Iron Nickel Phosphide Research Articles

Oxygen-Doped Nickel Iron Phosphide Nanocube Arrays Grown on Ni Foam for Oxygen Evolution Electrocatalysis.

A rationally designed oxygen evolution reaction (OER) catalyst with advanced structural and compositional superiority is highly desirable to optimize electrocatalytic performance. Prussian blue analogues (PBAs) with adjustable element compositions and accessible porous structures represent a promising precursor for the preparation of OER catalysts. Herein, oxygen-doped nickel iron phosphide nanocube arrays (Ni2 P/(NiFe)2 P(O) NAs) grown on Ni foam is rationally designed and fabricated from PBAs. The porous structure and the synergistic effect of Ni and Fe enable superior electrocatalytic performance and stability toward the OER in alkaline electrolytes. Density functional theory calculations reveal that Fe-incorporated Ni2 P can generate new active sites on the Fe atoms, and the energy barriers of the intermediates and products are decreased efficiently in the presence of surface doped oxygen, both processes are crucial factors for enhanced catalytic performances. In 1 m KOH, the Ni2 P/(NiFe)2 P(O) NAs afford current densities of 10 and 800 mA cm-2 at overpotentials of 150 and 530 mV, respectively, which outperform the commercial noble metal IrO2 . Ni2 P/(NiFe)2 P(O) NAs also have long-term stability over 100 h at a high current density. The present approach may provide a new avenue for the controlled assembly of nanoarrays for energy storage and conversion applications.

Fabrication of Core–Sheath NiCoP@FePx Nanoarrays for Efficient Electrocatalytic Hydrogen Evolution

Construction of effective, stable, eco-friendly, and earth-abundant electrocatalysts that substitute noble metals for hydrogen evolution reaction (HER) is essential for developing renewable and clean energy. Here we report a layer-by-layer assembly route to fabricate core–sheath structured nanoarrays composed of nickel cobalt phosphide and iron phosphide (NCP@FePx) on a conductive Ni wire by atomic layer deposition (ALD). The as-fabricated multimetallic phosphide exhibits high electrocatalytic activity in both alkaline and acidic media, with small overpotentials of 82.5 and 96 mV at 10 mA cm–2, respectively. The self-supported electrode displays superior long-term stability and favorable durability. The excellent activity is originated from the unique core–sheath structure, and the synergistic effects of the FePx sheath and the NCP core contributed to the enhanced activity. The present ALD-assisted layer-by-layer strategy may provide a general route for the controlled fabrication of nanostructured electro...

Ternary nickel iron phosphide supported on nickel foam as a high-efficiency electrocatalyst for overall water splitting

Electrochemical water splitting is a promising technology for mass hydrogen production. Efficient, stable, and cheap electrocatalysts are keys to realizing this strategy. However, high price and preciousness of commonly used noble metal based catalysts severely hinder this realization. Herein, we report nickel iron phosphide (Ni-FexP) bifunctional electrocatalyst via the in-situ growth of NiFe(OH)x on nickel foam (NiFe(OH)x/NF) followed by low-temperature phosphidation. As a hydrogen evolution reaction (HER) catalyst, the Ni-FexP/NF only needs an overpotential of 119 mV to drive a current density of −10 mA/cm2 in a base media. It also shows excellent activity toward oxygen evolution reaction (OER) with low overpotentials of 254 mV, 267 mV, and 282 mV at 50, 100 and 200 mA/cm2, respectively. Moreover, when this bifunctional catalyst is used for overall water splitting, a low cell voltage of 1.62 V is needed to deliver a current density of 10 mA/cm2, which is superior to commercial electrolyzer and it also shows remarkable stability.

An Infrared Spectroscopic Study Toward the Formation of Alkylphosphonic Acids and Their Precursors in Extraterrestrial Environments.

