Iron Phosphide Research Articles

MoP assists the promotion on Fe2P and FeN4 for oxygen reduction and zinc-air battery

It is of great significance but remains challenging to simultaneously development cost-effective and efficient non-noble metal electrocatalysts (NNMEs) for oxygen reduction reaction (ORR) in both alkaline and acidic solutions. In current work, a multi-component synergism system is developed, which is comprised of molybdenum phosphide (MoP) shell onto iron phosphide clusters anchored on carbon matrixes that embedded with numerous FeN4 species (MoP/Fe2P-FeN4). The optimized MoP/Fe2P-FeN4 electrocatalyst delivers a synergistic enhancement in both alkaline and acidic ORR performances: E1/2: 0.885 V (0.1 M KOH electrolyte) and E1/2: 0.742 V (0.1 M HClO4 electrolyte). Furthermore, the equipped zinc-air batteries (ZABs) of MoP/Fe2P-FeN4 exhibit a power density of 140.6 mW cm−2@219.6 mA cm−2, which surpasses the corresponding Fe2P-FeN4 and commercial Pt/C catalyst. The computational calculations reveal that MoP/Fe2P-FeN4 shows a relative increase of d-band center closer to Fermin level than Fe2P-FeN4, tuning the rate-determining step to conversion of *O to *OOH intermediate, thus significant reducing the energy barrier and enhancing ORR activity. This strategy opens new opportunities to rational design of Fe-based nanocomposites for stimulated ORR and further ZAB activities.

Effective synergism of electrooxidation on persulfate activation with iron phosphide for the removal of phenol and arsenic: Performance and mechanism

Effective synergism of electrooxidation on persulfate activation with iron phosphide for the removal of phenol and arsenic: Performance and mechanism

Construction of magnetic FeP/CdS composites as photo‐Fenton‐like catalysts to realize high‐efficiency degradation of tetracycline hydrochloride

Photocatalysis is an efficient technology for the degradation of pollutants. However, it still needs to be improved. In this study, magnetic Z‐scheme FeP/CdS composites heterojunction photocatalysts were prepared by a facile hydrothermal method, and the structure, morphology, optical and photocatalytic properties of the prepared composites were investigated in detail. The efficiency of tetracycline hydrochloride (TCH) removal by FeP/CdS composites was investigated under different reaction conditions (including different FeP and CdS ratios, catalyst dosage, hydrogen peroxide consumption, temperature, and initial pH). FeP/CdS composites exhibited better catalytic performance compared with pure components. The F1Cd1 composite (mass ratio of FeP to CdS is 1:1) achieved 92.7% removal efficiency of TCH, moreover, the F1Cd1 composite still exhibits a high stability after five consecutive cycles. The capture experiments on the active material showed that the removal of TCH by the F1Cd1 composite was mainly dominated by •OH; however, •O2−, e‐, and h+ played a minor role, and the degradation mechanism was revealed by combining various characterization techniques. The introduction of cadmium sulfide formed an effective photogenerated carrier transport channel at the interface with the iron phosphide surface, which could accelerate the transfer and separation of photo‐excited e‐/h+ pairs, thus improving the degradation performance of TCH.

Iron phosphide nanoparticles anchored on 3D nitrogen-doped graphene as an efficient electrocatalysts for hydrogen evolution reaction in alkaline media

Electrocatalysts play a crucial role in hydrogen evolution reaction (HER), facilitating a clean and sustainable generation of hydrogen energy. To promote the HER process, it is imperative to employ highly efficient, stable, and cost-effective electrocatalysts. This research focuses on the design of iron phosphide nanoparticles anchored onto a porous three-dimensional nitrogen-doped graphene (FeP@3DNG). The porous framework of 3DNG serves a multifaceted purpose: it prevents the aggregation of FeP nanoparticles during phosphidation, safeguards the FeP electrocatalyst from oxidation during the HER, and simultaneously enhances electrical conductivity and stability. Notably, the FeP@3DNG nanocomposite demonstrated the efficient activity and highest HER activity with an overpotential of 76 mV to achieve 10 mA cm−2 and a small Tafel slope of 40.2 mV dec−1 as well as good long-term durability for 20 h in 1.0 M KOH solution. The high performance of the FeP@3DNG nanocomposite can be primarily corresponded to the synergistic effects of the highly active of FeP nanoparticles and advantages of porous three-dimensional graphene with excellent electrocatalytic activity, high specific surface area, and chemical stability, thus, resulting in the improvement the overall electrocatalytic activity.

