Synthesis and characterizations of Ni-NiO nanoparticles on PDDA-modified graphene for oxygen reduction reaction

An efficient strategy to boost photoelectrochemical water oxidation of g-C3N4 films modified with NiO as cocatalyst

The successful synthesis of carbon nitride films plays a crucial role in photoelectrochemical (PEC) water oxidation reactions. However, a significant technical challenge is that the contact between the g-C3N4 layer and the fluorine-doped tin oxide (FTO) substrate is suboptimal, as well as the recombination of photogenerated electrons and holes is grievous, directly affecting the effective charge transport and the overall photocatalytic efficiency. Herein, we fabricated a g-C3N4 thin photoanode through simple chemical vapor deposition, NiO cocatalyst was modified on the surface of g-C3N4 thin photoanode via electro-deposition and followed by calcination, aiming at improving the transfer of photogenerated charge carriers. As expected, the recombination of photogenerated electrons and holes is effectively suppressed the g-C3N4 thin photoanode after introducing NiO cocatalyst. Moreover, the superior electrical conductivity of NiO reduces charge transport resistance and allows photogenerated holes to be rapid injected into the electrolyte to participate in the water oxidation reaction. As such, the NiO-60s (the deposition time of NiO is 60 s) photoanode exhibits a higher photocurrent density and much negative onset potential than g-C3N4. which is of great benefit to designing effective g-C3N4 based photoanode for PEC water oxidation reaction.

Green NiO nanoparticle-integrated PVA-alginate hydrogel: potent nanocatalyst for efficient reduction of anthropogenic water pollutants

Hydrogel nanocatalyst composed of nickel oxide (NiO) nanoparticles embedded in PVA-alginate hydrogels were potentially explored toward the reduction of anthropogenic water pollutants. The NiO nanoparticles was accomplished via green method using waste pineapple peel extract. The formation of the nanoparticles was affirmed from different analytical techniques such as UV-Vis, FTIR, XRD, TGA, FESEM, and EDS. Spherical NiO nanoparticles were obtained having an average size of 11.5 nm. The nano NiO were then integrated into PVA-alginate hydrogel matrix forming a nanocomposite hydrogel (PVALg@ NiO). The integration of nano NiO rendered an improved thermal stability to the parent hydrogel. The PVALg@ NiO hydrogel was utilized as a catalyst in the reduction of 4-nitrophenol (4-NP), potassium hexacyanoferrate (III), rhodamine B (RhB), methyl orange (MO), and malachite green (MG) in the presence of a reducing agent, i.e., NaBH4. Under optimized conditions, the reduction reactions were completed by 4.0 min and 3.0 min for 4-NP and potassium hexacyanoferrate (III), respectively, and the rate constant was estimated to be 1.14 min-1 and 2.15 min-1. The rate of reduction was found to be faster for the dyes and the respective rate constants were be 0.17 s-1 for RhB, MG and 0.05 s-1 for MO. The PVALg@ NiO hydrogel nanocatalyst demonstrated a recyclability of four runs without any perceptible diminution in its catalytic mettle. The efficacy of the PVALg@ NiO hydrogel nanocatalyst was further examined for the reduction of dyes in real water samples collected from different sources and the results affirm its high catalytic potential. Thus, this study paves the path for the development of a sustainable hydrogel nanocatalyst for reduction of hazardous pollutants in wastewater treatment.

Spherical Ni/NiO nanoparticles decorated on nanoporous carbon (NNC) as an active electrode material for urea and water oxidation reactions

Herein, we report a chemical method for scalable synthesis of spherical Ni/NiO nanoparticle-decorated nanoporous carbon (NNC) based electrocatalytic system using a simple and easy chemical method with ultra-high activity towards urea electrooxidation. Morphological analysis by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) confirms the formation of Ni/NiO NPs on highly nanoporous carbon with an average size of ∼50 nm. X-ray diffraction (XRD) confirms NNC with a face-centred cubic (FCC) crystal structure. Ni/NiO NPs intercalated with nanoporous carbon exhibited the best electrocatalytic performance towards urea oxidation with an ultra-low onset potential of ∼0.33 V vs. SCE, and faster electrokinetic mechanism confirmed from Tafel slope (∼45 mV dec-1), EIS Rct (∼6.98 Ω), and long term durability for 7 h at 10 mA cm-2 with high CO poisoning tolerance. This work affords noble metal-free electrocatalysts for novel appliances and remarkable potential for urea determination, hydrogen generation, real-time water remediation, and energy conversion.