The only known phosphorus-containing organic compounds of extraterrestrial origin, alkylphosphonic acids, were discovered in the Murchison meteorite and have accelerated the hypothesis that reduced oxidation states of phosphorus were delivered to early Earth and served as a prebiotic source of phosphorus. While previous studies looking into the formation of these alkylphosphonic acids have focused on the iron-nickel phosphide mineral schreibersite and phosphorous acid as a source of phosphorus, this work utilizes phosphine (PH3), which has been discovered in the circumstellar envelope of IRC +10216, in the atmosphere of Jupiter and Saturn, and believed to be the phosphorus carrier in comet 67P/Churyumov-Gerasimenko. Phosphine ices prepared with interstellar molecules such as carbon dioxide, water, and methane were subjected to electron irradiation, which simulates the secondary electrons produced from galactic cosmic rays penetrating the ice, and probed using infrared spectroscopy to understand the possible formation of alkylphosphonic acids and their precursors on interstellar icy grains that could become incorporated into meteorites such as Murchison. We present the first study and results on the possible synthesis of alkylphosphonic acids produced from phosphine-mixed ices under interstellar conditions. All functional groups of alkylphosphonic acids were detected through infrared spectroscopically, suggesting that this class of molecules can be formed in interstellar ices.

Self-supported ternary Ni-Fe-P nanosheets derived from metal-organic frameworks as efficient overall water splitting electrocatalysts

Developing cost-effective, highly-efficient and stable electrocatalysts is of significance to replace noble metal based materials for overall water electrolysis. In this paper, nickel-iron phosphide nanosheets on nickel foam (Ni-Fe-P/NF) were synthesized through in-situ chemical etching and subsequently phosphating treatment. The Ni foam utilized in this work not only serves as conductive substrate and metal current collector, but also as nickel source for the growth of metal organic frameworks (i.e. Prussian blue analogue pyramids), which were then converted to Ni-Fe-P nanosheets via phosphating. Benefiting from the unique nanostructure, Fe incorporation, and the high conductivity of nickel foam, the resulting Ni-Fe-P/NF could be used as self-supported and binder-free working electrode with superior overall electrochemical water splitting performance. Electrochemical measurement demonstrates that the Ni-Fe-P/NF exhibits excellent electrocatalytic activities with overpotentials of 98 mV for HER and 168 mV for OER to deliver current densities of 10 mA cm−2 in 1 M KOH solution. Furthermore, the Ni-Fe-P/NF catalyst was also employed as both as anode and cathode for overall water electrolysis, and shows extraordinary activities with low voltage of only 1.486 V to yield 10 mA cm−2 and outstanding cycling stability with negligible voltage elevation after chronopotentiometry determination for 200 h. This work highlights that direct growth of metal organic frameworks on conductive substrates is an effective method to explore electrocatalysts for multifunctional electrochemical applications.

Explore the properties and photocatalytic performance of iron-doped g-C3N4 nanosheets decorated with Ni2P

The splitting of water into hydrogen is a promising and sustainable approach for solar-to-chemical energy conversion process. To replace the role of noble-metal co-catalysts, earth-abundant and environmentally friendly materials nickel phosphide was introduced into hydrogen evolution system. In this work, a highly efficient and robust heterogeneous photocatalytic hydrogen evolution system was established for the first time by using In situ phosphating nickel ions on the iron-doped graphite carbon nitride. Among all the photocatalysts employed, the 5wt% Ni2P/0.5-Fe3+ doped g-C3N4 nanosheets (weight ratio) composite shows the highest H2 evolution rate of 397μmolh−1g−1 under visible light irradiation, which is 71 times higher than that of bulk g-C3N4. The photocatalyst also shows excellent stability with a hydrogen evolution rate of 1891μmolh−1g−1 for the first 5h under visible light irradiation. Based on detailed analyses of characterizations, the enhanced photocatalytic performance can be directly ascribed to the presence of Ni2P co-catalyst, which could promote the charge transfer both in the photocatalyst and photocatalyst/solution interface. Meanwhile, the synergistic effect of the iron ion and nickel phosphide has good absorption ability of visible light and can reduce the recombination of electrons and holes within the catalyst. This work may provide a novel co-catalyst for the rational design of g-C3N4-based photocatalyst.

