Iron Phosphide Research Articles

Achieving high-capacity and durable sodium storage by constructing a binder-free nanotube array architecture of iron phosphide/carbon

The conversion-type anode material of iron phosphide (FeP) promises enormous prospects for Na-ion battery technology due to its high theoretical capacity and cost-effectiveness. However, the poor reaction kinetics and large volume expansion of FeP significantly degrade the sodium storage, which remains a daunting challenge. Herein, we demonstrate a binder-free nanotube array architecture constructed by FeP@C hybrid on carbon cloth as advanced anodes to achieve fast and stable sodium storage. The nanotubular structure functions in multiple roles of providing short electron/ion transport distances, smooth electrolyte diffusion channels, and abundant active sites. The carbon layer could not only pave high-speed pathways for electron conductance but also cushion the volume change of FeP. Benefiting from these structural virtues, the FeP@C anode receives a high reversible capacity of 881.7 mAh/g at 0.1 A/g, along with a high initial Coulombic efficiency of 90% and excellent rate capability and cyclability in half and full cells. Moreover, the sodium energy reaction kinetics and mechanism of FeP@C are systematically studied. The present work offers a rational design and construction of high-capacity anode materials for high-energy–density Na-ion batteries.

Iron phosphide nanoparticles anchored on N-doped carbon as efficient electrocatalysts for nitrate reduction reaction

Electrochemical transformation nitrate to ammonia at ambient conditions is a green alternative approach to the conventional Haber-Bosch process, while suffering from a restricted ammonia yield rate owing to the multi-step electron and proton transfer. Herein, we reported a quintessential bubble-like iron phosphides nanoparticles anchored on N-doped carbon framework (FeP@NC) electrocatalyst for nitrate reduction reaction (NO3RR). The FeP@NC catalyst exhibits 93.12 % NH3 faradaic efficiency (FE) at −0.5 V with the yield rate of 626.07 mmol h−1 gcat−1, superior over these for Fe@NC. DFT calculations indicate that the phosphorization promotes the absorption of NO3− and following hydrogenation, beneficial for NO3RR. This study provides a reference of transition metal phosphides for efficient NO3− removal and conversion.

Comparative study on prussian blue analogue derived iron nickel oxide, sulfide and phosphide as electrode materials for supercapacitors

Over the past decades, although metal oxides, sulfides and phosphides have developed as materials for supercapacitors (SCs), their SCs` performance should be deeply studied. In this work, FeNi-Prussian blue analogue (FeNi-PBA) was prepared via a simple co-precipitation method and served as a sacrificial template to prepare iron nickel oxide (NiFe2O4), sulfides (FeS/NiS2) and phosphides (Fe2P/Ni2P), whose capabilities for SCs were compared, respectively. The electrochemical results confirmed that the specific capacitance of FeS/NiS2 was 490.6 F g−1 much higher than those of NiFe2O4 (86 F g−1) and Fe2P/Ni2P (174.6 F g−1) at the current density of 1 A g−1. Therefore, the FeNiSx delivered the best electrochemical properties among them, because FeS/NiS2 composed by FeS/NiS2 heterostructure with sulfur vacancies provided an intimate/compact interfacial arrangement which better synergized the polyatomic conductivity and a large number of redox-active sites to bring about excellent electrochemical performance. Furthermore, FeS/NiS2 and activated carbon (AC) were employed to fabricate an asymmetric supercapacitor (ASC), which achieved the energy density of 54.34 Wh·kg−1 and the power density of 1349.13 W·kg−1, and could power a commercial light-emitting diode light. Among FeNiOx, FeS/NiS2 and Fe2P/Ni2P, FeS/NiS2 can be a potential electrode material for SCs attributing to its heterostructure and sulfur vacancies favourable for multi-atom conductivity and numerous redox-active sites. This work evidences that metal sulfides deliver the superior SCs` performance than the corresponding metal oxides and phosphides.

