Industrial byproduct steel slag as a cost-effective and sustainable kinetic promoter for CO2 hydrate ocean storage and sequestration

• Cost-effective kinetic promoters for hydrate-based CO 2 ocean storage were proposed. • Steel slag demonstrated a superior promotion effect on hydrate nucleation and growth. • Hydrophilic surface and pH-neutralizing effect play a critical role in promotion. • The use of steel slag was validated using seawater collected from the East Sea of Korea. • Steel slag has potential as an economic and sustainable solution for ocean CO 2 storage.