 µmol mg ⁻¹ h ⁻¹ . This performance considerably exceeds that of both commercial Pt@C (62%, 2007.2 µmol mg ⁻¹ h ⁻¹ ) and control NC (54%, 898.3 µmol mg ⁻¹ h ⁻¹ ) catalysts. Furthermore, the CoN ₄ atomic sites and Co clusters collaboratively reduce the affinity for S ₈ and produce a desulfurization interface that mitigates electrode passivation and improves catalyst stability, resulting in a potential retention of 80.5% after 7‐cycles. This study provides valuable insight into tailoring the interfacial microenvironment using atom/cluster ensembles for efficient electrocatalytic S ₈ synthesis from SO ₂ .