Transition Metal Phosphides Research Articles

Transition metal phosphide-based oxygen electrocatalysts for aqueous zinc-air batteries.

Electrically rechargeable zinc-air batteries (ZABs) are emerging as promising energy storage devices in the post-lithium era, leveraging the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the air cathodes. Efficient bifunctional oxygen electrocatalysts, capable of catalyzing both the ORR and OER, are essential for the operation of rechargeable ZABs. Traditional Pt- and RuO2/IrO2-based catalysts are not ideal, as they lack sufficient bifunctional ORR and OER activity, exhibit limited long-term durability, require high overpotentials and are expensive. In contrast, non-precious metal-based catalysts, including transition metal phosphides (TMPs), have gained significant attention for their promising bifunctional catalytic properties, making them attractive candidates for ZABs. Despite encouraging lab-scale achievements, translating these advancements into market-ready applications remains challenging due to suboptimal energy performance. Rationally engineered bifunctional TMPs hold great potential for overcoming these challenges and meeting the requirements of rechargeable ZABs. This feature article reviews recent progress in the development of TMP-based catalysts for ZABs, providing a comprehensive overview of ZAB fundamentals and strategies for catalyst design, synthesis, and engineering. A particular emphasis is placed on widely studied bifunctional Fe, Co, and Ni phosphides, along with approaches to enhance their catalytic performance. Key performance metrics are critically evaluated, including the potential gap (ΔE) between the ORR and the OER, specific capacity, peak power density, and charge-discharge cycling stability. Finally, this feature article discusses the challenges faced in TMP-based ZABs, proposes strategies to address these issues, and explores future directions for improving their rechargeability to meet the demands of commercial-scale energy storage technologies.

A review on the synthesis and lithium storage properties of metal phosphides derived from metal‐organic framework

Transition metal phosphides (TMPs) are considered as a promising anode material for LIBs due to their potential high theoretical capacity, suitable lithiation potential and low polarization, but low conductivity and severe volume expansion limit the performance of TMPs. Since metal‐organic framework (MOFs)‐derived materials can inherit the advantages of MOFs, MOFs‐derived metal phosphides have been widely used as anodes for LIBs and exhibit outstanding electrochemical performance. The MOFs derivatization strategy can be used to achieve the adjustment and optimization of the components and structure of metal phosphide composites, such as constructing rich heterojunction structure or designing stable carbon skeleton structure. These modifications effectively improve the electronic structure and structural stability of metal‐phosphide composites, thus solving the current problems of TMPs. In conclusion, this paper systematically summarizes the basic strategies for the modification and preparation of TMPs applied to the field of energy conversion and energy storage from the phosphorus source used in the preparation of TMPs, and finally compares the preparation methods, modification and lithium storage properties of monometallic/bimetallic phosphides derived from MOFs, and looks ahead to the characteristics and possible future development of the metal phosphides obtained by derivatization of MOFs as precursor.

A non-noble metal photocatalyst CoP/g-C3N4 with high efficiency for hydrogen evolution under visible light

A non-noble metal photocatalyst CoP/g-C3N4 with high efficiency was prepared by loading transition metal phosphide CoP tightly on the surface of non-noble metal g-C3N4 using the improved impregnation method. The surface of g-C3N4 is tightly loaded by CoP, and the electrons can be separated and transferred effectively, so as to effectively improve the performance of g-C3N4 photocatalytic hydrogen evolution. When CoP is 5% in CoP/g-C3N4, the photocatalytic activity of hydrogen evolution is the highest, and the yield of hydrogen production reached an amazing 375 μmol h−1g−1, while g-C3N4 was only 35 μmol h−1g−1. Moreover, CoP/g-C3N4 has excellent stability for hydrogen production. The photocatalytic reaction mechanism of CoP/g-C3N4 is also proposed.

Triacylphosphines as a Novel Class of Phosphorus Sources for the Synthesis of Transition Metal Phosphide Nanoparticles.