Partial-sacrificial-template Synthesis of Fe/Ni Phosphides on Ni Foam: a Strongly Stabilized and Efficient Catalyst for Electrochemical Water Splitting

Electrochemical water splitting is considered to be one of the most promising strategies for clean and efficient hydrogen production. In this paper, an in-situ growth of iron-nickel phosphide on nickel foam (FeNiPx/NF) is demonstrated as a self-supported ternary catalyst for electrochemical water splitting. The FeNiPx/NF were prepared by a thermo-reaction between NaH2PO2 and NiFe hydroxide precursors that are in situ grown on Ni foam via a simple chemical precipitation reaction. In this newly proposed method, the nickel foam not only acts as an electrode substrate, but also serves as a slow-release Ni source in the reaction due to its oxidation by Fe3+ in solution. Benefiting from collaborative advantages of bimetallic composite, metallic phosphide, and unique electrode fabrication, the FeNiPx/NF exhibits extraordinarily high activities for both OER and HER with low overpotentials of of 192 and 106mV at 10mAcm−2, 236 and 161mV at 100mAcm−2, respectively. The voltage during the galvanostatic electrolysis is well maintained for almost 400h without any visible elevation, representing the few most stable noble-metal-free catalysts for water splitting.

Scalable Two-Step Synthesis of Nickel–Iron Phosphide Electrodes for Stable and Efficient Electrocatalytic Hydrogen Evolution

The development of efficient, durable, and inexpensive hydrogen evolution electrodes remains a key challenge for realizing a sustainable H2 fuel production via electrocatalytic water splitting. Herein, nickel–iron phosphide porous films with precisely controlled metal content were synthesized on Ti foil using a simple and scalable two-step strategy of spray-pyrolysis deposition followed by low-temperature phosphidation. The nickel–iron phosphide of an optimized Ni:Fe ratio of 1:4 demonstrated excellent overall catalytic activity for hydrogen evolution reaction (HER) in 0.5 M H2SO4, achieving current densities of −10 and −30 mA cm–2 at overpotentials of 101 and 123 mV, respectively, with a Tafel slope of 43 mV dec–1. Detailed analysis obtained by X-ray diffraction, electron microscopy, electrochemistry, and X-ray photoelectron spectroscopy revealed that the superior overall HER activity of nickel–iron phosphide as compared to nickel phosphide and iron phosphide was a combined effect of differences in the morphology (real surface area) and the intrinsic catalytic properties (electronic structure). Together with a long-term stability and a near-100% Faradaic efficiency, the nickel–iron phosphide electrodes produced in this study provide blueprints for large-scale H2 production.

Earth's Phosphides in Levant and insights into the source of Archean prebiotic phosphorus.

Natural phosphides - the minerals containing phosphorus in a redox state lower than zero – are common constituents of meteorites but virtually unknown on the Earth. Herein we present the first rich occurrence of iron-nickel phosphides of terrestrial origin. Phosphide-bearing rocks are exposed in three localities in the surroundings of the Dead Sea, Levant: in the northern Negev Desert, Israel and Transjordan Plateau, south of Amman, Jordan. Seven minerals from the ternary Fe-Ni-P system have been identified with five of them, NiP2, Ni5P4, Ni2P, FeP and FeP2, previously unknown in nature. The results of the present study could provide a new insight on the terrestrial origin of natural phosphides – the most likely source of reactive prebiotic phosphorus at the times of the early Earth.

Mineralogy texture and chemistry of the Ellicott meteorite using scanning electron microscope and energy disperse spectroscopy (SEM/EDS)

Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and Raman spectroscopy have been used to determine the chemistry and mineral components of Ellicott meteorite. Mineral phases and interstitial matrix in the meteorite slab were detected using backscattered electron mode (BSE) and scanning electron microprobe (SEM) and were assessed from atomic proportions of constituent elements, obtained by the EDS analysis. SEM/EDS and Raman shift analyses of mineral phases showed that Ellicott meteorite is characterized by the predominance of Fe-rich (Fe, Ni) alloy kamacite and Ni-Co-rich magnetite. The Iron-nickel phosphide minerals that are called schreibersite and rhabdites along with rare gold have been detected within the kamacite groundmass of meteorite. The presence of Neumann lines, which appear as fine parallel lines running in (up to) four directions, indicates impact with another body. These lines are caused by twinning due to the postconsolidation compression. The chemistry, particularly the lesser content of Ni and texture of unusual abundance ribbons of the iron-phosphide rhabdites and schreibersite where the Widmanstatten texture disappears after the etching by nitric acid, suggests that the Ellicott meteorite is an iron meteorite, hexahedrite type, IIG group.

