Sulphur and nitrogen-doped metal-free microalgal carbon catalysts for very active dehydrogenation of sodium borohydride in methanol

Abstract

Micro algae based on Spirulina platensis is successfully used for the synthesis of S and N-doped metal-free carbon materials. The procedure consists of three stages; (i) Activated carbon production by KOH activation in CO2 atmosphere (S-AC), (ii) S atom doping to the obtained S-AC using sulphuric acid by hydrothermal activation (S-AC-S), (iii) N atom doping by hydrothermal activation to S-AC obtained using nitric acid (S-AC-S-N). The S and N doped metal-free catalysts are used for H2 release in NaBH4 methanolysis reaction (NaBH4-MR) for the first time. The metal-free carbon catalysts are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM-EDS), X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption and elemental analysis (CHNS) methods. When the HGR values obtained for S-AC-S-N (26,000 mL min−1 g−1) and S-AC (2641 mL min−1 g−1) are compared, there is a 9.84-fold increase. Activation energy (Ea) value for S-AC-S-N was 10.59 kJ mol−1.