Transition metal phosphide (TMP) nanoparticles (NPs) are versatile materials for energy conversion/storage applications due to their robustness and many possibilities to tailor NPs' electronic, physical, and chemical properties. One of the hurdles toward their broader implementation is their challenging synthesis exacerbated by the limited choice of phosphorus precursors. On the one hand, the synthesis of TMP NPs can employ various alkyl- or arylphosphines requiring prolonged heating at high temperatures, while on the other hand, highly reactive P(SiMe3)3, white phosphorus, or PH3 pose additional obstacles associated with their hazardous nature, high cost, and limited availability. This work introduces the use of acylphosphines as a new class of phosphorus sources for synthesizing phosphide NPs. They are shown to react with respective metal chlorides at moderate temperatures as low as 250°C yielding poorly crystalline NPs, which can later be crystallized at 305°C. After ligand stripping with HPF6, NPs are found to be an effective electrocatalyst for the hydrogen evolution reaction in the acidic medium exhibiting overpotentials as low as 50mV at a current density of 10mAcm-2, which is among the lowest overpotentials for these materials and is quite competitive to commercial platinum-based catalysts.

Heterostructures with transition metal sulfides and transition metal phosphide: NiMnS/FeP achieve efficient seawater OER

Heterostructures with transition metal sulfides and transition metal phosphide: NiMnS/FeP achieve efficient seawater OER

Ni2P/Cu3P bimetallic phosphide embedded in nitrogen-doped carbon as SIB anode: Constructed hetero interface promoting fast Na+ diffusion and storage performance

Transition metal phosphides (TMPs) have attracted widespread attention as electrode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, various bonding types, metallic characteristics, and low cost. However their sluggish reaction kinetics and inferior capacity decay severely hamper their application. Designing TMPs with novel nano/microstructures effectively overcomes these challenges. Herein, Nickel Phosphide/Copper Phosphide embedded in nitrogen-doped carbon (Ni2P/Cu3P@NC) was synthesized by carbonization and phosphidation process. When used as an SIB anode, Ni2P/Cu3P@NC exhibited a reversible specific capacity of 530 mAh/g after 200 cycles at 0.2 A/g, 428 mAh/g after 1000 cycles at 1.0 A/g, and good rate capability (334 mAh/g at 2.0 A/g). Ex-situ XRD combined with in-situ EIS confirm the irreversible conversion mechanism. Density Functional Theory (DFT) calculations show that the heterointerface formed between Ni2P and Cu3P serves as a channel for fast ion delivery and promotes Na+ storage performance. Furthermore, the practical application was further investigated by assembling Ni2P/Cu3P@NC//Na3V2(PO4)3 full cells.

Deciphering the surface electrochemical reconstruction of ruthenium-cobalt-nickel phosphide for efficient high-current hydrogen evolution and overall water splitting.

Development of efficient and stable bifunctional transition metal phosphide catalysts is critical for advancing hydrogen production technologies. Herein, RuCo co-doped Ni8P3 (RuCoNiP) was designed and synthesized by one-step electrodeposition for Ni electronic structure modulation, and evolved to RuCoNiP@α-Ni(OH)2 and RuCoNiP@Co/Ni(OH)x heterointerfaces by self-assembled reconstruction during HER and OER processes, respectively. RuCoNiP@α-Ni(OH)2 enhances HER activity (305.8mV@-1000mAcm-2) and stability (100h@-1000mAcm-2) by weakening OH* and H* competitive adsorption. Density functional theory (DFT) calculations revel that the ΔGH* of Ni site (RuCoNiP) is reduced by the assignment of a large number of Ni d-states at the Fermi level by RuCo doping, which synergistically interacts with the enhanced adsorption of α-Ni(OH)2 to OH*, resulting in a lower energy barrier for hydrogen adsorption-desorption. Moreover, RuCoNiP@Co/Ni(OH)x relies on M(OH)x to enhance the activity (351.4mV@1000mAcm-2) and stability (100h@1000mAcm-2) of OER. Dual-electrode system RuCoNiP@α-Ni(OH)2//RuCoNiP@Co/Ni(OH)x demonstrates an ultra-low battery voltage (1.95V@1000mAcm-2) and excellent stability (50h@1000mAcm-2). This efficient synthetic strategy and the self-assembled heterojunction structure offer a promising path for developing efficient overall water-splitting catalysts.

