Different green synthesis methods of Co3O4 NPs using aloe vera leaves: enhance H2 and O2 production from NaBH4 hydrolysis and H2O2 decomposition

Abstract Green synthesis of cobalt oxide nanoparticles (Co 3 O 4 NPs) was achieved using aloe vera leaves via hydrothermal, microwave irradiation, and co-precipitation methods. XRD analysis confirmed the high purity and crystallinity of the catalysts, as no other phases or impurities were observed in the crystal lattice. Catalysts’ morphology was visualized by FESEM images that showed flower-like morphology for AHT and capsule-like shapes for AMW and AWB. The chemical environment was identified by XPS analysis, which also confirmed the synthesis of Co 3 O 4 NPs by the presence of Co 2+ and Co 3+ ions on the catalysts’ surface. All catalysts exhibited dual functionality: catalyzing NaBH 4 hydrolysis and H 2 O 2 decomposition. During NaBH 4 hydrolysis, AHT demonstrated superior catalytic performance with a hydrogen generation rate (HGR) of 4267 ml.min − 1 .g − 1 at 45 °C. Further study on the efficient catalyst (AHT) was performed to evaluate the effect of catalyst weight, NaBH 4 concentration, alkalinity, and recyclability on catalytic activity. In H 2 O 2 decomposition, AWB displayed higher activity with a lower activation energy (E a ) of 39.66 kJ/mol.