In situ generated nickel on cerium oxide nanoparticle for efficient catalytic reduction of 4-nitrophenol

Abstract

Efficient and economic catalysts are required for the large scale degradation of hazardous pollutants. In the present work, two nickel (5 wt%) based compounds, Ni(NO₃)₂ and NiO, immobilized over a CeO₂ surface were tested for the reduction of 4-nitrophenol. Size, structural and surface properties of the catalyst were characterized by XRD, SEM & TEM – EDX, FTIR and Raman spectroscopy. UV-visible spectroscopic results indicated the better catalytic performance of the Ni(NO₃)₂ support than that of NiO supported CeO₂. The reduction rate of 4-nitrophenol in the presence of the Ni(NO₃)₂ support was found to be 12 times faster than that of NiO supported CeO₂. The time-dependent Raman spectroscopic investigation demonstrated that the performance of Ni(NO₃)₂ supported CeO₂ arises from the in situ generation of nickel in the presence of an excess of sodium borohydride in the reduction of 4-nitrophenol. Further, the reversible conversion of nickel to nickel nitrate enabled the recyclability of the Ni(NO₃)₂ supported CeO₂. The formation of nickel was found to be important for the reduction of 4-nitrophenol as NiO supported CeO₂ did not form nickel thereby exhibiting poor catalytic activity. Thus, the present work showcases the in situ generation of nickel as a novel strategy for the catalytic reduction of 4-nitrophenol.