Electrochemical Sulfion Upgrading to Multicolor Sulfur Quantum Dots Coupled with Hydrogen Production via Hybrid Electrolysis

ABSTRACT Sulfur quantum dots (SQDs) represent an emerging class of metal‐free, biocompatible luminescent nanomaterials, yet their synthesis remains challenged by harsh conditions, high energy consumption, and limited scalability. Herein, we report a highly value‐added strategy coupling SQD synthesis with hydrogen production through sulfion (S 2 − ) oxidation reaction (SOR) assisted alkaline‐modified seawater electrolysis (SWE). Such coupling substantially lowers the energy demand for electrolysis and effectively circumvents the interfering chlorine evolution at the anode. An efficient and stable cobalt single‐atom catalyst (Co‐SAs‐PNC) is developed to boost SOR, achieving a large current density of 500 mA cm − 2 at 0.536 V vs. reversible hydrogen electrode in alkaline‐modified natural seawater and operating stably for 116 h. A flow cell comprising Co‐SAs‐PNC as the anode catalyst and commercial Pt/C as the cathode catalyst requires only 1.01 V to reach 500 mA cm − 2 and shows outstanding durability of >450 h. Besides valuable hydrogen generated at the cathode, the polysulfides electrochemically derived at the anode can be readily converted to multicolor photoluminescent SQDs. Comprehensive in situ/operando experiments and theoretical calculations elucidate the SOR mechanism at isolated Co sites. This work not only opens a new avenue for sustainable SQD production but also remarkably enhances the economic viability of the SWE technology.