Evidence for reactive reduced phosphorus species in the early Archean ocean

It has been hypothesized that before the emergence of modern DNA-RNA-protein life, biology evolved from an "RNA world." However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive. Recently, it has been proposed that during the Hadean-Archean heavy bombardment by extraterrestrial impactors, meteorites would have provided reactive P in the form of the iron-nickel phosphide mineral schreibersite. This reacts in water, releasing soluble and reactive reduced P species, such as phosphite, that could then be readily incorporated into prebiotic molecules. Here, we report the occurrence of phosphite in early Archean marine carbonates at levels indicating that this was an abundant dissolved species in the ocean before 3.5 Ga. Additionally, we show that schreibersite readily reacts with an aqueous solution of glycerol to generate phosphite and the membrane biomolecule glycerol-phosphate under mild thermal conditions, with this synthesis using a mineral source of P. Phosphite derived from schreibersite was, hence, a plausible reagent in the prebiotic synthesis of phosphorylated biomolecules and was also present on the early Earth in quantities large enough to have affected the redox state of P in the ocean. Phosphorylated biomolecules like RNA may, thus, have first formed from the reaction of reduced P species with the prebiotic organic milieu on the early Earth.

Mössbauer spectroscopy with a high velocity resolution applied for the study of meteoritic iron-bearing minerals

Mössbauer spectroscopy with a high velocity resolution was applied for study of iron-bearing minerals in different meteorites. The possibility of technique to reveal small variations in Mössbauer hyperfine parameters of the 57Fe in the non-equivalent M1 and M2 sites in olivines from Farmington L5 and Tsarev L5 ordinary chondrites and from Omolon and Seymchan pallasites was demonstrated. The necessity of accounting for the Fe and Ni occupation probabilities in the local microenvironments for non-equivalent sites M1, M2 and M3 in schreibersite, an iron nickel phosphide from Sikhote-Alin iron meteorite, in the fit of its Mössbauer spectra was shown. Variations in Mössbauer parameters of metal samples from visually different areas at the saw-cut surface of Chinga iron meteorite fragment with unknown origin were observed; these variations may be related to different metal phase composition and local variations of Ni concentration in the metal phases in these areas.

Ligand and Ensemble Effects in Bimetallic NiFe Phosphide Catalysts for the Hydrodeoxygenation of 2-Methyltetrahydrofuran

A series of supported nickel–iron phosphide catalysts were used to study the hydrodeoxygenation (HDO) of 2-methyltetrahydrofuran (2-MTHF), a model compound for biomass-derived pyrolysis oil. The catalysts were prepared by incipient wetness impregnation of the active components onto potassium ion-exchanged USY zeolites followed by temperature-programmed reduction. The samples were denoted as Ni2P/KUSY, NiFeP(3:1)/KUSY, NiFeP(1:1)/KUSY, NiFeP(1:3)/KUSY, and FeP/KUSY, where the numbers in parenthesis are the Ni:Fe molar ratios. The results of the studies can be understood from ensemble and ligand effects. X-ray diffraction analysis indicated the presence of alloys in the mixed composition samples, and this was supported by CO chemisorption and infrared measurements. Uptakes of CO decreased as the iron content increased, suggesting that iron present on the surface of the catalysts blocked chemisorption sites. Fourier transform infrared (FTIR) measurements showed a single peak for linearly adsorbed CO whose intensity decreased with Fe content, in agreement with the uptake results. Moreover, the FTIR peak shifted monotonically consistent with a ligand effect in an alloy formed in the Ni2P and FeP particles. The reactivity in 2-MTHF HDO was studied at 250–325 °C and 0.5 MPa and it was found that the conversion was highest for the Ni2P/KUSY sample and decreased steadily with Fe content. However, the turnover frequency did not change significantly, indicating that the rate-determing step was activation of 2-MTHF on single Ni sites. The selectivity at low conversion (3 %) changed from mostly n-pentane and n-butane for Ni2P/KUSY to mostly 1-pentanol for the iron-containing samples, suggesting that in subsequent steps an ensemble effect was operational with the iron influencing the reaction chemistry. At high conversion (70 %) all the samples produced mostly n-pentane and n-butane.

