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 .