(679a) Invited - Reactive Precipitation of Anhydrous Alkali Sulfide Nanocrystals with Concomitant Abatement of Hydrogen Sulfide and Co-Generation of Hydrogen

Anhydrous alkali sulfide (M₂S, M = Li and Na) nanocrystals (NCs) are important materials central to the development of next generation cathodes and solid state electrolytes for advanced batteries, but not commercially available at present. This work reports an innovative method to directly synthesize M₂S-NCs through alcohol-mediated reactions between alkali metals and hydrogen sulfide (H₂S). In the first step the alkali metal is complexed with alcohol in solution, forming metal alkoxide (ROM) and releasing hydrogen (H₂). Next, H₂S is bubbled through the ROM solution, where both chemicals are completely consumed to produce phase-pure M₂S-NC precipitates and regenerating alcohol that can be recycled. The M₂S-NC morphology may be tuned through choice of the alcohol and solvent. Both synthetic steps are thermodynamically favorable (∆G_m^o < -100 kJ/mol), proceeding rapidly to completion at ambient temperature with ~100% atom efficiency. The net result, H₂S + 2M => M₂S + H₂, provides abatement of the hazardous industrial waste H₂S and delivers two value-added products that naturally phase separate for easy recovery. This scalable approach provides an energy-efficient and environmentally-benign solution to the production of nanostructured materials required in emerging battery technologies.