Development of Three-Dimensional Nickel-Cobalt Oxide Nanoflowers for Superior Photocatalytic Degradation of Food Colorant Dyes: Catalyst Properties and Reaction Kinetic Study.

Abstract

In this work, we present three-dimensional flower-like nickel-cobalt oxide (F-NCO) nanosheets developed in a facile, eco-friendly hydrothermal route to apply as photocatalysts for food colorant Allura Red AC dye removal under light illumination. Using Brunauer-Emmett-Teller analysis, it was found that the F-NCO nanosheets displayed a surface area of ∼53.65 m2/g and a Barrett-Joyner-Halenda pore size of ∼14 nm, which was also confirmed by the calculated crystallite size of ∼15 nm using powder X-ray diffraction (XRD) analysis. From Williamson-Hall analysis of XRD spectra, F-NCO nanosheets revealed a crystal-lattice strain of ∼3.42 × 10-3 and a dislocation density of ∼4.397 × 1015 lines/m2 in the crystal structure. Transmission electron microscopy analysis revealed that F-NCO nanosheets accumulated to form flower-like nanostructures of <100 nm length with a d-spacing of ∼2.6 Å, which is attributed to the (311) crystallographic plane (α = γ = β = 90°, a = b = c = 8.110 Å, JCPDS No. 00-020-0781) of the cubic phase. The F-NCO nanosheets exhibited an excellent photocatalytic efficiency of ∼94.75% in ∼10 min with sodium borohydride under UV light. The Langmuir-Hinshelwood model determined pseudo-first-order reaction kinetics of dye degradation using the versus time plot. The kinetic study produced a first-order rate constant (k) of ∼0.219 min-1, resulting in ∼3.16 min half-life (t1/2) for the F-NCO-catalyzed degradation reaction. Thus outstanding photocatalytic performance of F-NCO nanosheets would display their huge potential for organic-pollutant removal from water with exceptional recyclability for wide research applications in the future.