Nanoraspberry-like palladium/spongy nickel oxide for electrooxidation of five light fuels

The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage.     

Catalytic combustion of methane over a highly active and stable NiO/CeO2 catalyst

In the last decades, many reports dealing with technology for the catalytic combustion of methane (CH₄) have been published. Recently, attention has increasingly focused on the synthesis and catalytic activity of nickel oxides. In this paper, a NiO/CeO₂ catalyst with high catalytic performance in methane combustion was synthesized via a facile impregnation method, and its catalytic activity, stability, and water-resistance during CH₄ combustion were investigated. X-ray diffraction, low-temperature N₂ adsorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, hydrogen temperature programmed reduction, methane temperature programmed surface reaction, Raman spectroscopy, electron paramagnetic resonance, and transmission electron microscope characterization of the catalyst were conducted to determine the origin of its high catalytic activity and stability in detail. The incorporation of NiO was found to enhance the concentration of oxygen vacancies, as well as the activity and amount of surface oxygen. As a result, the mobility of bulk oxygen in CeO₂ was increased. The presence of CeO₂ prevented the aggregation of NiO, enhanced reduction by NiO, and provided more oxygen species for the combustion of CH₄. The results of a kinetics study indicated that the reaction order was about 1.07 for CH₄ and about 0.10 for O₂ over the NiO/CeO₂ catalyst.     

Enhancing the flash-sinterability of BaZr0.1Ce0.7Y0.2O3-δ proton-conducting electrolyte by nickel oxide doping for possible application in SOFCs

In the present work, effects of nickel oxide doping on flash-sinterability of BaZr_0.1Ce_0.7Y_0.2O_3-δ compound were investigated. A single-phase BZCY7 powder was synthesized by the solid-state reaction route. The effects of using 0.5, 1, 1.5, and 2 wt% of NiO additive on flash sintering of BZCY7 samples were examined. It was revealed that using 0.5 wt% of NiO additive can reduce the onset temperature of flash sintering in all the applied electric fields in the range of 100–500 V/cm and significantly enhances the sinterability of the BZCY7 compound. Microstructural investigations, using field emission scanning electron microscopy and energy-dispersive X-ray mapping, showed that NiO doping can lead to larger grain sizes, while no detectable segregation or second phase was observed. Utilizing electrochemical impedance spectroscopy, the total conductivity of samples at 600 and 700 °C was measured as 4.4 × 10^?3 and 7.0 × 10^?3 S/cm for the undoped BZCY7, and 8.6 × 10^?3 and 1.4 × 10^?2 S/cm for the 0.5 wt% NiO doped BZCY7 sample, respectively. The activation energies of conduction were determined as 0.37 and 0.41 eV for the doped and undoped samples, which represent the presence of predominant and facile protonic conduction.     

Ni/La2O3 catalysts for dry reforming of methane: Effect of La2O3 synthesis conditions on the structural properties and catalytic performances

10 wt%Ni/La₂O₃ catalysts for dry reforming of methane (DRM) were synthesized by wetness impregnation of lanthana supports prepared using sol-gel citric method with and without NH₃ addition (Ni–La CA-NH₃ and Ni–La CA, respectively). The support preparation conditions affect the nature, phase composition, and distribution of Ni phases (LaNiO₃, NiO and La₃Ni₂O₆). The gradient temperature DRM tests (400–800 °C) reveal higher catalytic activity of Ni–La CA (at 650 °C, X(CO₂) = 65.7%, X(CH₄) = 54.6%, H₂/CO = 0.71). The Ni–La CA-NH₃ shows higher stability (at 650 °C and 24 h, X(CO₂): 73.7% => 76.4%, X(CH₄): 64.7% => 64.6%, H₂/CO: 0.77 => 0.72). For both catalysts, La₂O₂CO₃ phase is formed after long run tests at 650 °C 24 h, with the greater TGA weight loss and stronger deactivation being observed for Ni–La CA. The H₂-reduced Ni La CA-NH₃ features ultrasmall (1–2 nm) Ni NPs strongly interacting with the support. Catalyst nature affects the amount of carbon coke formed.     

Multispectral photodetection using low-cost sputtered NiO/Ag/ITO heterostructure: From design concept to elaboration

High-performance multispectral photodetectors (PDs) are highly attractive for the emerging optoelectronic applications. In this work, a new broadband PD based on p-NiO/Ag/n-ITO heterostructure was fabricated by RF magnetron sputtering technique at room temperature. The tri-layered structure offering multispectral detection property was first identified using theoretical calculations based on combined FDTD and Particle Swarm Optimization (PSO) techniques. The crystal structure of the elaborated sensor was analyzed using X-ray diffraction (XRD) method. The device optical properties were investigated by UV–Vis–NIR spectroscopy. The NiO/Ag/ITO heterostructured PD shows a high average absorbance of 63% over a wide spectrum range of [200 nm–1100nm]. Compared with NiO and ITO thin-films, the performances of the heterostructured device are considerably enhanced. It was found that the prepared PD with NiO/Ag/ITO heterostructure merges the benefits of multispectral photodetection with reduced optical losses and efficient transfer of photo-induced carrier. The device demonstrated a high I_ON/I_OFF ratio of 78 dB and an enhanced responsivity under UV, visible and NIR lights (171 mA/W at 365 nm, 67 mA/W at 550 nm and 93 mA/W at 850 nm). The broadband photodetection property enabled by the optimized NiO/Ag/ITO heterostructure opens a new route for the elaboration of low-cost devices that can offer multiple sensing purposes, which are highly suitable for optoelectronic applications.     

