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

Abstract

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.