Hydrogen production through glycerol steam reforming over beehive-biomimetic graphene-encapsulated nickel catalysts

Graphene-encapsulated nickel catalysts were synthesized and attached to SiO2 skeleton, vividly described as "beehive-biomimetic catalysts". Rice husk char (RHC) served as the carbonaceous source in the synthesis. Different catalysts with nickel embedded inside graphene were tested in glycerol steam reforming (GSR) at 550, 600 and 650 degrees C. Catalysts were characterized by X-ray powder diffraction (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The effects of pretreating RHC or reaction temperature on yield of H-2, selectivity of gaseous products, and molar ratios of H-2/CO and CO/CO2 were investigated. The catalyst with acid-treated RHC as the carbon precursor exhibited better catalytic activity and durability in GSR. It delivered a higher H-2 yield of 5.09 mol H-2/mol glycerol and a higher H-2/CO ratio of 6.79 at 600 degrees C. The multilayered graphene prevented the oxidation, sintering, or acid corrosion of inner nickel without sacrificing its activity. The SiO2 skeleton also enhanced thermal stability of the catalyst. (C) 2019 Elsevier Ltd. All rights reserved.