Study of electrochemical and photoelectrochemical properties of nickel phosphide semiconductors (original) (raw)
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Surface and Interface Analysis, 2008
A surface analysis has been conducted on a series of electrodeposited nickel-phosphorus (Ni–P) alloys containing from 6 to 29 at.% phosphorus, using X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES). No changes in core-level binding energies, Ni2p3/2 and Ni2p1/2, P2p, P2s, or X-ray excited NiLMM and PKLL Auger lines were observed regardless of phosphorus concentration. The only systematic differences observed concerned: (i) the binding energy of the Ni2p satellite peak, (ii) the fine structure of the NiLMM Auger lines, (iii) the percentage of the satellite in the total Ni2p3/2 spectrum and (iv) the valence band density of states in the Ni3d electrons region, all related to the electronic structure of the Ni–P alloys. For the first time, it has been possible to describe and rationalise the influence of (phosphorus) ligand concentration on the electronic structure of nickel-based alloys, using a screening model proposed in the literature for clarifying the role of substituents on the electronic structure of conductor compounds of nickel. As the phosphorus content increases, the number of non-bonding Ni3d electrons decreases. Thus the d-type core-hole screening is less pronounced and the binding energy of the satellite for the final state with a filled Ni4s shell increases. Copyright © 2008 John Wiley & Sons, Ltd.
Nickel Phosphide Nanoparticles with Hollow, Solid, and Amorphous Structures
Chemistry of Materials, 2009
Conversion of unary metal nanoparticles (NPs) upon exposure to oxygen, sulfur, selenium, and phophorus precursors usually produces hollow metal oxide, sulfide, selenide, or phosphide NPs through the Kirkendall effect. Here, nanostructural control of mixed-phase Ni 2 P/Ni 12 P 5 (represented as Ni x P y ) NPs prepared through the thermolysis of nickel acetylacetonate using trioctylphosphine (TOP) as a ligand and phosphorus precursor is reported. The P:Ni molar ratio controls the NP size and is the key factor in determining the nanostructure. For P:Ni molar ratios of 1-3, nickel NPs form below 240°C and subsequently convert to crystalline-hollow Ni x P y NPs at 300°C. For higher P:Ni ratios, a Ni-TOP complex forms that requires higher temperatures for NP growth, thus favoring direct formation of Ni x P y rather than nickel. Consequently, for P:Ni molar ratios of >9, amorphous-solid Ni x P y NPs form at 240°C and become crystalline-solid Ni x P y NPs at 300°C. For intermediate P:Ni molar ratios of ∼6, both growth mechanisms result in a mixture of hollow and solid Ni x P y NPs. Similar results have been obtained using tributylphosphine or triphenylphosphine as the phosphorus source, but trioctylphosphine oxide cannot serve as a phosphorus source.
Crystals
Herein, we present the investigation of catalytical and fluorescence properties for Ni11(HPO3)8(OH)6 materials obtained through a hydrothermal approach. As part of the constant search for new materials that are both cost effective and electrocatalytically active for the oxygen evolution reaction (OER) in alkaline medium, the present study involves several graphite electrodes modified with Ni11(HPO3)8(OH)6 mixed with reduced graphene oxide (rGO) and carbon black. The experimental results obtained in 0.1 mol L–1 KOH electrolyte solution show the electrode modified with rGO, 5 mg carbon black and 1 mg nickel phosphite as displaying the highest current density. This performance can be attributed to the synergistic effect between nickel phosphite and the carbon materials. Investigation of the electrode’s OER performance in 0.1 mol L–1 KOH solution revealed a Tafel slope value of just 46 mV dec–1. By increasing the concentration to 0.5 and 1 mol L–1, this value increased as well, but ther...
Journal of Materials Research
Recently, highly active, easy-to-make, and efficient bifunctional electrocatalysts have attracted tremendous attention because of their potential applications in clean energy. Herein, we report a simple, one-step approach for fabricating three-dimensional (3D) NiP nanorod arrays by direct phosphorization of commercial nickel foam (Ni foam) with different times. When used as a 3D electrode for oxygen evolution reaction, the obtained NiP nanorods with two hours of phosphatization treatment display high activity with an overpotential of 270 mV required to generate a current density of 30 mA/cm 2 and excellent stability in 1.0 M KOH. Additionally, the NiP nanorod arrays are also highly active for electrocatalyzing the hydrogen evolution reaction in the alkaline media. As a result, the bifunctional NiP catalysts enabled a highly performed overall water splitting, in which a low applied external potential of 1.6 V led to a stabilized catalytic current density of 10 mA/cm 2 over 12 h.