Decoupling the Kinetic Essence of Iron‐Based Anodes through Anionic Modulation for Rational Potassium‐Ion Battery Design

AbstractPotassium‐ion batteries (PIBs) have favorable characteristics in terms of cell voltage and cost efficiency, making them a promising technology for grid‐scale energy storage. The rational design of suitable electrode materials on a theoretical basis, aiming at high power and energy density, is of paramount importance to bring this battery technology to the practical market. In this paper, a series of iron‐based compounds with different non‐metal anions are selectively synthesized to investigate the nature of kinetic differences induced by anionic modulation. A combination of experimental characterization and theoretical calculation reveals that iron phosphide, with its moderate adsorption energy (Ea) and lowest diffusion barrier (Eb), exhibits the best cycling and rate properties at low electrochemical polarization, which is related to the narrow Δd‐p band center gap that facilitates ion transfer. In addition, the optimization of the electrolyte formula results in the carbon‐supported iron phosphide anode running stably over 2000 cycles at 0.5 A g−1 and exhibiting a high rate capacity of 81.1 mAh g−1 at 2 A g−1. The superior electrochemical properties are attributed to the robust KF‐rich solid electrolyte interphase formed by the highly compatible KFSI in ethylene carbonate (EC)/diethyl carbonate (DEC) configuration.

Zinc-rich polyester powder coatings with iron phosphide: Lower zinc content and higher corrosion resistance

Zinc-rich polyester powder coatings with iron phosphide: Lower zinc content and higher corrosion resistance

Enhancing Properties with Distortion: A Comparative Study of Two Iron Phosphide Fe2P Polymorphs

Enhancing Properties with Distortion: A Comparative Study of Two Iron Phosphide Fe₂P Polymorphs

Self-supported iron-based bimetallic phosphide catalytic electrode for efficient hydrogen evolution reaction at high current density

Cheap Fe foam (IF) was entirely transformed to the robust and high output CoFe-P NAs/IF electrode via facile soaking-phosphorization approach. The as-prepared CoFe-P NAs/IF exhibits remarkable HER activity and stability under industrial conditions.

Air-stable iron phosphide catalysts for electric field-assisted low-temperature ammonia synthesis

Catalytic reactions in an electric field for ammonia synthesis.

High-capacity all-solid-state Li-ion battery using MOF-derived carbon-encapsulated iron phosphide as anode material

Iron Phosphide (Fe2P) particles embedded within in-situ generated tubular carbon structures uniformly doped with nitrogen heteroatoms (Fe2P @ NC) have been investigated as an anode in all-solid-state lithium-ion batteries (ASSLIBs). The designed morphology offered a number of suitable features, such as high conductivity, robust framework, and abundant redox active sites for augmenting overall battery performance. As anode, Fe2P @ NC has provided a high lithiation/delithiation capacity of 1214.8 mA h/g /1367.01 mA h/g at a current density of 66.6 mA/g (100 μA) with a high coulombic efficiency (>100%). Further, Fe2P @ NC also demonstrated an excellent rate performance and moderate structural stability during cycling. The charge storing mechanism for Fe2P @ NC investigated via ex-situ X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) studies indicates irreversible conversion of Fe2P → Li3P & Fe in the initial cycle and reversible Li3P ↔ LiP reaction in subsequent cycles. Analysis of reaction kinetics for Fe2P @ NC nanocomposite is carried out using CV measurements at different scan rates. This study explores the possibility of MOF-derived iron-phosphide-based composite material as a high-performance anode for ASSLIBs.

(Invited) Tuning the Activity of Iron Phosphide Electrocatalysts for Sustainable Energy Conversion