Self-supporting trace Pt-decorated ternary metal phosphide as efficient bifunctional electrocatalyst for water splitting

Compared to monofunctional catalysts, the preparation of bifunctional materials with HER and OER activities holds greater significance for the separation of hydrogen from water electrolysis. In this study, we synthesized a self-supported bifunctional catalyst using ternary transition metal (Ni, Fe, Co) phosphide adorned with trace Pt for water splitting (P-Fe6Co3Ni/Pt/NF). As the main catalytic kernel toward HER, the Pt nanoparticles underwent uniform in situ reduction on the Ni foam, avoiding clustering due to the protective effect of iron and cobalt phosphides. This exposed more active sites, improving HER kinetics. In the OER process, the deposited Fe and Co were confirmed to play a pivotal role and will undergo oxidation to oxyhydroxides during structural reconstruction. In addition to enhancing conductivity, the Mott-Schottky test revealed that Pt can facilitate the formation of more active sites, leading to a lower potential for the OER reaction. Ultimately, P-Fe6Co3Ni/Pt/NF required only an overpotential of 32.8 mV in HER to reach the current density of 10 mA cm−2, demonstrating excellent OER activity with a low overpotential of 259.9 mV at current density of 20 mA cm−2. When employed as cathode and anode in water electrolysis, P-Fe6Co3Ni/Pt/NF necessitated only 1.6 V cell voltage to achieve the current density of 10 mA cm−2. This study provides a reference for designing other highly efficient Pt-based electrocatalyst, thereby promoting the widespread application of water electrolysis in hydrogen production.

Catalytic Deoxygenation of Palm Oil Over Iron Phosphide Supported on Nanoporous Carbon Derived from Vinasse Waste for Green Diesel Production.

The vinasse waste was effectively converted to nanoporous carbon (NPC) via hydrothermal carbonization with potassium hydroxide (KOH) activation. The nanoporous carbon (NPC) exhibited a maximum surface area of 1018 m2/g and it was utilized as a catalyst for the conversion of palm oil into green diesel fuel. The supported NPC catalyst was fabricated via a wet impregnation technique, where finely distributed iron phosphide (FeP) particles were cemented. The FeP/NPC catalyst was evaluated for its physicochemical characteristics using various techniques including X-ray diffraction (XRD), nitrogen sorption analyzer, transmission electron microscopy (TEM), and energy dispersive X-ray spectrometry (EDS) mapping. An investigation was conducted to examine the effects of different temperatures (ranging from 280 to 360 °C) on the conversion of palm oil through deoxygenation reactions. The FeP/NPC catalyst exhibited remarkable particle dispersion and surface area. At a reaction temperature of 340 °C, the FeP/NPC catalyst had the best selectivity for green diesel, reaching 68.5%. The finding implies that FeP catalysts, when supported, hold significant promise for converting triglycerides into renewable diesel fuel. Moreover, they provide the advantage of being more cost-effective than valuable metals, while demonstrating excellent catalytic efficiency in the production of biofuels. Furthermore, it has been shown that the FeP/NPC catalyst can be recycled by subjecting it to heat treatment to remove impurities and obtain reduction.

Identification of true active sites in N-doped carbon-supported Fe2P nanoparticles toward oxygen reduction reaction

Transition metal-based nanoparticles (NPs) are emerging as potential alternatives to platinum for catalyzing the oxygen reduction reaction (ORR) in zinc-air batteries (ZAB). However, the simultaneous coexistence of single-atom moieties in the preparation of NPs is inevitable, and the structural complexity of catalysts poses a great challenge to identifying the true active site. Herein, by employing in situ and ex situ XAS analysis, we demonstrate the coexistence of single-atom moieties and iron phosphide NPs in the N, P co-doped porous carbon (in short, Fe-N4-Fe2P NPs/NPC), and identify that ORR predominantly proceeds via the atomic-dispersed Fe-N4 sites, while the presence of Fe2P NPs exerts an inhibitory effect by decreasing the site utilization and impeding mass transfer of reactants. The single-atom catalyst Fe-N4/NPC displays a half-wave potential of 0.873 V, surpassing both Fe-N4-Fe2P NPs/NPC (0.858 V) and commercial Pt/C (0.842 V) in alkaline condition. In addition, the ZAB based on Fe-N4/NPC achieves a peak power density of 140.3 mW cm−2, outperforming that of Pt/C-based ZAB (91.8 mW cm−2) and exhibits excellent long-term stability. This study provides insight into the identification of true active sites of supported ORR catalysts and offers an approach for developing highly efficient, nonprecious metal-based catalysts for high-energy–density metal-air batteries.