Structural, optoelectronic and electrochemical properties of nickel oxide films
Journal of Materials Science: Materials in Electronics, 2009
Thin nickel oxide (NiO) films were deposited by the electron beam evaporation technique. The films were post annealed in air at 450-500°C for 5 h and the effect of annealing on the structural, microstructural, electrical and optical properties were studied. X-ray diffraction studies indicated the polycrystalline nature of the films. The microstructural parameters were evaluated. The band gap of the films was found to be about 3.60 eV. Electrical resistivity of the films was 4.5 9 10-4 X cm. FTIR studies indicated a broad spectrum centered at 461.6 cm-1. Cyclic voltammetry studies in 1 M KOH solution revealed good electronic electrochromic behaviour.
Electronic Structure of Nanostructured Nickel Oxide Using Ni 2p XPS Analysis
Journal of Nanoparticle Research, 2002
We examine the electronic structure of nanostructured nickel oxide with an average particle size of 4–5?nm using Ni 2p X-ray photoelectron spectrum. The most striking features of the spectrum are the Ni 2p main line broadening and an increase in the relative intensity of the ~ 1.5?eV satellite. We explain the observations as due to an enhancement in the non-local
Dual-energy application of NiO: Electrochemical and Photovoltaic properties
Optik, 2018
In the present work, we report the synthesis of Nickel oxide (NiO) nanoparticles employing hydrothermal technique. The surface morphology, crystal structure, porosity and vibrational response were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), surface area and pore size analyzer, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. FESEM images confirm flower-like morphology of assynthesized sample. XRD result reveal its polycrystalline nature and cubic structure of asprepared NiO nanoparticles. FTIR results identified the surface functional groups attached with the molecules while Raman peaks show the characteristic vibrational mode and magnon excitation. Pore size and surface area analysis reveal the porosity in the synthesized sample and indicates its suitability use for electrochemical and photovoltaic devices. It was found that the NiO sample offered specific capacitance as high as 47.6 F g-1 (at scan rate of 10 mV s-1), when employed as working electrode in two-electrode assembly. Also, the synthesized sample provided efficiency of 0.92%, when employed to fabricate dye-sensitized solar cell. It is therefore a worthy candidate for further research.
Photosynthesis and structure of electroless Ni–P films by synchrotron x-ray irradiation
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2007
The authors describe an electroless deposition method for thin films, based on the irradiation by an x-ray beam emitted by a synchrotron source. Specifically, NiP films were deposited at room temperature. This synthesis is a unique combination of photochemical and electrochemical processes. The influence of the pH value on the formation and structural properties of the films was examined by various characterization tools including scanning electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Real time monitoring of the deposition process by coherent x-ray microscopy reveals that the formation of hydrogen bubbles leads to a self-catalysis effect without a preexisting catalyst. The mechanisms underlying the deposition process are discussed in details.
ElectroCatalytic Activity of Nickel Foam with Co, Mo, and Ni Phosphide Nanostructures
Plasma
In this study, the electrocatalytic activity of nickel foam, which is activated by cobalt, molybdenum, and nickel phosphide nanostructures, is prepared by the plasma hydrothermal method for use in the release of hydrogen and oxygen. The morphology and crystallographic structure of the synthesized phosphide specimens were examined by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Moreover, the electrolysis activity for these sets of specimens was investigated using the Tafel polarization curve or linear sweep voltammetry, cyclic voltammetry, as well as by means of the electrochemical impedance spectroscopy technique. Preliminary results show that nickel phosphide presents the highest electrocatalytic activity than the other phosphides developed in this research. In this regard, it presents an electrocatalytic activity to release hydrogen and oxygen of around −1.7 and 0.82 mV, which is measured at a current density of 100 mA·cm−2...