Synthesis, characterization, optical and magnetic properties of pure and Mn, Fe and Zn doped NiO nanoparticles

Nanostructured Mn@NiO composite for addressing multi-pollutant challenges in petroleum-contaminated water

Efficient catalysts play a pivotal role in advancing eco-friendly water treatment strategies, particularly in the removal of diverse organic contaminants found in water-petroleum sources. This study addresses the multifaceted challenges posed by contaminants, encompassing a spectrum of heavy metals such as As, Cd, Cr, Mn, Mo, Ni, Pb, Sb, Se, and Zn alongside pollutants like oily water (OIW), total suspended solids (TSS), chemical oxygen demand (COD), dyes, and pharmaceuticals, posing threats to both aquatic and terrestrial ecosystems. Herein, we present the synthesis of biogenically derived Mn@NiO nanocomposite (NC) photocatalysts, a sustainable methodology employing an aqueous Rosmarinus officinalis L. extract, yielding particles with a size of 36.7 nm. The catalyst demonstrates exceptional efficacy in removing heavy metals, achieving rates exceeding 99-100% within 30 min, alongside notable removal efficiencies for OIW (98%), TSS (87%), and COD (98%). Furthermore, our photodegradation experiments showed remarkable efficiencies, with 94% degradation for Rose Bengal (RB) and 96% for methylene blue (MB) within 120 min. The degradation kinetics adhere to pseudo-first-order behavior, with rate constants of 0.0227 min-1 for RB and 0.0370 min-1 for MB. Additionally, the NC exhibits significant antibiotic degradation rates of 97% for cephalexin (CEX) and 96% for amoxicillin (AMOX). The enhanced photocatalytic performance is attributed to the synergistic interplay between the Mn and NiO nanostructures, augmenting responsiveness to sunlight while mitigating electron-hole pair recombination. Notably, the catalyst demonstrates outstanding stability and reusability across multiple cycles, maintaining its stable nanostructure without compromise.

Electro-chemical studies of Zn doped nickel oxide nanoparticles synthesized via solution combustion method using green and chemical fuels

This study presents a new green solution combustion method (aloe vera gel extract as fuel) and chemical method (glucose as fuel) to synthesise Zn-doped nickel oxide nanoparticles (Zn:NiO NPs). The face centered cubic crystal structure (FCC) phase was validated by PXRD, while the produced samples' spongy, spherical, agglomerated, and porous characteristics were shown by electron microscopy. The energy band gap values of 4.21 eV and 4.09 eV, respectively, were deduced for green and chemically synthesized Zn:NiO NPs. The reversibility was demonstrated by cyclic voltammetry with a lower EO-ER value for the green-Zn:NiO electrode. The studies on electrochemical impedance confirmed strong conductivity for the NPs by demonstrating a low charge transfer resistance. The Zn:NiO NPs are easily convertible into a stable electrode material that may be used in supercapacitors. According to the findings, Zn:NiO is an economical and promising material for use in supercapacitors in the future.

Engineering of Co3O4 electrode via Ni and Cu-doping for supercapacitor application

Although cobalt oxides show great promise as supercapacitor electrode materials, their slow kinetics and low conductivity make them unsuitable for widespread application. We developed Ni and Cu-doped Co3O4 nanoparticles (NPs) via a simple chemical co-precipitation method without the aid of a surfactant. The samples were analyzed for their composition, function group, band gap, structure/morphology, thermal property, surface area and electrochemical property using X-ray diffraction (XRD), ICP-OES, Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV-Vis), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and/or Differential thermal analysis (DTA), Brunauer-Emmett-Teller (BET), and Impedance Spectroscopy (EIS), Cyclic voltammetry (CV), respectively. Notably, for the prepared sample, the addition of Cu to Co3O4 NPs results in a 11.5-fold increase in specific surface area (573.78 m2 g-1) and a decrease in charge transfer resistance. As a result, the Ni doped Co3O4 electrode exhibits a high specific capacitance of 749 F g-1, 1.75 times greater than the pristine Co3O4 electrode's 426 F g-1. The electrode's enhanced surface area and electronic conductivity are credited with the significant improvement in electrochemical performance. The produced Ni doped Co3O4 electrode has the potential to be employed in supercapacitor systems, as the obtained findings amply demonstrated.