SO3H-functionalized carbon fibers for the catalytic transformation of glycerol to glycerol tert-butyl ethers

Carbon fibers (CFs) of high quality were produced from hydrocarbons such as isobutane or ethylene using the catalytic chemical vapor deposition method (CCVD) and Ni catalyst. The as-prepared samples were functionalized with acidic groups using concentrated sulfuric acid or 4-benzenediazonium sulfonate (BDS) generated in situ from sulfanilic acid and sodium nitrite. The morphological features of the materials were confirmed by transmission electron microscopy, whereas their physicochemical properties were characterized by means of elemental and textural analyses, thermogravimetric (TG) method, Raman spectroscopy, potentiometric back titration, and X-ray diffraction analysis. The obtained CFs were used as catalysts in glycerol etherification with tert-butyl alcohol at 110 °C under autogenous pressure. The BDS-modified CFs were particularly effective in the reaction, showing high glycerol conversions (of about 45-55% after 6 h) and substantial yields of mono- and di-glycerol ethers. It was found that the chemistry of the sample surface was crucial for the process. The high concentration of -SO₃H groups decorating CFs boosted the formation of di- and tri-tert-butyl glycerol ethers. Surface oxygen functionalities also had a positive effect on the reaction, however, their impact on the catalytic performances of CFs was significantly weaker compared to that shown by -SO₃H groups and it was probably due to the adsorption of reagents on the catalyst surface.

Electrochemical tuning of a Cu3P/Ni2P hybrid for a promoted hydrogen evolution reaction

Developing novel and high performance electrocatalysts for use in hydrogen evolution reactions (HER) as substitutes for noble metal based electrocatalysts is imperative and, so far, has been a challenge. Herein, a self-supported Cu₃P/Ni₂P hybrid on nickel foam (Cu₃P/Ni₂P@NF) is prepared by a simple galvanic replacement reaction coupled with phosphorization. Subsequently, Cu₃P/Ni₂P@NF is modified by conducting cyclic voltammetry scans in 0.5 M H₂SO₄ solution. Interestingly, after electrochemical tuning, the as-prepared Cu₃P/Ni₂P@NF exhibits significantly enhanced HER activity. Particularly, the resultant Cu₃P/Ni₂P@NF catalyst after 4000 cycles exhibits superior catalytic activity and long-term stability for HER with an overpotential of only 67 mV at the current density of 10 mA cm^-2, and a low Tafel slope of 43.9 mV dec^-1. The improved HER performance is attributed to the increased intrinsic activity of the Cu₃P/Ni₂P@NF with its optimized crystal and electronic structure, as well as an increased number of accessible active sites due to surface dissolution and recrystallization induced by electrochemical modification.

Corrosion Resistance and Thermal Conductivity Enhancement of Reduced Graphene Oxide–BaSO4–Epoxy Composites

The results of studies on the corrosion protectiveness and thermal conductivity of reduced graphene oxide–BaSO4 epoxy composites are reported here. A commercial epoxy resin and reduced graphene oxide (rGO) were blended with a hardening reagent and then mixed with prepared BaSO4–epoxy resin (B–epoxy). The reduced graphene oxide–BaSO4–epoxy composite (rGO–B–epoxy) paste was used to coat the surfaces of Al 7205 alloy and the corrosion and thermal properties were investigated. A corrosion test in a 3.5 wt% synthetic sea water solution showed that the composite coating containing BaSO4 had the best corrosion resistance. Moreover, the rGO–B–epoxy composite showed better protection against corrosion than the epoxy alone. The rGO–B–epoxy composite with 5 wt% BaSO4 had an in-plane coefficient of thermal conductivity of approximately 165.0 W/m K, and the in-plane thermal diffusivity was 71.38 mm2/s. In standard thermal conductivity tests, all three samples had values below 40 W/m K. The rGO–B–epoxy composites showed good surface corrosion protection and in-plane thermal conductivity.

