Metal-free catalysts with phosphorus and oxygen doped on carbon-based on Chlorella Vulgaris microalgae for hydrogen generation via sodium borohydride methanolysis reaction

Metal-free catalysts (C-KOH-P) containing phosphorus (P) and oxygen (O) prepared by the modification with phosphoric acid (H3PO4) of activated carbon (C-KOH) obtained by activation of Chlorella Vulgaris microalgae with potassium hydroxide (KOH) were investigated for the hydrogen (H-2) generation reaction from methanolysis of sodium borohydride (NaBH4). Elemental analysis, XRD, FTIR, ICP-MS, and nitrogen adsorption were used to analyze the characteristics of metal-free catalysts. The results showed that groups containing 0 and P were attached to the carbon sample. In the study, the hydrogen production rates (HGR) obtained with metal-free C-KOH and C-KOH-P catalysts were 3250 and 10,263 mL/min/g, respectively. These HGR values are better than most values obtained for many catalysts presented in the literature. Besides, relatively low activation energy (Ea) of 27.9 kJ/mol was obtained for this metal-free catalyst. The C-KOH-P metal-free catalyst showed ideal reusability with 100% conversion and a partial reduction in the H-2 production studies of NaBH4 methanolysis after five consecutive uses. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Metal-free catalysts containing phosphorus and oxygen were prepared by modifying activated carbon obtained from Chlorella Vulgaris microalgae with phosphoric acid. These catalysts showed excellent hydrogen production rates and relatively low activation energy, demonstrating high efficiency in hydrogen generation reactions.