Comparative catalytic properties of Ni(OH)₂ and NiO nanoparticles towards the degradation of nitrite (NO₂¯) and nitric oxide (NO)

Abstract

Nitrite (NO₂¯) and nitric oxide (NO) have been identified as an environmentally hazardous analytes from discharged industrial effluents. Thus in this study, nickel oxide (NiO) and nickel hydroxide (Ni(OH)₂) nanoparticles were synthesized using the complexation - precipitation method and their catalytic properties towards NO₂¯ and NO investigated. The suc cess of the synthesised nanoparticles was confirmed using characterisation techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and the Fourier transformed infrared (FTIR) spectroscopy. The sizes of the synthesized NiO and Ni(OH)₂ nanoparticles were estimated to be 5.39 and 5.07 nm respectively. The catalytic behaviour of NiO and Ni(OH)₂ nanoparticles towards the oxidative degradation of NO and NO₂¯ in acidic and neutral media respectively was studied using UV- Vis spectrophotometer. Result indicated that NiO nanoparticles demonstrated better catalytic properties at different reaction time towards NO₂¯ and NO oxidation compared to Ni(OH)₂ , while NiO and Ni(OH)₂ at nano scale showed enhanced catalysis towards the analytes compared with the bulk Ni salt. The bulk Ni salt did not show any sensing properties towards NO₂¯. However in NO, the absorbance intensity due to the generation of nitrate (NO₂¯) was five times higher in the presence of NiO nanoparticles compared with the bulk Ni salt. The improved catalysis of Ni(OH)₂ and NiO nanoparticles in this study was attributed to effective pore sizes and large surface area which expose the analytes to more catalytic site . The nanoparticles are simple to prepare, therefore can be used for the fabrication of a simple, portable, miniaturized nitrite and nitric oxide nanosensor for potential clinical and analytical application.