Enhanced hydrogen generation from NaBH4 hydrolysis over green-synthesized Co₃O₄ catalysts through control of parsley ratio and calcination temperature

Abstract This study examined the influence of varying ratios of parsley leaves to cobalt ions and the impact on the catalytic efficiency of Co 3 O 4 NPs. XRD confirmed the cubic crystalline structure of Co 3 O 4 nanoparticles (NPs); meanwhile, FT-IR and XPS verified the spinel structure, indicating the presence of Co 2+ and Co 3+ ions and highlighting the contribution of phytochemicals from the green source through carbon species. FE-SEM images revealed spherical nanoparticles with some agglomeration at lower calcination temperatures and different ratios, whereas PWB600 and PWB900 showed capsule-like morphologies with increased surface porosity. During NaBH 4 hydrolysis, the hydrogen generation rate (HGR) increased with parsley leaf amounts up to 100 g, then declined at 150 g. The PWB400-100 catalyst demonstrated superior performance among various parsley-to-cobalt ratios, reaching a maximum HGR of 4002 ml.min − 1 .g − 1 at 45 °C and an activation energy of 79.15 kJ.mol − 1 . Calcination treatment notably enhanced Co 3 O 4 catalysts’ activity during NaBH 4 hydrolysis. The PWB900 catalyst achieved the highest HGR of 8308 ml.min − 1 .g − 1 at 45 °C, with an activation energy of 62.78 kJ.mol − 1 .