Fabrication of capped Ni-Sio2 nano-catalyst and study of its catalytic efficacy toward organic nitro reduction process

Abstract

Immobilization of transition metal-based nano-catalysts with bio-based supports have gained desirable interest. Herein, SiO2 nanoparticles from sugarcane bagasse (SCB) were utilized as a support to stabilize Ni NPs based nano-catalyst with different mass ratios (1:1, 1:2, and 1:3 of Ni and SiO2) by a facile in-situ reduction in the presence of a capping agent CTAB. A capped nano silica powder was obtained by hydrolysis and condensation reaction from SCB ash using CTAB and sulfuric acid in a biphasic medium. Capped Ni-SiO2 nano-catalyst has been prepared by the reduction of nickel(II) chloride using hydrazine hydrate, N2H4.H2O and sodium hydroxide, NaOH in the presence of capped SiO2 NPs. FESEM, EDX, FTIR, and XRD analysis were employed to investigate the morphology and chemical nature of capped Ni-SiO2 nano-catalysts. FESEM analysis revealed that spherical SiO2 NPs with scattered pores and soft spongy suggested CTAB capping with an average diameter of 64 nm. It was also observed that Ni NPs have spherical particles with coral clusters with an average size of 54 nm. The FESEM of capped Ni-SiO2 nano-catalyst demonstrated the Ni NPs were well-dispersed onto the surface of the SiO2 NPs with the help of the capping agent CTAB with chain like nano-architectured. FTIR bands at 1060 cm-1 of capped Ni-SiO2 nano-catalyst conformed the formation of Si-O-Ni bond. The EDX spectrum showed that Ni, O, and Si were uniformly distributed in the capped Ni-SiO2 nano-catalyst. XRD patterns of the synthesized capped SiO2 NPs formed an amorphous structure, whereas the Ni NPs and capped Ni-SiO2 nano-catalysts formed face centered cubic (fcc) structures, indicating the purity and crystallinity of the samples. The catalytic activity of synthesized capped Ni-SiO2 nano-catalyst with different mass ratio (1:1, 1:2, and 1:3 of Ni and SiO2) was investigated utilizing UV-vis spectra to reduce 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The well-dispersed capped Ni-SiO2 (1:2) nano-catalyst has shown a good catalytic performance. The rate constant k, activity parameter K, and turnover frequency (TOF) of the nano-catalyst are 0.2725 min-1, 0.4087 mg-1 min-1, and 0.1084 h-1, respectively for capped Ni-SiO2 (1:2) nano-catalyst. Moreover, capped Ni-SiO2 nano catalyst has shown a good cycle stability and can achieve 89% 4-NP conversion to 4-AP even after 10 cycles.