Electrocatalysis is a promising approach for the sustainable conversion of renewable energy sources, such as solar and wind power, into chemical energy that can be stored and used on demand. By harnessing renewable electricity to drive electrochemical reactions, we can produce fuels and chemicals in a way that is both clean and cost-effective. As we continue to develop new electrocatalytic materials and improve the efficiency of existing processes, the potential for electrocatalysis to transform our energy system will only continue to grow.We report the use of iron phosphide (Fe2P, FeP) in several electrocatalytic applications, such as reduction of nitrate ions (NO3), hydrogen and oxygen evolution studies. The electrochemical reduction of the nitrate ion (NO3), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach to achieving green energy conservation. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product using a bi-potentiostat was achieved by electrooxidation of NH3 to nitrogen (N2) on a Pt electrode. The Fe2P catalyst exhibits the highest Faradaic efficiency (96%) for NH3 generation with a yield (0.25 mmol h−1 cm-−2 or 2.10 mg h−1 cm−2) at −0.55 V vs. reversible hydrogen electrode (RHE). To get relevant information about the reaction mechanisms and the fundamental origins behind the better performance of Fe2P, density functional theory (DFT) calculations were performed.In addition to NH3 synthesis, the iron phosphide catalyst was used in electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) studies. To enhance the catalytic activities of the obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Heat-treatment at 500°C under a reductive atmosphere induced structural changes in the samples: (i) Fe2P yielded a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M H2SO4. The lowest HER electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with a Fe2P/FeP−500°C catalyst. The intrinsic activity of FeP catalysts was also tuned and studied for OER.

Heteroatom-Doped Carbon-Shelled Iron Phosphide Microcuboids as Freestanding Negative Electrodes for Long Cycling Sodium-Ion Batteries

Energy storage devices (ESDs) have become indispensable for maximum renewable energy penetration and progress towards the elimination of fossil fuels in electricity generation. Also, high-performance ESDs are urgently needed for wearable and flexible devices, electric vehicles, and internet of things (IOT) applications. Lithium-ion batteries (LIBs) presently occupy the largest share of the EES market, however the cost-per watt stored is too high and the finite supply of Li means that they cannot offer a long-term solution to the world’s energy challenge. On the other hand, sodium-ion batteries (SIBs) are regarded as complementary ESDs and potential replacements for LIBs due to their relatively lower cost, abundance, and uniform global distribution of Na.[1] Furthermore, SIBs can operate in a wide temperature range and inert with Al, benefiting the construction of low cost and safe ESDs. Nonetheless, the performance of SIBs is limited by sluggish diffusion of Na+ in Na-insertion materials owing to large size of Na+ (1.02 Å).[2]The major challenge to developing SIBs is the lack of suitable electrode materials capable of efficiently accommodating Na+. SIBs are rocking-chair cells like LIBs, however, Na-ion storage in traditional graphite is extremely poor (< 35 mAh g-1) due to insufficient interlayer spacing.[3] Phosphorous presents the highest theoretical capacity (2596 mAh g-1) for a SIB anode, however, it suffers from poor cycling and large volume expansion (490 %) during sodiation/desodiation.[4,5] Low cost and environmentally benign iron phosphides present slightly better volume expansion and a theoretical capacity of 926 mAh g-1, but its charge storage mechanism is unclear.[6] The lack of suitable SIB anode with high capacity and long cycle life remains a major hurdle to the full-scale development of SIBs.In this work, we synthesized core-shell FeP microcuboids on freestanding carbon cloths substrate as a high capacity (< 800 mAh g-1), long-cycling anode for SIBs. The synthesized FeP microcuboids exhibit distinct physical and morphological features for efficient sodium-ion storage. It possesses a porous core within a 10 nm carbon shell, which enhances the surface area, enable fast Na+ diffusion and buffers the FeP anode against large volume variations during cycling. The integration of different heteroatoms including fluorine and nitrogen successfully improved the electronic conductivity and structural stability. Finally, using techniques such as in-situ X-ray diffraction analysis and ex-situ TEM and electroanalytical methods, we probed the conversion reaction storage mechanism and uncovered a pseudocapacitive dominated storage process. Finally, our work provides crucial insights on the rational design of high-performing metal-based phosphide anodes for alternative-ion batteries.

Carbon dots enhanced interfacial electron storage and transfer of iron phosphide for productively photocatalytic water splitting

Iron phosphide (FeP), as a low-cost and high-performance phosphide, not only has good stability but also possesses broad optical absorption, which can be used as a visible light or even near-infrared photocatalyst. However, their limited photocatalytic performance arises from the rapid charge recombination and a scarcity of active sites. Here, FeP was modified by introducing carbon dots (CDs), and the photocatalytic performance for H2 production of CDs/FeP reached 33.85 μmol/h/g, which improved significantly compared to that of the pristine FeP (6.65 μmol/h/g). The catalytic reaction goes through a 4-electron passway, which generates O2 and H2 simultaneously. CDs can not merely accelerate the interfacial charge delivery rate, but also can rapidly store photogenerated electrons, reducing the recombination of electrons and holes to improve the photocatalytic performance of FeP. This work provides a new perspective on enhancing the photocatalytic water activity of phosphides by improving electron transfer at the phosphide interface.

