Iron Nickel Phosphide Research Articles

Interfacial Regulation of Rice-Grain-like Iron-Nickel Phosphide Nanorods on Phosphorus-Doped Graphene Architectures as Bifunctional Electrocatalysts for Water Splitting.

The design of bimetallic metal-organic frameworks (MOFs) with a hierarchical structure is important to improve the electrocatalytic performance of catalysts due to their synergistic effect on different metal ions. In this work, the catalyst comprises bimetallic iron-nickel MOF-derived FeNi phosphides, intricately integrated with phosphorus-doped reduced graphene oxide architectures (FeNi2P-C/P-rGA) through the hydrothermal and phosphating treatments. The hierarchical architecture of the catalyst is beneficial for exposing active sites and facilitating electron transfer. The FeNi2P-C/P-rGA catalyst exhibits excellent performance in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Notably, FeNi2P-C/P-rGA requires only the overpotential of 93 and 210 mV to achieve a current density of 10 mA cm-2 for the HER and OER with small values of Tafel slope and charge transfer resistance, respectively. Furthermore, the catalyst exhibits boosted activity for overall water splitting with a low potential of 1.56 V. This work can be considered to extend the design of multilevel catalysts in the application of water splitting.

In Situ Hydroxide Growth over Nickel-Iron Phosphide with Enhanced Overall Water Splitting Performances.

In this work, three dimensional (3D) self-supported Ni-FeOH@Ni-FeP needle arrays with core-shell heterojunction structure are fabricated via in situ hydroxide growth over Ni-FeP surface. The as-prepared electrodes show an outstanding oxygen evolution reaction (OER) performance, only requiring the low overpotential of 232mV to reach 200mAcm-2 with the Tafel slop of 40mVdec-1. For overall water splitting, an alkaline electrolyzer with these electrodes only requires a cell voltage of 2.14V to reach 1Acm-2. Mechanistic investigations for such excellent electrocatalytic performances are utilized by in situ Raman spectroscopy in conjunction with density functional theory (DFT) calculations. The computation results present that Ni-FeOH@Ni-FeP attains better intrinsic conductivity and the D-band center (close to that of the ideal catalyst), thus giving superior excellent catalytic performances. Likewise, the surface Ni-FeOH layer can improve the structural stability of Ni-FeP cores and attenuate the eventual formation of irreversible FeOOH products. More importantly, the appearance of FeOOH intermediates can effectively decrease the energy barrier of NiOOH intermediates, and then rapidly accelerate the sluggish reaction dynamics, as well as further enhance the electrocatalytic activities, reversibility and cycling stability.

Electron Manipulation and Surface Reconstruction of Bimetallic Iron-Nickel Phosphide Nanotubes for Enhanced Alkaline Water Electrolysis.

Developing high-efficiency and stable bifunctional electrocatalysts for water splitting remains a great challenge. Herein, NiMoO4 nanowires as sacrificial templates to synthesize Mo-doped NiFe Prussian blue analogs are employed, which can be easily phosphorized to Mo-doped Fe2xNi2(1-x)P nanotubes (Mo-FeNiP NTs). This synthesis method enables the controlled etching of NiMoO4 nanowires that results in a unique hollow nanotube architecture. As a bifunctional catalyst, the Mo-FeNiP NTs present lower overpotential and Tafel slope of 151.3 (232.6) mV at 100 mA cm-2 and 76.2 (64.7) mV dec-1 for HER (OER), respectively. Additionally, it only requires an ultralow cell voltage of 1.47 V to achieve 10 mA cm-2 for overall water splitting and can steadily operate for 200 h at 100 mA cm-2. First-principles calculations demonstrate that Mo doping can effectively adjust the electron redistribution of the Ni hollow sites to optimize the hydrogen adsorption-free energy for HER. Besides, in situ Raman characterization reveals the dissolving of doped Mo can promote a rapid surface reconstruction on Mo-FeNiP NTs to dynamically stable (Fe)Ni-oxyhydroxide layers, serving as the actual active species for OER. The work proposes a rational approach addressed by electron manipulation and surface reconstruction of bimetallic phosphides to regulate both the HER and OER activity.