Controlled synthesis and magnetic properties of nickel phosphide and bimetallic iron–nickel phosphide nanorods

Nickel phosphide (Ni2P) and bimetallic iron–nickel phosphides [(Fe x Ni y )2P] nanorods were fabricated by a seeded growth strategy. This strategy utilized pre-synthesized Fe3O4 nanoparticles as seeds and the thermal decomposition of metal precursors by multiple injections in a solution containing trioctylphosphine and didodecyldimethylammonium bromide (DDAB). The nanorods were characterized by transmission electron microscopy, X-ray diffraction, and magnetic measurements were carried out using superconducting quantum interference device (SQUID). The rod length was tunable, ranging from 10 to 110 nm depending on the number of injections, whereas the diameter of the rods was nearly 6 nm. It was found that the rod size increased with the number of injections under the constant total injection concentration and reaction time. In addition, the effect of the DDAB quantity used as a co-surfactant was studied, which showed that an optimum quantity was required to achieve uniform nanorods. Magnetic characterizations were performed over the two kinds of nanorods to identify their respective magnetic phases. The results demonstrated that the Ni2P nanorods were defined as a Curie–Weiss paramagnet, whereas the (Fe x Ni y )2P nanorods exhibited superparamagnetic characteristics.

Elasticity and anisotropy of iron-nickel phosphides at high pressures

[1] Geochemical estimates indicate that around 90% of the planet's inventory of phosphorus is likely to be sequestered in the Earth's core. Iron phosphides such as scheirbisites (Fe3P) are commonly found in iron meteorites. Recently, melliniite (Fe,Ni)4P with 12.2 wt% phosphorus has been reported in iron-meteorites. Using static electronic structure calculations, we predict that Fe4P is unlikely to dissociate into Fe3P and hcp Fe at inner core conditions. Among the different structural varieties of Fe4P, we find the cubic polymorph with P213 space group symmetry to be stable over a wide range of geophysically relevant pressures. We have determined the equation of state and the full elastic constant tensor of the stable (Fe,Ni)4P phase at pressures up to 400 GPa. Upon compression, Fe4P undergoes a ferromagnetic (fm) to nonmagnetic (nm) transition at 80 GPa. In nonmagnetic (Fe,Ni)4P, nickel incorporation results in reduction of the P- and S-wave velocities. However, incorporation of nickel enhances the P- and S-wave anisotropy.

Study of rhabdite (iron nickel phosphide) microcrystals extracted from Sikhote–Alin iron meteorite by magnetization measurements and Mössbauer spectroscopy

Study of rhabdite (iron nickel phosphide) microcrystals extracted from Sikhote–Alin iron meteorite was made using scanning electron microscopy, X-ray diffraction, magnetic measurements and Mössbauer spectroscopy with a high velocity resolution at various temperatures. The Curie temperature for iron nickel phosphide microcrystals was evaluated in the range of 345–355 K. On the basis of Mössbauer data the temperature dependences of magnetic hyperfine fields for Fe atoms in the M1, M2 and M3 sites of rhabdite were shown as well as Fe and Ni occupancies of these sites were evaluated.

Temperature dependent high velocity resolution Mössbauer spectroscopic study of iron nickel phosphide microcrystals (rhabdites) extracted from Sikhote-Alin iron meteorite

Iron nickel phosphide microcrystals (rhabdites) extracted from Sikhote-Alin iron meteorite fragment were studied using Mössbauer spectroscopy with a high velocity resolution at various temperatures. Mössbauer spectra of rhabdites demonstrated superparamagnetic behavior. Low temperature rhabdite spectra were fitted using a model with six magnetic sextets two pairs of which were related to crystallographically non-equivalent sites M1, M2 and M3 occupied by Fe and Ni atoms in different ways. Temperature dependencies of correspondent magnetic hyperfine fields were evaluated. On the basis of relative areas of spectral components and results of rhabdite chemical analysis the average numbers of Fe and Ni atoms occupied the M1, M2 and M3 sites, respectively, were evaluated.