Zinc-rich polyester powder coatings with iron Phosphide: Lower zinc content and higher corrosion resistance

Many conductive fillers such as carbon black, carbon nanotube and graphene, have been developed to reduce zinc content for zinc-rich coatings, but very few of them could reduce zinc content by 10 % while maintaining the original corrosion protection ability. The carbon-based conductive additives have the issue of corrosion promotion after cathodic protection. In this study, low-cost iron based conductive additive, iron phosphide was used to reduce zinc content in environmentally friendly zinc-rich polyester powder coatings. We investigated the anti-corrosive performance of the prepared coatings by open circuit potential, electrochemical impedance spectroscopy measurements and neutral salt spray tests. The corrosion products were analyzed with Raman spectroscopy, X-ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. It was found that iron phosphide, due to its conductive nature, inert chemistry, activation function and barrier effect of the lamellar shape, can establish cathodic protection at a low zinc content of 45 wt% with an active protection period of 20 days. It can replace 10 wt% of zinc in 75 wt% zinc-rich polyester powder coatings while maintaining the original cathodic protection ability, as long as 86 days for a 40 μm film. In addition, iron phosphide can significantly inhibit localized corrosion and decrease corrosion creepage by about 20 % during 2500 h salt spray tests. Moreover, a possible corrosion protection mechanism for iron phosphide in zinc-rich polyester coatings was proposed.

Concurrent electrocatalytic hydrogen evolution and polyethylene terephthalate plastics reforming by self-supported amorphous cobalt iron phosphide electrode

The electrocatalytic hydrogen evolution reaction (HER) coupled with oxidative transformation of plastics into commodity chemical is a promising tactic to relieve the energy shortage and white pollution problems via sustainable and profitable manner, which necessitates highly active bifunctional catalytic electrode and meticulous construction of electrolysis system. Herein, a self-supported amorphous cobalt iron phosphide onto nickel foam (NF) substrate, labeled as CoFe-P/NF, was prepared by electrodeposition, which served as bifunctional catalytic electrode for alkali hydrogen evolution reaction (HER) and selective electrooxidation of polyethylene terephthalate (PET) plastic hydrolysate toward formate. Benefiting from the abundant catalytic sites within amorphous structure, the interelement synergy and sufficient exposure of catalyst to electrolyte, the self-supported CoFe-P/NF electrode displayed low overpotential (η100 of 168 mV at current density of J = 100 mA cm−2), decent stability for HER and fine tolerance to PET monomers. The CoFe-P/NF electrode could also catalyze selective electrooxidation of ethylene glycol (EG) component in PET hydrolysate to formate with high productivity (0.1 mmol cm-2h−1) and faradaic efficiency (FE, 90 %) at 1.5 V. The PET hydrolysate electrolysis system based on CoFe-P/NF enabled coproduction of H2 and value added formate at lower voltage (1.52 V at J = 20 mA cm−2) and energy consumption (84 % at J = 200 mA cm−2) relative to water electrolysis. This work showcases the coproduction of H2 fuel and formate by electrolysis of PET hydrolysate via rational design of bifunctional catalytic electrode. We believe such type of versatile catalytic electrodes can find application scenarios in electrosynthesis of more commodity chemicals and energy devices beyond the case herein.

Formation of Iron Phosphide Nanobundles from an Iron Oxyhydroxide Precursor.