ALD Synthesis of Transition Metal Phosphides

The ever-increasing global energy demand together with the environmental issue originated from the use of fossil fuel, has triggered an intense search for sustainable and clean energy alternatives, such us hydrogen energy, biomass and solar energy among others. In this context, a pivotal key to deliver sustainable and superior energy systems lies on the rational design and development of high-quality and cost-effective catalyst offering enhanced stability, activity and selectivity. Consequently, intense efforts have been devoted in the search and synthesis of new catalyst materials to replace the scarce and expensive traditional noble metals (e.g. Pt, Pd, Au and Ru) for energy conversion and energy storage applications.Among the recently explored novel catalyst materials, metal phosphides (MPs) have emerged in recent years, attracting significant attention thanks to their intriguing properties [1]. In particular transition metal phosphides (TMPs) exhibit striking properties. The moderately strong M−P bonds lend outstanding mechanical properties, high thermal stability and outstanding chemical resistance to chemical attack and oxidation in acidic and alkaline solutions. Additionally, Co, Ni, Mo-based phosphides demonstrated excellent catalytic and bifunctional properties, in particular towards water splitting as both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) [2,3].Herein, we present the synthesis of TMPs by thermal Atomic Layer Deposition (ALD) based on the use of different transition metal precursors and tris(trimethylsilyl)phosphine. The physical and chemical properties of the resulting TMPs thin films were extensively characterized by different methods, including atomic force microscopy, X-ray photoelectron spectroscopy and X-Ray diffraction. The presentation will introduce and describe the synthesis of the TMPs and the corresponding physical and electrochemical characterization toward electrocatalytic application.[1] Z. Pu, T. Liu, I. S. Amiinu, R. Cheng, P. Wang, C. Zhang, P. Ji, W. Hu, J. Liu, S. Mu, Transition-metal phosphides: activity origin, energy–related electrocatalysis applications, and synthetic strategies, Adv. Funct. Mater., 2020, 30, 2004009.[2] C.C. Weng, J.T. Ren, Z.Y. Yuan, Transition Metal Phosphide-Based Materials for Efficient Electrochemical Hydrogen Evolution: A Critical Review, ChemSusChem, 2020, 13, 3357-3375.[3] C.-J. Huang, H.-M. Xu, T.-Y. Shuai, Q.-N. Zhan, Z.-J. Zhang, G.-R. Li, A review of modulation strategies for improving catalytic performance of transition metal phosphides for oxygen evolution reaction, Applied Catalysis B: Environmental, 2023, 325, 122313.

Enhancement of Alkaline OER Performance of the Electroplated Ni-P Catalysts Using Electrochemical Dealloying Technique

With the growing attention on renewable energy, hydrogen is receiving attention as an energy carrier to resolve the temporal and spatial constraints of renewable energy. Electrical energy generated from renewable energy can be efficiently stored and transported in the form of hydrogen. Here, water electrolysis consists of two reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the high activation energy of OER is the main bottleneck of water electrolysis. Consequently, highly active catalysts are indispensable. Currently, the Pt- and Ir-based noble metal catalysts boast the highest performance for OER, but face significant commercialization hurdles due to their high cost.Transition metal-based compounds are promising as substitutes of Platinum group materials for OER catalysts due to their high catalytic activity and earth-abundant properties. In particular, transition metal phosphides (TMPs) such as Ni-P are receiving much attention due to its remarkable catalytic performance approaching that of Pt-based one. In Ni-P, electrons are transferred from Ni to P due to the difference in electronegativity, allowing the energy of the HER and OER intermediate to be controlled for optimal activity. Furthermore, the Ni-P synthesized through electrodeposition has high potential as a promising substitute because they can have a variety of P ratios on the N-P surface, that can significantly affect catalytic activity and improve it more. Unfortunately, however, the electrodeposited Ni-P mostly has a flat and aggregated morphology, resulting in a low surface area and hence low catalytic performance. Therefore, to maximize the catalytic performance of the electroplated Ni-P. it is necessary to increase in surface area and number of active sites as well as the optimization of surficial P ratio.In this context, we propose a morphology control method using electrochemical dealloying, which can greatly increase the surface area of the electroplated Ni-P. Specifically, under acidic conditions, a potential higher than the reduction potential of Ni causes partial dealloying of Ni on the Ni-P catalyst. Then, the partial dealloyed Ni creates defects between grains and forms a porous structure. As a result, the surface of the dealloyed Ni-P catalyst was exposed along the grain boundaries through SEM, and a quantitative increase in surface area was confirmed through cyclic voltammetry (CV). In addition, it was confirmed through XPS analysis that the bond between Ni and P became stronger, and based on this, it was confirmed that the tafel slope and TOF of the catalyst increased. The increase in overall performance of the catalyst was confirmed through the polarization curve as surface area and intrinsic activity increased. Figure 1

