The natural, most abundant sulfide mineral of pyrite was modified using polyethyleneimine (PEI) for use as a catalyst in H-2 release reactions from NaBH4 in methanol. The catalytic performances of pyrite, pyrite-PEI, and protonated pyrite-PEI (pyrite-PEI+) were compared and the hydrogen generation rate (HGR) values of 795 +/- 26, 2883 +/- 190, and 4320 +/- 188 mL H-2/(g of catalyst x min)(-1) were measured for H-2 production from NaBH4 methanolysis. The effect of methanol:water mixture at various ratios, the amount of catalyst, the concentration of NaBH4, and temperature on H-2 production from NaBH4 in methanol catalyzed by pyrite-PEr were investigated. The activation energies for pyrite-PEI, and pyrite-PEI+ catalyzed H-2 release reactions were calculated as 47.2 and 36.8 kJ/mol, respectively. It was found that the activity % for the pyrite-PEI+ catalyst decreased to 76.2 +/- 2.7% after five consecutive uses with 100% conversion for each re-use study. Furthermore, the re-generation of pyrite-PEI+ catalyst after the 5th usage was readily ensured by HCl treatment to completely recover and further increase the activity% of the catalyst. Therefore, pyrite was shown to be a useful re-generable and economic green catalyst for H-2 production in many potential applications. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.