Green synthesis of carbon nanomaterials from sugarcane bagasse using bio-silica supported bimetallic nickel-based catalysts

Sugarcane bagasse (SCB) can be considered as an inexpensive and abundant source for the production of valuable carbon nanomaterials (CNMs). Herein, the synthesis of CNMs via sugarcane bagasse (SCB) pyrolysis was investigated using a simple two-stage process. Bio-silica extracted from rice husk (RH-SiO2) was loaded with 50%Ni, 40%Ni-10%Cu, 40%Ni-10%Mo, and 40%Ni-10%Co and evaluated as catalysts for the production of CNMs from pyrolysis products. The fresh catalysts were characterized by XRD, H-2-TPR, and CO2-TPD analyses, while the spent catalysts were characterized using TEM and Raman spectroscopy. The XRD and TPR results of the fresh catalysts demonstrated the existence of non-interacted NiO species in the monometallic Ni/RH-SiO2 catalyst. However, mixed oxides of NixCu1-xO, NiMoO4, and NiCo2O4 species were presented in Ni-Cu, Ni-Mo, and Ni-Co catalysts, respectively, in addition to non-interacted NiO species. TEM images revealed the presence of both carbon nanotubes (CNTs) and graphene nanosheets (GNSs) depending on the catalyst type. The results showed that the presence of mixed oxide species in the catalyst was associated with CNTs formation, while the existence of agglomerated Ni particles was correlated to GNSs formation. The catalytic activity of the catalysts in terms of carbon yield was arranged as follows: 50%Ni > 40%Ni-10%Co > 40%Ni-10%Cu > 40%Ni-10%Mo. Raman spectra proved the production of high-quality CNMs using all Ni-based catalysts.