Nickel Nanoflowers with Controllable Cation Vacancy for Enhanced Electrochemical Nitrogen Reduction

The key to the design of electrochemical nitrogen reduction (NRR) catalysts is that the reaction sites can not only activate the N≡N bond but also have high catalytic selectivity. Vacancy engineering is an effective way to modulate active sites, and cation vacancies are considered to have enormous potential in tuning catalytic selectivity. However, research on NRR activity is still at an early stage due to the difficulty in preparation and precise regulation. Here, we provided an adjusted method of cation vacancy through topotactic transformation, which combines solvothermal reduction with etching via lattice confinement effect to accomplish precursor reduction and vacancy construction while maintaining consistent material morphologies. Based on the topotactic transformation, NiAl-LDH precursor was reduced to Ni metal nanoflower, while Al is simultaneously etched by alkali, thus the precise tunability of the cation vacancy can be achieved by adjusting the Al content in the LDH. The Ni nanoflower achieved excellent stability and high ammonia yield by adjusting the vacancy concentration. In addition, the insight into the selectivity and intrinsic activity of cation vacancies on NRR process has been revealed. For the reaction selectivity, the cation vacancy is beneficial to activate N≡N but not conducive to the HER process. For the intrinsic NRR activity, the generation of cation vacancies can also significantly reduce the energy barrier of NRR process and accelerate the reaction kinetics.

Green synthesis of nickel oxide nanoparticles using Salvia hispanica L. (chia) seeds extract and studies of their photocatalytic activity and cytotoxicity effects

The physical and chemical properties of Nickel oxide nanoparticles (NiO-NPs) have attracted the attention of many and in this regard, this study was performed to produce NiO-NPs by the means of Salvia hispanica L. (chia) seeds extract as the capping agent. Physical and morphological features of the obtained NiO-NPs were examined through the application of TGA, FTIR, UV-Vis, XRD, FESEM/EDAX/PSA, and VSM procedures. According to the FESEM/PSA images, the biosynthesized NiO-NPs contained a spherical shape and a size of about 30 nm, while the results of the EDAX study approved the existence of oxygen and nickel elements in the structure of this product. Furthermore, certain corresponding peaks to the crystal structure of NiO-NPs were observed throughout the XRD pattern. Next to the superparamagnetic behavior that was detected in the results of VSM analysis, the cytotoxicity effect of NiO-NPs was not reported to be dependent on concentration. Considering the high photocatalytic capacity along with the low cytotoxic effects of NiO-NPs, we can suggest the applicability of this product for various applications such as disease control and removal of residual toxins.

Rapid photocatalytic degradation of cationic organic dyes using Li-doped Ni/NiO nanocomposites and their electrochemical performance

This work reports novel bi-functional Li-doped Ni/NiO nanocomposites as potential candidates for energy storage and water treatment applications.

Reinforcement of Epoxy Resin by Additives of Amine-Functionalized Graphene Nanosheets

In this study, graphene oxide (GO) nanosheets were modified with an amine functional group to obtain amine-functionalized graphene (AMG) nanosheets and then blended with the aniline curing agent of bisphenol-A (BPA) epoxy resin to crosslink BPA epoxy resin. The AMG-blended curing agent and BPA epoxy resin formed an intermolecular hydrogen bond that was stronger than the π–π stacking force between benzene rings of graphene nanosheets. Therefore, AMG nanosheets exhibited excellent dispersion in the aniline curing agent. The amine group of AMG-blended curing agents and the epoxy functional group of BPA epoxy resin exhibited strong chemical activity and underwent crosslinking and polymerization. AMG nanosheets were mixed with BPA epoxy resin to form a crosslinked structure through the epoxy ring-opening polymerization of the resin. The mechanical properties of the epoxy resin nanocomposites were significantly improved by the added 1 wt.% AMG nanosheets. The tensile strength was enhanced by 98.1% by adding 1 wt.% AMG in epoxy. Furthermore, the impact resistance of the epoxy resin was enhanced by 124.4% after adding 2.67 wt.% of AMG nanosheets. Compared with other reinforced fillers, AMG nanosheets are very light and can therefore be used as nanocomposite materials in coating applications, the automotive industry, aerospace sheet materials, wind power generation, and other fields.