Electrochemical Nitrogen Fixation at Phosphide Catalyst in Alkaline Medium: Electrocatalytic Approach Toward Validation and Determination of Ammonium Product

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. Supplementary diagnostic experiments have also been carried out to control purity of nitrogen gas and to identify potential contaminants. To comment on general catalytic activity of Fe2P during electroreductions in alkaline medium, we have performed additional comparative measurements using such redox probes as O2, CO2, NO3 - and NO2 -.

Amorphous W-doped iron phosphide with superhydrophilic surface to boost water-splitting under large current density

Electrochemical water-splitting is an effective approach for producing hydrogen without producing any pollutants, but its large-scale development is hampered by the lack of low-cost and efficient electrocatalysts. Therefore, it is essential to explore efficient and low-cost non-precious catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, W-doped Fe-P/IF amorphous nanoflake arrays (W-Fe-P/IF) are synthesized by corrosive avenue and following low-temperature phosphorization. Benefiting from the superhydrophilic surface, amorphous structure, nanosheet morphology and abundant active sites, the synthesized catalysts exhibited good catalytic performance. Therefore, the W-Fe-P/IF electrocatalyst onws low overpotentials of 35, 67, and 105 mV to achieve 10 mA cm−2 in 1 M KOH, 1 M KOH + seawater, and 1 M PBS, respectively. In addition, it also exhibits low voltage of 1.63 V to obtain 10 mA cm−2 coupled with excellent stability under 500 mA cm−2. The work provides a new strategy for the preparation of highly-efficient and low-cost non-precious electrocatalysts on renewable energy-related applications.

Highly selective electrochemical reduction of nitrate-to-ammonia using iron phosphide self-supported electrode

Highly selective electrochemical reduction of nitrate-to-ammonia using iron phosphide self-supported electrode

Uniformly deposition of iron phosphide quantum dots on the microscopic spongy B-C3N4 and its efficient degradation of ciprofloxacin by photo-self-Fenton process

In this research, iron phosphide quantum dots (FeP QDs) are synthesized and anchored on the microporous spongy BxCN uniformly through a novel hydrothermal-phosphorization processes. FeP@BxCN shows excellent photo-self-Fenton capability and applies to eliminate CIP from aqueous solution. Results indicate both photocatalysis and self-Fenton processes contribute to CIP degradation (photocatalysis: 69.1 %; self-Fenton: 28.2 %). The decoration of FeP QDs could effectively suppress the recombination of photogenerated carriers and improve the photocatalysis performance. They also accelerate the transformation of in situ H2O2 to •OH radicals thus enhance the efficiency of self-Fenton process. Furthermore, FeP QDs shows pretty low consumption during the self-Fenton process because of the regeneration mechanism between cationic iron species, H2O2 and anionic phosphorus. The existence of intermediate valence iron (Feɛ+) and anionic phosphorus (Pɛ-) ensured the regeneration of Fe(II) and the circulation between Fe(II), Feɛ+ and Fe(III). Optimal CIP degradation efficiency could be achieved under neutral condition and the corresponding CIP removal efficiency are 97.3 % when the initial concentration is 30 mg•L−1 and reaction within 120 min. Results propose a meaningful exploration for antibiotics degradation via photocatalytic-self-Fenton technology.

The (In)Stability of Heterostructures During the Oxygen Evolution Reaction

AbstractThe urgent need for efficient oxygen evolution reaction (OER) catalysts has led to the development and publication of many heterostructured catalysts. The application of such catalysts with multiple phases tremendously increases the material design dimensions, and numerous interface‐related effects can tune the OER performance. In this regard, multiple of these heterostructured electrodes show remarkable OER activities. However, it is not clear if these carefully designed interfaces remain under prolonged OER conditions. Herein, a molecular approach is used to synthesize four different nickel‐iron phosphide (heterostructured) materials and deposit them on fluorine‐doped tin oxide and nickel foam electrodes. The OER performance of the eight electrodes and the reconstruction of the four materials is investigated by in‐situ spectroscopy after one day of operation, enabled by a freeze‐quench approach. The most active electrode is also applied under industrial OER conditions and for the value‐added oxidation of alcohols to ketones. Before catalysis, this electrode comprises crystalline 4 nm nickel phosphide particles on an amorphous iron phosphide matrix. However, after 24 h, a homogenous nickel‐iron oxyhydroxide phase has formed. This work questions to which extent the design of heterostructures is a suitable strategy for non‐noble metal OER catalysis.