Effect of Fe on Calcined Ni(OH)2 Anode in Alkaline Water Electrolysis

Ni (hydr)oxide is a promising and inexpensive material for oxygen evolution reaction (OER) catalysts and is known to dramatically increase the activity when used with Fe. Herein, we basified a Ni(II) solution and coated layered Ni(OH)2 on Ni coins to prepare a template with high stability and activity. To evaluate the stability and catalytic activity during high-current-density operation, we analyzed the electrochemical and physicochemical properties before and after constant current (CC) operation. The electrode with a Ni(OH)2 surface exhibited higher initial activity than that with a NiO surface; however, after the OER operation at a high-current density, degradation occurred owing to structural destruction. The activity of the electrodes with a NiO surface improved after the CC operation because of the changes on the electrode-surface caused by the CC operation and the subsequent Fe incorporation from the Fe impurity in the electrolyte. After confirming the improvement in activity due to Fe, we prepared NiFe-oxide electrodes with improved catalytic activity and optimized the Ni precursor and Fe loading solution concentrations. The Ni-Fe oxide electrode prepared under the optimal concentrations exhibited an overpotential of 287 mV at a current density of 10 mA/cm2, and a tafel slope of 37 mV dec−1, indicating an improvement in the OER activity.

Synthesis and Investigation of Pure and Cu-Doped NiO Nanofilms for Future Applications in Wastewater Treatment Rejected by Textile Industry

Pure and Cu-doped NiO films were synthesized via a soft chemical process. They were deposited on glass substrates heated to 400 °C. Different atomic percentage ratios (2, 4, 6, 8, and 10%) of Cu-doping were used. The prepared samples were characterized by several techniques such as X-ray diffraction for crystallographic study, SEM and AFM for microstructural and morphological properties, and UV-Visible spectroscopy for optical and photocatalytical analysis. XRD results of pure and Cu-doped NiO films indicated the formation of NiO polycrystalline phases under a cubic structure with a favored orientation along the (200) plane noticed in all sprayed films. SEM images revealed the formation of NiO nanoparticles of spherical forms whose sizes increase and agglomerate with increasing Cu-doping. At 10% Cu-doping, NiO agglomeration was extended to the whole surface. AFM images showed a textured and rough surface composed of NiO nanoparticles of average size varying from 16 to 10 nm depending on Cu-doping concentration. UV-visible spectroscopy confirmed the transparency of NiO films and their semiconducting character with a band gap ranging from 3.4450 eV to 2.8648 eV. The photocatalytical properties of pure and Cu-NiO films were enhanced by Cu-doping particles as revealed by the degradation of methylene blue (MB) solution subjected to irradiation.

Synthesis and Characterization of Highly Photocatalytic Active Ce and Cu Co-Doped Novel Spray Pyrolysis Developed MoO3 Films for Photocatalytic Degradation of Eosin-Y Dye

The current work deals with the fabrication of novel MoO3 nanostructured films with Ce and Cu co-doping through the spray pyrolysis route on a glass substrate maintained at 460 °C for the first time. The phase of developed films was approved by an X-ray diffraction study, and the crystallite size was determined between 82 and 92 nm. The optical transmission of the developed films was noticed to be reduced with doping and found between 45 and 90% for all films, and the absorption edge shifted to a higher wavelength with doping. The optical energy gap of the fabricated films was found to be reduced from 3.85 to 3.28 eV with doping. The developed films were used to degrade the harmful Eosin-Y dye under UV light. The system with 2% Ce and 1% Cu-doped MoO3 turned out to be the most effective catalyst for photodegradation of the dye in a period of 3H and almost degrade it. Hence, the MoO3 films prepared with 2% Ce and 1% Cu will be highly applicable as photocatalysts for the removal of hazardous dye from wastewater.