An Electrochemical Approach for the Selective Detection of Cancer Metabolic Creatine Biomarker with Porous Nano-Formulated CMNO Materials Decorated Glassy Carbon Electrode

The facile wet-chemical technique was used to prepare the low-dimensional nano-formulated porous mixed metal oxide nanomaterials (CuO.Mn2O3.NiO; CMNO NMs) in an alkaline medium at low temperature. Detailed structural, morphological, crystalline, and functional characterization of CMNO NMs were performed by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS) analyses. An efficient and selective creatine (CA) sensor probe was fabricated by using CMNO NMs decorated onto glassy carbon electrode (GCE) as CMNO NMs/GCE by using Nafion adhesive (5% suspension in ethanol). The relation of current versus the concentration of CA was plotted to draw a calibration curve of the CMNO NMs/GCE sensor probe, which was found to have a very linear value (r2 = 0.9995) over a large dynamic range (LDR: 0.1 nM~0.1 mM) for selective CA detection. The slope of LDR by considering the active surface area of GCE (0.0316 cm2) was applied to estimate the sensor sensitivity (14.6308 µAµM-1 cm-2). Moreover, the detection limit (21.63 ± 0.05 pM) of CMNO MNs modified GCE was calculated from the signal/noise (S/N) ratio at 3. As a CA sensor probe, it exhibited long-term stability, good reproducibility, and fast response time in the detection of CA by electrochemical approach. Therefore, this research technique is introduced as a promising platform to develop an efficient sensor probe for cancer metabolic biomarker by using nano-formulated mixed metal oxides for biochemical as well as biomedical research for the safety of health care fields.

Two-Dimensional Earth-Abundant Transition Metal Oxides Nanomaterials: Synthesis and Application in Electrochemical Oxygen Evolution Reaction

Development of a universal synthetic strategy for two-dimensional (2D) Earth-abundant transition metal oxides nanomaterials is highly vital toward numerous electrochemical applications. Herein, a facile and general synthesis of highly ordered two-dimensional metal oxides nanomaterials includes Co₃O₄, NiO, CuO, and Fe₃O₄ nanosheets as an electrocatalyst for oxygen evolution reaction (OER) is demonstrated. Among the synthesized 2D transition metal oxides, the Co₃O₄ nanosheet exhibits smallest overpotential (η) of ∼384.0 mV at a current density of 10.0 mA cm^-2 and Tafel slope of ∼52.0 mV dec^-1, highest mass activity of ∼112.3 A g^-1 at the overpotential of ∼384.0 mV, and high turn over frequency (TOF) of 0.099 s^-1, which is relatively favorable with state-of-the-art RuO₂ catalyst. The present synthetic approach may unlock a brand new pathway to prepare shape-controlled Earth-abundant transition metal oxides nanomaterials for electrocatalytic OER.

Nickel(II) Nanoparticles Immobilized on EDTA-Modified Fe3O4@SiO2 Nanospheres as Efficient and Recyclable Catalysts for Ligand-Free Suzuki-Miyaura Coupling of Aryl Carbamates and Sulfamates

A highly efficient and air-, thermal-, and moisture-stable nickel-based catalyst with excellent magnetic properties supported on silica-coated magnetic Fe₃O₄ nanoparticles was successfully synthesized. It was well characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, thermogravimetric analysis, dynamic light scattering (DLS), X-ray photoelectron spectroscopy, vibration sample magnetometry, energy-dispersive X-ray analysis, inductively coupled plasma analysis, and nitrogen adsorption-desorption isotherm analysis. The Suzuki-Miyaura coupling reaction between aryl carbamates and/or sulfamates with arylboronic acids was selected to demonstrate the catalytic activity and efficiency of the as-prepared magnetic nanocatalyst. Using the mentioned heterogeneous nanocatalyst in such reactions generated corresponding products in good to excellent yields in which the catalyst could easily be recovered from the reaction mixture with an external magnetic field to reuse directly for the next several cycles without significant loss of its activity.

N-Arylation of (hetero)arylamines using aryl sulfamates and carbamates via C–O bond activation enabled by a reusable and durable nickel(0) catalyst

An effective and general aryl amination protocol has been developed using a magnetically recoverable Ni(0) based nanocatalyst.