An analysis of Fe and Ni distribution in M1, M2 and M3 sites of iron–nickel phosphides extracted from Sikhote-Alin meteorite using Mössbauer spectroscopy with a high velocity resolution

Study of two iron–nickel phosphides crystals (rhabdite and schreibersite) extracted from Sikhote-Alin (IIAB) iron meteorite was performed using Mössbauer spectroscopy with a high velocity resolution at various temperatures. On the basis of Mössbauer data the temperature dependences of magnetic hyperfine fields for Fe atoms in the crystallographically non-equivalent M1, M2 and M3 sites of rhabdite were shown as well as Fe and Ni occupancies of these sites were evaluated for both phosphides.

Mössbauer spectroscopy investigation and hydrodesulfurization properties of iron–nickel phosphide catalysts

Unsupported and silica-supported Fe x Ni 2− x P y catalysts having a range of metal compositions (0 < x ⩽ 2.0) were investigated using Mössbauer spectroscopy, and the results correlated with the surface and hydrodesulfurization (HDS) properties of the supported catalysts. Mössbauer spectroscopy permits determination of the relative site occupancy of Fe atoms in tetrahedral (M(1)) and pyramidal (M(2)) sites in the Fe x Ni 2− x P y materials. Fe atoms preferentially occupy M(2) sites for materials with significant Fe contents ( x > ∼0.60), but the Fe site preference reverses as the Fe content decreases ( x < ∼0.60). Similar occupation trends are observed for the unsupported and silica-supported Fe x Ni 2− x P y materials. Thiophene HDS measurements of the Fe x Ni 2− x P y /SiO 2 catalysts revealed catalysts with high Fe contents (0.80 ⩽ x ⩽ 2.00) to have low activities, while the activities of Ni-rich catalysts increased dramatically with increased Ni content (0.03 ⩽ x ⩽ 0.60). The highest HDS activity was measured for a catalyst having a nominal precursor composition of Fe 0.03Ni 1.97P 2.00/SiO 2; this catalyst was 40% more active than a optimized nickel phosphide catalyst prepared from a precursor having a nominal composition of Ni 2.00P 1.60/SiO 2. The 25 wt.% Fe 0.03Ni 1.97P 2.00/SiO 2 catalyst also had a dibenzothiophene HDS activity just over 10% higher than that of the 25 wt.% Ni 2.00P 1.60/SiO 2 catalyst at 548 K. The trend of increasing HDS activity for the Fe x Ni 2− x P y /SiO 2 catalysts correlates with preferential Fe occupation of M(1) sites (and, therefore, Ni occupation of M(2) sites). Supported by X-ray photoelectron spectroscopy and oxygen chemisorption measurements, we conclude that the high activity of Ni-rich Fe x Ni 2− x P y /SiO 2 catalysts can be traced to a high surface density of Ni in M(2) sites that are resistant to site blockage due to S incorporation.

Mossbauer spectroscopy with high velocity resolution in the study of iron-bearing minerals in meteorites

Application of Mossbauer spectroscopy with a higher velocity resolution than commonly applied appeared to be useful for obtaining hyperfine parameters of 57 Fe nuclei with a lower experimental error and for a better fit of complicated spectra. The study of iron-bearing phases in ordinary and carbonaceous chondrites as well as iron meteorite and extracted iron-nickel phosphides by Mossbauer spectroscopy with an improved velocity resolution (measurement in 4096 channels, presentation in 1024 channels) demonstrated new results which had not been obtained from Mossbauer spectra measured in 512 channels or less. In particular, it was possible to reveal spectral components related to M1 and M2 sites in olivine and pyroxene in Mossbauer spectra of bulk samples of ordinary chondrites and then to evaluate the temperatures of equilibrium cation distribution. Moreover, differences in small variations of Mossbauer hyperfine parameters were obtained for 57 Fe in M1 and M2 sites for both olivine and pyroxene.