Iron phosphide (FeP) nanoparticles have excellent properties such as fast charge transfer kinetics, high electrical conductivity, and high stability, making them a promising catalyst for hydrogen evolution reaction (HER). A challenge to the wide use of iron phosphide nanomaterials for this application is the available synthesis protocols that limit control over the resulting crystalline phase of the product. In this study, we report a method for synthesizing FeP through a solution-based process. Here, we use iron oxyhydroxide (β-FeOOH) as a cost-effective, environmentally friendly, and air-stable source of iron, along with tri-n-octylphosphine (TOP) as the phosphorus source and solvent. FeP is formed in a nanobundle morphology in the solution phase reaction at a temperature of 320 °C. The materials were characterized by pXRD and transmission electron microscopy (TEM). The optimization parameters evaluated to produce the phosphorus-rich FeP phase included the reaction rate, time, amount of TOP, and reaction temperature. Mixtures of Fe2P and FeP phases were obtained at shorter reaction times and slow heating rates (4.5 °C /min), while longer reaction times and faster heating rates (18.8 °C/min) favored the formation of phosphorus-rich FeP. Overall, the reaction lever that consistently yielded FeP as the predominant crystalline phase was a fast heat rate.

In-situ rooting biconical-nanorods-like Co-doped FeP @carbon architectures toward enhanced lithium storage performance

With desirable high capacity, theoretical work voltage and abundant resources, iron phosphide (FeP) has been garnered much consideration as a hopeful anode material for lithium-ion batteries (LIBs). Nevertheless, structural stability and low electronic conductivity restrict its application. Herein, metal organic frameworks (MOFs)-derived biconical-nanorods-like Co-doped FeP confined by phosphorus-doped carbon (Co-doped FeP@P-C) is successfully prepared. The unique biconical-nanorods-like structure, MOFs in-situ derived carbon coating and Co-doping can accelerate the ion and electron transport efficiency, supply abundant reaction active sites and moderate the volume expansion of FeP material. Benefiting from these merits, the as-prepared Co-doped FeP@P-C anode manifests a high Li+ storage capacity (784 mAh/g at 0.2 A g−1) and long-term stability (555.6 mAh/g at 1 A g−1 after 700 cycles). The experimental studies coupled with density functional theory (DFT) theoretical calculations uncover the effect of Co-doping on boosting charge transfer and enriching the reaction active sites in FeP@P-C anode. Furthermore, the electrochemical kinetic analysis revealed the underlying mechanism of lithium storage in detail, ex-situ X-ray diffraction and X-ray photoelectron spectroscopy analysis. LiCoO2//Co-doped FeP@P-C full-cells are successfully assembled and exhibit relatively high reversible capacity. The present work can provide a rational design and promising cation doping strategy for other metal phosphide anode materials for LIBs.

Efficient electrochemical nitrogen fixation at iron phosphide (Fe2P) catalyst in alkaline medium

A catalytic system based on iron phosphide (Fe2P) has exhibited electrocatalytic activity toward N2-reduction reaction in alkaline medium (0.5 mol dm−3 NaOH). Based on voltammetric stripping-type electroanalytical measurements, Raman spectroscopic and spectrophotometric data, it can be stated that the Fe2P catalyst facilitates conversion of N2 to NH3, and the process is fairly selective with respect to the competing hydrogen evolution. A series of diagnostic electrocatalytic experiments (utilizing platinum nanoparticles and HKUST-1) have been proposed and performed to control purity of nitrogen gas and to probe presence of potential contaminants such as ammonia, nitrogen oxo-species and oxygen. On the whole, the results are consistent with the view that the interfacial reduced-iron (Fe0) centers, while existing within the network of P sites, induce activation and reduction of nitrogen, parallel to the water splitting (reduction) to hydrogen. It is apparent from Tafel plots and impedance measurements that mechanism and dynamics of nitrogen reduction depends on the applied electroreduction potential. The catalytic system exhibits certain tolerance with respect to the competitive hydrogen evolution and gives (during electrolysis at -0.4 V vs. RHE) the Faradaic efficiency, namely, the selectivity (molar) efficiency, toward production of NH3 on the level of 60%. Under such conditions, the NH3-yield rate has been found to be equal to 7.5 µmol cm−2 h−1 (21 µmol m−2 s−1). By referring to classic concepts of electrochemical kinetic analysis, the rate constant in heterogeneous units has been found to be on the moderate level of 1-2*10−4 cm s−1 (at -0.4 V). The above mentioned iron-phosphorous active sites, which are generated on surfaces of Fe2P particles, have also been demonstrated to exhibit strong catalytic properties during reductions of other electrochemically inert reactants, such as oxygen, nitrites and nitrates.