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.

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.

Bimetallic iron-nickel phosphide as efficient peroxymonosulfate activator for tetracycline hydrochloride degradation: Performance and mechanism

Sulfate radical-based advanced oxidation processes with (SR-AOPs) are widely employed to degrade organic pollutants due to their high efficiency, cost-effectiveness and safety. In this study, a highly active and stable FeNiP was successfully prepared by reduction and heat treatment. FeNiP exhibited high performance of peroxymonosulfate (PMS) activation for tetracycline hydrochloride (TC) removal. Over a wide pH range, an impressive TC degaradation efficiency 97.86% was achieved within 60 min employing 0.1 g/L FeNiP and 0.2 g/L PMS at room temperature. Both free radicals of SO4·-, ·OH, ·O2− and non-free radicals of 1O2 participated the TC degradation in the FeNiP/PMS system. The PMS activation ability was greatly enhanced by the cycling between Ni and Fe bimetal, and the active site regeneration was achieved due to the existence of the negatively charged Pn−. Moreover, the FeNiP/PMS system exhibited substantial TC degradation levels in both simulated real-world disturbance scenarios and practical water tests. Cycling experiments further affirmed the robust stability of FeNiP catalyst, demonstrating sustained degradation efficiency of approximately 80% even after four cycles. These findings illuminate its promising potential across natural water bodies, presenting an innovative catalyst construction approach for PMS activation in the degradation of antibiotic pollutants.

Hardness and tribological behaviour of annealed electroless nickel phosphorus composite layers with incorporated boron particles

In this study, a possible alternative to hard chromium coatings is investigated. Amorphous boron particles have been incorporated in electroless nickel‑phosphorus (NiP) deposits, yielding a dispersion coating. The distribution of the particles is homogenous and the maximum mass fraction of particles embedded in the coating is 6.2 ± 0.2 wt%. Measurements of the zeta potential and particle size of amorphous boron particles in a diluted electrolyte showed that the particles withstood agglomeration until 120 days. Primary and secondary hardness maxima are observed after thermal annealing at 400 °C and 860 °C due to the formation of nickel phosphide, nickel boride and nickel boride phosphide phases. X-ray diffractometry shows an increase in nickel and nickel phosphide crystal size at 400 °C before levelling off at 600 °C. The annealing duration should be kept between 30 and 60 min for optimal hardness. The wear resistance increases when the coating is annealed at 400 °C. DSC measurements on nickel phosphorus incorporated with boron particles, Ni-P-B, bulk material with P-content (9.6 ± 0,6 wt%) and B-content (4.5 ± 0.8 wt%) showed that the solidus line lies at 926 °C, which is why a maximum annealing temperature of 860 °C was chosen to avoid melting of the material. The relative texture and phase coefficients, RTC and RPC, showed that the nickel phase is preferred in the NiP system at 400 °C and 600 °C while the Ni3P phase is preferred in the Ni-P-B system at the same annealing temperature. REM and EDX area analyses are used to show the areal distribution of nickel, phosphorus, and boron before and after the annealing process along the thickness of the coating. A diffusion layer between substrate and coating that contains iron nickel boride and iron nickel phosphide lamellar structure is observed.

Efficient and selective electrosynthesis of 4-aminophenol at circumneutral pH from the electrocatalytic reduction of nitrophenol over the nickel-iron phosphide modified electrode