Integrated Iron Phosphides and Cobalt Oxide Electrocatalyst For Enhanced Hydrogen and Oxygen Evolution Reactions: A Study on Activity and Stability Factors.

Integrated Iron Phosphides and Cobalt Oxide Electrocatalyst For Enhanced Hydrogen and Oxygen Evolution Reactions: A Study on Activity and Stability Factors.

Synergistic impact of dual active sites in Nb-Fe2P nanoparticles on electrocatalytic nitrate reduction with high selectivity

The electrochemical transformation of nitrate into ammonia offers a promising alternative to the traditional Haber-Bosch process. The nitrate reduction reaction (NO3–RR) involves complex multi-electron/proton processes and faces competition from hydrogen evolution reactions, leading to low Faraday efficiency and diminished ammonia production. This study introduces carbon-supported niobium-doped iron phosphide nanoparticles (Nb-Fe2P) electrocatalysts, synthesized using deep eutectic solvent (DES). These electrocatalysts achieved an exceptional ammonia yield of 9.7 mg h−1 cm−2 and a Faraday efficiency of 95.8 % in the NO3–RR. Both experimental and theoretical studies reveal that the dual active sites of Fe and Nb significantly enhance the generation of active hydrogen and expedite the utilization of nitrogen-containing intermediates. This innovative approach, focusing on active hydrogen balance, offers a strategic pathway for developing highly efficient NO3–RR electrocatalysts by promoting the dissociation of H2O.

Effective tribological performance-oriented concentration optimization of lubricant additives based on a machine learning approach

The tribological performance of lubricant is significantly affected by additive concentration. To realize optimization of additive concentrations, an eXtreme Gradient Boosting machine learning method was proposed to predict the tribological performance of a lubricant, reflected by wear volume, with data collected from four-ball friction experiments. The Shapley Additive exPlanation tool was used to explain the predictions of the model. Particle swarm optimization was used to optimize additive concentration proportions. The tribological properties of grease additives were verified through validation experiment. The chemical components of wear scars include MXenes, carbon films, iron oxides, and iron phosphides, which facilitate direct contact between friction surfaces. This study provides a novel data-driven approach for optimization of additive concentrations with effective and predictable tribological performance.

Electrochemical selection of ferrous phosphide (FexP) as efficient catalyst for wastewater treatment: Performance and mechanism

Iron phosphide (FexP) has a great potential for electrochemical catalysis attributing to its outstanding electrical conductivity and activity. In the present study, a series of FexP (FeP, Fe2P and Fe3P) were carried out as catalysts for the oxidation of phenol from wastewater by the heterogeneous EF processes. Compared with FeP and Fe2P catalysts, Fe3P has shown significant two-electron oxygen reduction activity and H2O2 selectivity (90–100 %). The degradation efficiencies of phenol in Fe3P/EF (100 %) were higher than those in Fe2P/EF (91 %) and FeP/EF (67 %) upon 60-min electrochemical oxidation under pH 7. The Fe3P-CF/EF system could broaden the range of solution pH, as well the decay kinetics of phenol was enhanced by 1.5–2.4 times and the disposal cost was reduced by 33–41 % compared with FeP/EF and Fe2P/EF. Feɑ+ in Fe3P could promote the generation of •OH via accelerating Fe(II)/Fe(III) cycle and accelerating the transfer rate of electrons between Fe3P and H2O2. It was proved that •OH played a dominant role in removing phenol with the electron spin resonance (ESR) tests and trapping experiments. This work selected the most effective FexP catalyst in heterogeneous EF process and would bring new insights for organics removal from wastewater via H2O2 activation.

Three-dimensional N-doped graphene coated with B-doped iron phosphide electrocatalysts: Nonmetallic element co-modification for enhanced dual-pH hydrogen evolution reaction

The construction of cost-effective and highly active transition metal phosphide-based electrocatalysts instead of noble metals through a feasible strategy is crucial for addressing the energy crisis. Herein, a novel three-dimensional structure N-doped RGO coated with a ‘worm-like’ B-doped FeP electrocatalyst (B-FeP/N-RGO) was successfully developed using a multi-step reaction. The composite catalyst possesses a unique three-dimensional structure that facilitates rapid mass transfer, gas release and exposure of abundant active sites, and non-metallic element doping optimizes the electronic structure of the matrix, which together improve the hydrogen evolution reaction performance. Notably, the B-FeP/N-RGO catalysts can achieve a current density of 10 mA cm−2 in both acidic and alkaline electrolytes with overpotentials of only 125 and 176 mV, while maintaining long-term stability. This study offers a promising approach for designing and fabricating highly efficient three-dimensional electrocatalysts that do not rely on noble-metals and are suitable for a wide pH range.