High-mass-loading cobalt iron phosphide@nickel vanadium layered double hydroxide heterogeneous nanosheet arrays for hybrid supercapacitors

Designing multidimensional heterostructures on flexible substrates is an efficient approach to resolve the low energy density of supercapacitors. Herein, a three-dimensional (3D) porous cobalt iron phosphide (CoFeP)@nickel vanadium-layered double hydroxide (NiV-LDH) heterostructure has been prepared anchored on carbon cloth (CC) substrate. In this nanoarchitecture, NiV-LDH nanosheets are densely wrapped on the surface of CoFeP nanosheets, which forms a hierarchically porous framework with an enlarged surface area and accessible pore channels. Benefiting from the strong interaction and synergistic effect between CoFeP and NiV-LDH, the well-defined heterostructure can realize simultaneously rich redox active sites, rapid reaction dynamics, and good structural stability. Thus, the binder-free CoFeP@NiV-LDH electrode with a high mass loading of 6.47 mg cm−2 displays a significantly increased specific capacity of 903.1C g−1 (2.35C cm−2) at 1 A g−1 and enhanced rate capability when compared to pristine CoFeP and NiV-LDH. Additionally, the assembled hybrid supercapacitor (HSC) yields an energy density of 77.9 Wh kg−1/0.98 Wh cm−2 and excellent long-term stability. This research proposes a rational route for designing heterogeneous micro-/nanoarchitectures with commercial-level mass loading for the practical application of high-energy-density supercapacitors.

Iron phosphide nanocrystals as an air-stable heterogeneous catalyst for liquid-phase nitrile hydrogenation

Iron-based heterogeneous catalysts are ideal metal catalysts owing to their abundance and low-toxicity. However, conventional iron nanoparticle catalysts exhibit extremely low activity in liquid-phase reactions and lack air stability. Previous attempts to encapsulate iron nanoparticles in shell materials toward air stability improvement were offset by the low activity of the iron nanoparticles. To overcome the trade-off between activity and stability in conventional iron nanoparticle catalysts, we developed air-stable iron phosphide nanocrystal catalysts. The iron phosphide nanocrystal exhibits high activity for liquid-phase nitrile hydrogenation, whereas the conventional iron nanoparticles demonstrate no activity. Furthermore, the air stability of the iron phosphide nanocrystal allows facile immobilization on appropriate supports, wherein TiO2 enhances the activity. The resulting TiO2-supported iron phosphide nanocrystal successfully converts various nitriles to primary amines and demonstrates high reusability. The development of air-stable and active iron phosphide nanocrystal catalysts significantly expands the application scope of iron catalysts.

Enhancement of hydrogen evolution activity by tailoring the electronic structure in ruthenium-heteroatom-doped cobalt iron phosphide nanoframes

Designing cost-effective and highly efficient electrocatalysts for hydrogen evolution reaction (HER) in alkaline media at high current densities is challenging. In this study, we adopted Ru heteroatom doping and an open nanoframe structure to obtain excellent HER catalytic performance. X-ray photoelectron spectroscopy (XPS) visualized the electron transfer due to Ru heteroatom doping in transition metal phosphides, to observe the modulated electronic structure of the Ru-doped CoFeP nanoframe (RCFP/NF). Density functional theory (DFT) calculations and XPS analysis confirmed a d-band center downshift of the RCFP/NF, demonstrating the regulation of the optimal adsorbates (OH*/H*) adsorption free energies. Consequently, RCFP/NF with 4.7 wt % of Ru exhibits a low overpotential of 112 mV, 191 mV, and 219 mV at current densities of 10 mA cm−2, 100 mA cm−2, and 500 mA cm−2, respectively, and an excellent stability for 100 h at a high current density of 100 mA cm−2. This outstanding HER performance at high current density was attributed to the hydrophilic and aerophobic properties of the RCFP/NF catalyst surface that facilitate the exposure of active sites and H2 gas desorption.