The efficient and sustainable synthesis of 4-aminophenol (4-AP) from the electrocatalytic reduction of 4-nitrophenol (e-NPR) with water as the proton source relies on the development of robust electrocatalysts that readily expedite the kinetics of e-NPR and generate 4-AP with high selectivity at environmentally-benign conditions. In this study, we report on the efficient and sustainable electrosynthesis of 4-AP at circumneutral pH using the micro-structured nickel-iron phosphide modified electrode (CP|microNiFeP). The effects of the iron content of the prepared CP|microNiFeP electrodes as well as electrolysis conditions, including the electrolyte pH, applied potential, and electrolysis duration, on the electrosynthesis of 4-AP were thoroughly examined through a series of controlled-potential electrolyses (CPEs). Under optimal conditions, the CP|microNiFeP electrode exhibited a turnover frequency of 7.25 ± 0.05 h−1 for the generation of 4-AP at 0.0 V vs. RHE and achieved a high 4-NP conversion of 92.29 ± 1.47% with high selectivity for 4-AP generation (SAP:85.77 ± 2.21%) after 8-h CPE at −0.15 V vs. RHE in the H-cell. In addition, the scale-up electrosynthesis of 4-AP with a flow-type electrolyzer was also demonstrated. The 3-h electrolysis using the flow-type electrolyzer resulted in a high 4-NP conversion (93.84 ± 0.84%) with a high SAP (86.32 ± 1.05%). The possible reaction pathways of e-NPR have been proposed, and 4,4′-dihydroxyazobenzene and dimers were identified as the main side products.

Molybdate intercalated nickel–iron-layered double hydroxide derived Mo-doped nickel–iron phosphide nanoflowers for efficient oxygen evolution reaction

Molybdate intercalated nickel–iron-layered double hydroxide derived Mo-doped nickel–iron phosphide nanoflowers for efficient oxygen evolution reaction

One-pot synthesis of crystalline structure: Nickel-iron phosphide and selenide for hydrogen production in alkaline water splitting

Electrocatalytically active nanocomposites play a vital role in energy generation, conversion, and storage technologies. Transition metal-based catalysts such as nickel and iron and their pnictide (phosphide), and chalcogenide (selenide) compounds exhibit good activity for hydrogen evolution reaction (HER) in the alkaline environment. In this study, transition metals-based catalysts (Ni-P-Se, Fe-P-Se, and Ni-Fe-P-Se) solutions were prepared using a simple one-pot method. Prepared solutions were deposited on Ni foam, and different characterization techniques were used to determine the composition, structure, and morphology of as-prepared catalysts. Furthermore, it was found that Ni-Fe-P-Se as a cathode material showed better HER performance compared to other investigated materials with the overpotential value of 316 mV at 10 mA cm-2 current density and 89 mV dec-1 Tafel slope value. The stability tests of the as-prepared catalyst confirmed that the synergistic effect between various elements enhances the electrocatalytic performance for up to 24 hours, providing a fair, stable nature of Ni-Fe-P-Se based sample.

Vertically aligned nickel-iron-phosphide nanosheets on three-dimensional porous nickel foam for overall water splitting

A low-cost, earth-abundant and efficient bifunctional electrocatalysts for overall electrochemical water splitting is an important development in the field of electrochemistry. In this work, nickel-iron phosphide (NiFeP) nanosheets on three-dimensional (3D) porous interconnected nickel foam with rich active sites are processed by two-step synthesis. Conversion of nickel foam to nickel iron layered double hydroxide (NiFeLDH) by low-temperature hydrothermal reaction followed by thermal phosphidation using red phosphorus as the source. The thermal phosphidation process is optimized with respect to temperature and duration. The electrochemical performances of the electrocatalyst are strongly depends on the phosphidation temperature and duration. The NiFeP (NFP) electrocatalyst synthesized at 500 °C for 30 mins (NFP500–30) shows the overall water splitting voltage of 1.69 V at 50 mA/cm2 in 1.0 M KOH. The improvement in electrocatalyst performance is attributed to the Fe substitution, vertically aligned nanostructure surface with abundant active sites and 3D porous interconnect network structure. The electrocatalyst exhibits robust durability with high conductivity and excellent corrosion resistance.

