Highly dispersed Ru@Carbon quantum dots for efficient hydrogen generation from sodium and potassium borohydride hydrolysis

Efficient hydrogen release from borohydrides requires catalysts that maximize metal utilization and substrate accessibility in aqueous media. Herein, ruthenium species were hydrothermally incorporated onto caffeine-derived carbon quantum dots (CQDs), producing a highly dispersed Ru@CQDs catalyst. Its performance was comparatively evaluated for hydrogen generation via sodium borohydride (NaBH₄) and potassium borohydride (KBH₄) hydrolysis under identical conditions. Structural and spectroscopic analyses confirmed the conversion of caffeine into CQDs and were consistent with the incorporation of Ru species into the CQD framework. Under optimized conditions at 303 K, NaBH₄ hydrolysis afforded a hydrogen generation rate of 34,248 mL g⁻¹ min⁻¹ with a TOF of 10,596.7 h⁻¹, while KBH₄ hydrolysis reached 29,782 mL g⁻¹ min⁻¹ with a TOF of 11,091 h⁻¹. Kinetic analysis showed apparent nth-order behavior for NaBH₄ and first-order kinetics for KBH₄, with activation energies of 44.58 and 44.27 kJ mol⁻¹, respectively. The results demonstrate Ru@CQDs are promising catalysts for efficient and controlled hydrogen production.