Bulk and Surface Effect of Metal Phosphides Catalysts on Hydrogen Evolution Reaction

Transition metal phosphides (MPs) are emerging earth-abundant catalysts for hydrogen evolution reaction (HER) due to their promising activity and stability. Even though further development is needed to meet real-world application needs, fundamental understanding of how MP catalysts can be improved is low. In this work, we present several different approaches to uncover the relationships of bulk (electronic structure) and surface (active sites) of the catalysts with HER activity and stability. We studied well-ordered crystalline materials as model systems to elucidate the aforementioned relationships. Anionic Si/P substitution in NiSi1-xPx compounds showed that the density of the states (DOS) at EF could be one of the key determinants on HER activity. The impact of DOS was further investigated by studying two polymorphs of Fe2P where upward shift of the d-band position was shown to enhance HER activity. Several surface termination effects were demonstrated on the mm-sized single crystals of Ni2P, Co2P, and Fe2P upon facet-dependent HER activity studies. Lastly, operando X-ray absorption spectroscopy of Ni and P K-edges of Ni-P catalysts clearly demonstrated that during the HER process, reduction occurred on the catalyst surface, but reduced state was only stable under applied reductive bias and quickly oxidized after turning off the potential, and this oxidized species did not appear to return to its original state.

Probing the Stability of Ni2P Nanoparticle Electrocatalysts via Operando Benchtop X-Ray Absorption Spectroscopy

The electrification of the petrochemical industry will greatly reduce greenhouse gas emissions in the manufacturing of commodity chemicals; however, electrification on a global scale is only achievable using earth-abundant materials for electrocatalysis in place of state-of-the-art catalysts made from precious metals. A promising catalyst that has been used for industrial hydrodesulfurization and electrocatalytic hydrogen evolution, nitrate reduction, carbon dioxide reduction, and oxygen evolution is Ni2P. Ni2P and other transition metal phosphides benefit from active site ensembles that moderate the binding of reaction intermediates, making them promising electrocatalysts for reactions beyond the ones listed, especially other hydrogenation reactions. However, Ni2P and other TMPs are susceptible to oxidation, which can lead to catalyst degradation and loss in certain conditions. Stability is an important part of catalysis; therefore, it is important to understand the degradation mechanism of Ni2P in order to mitigate corrosion, accurately predict surface reactivity, and prepare Ni2P for industrial electrocatalysis. Previous reports on Ni-P alloys found passivation regimes through anodic polarization but others saw complete dissolution at more oxidizing potentials. Bulk nickel phosphides have been shown to have a passivated surface, and characterization, often limited to ex-situ spectroscopy after the fact, has shown that the surface is composed of nickel hydroxides, phosphates, and oxyhydroxides. In the present work, operando Ni K-edge X-ray absorption spectroscopy and polarization are combined to understand the electrochemical degradation of Ni2P nanoparticles.Ni2P nanoparticles were synthesized by heating NiCl2 and tris(diethylamino)phosphine in oleylamine and thermally annealed at 450 °C under 5% H2/95% N2. Transmission-mode Ni K-edge X-ray absorption spectroscopy was conducted on benchtop spectrometers (easyXAFS) using a 3D-printed electrochemical cell designed for operando spectroscopy. Nanoparticles maximize surface to bulk atom ratio, which is beneficial both for electrocatalysis, less atoms are necessary to have the same number of active sites, and for X-ray absorption, spectra are more surface sensitive. The use of a benchtop spectrometer offers the flexibility to iterate on experiments on the fly and the power to acquire synchrotron quality data on a routine basis. Preliminary results in neutral phosphate buffered electrolyte indicate that Ni2P significantly oxidizes and dissolves at and beyond 0.8 V vs RHE which agrees with anodic polarization corrosion experiments. Ongoing work extends anodic polarization experiments to acidic and basic pH and probes the potentials at which oxidation is no longer reversible. We hypothesize that dissolution will be less severe with increased pH and reduction of oxidized species to Ni2P will no longer be possible after the onset of Ni dissolution.