Alkaline Media Regulated NiFe-LDH-Based Nickel–Iron Phosphides toward Robust Overall Water Splitting

The search for low-cost, high-performance, and robust stability bifunctional electrocatalysts to substitute noble metals-based counterparts for overall water splitting to generate clean and sustainable hydrogen energy is of great significance and challenges. Herein, a high-efficient bi-functional nickel–iron phosphide on NiFe alloy foam (denoted as e-NFP/NFF) with 3D coral-like nanostructure was controllably constructed by means of alkali etching and the introduction of non-metallic atoms P. The unique superhydrophilic coral-like structure can not only effectively facilitate the exposure of catalytic active sites and increase the electroactive surface area, but also accelerate charge transport and bubble release. Furthermore, owing to the synergistic effect between the bicomponent of nickel–iron phosphides as well as the strong electronic interactions of the multiple metal sites, the as-fabricated catalyst behaves with excellent bifunctional performance for the hydrogen evolution reaction (overpotentials of 132 and 286 mV at 10 and 300 mA·cm−2, respectively) and oxygen evolution reaction (overpotentials of 181 and 303 mV at 10 and 300 mA·cm−2, respectively) in alkaline electrolytes. Impressively, cells with integrated e-NFP/NFF electrodes as a cathode and anode require only a low cell voltage (1.58 V) to drive a current density of 10 mA·cm−2 for overall water splitting, along with remarkable stability in long-term electrochemical durability tests. This study provides a tunable synthetic strategy for the development of efficient and durable non-noble metal bifunctional catalysts based on the construction of an elaborate structure framework and rational design of the electronic structure.

Correction: Efficient direct lignin fuel cells enabled by hierarchical nickel–iron phosphide nanosheets as an anode catalyst

Correction for ‘Efficient direct lignin fuel cells enabled by hierarchical nickel–iron phosphide nanosheets as an anode catalyst’ by Fei Liu et al., Sustainable Energy Fuels, 2022, 6, 4866–4872, https://doi.org/10.1039/D2SE00930G.

Mn-doped nickel–iron phosphide heterointerface nanoflowers for efficient alkaline freshwater/seawater splitting at high current densities

To realize highly efficient and stable hydrogen production at high current densities, more efforts are devoted to developing outstanding water-splitting electrocatalysts. Herein, through a facile hydrothermal-phosphorization method, Mn-doped Ni2P/Fe2P was rationally designed and prepared as a high-performance bifunctional electrocatalyst for alkaline freshwater/seawater splitting. In alkaline seawater (freshwater) electrolyte, it merely needs low overpotentials of 358 (335) and 470 (405) mV to reach 1000 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. This electrocatalyst also shows excellent stability even at a high OER current density of 500 mA cm−2 for 200 h. Regarding the alkaline overall seawater splitting, Mn-doped Ni2P/Fe2P presents a low cell voltage of 2.02 V at 500 mA cm−2 and outstanding stability for 120 h at the same current. The X-ray absorption fine structure (XAFS) experimental analysis verifies that the Mn doping and Ni2P/Fe2P heterointerfaces can efficiently optimize the electrocatalyst’s electronic structure, leading to the improved intrinsic OER and HER activities. Meanwhile, the 3D nanoflower structure provides abundant exposed active sites, and the Mn doping and heterointerfaces can create more active sites. Besides, the high corrosion resistance resulting from nickel-iron phosphides makes the electrocatalyst become a good candidate for seawater splitting. This study provides a simple path to fabricate highly active and robust non-noble electrocatalysts for freshwater/seawater splitting at high current densities.

Facile electrochemical preparation of NiFeP submicron-spheres as an efficient electrocatalyst for the electrochemical hydrogenation of 4-nitrophenol at neutral pH