Band-Gap Engineering: A New Tool for Tailoring the Activity of Semiconducting Oxide Catalysts for CO Oxidation

Cation or anion vacancies in semiconducting oxides usually benefit activity for CO oxidation. To study the nature of vacancy engineering for a thermocatalytic reaction, we adopted lattice doping of cations with varied valence states to construct anion and cation vacancies in n-type and p-type semiconducting CeO₂ and NiO, respectively. Doping cations can effectively regulate the number of the vacancies, thus tailoring the activity for CO oxidation. The strong correlation of activation energy and specific activity with a catalyst band gap verified that the nature of vacancy engineering for activity of CeO₂ and NiO for CO oxidation can be attributed to tailoring of the band gap. The larger the vacancy amount, the smaller the band gap, and the lower the activation energy, thus giving a higher specific activity. Band-gap engineering, widely used for photocatalytic processes, can be a new tool for tailoring the activity of semiconducting oxide catalysts for thermocatalytic reactions.

In situ thermal decomposition route: Preparation and characterization of nano nickel, cobalt, and copper oxides using an aromatic amine complexes as a low-cost simple precursor

The main interest now is the development of metallic or inorganic-organic compounds to prepare nanoparticle materials. The use of new compounds could be beneficial and open a new method for preparing nanomaterials to control the size, shape, and size of the nanocrystals. In this article, the thermal decomposition of [M2(o-tol)2(H2O)8] Cl4 (where o-tol is ortho-tolidine compound, M = Ni2+, Co2+, Cu2+) new precursor complex was discussed in solid-state conditions. The thermal decomposition route showed that the synthesized three complexes were easily decomposed into NiO, Co3O4 and CuO nanoparticles. This decomposition was performed at low temperatures (~600°C) in atmospheric air without using any expensive and toxic solvent or complicated equipment. The obtained product was identified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). FT-IR, XRD and EDX analyses revealed that the NiO nanoparticles exhibit a face-centered-cubic lattice structure with a crystallite size of 9–12 nm. The formation of a highly pure spinel-type Co3O4 phase with cubic structure showed that the Co3O4 nanoparticles have a sphere-like morphology with an average size of 8–10 nm. The XRD patterns of the CuO confirmed that the monoclinic phase with the average diameter of the spherical nanoparticles was approximately 9–15 nm.

Magnetic homogeneity in Fe-Mn co-doped NiO nanoparticles

The effect of Fe and Mn co-doping on the magnetic properties of the antiferromagnetic (AFM) NiO nanoparticles which offer large potential for different magnetic applications have been studied. The Rietveld refinement fitting of powder x-ray diffractometry (XRD) patterns confirmed the phase formation of face-centred cubic crystal structure of NiO and average crystallite size lies in the short range of 32-38 nm. The cavity and broadband ferromagnetic resonance (FMR) measurements taken at room temperature demonstrate the smaller local magnetic inhomogeneity for 4%Mn-4%Fe co-doped NiO nanoparticles as compared to undoped, single doped and co-doped with different concentration NiO nanoparticles. The M-H loops revealed the room temperature ferromagnetism-like behaviour for higher Fe doping concentration and lower Mn doping concentration. This can be attributed to the double exchange interaction. The zero field cooled (ZFC) and field cooled (FC) dc magnetization curves showed a small surface freezing peak (at[Formula: see text] at low temperatures and a blocking peak (at [Formula: see text] at higher temperatures. For samples with 4%Mn-4%Fe and 2%Mn-6%Fe, the blocking peak was found at a relatively high temperature in comparison to other samples. This can be attributed to the presence of magnetic exchange interactions which block the magnetic spins against a thermal increase. The ZFC AC-susceptibility showed three peaks; a surface freezing peak at T_f, a blocking peak at T_B peak and an anomalous peak at T_x in between [Formula: see text] and [Formula: see text], which was found to be most prominent for the 4%Mn-4%Fe co-doped nanoparticles. The neutron diffraction pattern confirmed the AFM order of the core of the 4%Mn-4%Fe co-doped nanoparticles, which indicates an AFM coupling between the Fe²⁺ and Mn²⁺ ions and the Ni²⁺ ions through super-exchange interaction. Therefore, the origin of T_X peak can be attributed to the ferromagnetic coupling between the Fe²⁺ and Mn²⁺ ions which has a maximum strength at equal concentration. Thus, small and equal doping concentration of Fe and Mn in NiO nanoparticles increase the magnetic homogeneity which makes them attractive for magnetic applications.