Nonwoven Ni–NiO/carbon fibers for electrochemical water oxidation

The development of technologically efficient anodes for water oxidation is crucial to improve hydrogen production via water splitting. Electrodes based on metallic active sites dispersed in carbon matrices have been shown to be an attractive way to attain this goal. However, challenges remain to prevent catalyst agglomeration that otherwise can result in a decrease of performance over time.In this work, we report an alternative and efficient method to produce nickel-nickel oxide nanoparticles-embedded in carbon nanofibers (Ni–NiO/C), by the solution blow spinning (SBS) process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses show the carbon nanofibrillar matrix as a robust support, with well-dispersed nickel nanoparticles on the surface. The responses of the linear scanning voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy demonstrate how a small fraction of nickel on the fiber surface (≈1.2–5.3%) is enough to promote substantial improvement in performance (η = 278 and 309 mV vs RHE for 10 mA cm^?2) and a significant turnover frequency (TOF) values of 1.38 (η = 278) and 1.30 s^?1 (η = 309). These promising results are correlated with a large amount of Ni³⁺ present on the fiber surfaces, as identified by X-ray Photoelectron Spectroscopy (XPS). This work provides a low-cost and rapid preparation technique that can be extended for the manufacture of a wide variety of electrodes based on metals supported on carbon nanofibers.     

Dielectric properties and electromagnetic interference shielding studies of nickel oxide and tungsten oxide reinforced polyvinylchloride nanocomposites

ABSTRACT

Polyvinylchloride (PVC)/nickel oxide (NiO)/tungsten oxide (WO₃) nanocomposite films were prepared via solution casting technique. The crystallinity, morphology, and the analysis of dispersion state of PVC/NiO/WO₃ nanocomposite was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric studies of nanocomposite films were investigated and a maximum dielectric constant of 2.3 with dielectric loss (tan δ) of 2.4 was attained. The EMI shielding studies were carried out in the X and Ku-band frequency range (8 GHz-18 GHz). The maximum SE of 15.78 dB in X-band and 12.05 dB in Ku-band was achieved for 75/20/5 compositions of the PVC/NiO/WO₃ nanocomposite.     

Room temperature ferromagnetic ordering of NiO films through exchange coupling

NiO films were deposited by sputtering with a relatively high oxygen partial pressure, followed by subsequent annealing in air. The as-deposited film is amorphous. The amorphous film gradually turns to crystalline structure with the increase in annealing temperature. The film annealed at 673 K shows strong ferromagnetism at room temperature, whereas, there is no room-temperature ferromagnetic ordering for the as-deposited amorphous NiO film or the film after annealed at 873 K. The ferromagnetism is due to the finite size effect and the high Curie temperature above room temperature is associated with the interaction between ferromagnetic NiO crystalline nanoclusters and antiferromagnetic amorphous matrix.     

Impact of Ce-Loading on Ni-catalyst supported over La2O3+ZrO2 in methane reforming with CO2

This paper investigated the effect of doping Ni supported catalysts with different ceria loading. The catalysts (5%Ni+x%Ce/La₂O₃+ZrO₂, where x = 0, 1, 2, 2.5, 3, 5) were synthesized via the wet impregnation technique and tested for methane reforming with carbon dioxide at atmospheric pressure, 700 °C and 42, 000 ml/g_cat.h gas hourly space velocity. The fresh catalysts were subjected to different characterization techniques such as X-ray diffraction, Surface area and pore analysis, H₂-temperature programmed reduction, CO₂-temperature programmed desorption and thermogravimetric analysis (TGA). A fine correlation between characterization results and catalytic activity is found. The results of the reactions indicated that 5%Ni/La₂O₃+ZrO₂ has the lowest conversion which increased with the percentage loading of CeO₂ up to 2.5 wt % and then began to decline. This suggests that 2.5 wt % loading is the optimum for CH₄ and CO₂ conversion. This particular catalyst composition has NiO species that could be reduced easily, as well as dense and wide distribution of all type of basic sites with respect to other catalyst system. The used catalysts were again subjected to TGA and RAMAN analysis where the least carbon deposition and the least deactivation factor was observed for 5%Ni+5%Ce/La₂O₃+ZrO₂ catalysts.     

Solution blow spun nickel oxide/carbon nanocomposite hollow fibres as an efficient oxygen evolution reaction electrocatalyst

The development of efficient electrocatalysts for slow reaction of the oxygen evolution reaction (OER) is fundamental for viability of the electrochemical water splitting technologies. Here we report for the first time the synthesis of NiO/carbon hollow fibres (NiO-HF) by the Solution Blow Spinning (SBS) technique, and a study of their catalytic activity towards the OER in alkaline medium. The hollow fibres were obtained with ca. 300 nm in diameter consisting of agglomerated NiO nanoparticles with an average size of 50 nm which is close to the tubular wall thickness. The formation mechanism of the hollow structure was discussed. It was revealed that the carbon from polyenic branch of polyvinylpyrrolidone (PVP) resists the firing treatment and acts as an agglomerating agent, thus ensuring a conductive and percolating path between NiO nanoparticles along the fibres. A battery of electrochemical tests of NiO-HF supported by commercial Ni foam reveals excellent electrochemical activity for OER in 1 M KOH, in comparison with reference NiO nanoparticles (NiO-NP, diameter ca. 23 nm). NiO-HF attains an overpotential of 340 mV vs. RHE at a current density of 10 mA cm⁻², which is amongst the lowest values reported in the literature for undoped NiO. Chronopotentiometry reveals stable NiO-HF electrodes over 15 h under an electrolysis current of 25 mA cm⁻². Microscopic analysis shows that the fibrillar morphology is completely preserved after the electrolysis test. The remarkable performance of the NiO-HF catalyst is ascribed to the enhanced electronic conductivity resulting from the interpenetrating NiO-HF/carbon microstructure.