Nanoneedles like FeP engineered on Ni-Foam as an effective catalyst towards overall alkaline freshwater, urea, and seawater splitting

The slow kinetics of electrochemical urea and water oxidation processes at electrode surfaces, which can be recognised as promising resources for pollution-free hydrogen energy production, motivate the scientific community to design and fabricate low-cost, high-efficiency electrocatalysts. Because the performance of electrocatalysts is dependent on their structural, morphological, and electronic properties, herein, the tuning of these properties of Fe3O4@Ni-Foam via phosphorylation and sulfurization, yielding iron phosphide (FeP@Ni-Foam) and iron sulphide (FeS@Ni-Foam), with nanoneedles (along with microstructures) and nanoflower-like morphologies, respectively, is investigated. Among all the prepared samples, FeP is found to be the most effective electrocatalyst for the oxygen evolution process (OER), the urea oxidation reaction (UOR), and seawater electrolysis. The overpotentials observed for OER, UOR, and seawater splitting are significantly reduced when using FeP as compared to other materials, with values of 207 mV, 133 mV, and 287.1 mV, respectively, at a current density of 10 mA/cm2. The enhanced catalytic activity of FeP over FeS and Fe3O4 is attributed to morphological changes, improved electronic conductivity, and exceptional endurance. The theoretical studies reveal that FeP has a better density of states over the fermi level than FeS and Fe3O4, lowering the energy barriers for the OER and UOR processes and demonstrating significant catalytic activity towards these processes. This work demonstrates that phosphorylation and sulfurization treatments can alter morphologies and electrical characteristics, hence improving the catalytic activity of the materials.

Experimental study on pipeline corrosion behavior coupled with microorganisms and dynamic alternating current interference

Underground pipelines buried deeper than 1.5 m or in specific soil conditions are susceptible to microbial corrosion and dynamic alternating current (AC) interference. Yet, research on the coupled effects of these factors remains limited, leaving their mechanisms unclear. The study employed microbial activity tests, electrochemical experiments, and microscopic morphology characterization to elucidate the coupled effect of sulfate-reducing bacteria (SRB) and dynamic AC interference on buried metallic pipelines. Results show that sinusoidal AC significantly reduces SRB growth activity. Initially, the active microbial film produced by microbial metabolism inhibited corrosion but later exacerbating it as the microbial film detachment. Microscopic examination reveals as the interference time increases, the corrosion morphology changed from pitting corrosion to honeycomb/ulcer shapes, under SRB and different AC interference conditions. Moreover, sulfide corrosion products and iron phosphide formation accelerate corrosion, while rectification and alternating electric field effects further aggravate the process. These findings provide insights into the complex mechanisms of microbial and AC corrosion in buried pipelines, aiding in anti-corrosion strategies and layout optimization.

Anionic phosphorous and sulfur regulate self-supported Ni-Fe-based electrocatalyst for water-splitting under large current density

Nickel-iron based (Ni-Fe) catalysts are widely used in the electrolysis of water due to their high activity and low cost. However, the development of highly active non-precious metal catalysts is still a great challenge. Herein, self-supported nickel–iron phosphide is fabricated through a sulfurization/phosphorization approach (Ni-Fe-P-S-1/Ni-Fe-P-S-2). The prepared catalysts show excellent catalytic performance and stability. The HER performance of Ni-Fe-P-S-1 reaches 500 mA cm−2 with small overpotentials of 289 mV in alkaline freshwater. Meanwhile, the Ni-Fe-P-S-2 requires 312 and 375 mV to reach 500 mA cm−2 in alkaline freshwater and alkaline seawater for OER. Remarkably, at the current density of 500 mA cm−2, the Ni-Fe-P-S-1||Ni-Fe-P-S-2 electrolyzer requires only 1.85 V in alkaline. Interestingly, sustainable energies can power the electrolyzer effectively. The work provides methods for potentially promising and cost-effective electrocatalysts.