Electrochemical hydrogenation with water as the proton source serves as a clean and sustainable alternative to the removal and upcycling of 4-nitrophenol (4-NP), one of the major toxic pollutants commonly present in industrial wastewater effluents, into value-added chemicals (e.g., 4-aminophenol), but the development of high-performance electrocatalyst for electrochemical hydrogenation of 4-NP (e-NPR) at neutral pH remains challenging. Herein, we represent the facile electrochemical synthesis of micro-structured nickel-iron phosphide (microNiFeP), which acts as an efficient electrocatalyst in catalyzing hydrogen evolution reaction (HER) and e-NPR at neutral pH. The effects of electrosynthetic conditions on the physicochemical and electrocatalytic properties of microNiFeP were investigated and optimized. microNiFeP, prepared with optimized conditions, consisted of submicron-sized spheres (diameter: ∼ 200 nm) with wrinkled surface and exhibited promising HER activity, reaching a turnover frequency (TOF) of 47.18 ± 4.10 h-1 at − 0.2 V vs. reversible hydrogen electrode (RHE) at pH 7 in the absence of 4-NP. In the presence of 4-NP, however, microNiFeP exhibited high e-NPR activity and selectivity against HER. Notably, microNiFeP showed a TOF of 5.12 ± 0.48 h-1 for e-NPR at 0.0 V vs. RHE and enabled conversion of 89.6 ± 3.3 % with a Faradic efficiency of 81.98 ± 5.08 % for 4-aminophenol production after 8-h-controlled-potential electrolysis at − 0.2 V vs. RHE. Mechanistic studies reveal that e-NPR at microNiFeP involved the transfer of 5.3 ∼ 5.8 electrons and may involve the formation of 4,4'-dihydroxyazobenzene as one of the side products.

Electrodeposited amorphous nickel–iron phosphide and sulfide derived films for electrocatalytic oxygen evolution

The preparation of inexpensive and efficient electrocatalysts for oxygen evolution reaction (OER) is crucial in the widespread application of water electrolyzers. A simple one-step aqueous electrodeposition method is utilized to prepare amorphous nickel-iron sulfide (Ni–Fe–S) and phosphide (Ni–Fe–P) films on Ni foam. The deposited films are highly porous, and can convert to active electrocatalysts for OER. In 1 M KOH, the Ni–Fe–S shows the highest OER activity, and requires only 230 mV overpotential to reach 0.05 A cm−2 OER current densities. The Fe–Ni–S also sustains the 30 h 0.05 A cm−2 galvanostatic OER test. Ex-situ characterizations show that sulfur in the Fe–Ni–S is oxidized and leached into the solution during OER, and that (oxy)hydroxide layer is formed at the surface. The adsorption energy of the hydroxyl group, an OER intermediate, is tuned by the electron interaction between the Ni and Fe, and the Ni–Fe–S exhibits the optimum hydroxyl group adsorption energy and the most facile OER kinetics. Also, higher intrinsic OER activity is observed for the electrodeposited amorphous nickel phosphide-derived film than the amorphous nickel sulfide-derived film.

A Unique NiOOH@FeOOH Heteroarchitecture for Enhanced Oxygen Evolution in Saline Water.

The development of highly efficient non-precious metal electrocatalysts for the oxygen evolution reaction (OER) in low-grade or saline water is currently of great importance for the large-scale production of hydrogen. In this study, by using an electrochemical activation pretreatment, metal oxy(hydroxide) nanosheet structures derived from self-supported nickel-iron phosphide and nitride nanoarrays grown on Ni foam are successfully fabricated for OER catalysis in saline water. It is demonstrated that the different NiOOH and NiOOH@FeOOH (NiOOH grown on FeOOH) structures are generated from nickel-iron nitride and phosphide, respectively, after electrochemical activation. In particular, the NiOOH@FeOOH heteroarchitecture shows outstanding electrocatalytic performance with an ultralow overpotential of 292mV to drive the current density of 500mAcm-2 . An unconventional dual-sites mechanism (UDSM) is proposed to address the OER process on NiOOH@FeOOH and show that the FeOOH underlayer plays a critical role regarding the enhanced OER activity of NiOOH. The new possible UDSM involving two reaction sites presents a different understanding of the OER process on multi-OH layer complexes, which is expected to guide the design of heteroarchitecture electrocatalysts.

