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, ecofriendly 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 m 2 /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 × 10 15 lines/m 2 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 ln

Hierarchically Uniform 2D Porous Sheet-like NiO/NiCo2O4: A High-Performance Positrode Material for All-Solid-State Hybrid Pseudocapacitors with Superior Ragone and Cyclic Efficiencies

“…In order to analyze the resistive-pseudocapacitive response performance of the NiO/NiCo 2 O 4 ||N-rGO ASSHPC device, the Bode plot ( phase angle vs frequency ), as shown in the inset of Figure I has been thoroughly examined. From the Bode plot, the relaxation time constant τ 0 value (estimated using the frequency value at a phase angle of −45°) of the NiO/NiCo 2 O 4 ||N-rGO ASSHPC device is estimated to be ∼0.69 s. The significantly low τ 0 value validates rapid transition from the resistive to capacitive behavior of the device, which is again ascribed to rich electro-microstructural coherence between the NiO/NiCo 2 O 4 and N-rGO leading to insignificant interfacial resistance, high charge mobility in the NiO/NiCo 2 O 4 and N-rGO, very low resistance during charge transfer in the NiO/NiCo 2 O 4 |PVA-KOH|N-rGO assembly, and rapid pseudocapacitive response during charge storage. , …”

“…48 The specific capacitance (C s /F g −1 ) values of the NiO/NiCo 2 O 4 ||N-rGO ASSHPC device have been estimated from the impedance data, using eq 8, and the corresponding C s vs f plot is presented in Figure 6I. 13,18 The energy density (E D in Wh kg −1 ) and power density (P D in W kg −1 ) of the NiO/NiCo 2 O 4 ||N-rGO ASSHPC device were evaluated under various rate (applied current density) operating conditions using the discharge current i (in mA), discharging time (Δt in h), operating potential window (ΔV in V), and total mass of electrode materials used in the pseudocapacitor device (m in g) using eqs 13 and 14. 7,11,12,23,25,29 S2 in the SI.…”

“…Further, due to the synergistic effect, the binary Ni- and Co-based oxide electrode materials show improved redox characteristics and pseudocapacitive charge storage efficiency as compared to their individual oxide counterparts (i.e., oxides of Ni and Co) . In this regard, spinel NiCo 2 O 4 has recently gained considerable attention due to its synthetic feasibility, microstructural tunability, and electrochemical versatility for redox reactions-based charge storage and other applications. − However, the charge storage, cyclic, and Ragone efficiencies of the mostly reported NiCo 2 O 4 -based pseudocapacitors are below the efficiencies of potentially used high-performance supercapacitors. In this regard, there is significant scope in the electromicrostructural manipulation of NiCo 2 O 4 , which can improve the overall charge storage, Ragone, and cyclic efficiencies of the fabricated pseudocapacitor devices.…”

Photocatalytic Degradation of Food and Juices Dyes via Photocatalytic Nanomaterials Synthesized through Green Synthetic Route: A Systematic Review

“…Flowers, such as nickel-cobalt oxide nanosheets, were successfully synthesized via an ecofriendly and cost-effective hydrothermal route which showed an excellent dye-degradation performance of 94.75% towards Allura red AC dye in 10 min under UV light irradiation [ 85 ]. There has been 96.12% degradation of the dye in 100 min at a pH of 4 using chitosan-coated nickel selenide nano-photocatalyst; another group of scientists reported that they had achieved 96.99% degradation within 6 min using CuO nanosheets with NaBH 4 acting as a reducing agent [ 36 ] compared to 90.54% degradation using CuO nanorods [ 86 ].…”

Synergistic Effects of Redox Couples and Oxygen Vacancies Improve the Tetracycline Degradation Property of La2NiMnO6

“…Antibiotics that remain in water are harmful to human health and ecosystems. Semiconductor photocatalyst technology has the merit of high efficiency and environmental protection and has become a promising method for water disinfection, , dye degradation, , and antibiotic degradation. , It is important to develop a catalyst that can effectively break down antibiotics.…”