Enhanced hydrogen production from sucrose-derived carbon quantum dots-supported Ru catalysts: A comparative study of KBH4 and NaBH4 hydrolysis

Abstract

Despite increasing interest in borohydride hydrolysis for hydrogen generation, limited studies have explored carbon quantum dots (CQDs) derived from low-cost, renewable sources such as sucrose as catalyst supports. In this study, sucrose-derived CQDs were synthesized via a green hydrothermal method and employed as a support material for Ru catalysts. A novel hydrogen potential catalytic activity (HPCA) metric was introduced to compare the performance of Ru@CQDs in the hydrolysis of sodium borohydride (SBH) and potassium borohydride (PBH), addressing the lack of normalized efficiency metrics across different hydrogen sources. The ideal conditions for each hydrolysis reaction were established based on the hydrogen generation rate (HGR) after studying various catalyst characteristics using UV–Vis, UV-PL, TEM, and FT-IR analyses. The HGR values using 4 % NaBH₄ and 4 % KBH₄ were 167,588 and 122,527 mL g⁻¹ min⁻¹, respectively. However, the hydrogen potential catalytic activity metrics (HPCA), calculated based on the hydrogen content of the sources, were 1.551,741 mL g⁻¹ min⁻¹ and 1.655,770 mL g⁻¹ min⁻¹ for NaBH₄ and KBH₄ hydrolysis, respectively. This indicates that the rate of hydrogen production during KBH₄ hydrolysis is higher than that during NaBH₄ hydrolysis. For each hydrolysis reaction, the catalyst's turnover frequency (TOF) was also determined to assess its effectiveness: 924.8 mol H₂.mol. Ru⁻¹.min⁻¹ for NaBH₄ hydrolysis and 573.3 mol H₂.mol Ru⁻¹.min⁻¹ for KBH₄ hydrolysis. Additionally, the experimental data on the kinetics and activation energy of the hydrolysis processes, as well as the catalyst's reusability, were analyzed.