Sustainable Green Synthesis of Sn-Modified Co Nanoparticle Catalysts from Tobacco Stem Extract for Hydrogen Generation via NaBH₄ Hydrolysis

In this study, cobalt and Sn-modified Co nanoparticle (NP) catalysts were synthesized using waste tobacco stem extract via an environmentally friendly plant-extract-assisted synthesis route, and their catalytic performance toward NaB₄ hydrolysis was systematically investigated. The effect of Sn incorporation on hydrogen generation was examined at different Sn contents, revealing that the catalyst containing 1 wt.% Sn exhibited the highest activity. Under identical reaction conditions, the hydrogen generation rate (HGR) increased from 1875 ml min⁻¹ g⁻¹ for monometallic Co NP catalysts to 5908 ml min⁻¹ g⁻¹ for Co–Sn NP catalysts containing 1 wt.% Sn. Kinetic analysis based on an nth-order reaction model demonstrated enhanced reaction kinetics in the presence of Co–Sn NP catalysts. The activation energy for NaBH₄ hydrolysis decreased from 49.8 kJ mol⁻¹ for Co NP catalysts to 31 kJ mol⁻¹ for Co–Sn NP catalysts, indicating a significant kinetic advantage upon Sn incorporation. Furthermore, the Co–Sn NP catalysts maintained considerable catalytic activity over five successive reaction cycles, highlighting their potential for practical hydrogen generation applications. These results demonstrate that plant-extract-assisted synthesized Co–Sn NP catalysts are promising, low-cost, and sustainable catalysts for hydrogen generation.