Three-dimensional ordered macroporous design of heterogeneous nickel-iron phosphide as bifunctional electrocatalyst for enhanced overall water splitting

Developing high-performance oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts is essential for overall water splitting. Herein, heterogeneous engineering-induced strategy was demonstrated by the synthesis of bimetallic Ni2P/FeP/Fe2P heterostructure with three-dimensional ordered macroporous structure (3DOM-Ni2P/FexP) as bifunctional catalyst. The heterogeneous interfaces formed by the three distinct phases can adjust the electron distribution and create abundant active sites to improve the catalytic performance. The 3DOM structure provides large specific surface area and good mass transfer for electrocatalytic reaction occurring at the solid-gas-electrolyte multiphase interfaces. Accordingly, the 3DOM-Ni2P/FexP showed remarkable OER and HER electrocatalytic activity in 1 M KOH electrolyte. Moreover, it demonstrates that the 3DOM-Ni2P/FexP turns out oxidation and transformation during the OER process. Computational results reveal the synergy of the converted Fe2O3/NiOOH, promoting the OER reaction energetics. In addition, an alkaline electrolyzer with the 3DOM-Ni2P/FexP as both the cathode and anode achieves excellent overall water splitting performance, with only 1.54 V voltage to obtain the current density of 10 mA cm−2. This present study gives a novel concept of heterogeneous engineering-induced bimetallic phosphide with macroporous structure design towards the high-performing OER and HER bifunctional electrocatalysts evolvement.

Bimetallic-MOF derived nickel-iron phosphide nanosheets on carbon cloth for efficacious oxygen evolution reaction

It is of momentously realistic significance to exploit highly efficacious and cost-effective non-noble metal electrocatalysts for oxygen evolution reaction (OER), considering its promising renewable energy application. Herein, a self-supporting electrocatalyst composed of nickel-iron phosphide nanosheets on carbon cloth (NiFeP@CC) is proposed for OER, which are derived from the phosphating treatment of two-dimensional NiFe-MOF nanosheets. The NiFeP@CC composite possesses the synergistic effect of bimetallic NiFe phosphides in promoting the OER, the fully exposed active sites of the nano-sheet structure and the fast charge/mass transfer from the hierarchical porous structure. Owing to the above structural features, the optimized NiFeP@CC presents an impressive OER performance in alkaline solution. The overpotential and Tafel slope are as low as 229 mV and 36.4 mV dec−1 under a current density of 10 mA cm−2, respectively, much superior to those for the commercial IrO2 catalyst. More excitingly, this self-supporting electrocatalyst also possesses an exceptionally high durability, showing no activity degradation for 25 h. This work offers a simple and feasible strategy for developing practically available OER catalysts with a high activity and stability.

Fe2P nanoparticles embedded on Ni2P nanosheets as highly efficient and stable bifunctional electrocatalysts for water splitting

• Fe 2 P nanoparticles embedded on Ni 2 P nanosheets has been synthesized. • Fe 2 P/Ni 2 P HS delivers superior catalytic performance for water splitting. • The electron redistribution near heterointerface optimizes the ΔG H* of P sites. • The Fe 2 P/Ni 2 P heterointerface results in abundant active sites. It is urgent to develop highly efficient, stable and low-cost bifunctional electrocatalysts for overall water splitting. Herein, an iron-nickel phosphide (Fe 2 P/Ni 2 P) heterostructure, constructed by Fe 2 P nanoparticles embedded on Ni 2 P nanosheets, is strategically fabricated on nickel foam via a facile process. As a bifunctional electrocatalyst, the Fe 2 P/Ni 2 P heterostructure delivers a very low overpotential of 64 mV (or 185 mV) to reach current density of 10 mA cm −2 for hydrogen (or oxygen) evolution reaction. When simultaneously employed as both the anode and cathode electrodes, it demonstrates an ultralow cell voltage of 1.49 V@10 mA cm −2 for full water splitting with nearly 100% Faradaic efficiency, and superior long-term stability even over 100 h. Density functional theory calculations manifest that a strong heterointerface interaction could cause electron redistribution near the Fe 2 P/Ni 2 P heterointerface and optimize the Δ G H* of P sites, thus enhancing catalytic activity. Additionally, the 3D porous heterostructure is benefit to expose rich active sites and facilitate ion diffusion and gas bubble release, thus promoting the catalytic performance. This work opens up a new strategical approach for rational design of metal phosphide-based heterostructures as highly efficient and stable bifunctional electrocatalysts for water splitting.