Facile fabrication, characterization and enhanced heterogeneous catalytic reduction of 4-nitrophenol using undoped and doped ZrO2 nanoparticles

Here, we successfully developed the undoped, Ni2+, Cu2+, and Zn2+ doped Zirconia nanoparticles (ZrO2 NPs) by a simple co-precipitation method at room temperature and characterized by various physicochemical measurement techniques to investigate their structure, morphology, and sizes of the particles. The bandgap energy values of doped and undoped ZrO2 NPs were estimated using optical absorption spectroscopy and it was found to be in the range of 4.1-4.4 eV. The UV (304-352 nm) and visible (402-415 nm) emissions and the oxygen vacancies and band gap of the particles were investigated through PL analysis. The structure, morphology, and well-dispersed particles with the size in the range of 10-40 nm of the prepared ZrO2 NPs were deliberated by SEM and TEM analysis. The Zr–O stretching vibration and Zr–O–Zr bending vibrations were confirmed through FTIR analysis. The catalytic reduction of 4-nitrophenol (4-NP) using NaBH4 as a reducing agent was studied by the prepared doped and undoped ZrO2 NPs. The efficient catalytic activity was observed in the presence of Cu2+ doped ZrO2 NPs than the Zn2+, Ni2+ doped and undoped ZrO2 NPs due to the small size and large surface area of the particles. The results showed that 97% conversion was achieved from 4-NP to 4-aminophenol (4-AP) within 90 min and stable up to 5 consecutive recycles.