Study of “Ni-doping” and “open-pore microstructure” as physico-electrochemical stimuli towards the electrocatalytic efficiency of Ni/NiO for the oxygen evolution reaction

Added “Ni-doping” and “open-pore microstructure” act as physico-electrochemical stimuli towards enhanced electrocatalytic efficiency and electromechanical stability of Ni/NiO for the low-overpotential oxygen evolution reaction in alkaline medium.

A Pt-free graphenaceous composite as an electro-catalyst for efficient oxygen reduction reaction

Use of Pt-based electro-catalysts for the oxygen reduction reaction (ORR) is a major hindrance in large-scale application of proton exchange membrane fuel cells (PEMFCs). Hence, new, cost-effective and high performance electro-catalysts are required for the commercial success of PEMFCs. In this work, a Pt-free magnesium oxide (MgO) decorated multi-layered reduced graphene oxide (MLGO) composite is tested as an electro-catalyst for the ORR. The ORR activity of MgO/MLGO in terms of diffusion-controlled current density is found to be superior (6.63 mA per cm2-geo) than that of in-house prepared Pt/rGO (5.96 mA per cm2-geo) and commercial Pt/C (5.02 mA per cm2-geo). The applicability of less expensive MgO/MLGO not only provides a new electro-catalyst but also provides a new direction in exploring metal oxide-based electro-catalysts for the ORR.

Core@shell structured Co–CoO@NC nanoparticles supported on nitrogen doped carbon with high catalytic activity for oxygen reduction reaction

A composite with a hierarchical structure consisting of nitrogen doped carbon nanosheets with the deposition of nitrogen doped carbon coated Co–CoO nanoparticles (Co–CoO@NC/NC) has been synthesized by a simple procedure involving the drying of the reaction mixture containing Co(NO₃)₂, glucose, and urea and its subsequent calcination. The drying step is found to be necessary to obtain a sample with small and uniformly sized Co–CoO nanoparticles. The calcination temperature has a great effect on the catalytic activity of the final product. Specifically, the sample prepared at the calcination temperature of 800 °C shows better catalytic activity of the oxygen reduction reaction (ORR). Urea in the reaction mixture is crucial to obtain the sample with the uniformly sized Co–CoO nanoparticles and also plays an important role in improving the catalytic activity of the Co–CoO@NC/NC. Additionally, there exists a strong electronic interaction between the Co–CoO nanoparticles and the NC. Most interestingly, the Co–CoO@NC/NC is highly efficient for the ORR and can deliver an ORR onset potential of 0.961 V vs. RHE and a half-wave potential of 0.868 V vs. RHE. Both the onset and half-wave potentials are higher than those of most catalysts reported previously and even close to those of the commercial Pt/C (the ORR onset and half-wave potential of the Pt/C are 0.962 and 0.861 V vs. RHE, respectively). This, together with its high stability, strongly suggests that the Co–CoO@NC/NC could be used as an efficient catalyst for the ORR.

A simple method has been developed for the synthesis of Co–CoO@NC/NC, which exhibits high and stable performance for the ORR.

Role of Ni in hetero-architectured NiO/Ni composites for enhanced catalytic performance

The effect of Ni in NiO/Ni nanocomposites and their contribution in photoelectrooxidation of dyes and substituted phenols were studied.

An efficient three-component synthesis of coumarin-3-carbamides by use of Ni–NiO nanoparticles as magnetically separable catalyst

An efficient and ecofriendly synthesis of coumarin-3-carbamides has been developed by a three-component reaction of 2-hydroxybenzaldehydes, aliphatic amines (p-/s-) and diethyl malonate using Ni–NiO nanoparticles as catalyst.

Self-assembly of large-scale P3HT patterns by confined evaporation in the capillary tube

Large-scale P3HT stripe patterns based on a controlled evaporation self-assembly method in a capillary tube have been fabricated.

Performance evaluation of highly conductive graphene (RGOHI–AcOH) and graphene/metal nanoparticle composites (RGO/Ni) coated on carbon cloth for supercapacitor applications

The application of graphene (RGO)-based composites as electrode materials in supercapacitors can be limited by the fabrication complexity and costs, and the non-environmentally friendly nature of the production process.