Novel dual metal ion-doped NiO (Ni0.9Cu0.1−xZnxO) nanoparticles developed by a solution combustion method for harmful contaminant removal from wastewater

Abstract

Recently, nanostructurally designed metal–oxide catalysts for water purification are in high demand. This study presents the synthesis of highly photocatalytically active tertiary zinc- and copper-doped nickel oxide nanoparticles (NPs), namely, Ni_0.9Cu_0.1−xZn_xO (where x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1). The method employed is a solution combustion approach utilizing urea as the fuel source. XRD showed that the NPs were cubic with crystallite sizes of 27 to 49 nm. FESEM and TEM/HRTEM/SAED analyses also confirmed that the NPs were low-dimensional, single-phasic, and porous. An optical investigation determined band gap values using the Kubelka–Munk method, revealing a considerable decrease from 3.01 to 2.50 eV (ΔE = 0.51 eV). The photoluminescence (PL) examination revealed an emission band at ∼650 nm for pure NiO and 680 nm for dual metal ion-doped Ni_0.9Cu_0.08Zn_0.02O, resulting in a significant reduction in the PL intensity (∼69%). BET surface area and XPS analyses were also conducted. Excellent photocatalytic degradation efficiency (∼95%) of methylene blue dye was observed using Ni_0.9Cu_0.08Zn_0.02O. Pre- and post-degradation Fourier-transformed infrared (FTIR) spectra confirmed the degradation of most of the MB dyes. The results reveal that the developed photocatalyst exhibits striking performance under natural sunlight, proposing that it could be highly useful in the treatment of wastewater.