Green synthesis of Co-based nanoparticles from Rheum ribes shell extract and determination of the effect of their activity on sodium borohydride hydrolysis

This study investigated the effect of Co(0) and Co-B NP catalysts synthesized by the green synthesis method using Rheum ribes shell extract on the NaBH₄ hydrolysis process for the first time, and determined the role of the green synthesis method in the catalyst activity. The investigation of the structure and surface morphology of the catalysts was evaluated using XRD, SEM–EDX, TEM, FTIR, and XPS analyses. The effect of catalysts on NaBH₄ was examined at different catalyst amounts, different NaBH₄/NaOH concentrations, and different temperature values. The Co(0) and CoB NPs catalysts achieved the greatest HGR values at a solution temperature of 30 °C, with values of 7326 mLmin⁻¹g⁻¹_cat and 12,524 mLmin⁻¹g⁻¹_cat, respectively. The calculated activation energies for Co(0) and Co-B NPs catalysts are 37.68 kJmol⁻¹ and 21.28 kJmol⁻¹, respectively. The green synthesis method synthesized Co(0) and Co-B catalysts significantly increased hydrogen production activity compared to the cobalt-based catalysts synthesized by other methods.