Mn‐Doped CoFeP Nanosheets as Effective Electrocatalysts for Superior Overall Water Splitting

For green hydrogen, the exploitation of advanced electrocatalysts is crucial, and transition metal phosphides have great potential in water splitting due to their abundant reserves and optimized electronic structure. Herein, a synergistic approach involving Mn doping and phosphorization is applied to CoFe‐layered double hydroxide nanoflowers to produce a series of bifunctional catalysts Mn‐doped CoFeP (Mn‐CoFeP). Electrochemical evaluations demonstrate that the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance of Mn(10%)‐CoFeP both have notable improvement in 1 M KOH, with the overpotentials of only 160 and 239 mV to achieve current densities of 10 and 100 mA cm−2, respectively. Comparative electrocatalytic analysis indicates that moderate Mn doping mainly contributes to improve the OER performance, while the phosphorization significantly enhances the HER activity, resulting in effective bifunctional catalysis. For overall water decomposition, a total hydrolysis electrolysis cell equipped with the Mn(10%)‐CoFeP bifunctional catalyst requires only 1.64 V to reach a current density of 10 mA cm−2. Furthermore, it performs stable operation for 10 h at a current density of 10 mA cm−2 with a current maintenance rate of 83.6%. This work offers new insights into preparing effective bifunctional electrocatalysts, advancing clean energy development.

Green preparation of high-efficiency mesoporous MoP electrocatalyst for hydrogen evolution

The production of hydrogen generation catalysts through inexpensive, green and sustainable route is urgently needed in the context of “double carbon”. In this work, a new mesoporous transition metal phosphide (P–MoP@C) as electrocatalytic hydrogen evolution catalyst was prepared by a soft template method using polyoxometalate (POM), biomass gallic acid and ammonium polyphosphate through one-step phosphating and calcination process. The mesoporous structure is formed by organic-organic self-assembly strategy facilitated by strong hydrogen bonding between the pyrogallol group on gallic acid and the block copolymer. P–MoP@C shows good catalytic and stability properties, with overpotentials of 149 and 162 mV in alkaline and acidic solutions, respectively, at a current density of 10 mA cm−2. The mesoporous structure adds up to the quantity of exposed active sites, accelerates the electron transfer rate, and improves the catalytic performance of P–MoP@C. The use of plant polyphenols as a carbon source for the synthesis of green and environmentally friendly hydrogen evolution catalysts provides some reference value for large-scale industrial production.

Surface charge rearrangement modulation of N, P co-doped carbon induced by iron-cobalt phosphide with cationic vacancies for efficient contaminant removal

Cationic vacancies engineering and interfacial engineering are effective strategies for transition metal phosphides (TMPs)-based electrocatalysts to modulate the electronic structure and improve the acidic stability. However, the complexity of the above dual-strategy coupling poses a challenge. Herein, a novel bifunctional electrocatalyst of N, P co-doped carbon-coated iron-cobalt phosphide with cationic vacancies (V-CoFeP@NPC/CC) is synthesized. The physicochemical properties and electrochemical behaviour of V-CoFeP@NPC/CC can be modulated through regulating the cationic vacancies type on CoFeP. Density function theory (DFT) calculation reveals that cationic vacancies, especially bicationic vacancies, endow electrocatalysts stronger charge transfer, strengthened charge rearrangement, optimized intermediate adsorption energy and lower energy barriers. As expected, the resulting V-CoFeP@NPC/CC electrocatalysts displays excellent durability, strong mineralisation capacity and wide adaptability, which can remove nearly 100 % tetracycline within 60 min. Encouragingly, V-CoFeP@NPC/CC also demonstrate satisfactory performance in simultaneous electrooxidative removal of contaminant and hydrogen evolution reaction. This study offers new insight into design and regulate TMPs-based electrocatalysts via introducing cationic vacancies and modulating multi-components.

Selective non-radical Co(IV)=O formation via precise nitrogen coordination of high-spin cobalt atoms

High-valent metal oxides (HVMOs) exhibited strong selective oxidation capabilities for organic contaminants in advanced oxidation processes (AOPs). However, their production was often limited by the strong binding of oxygen ligands to metals in high valence states. In this investigation, we fabricated a nitrogen-enriched CoMnP catalyst through the heteroatom doping of transition metal phosphides (TMPs), effectively boosting the production of HVMOs and exhibiting robust activation of peroxymonosulfate (PMS) for the breakdown of triadimefon (TDF). The Co(IV)=O was pinpointed as the key reactive oxygen species (ROS) driving the degradation of TDF. And the introduction of nitrogen was establishing a localized polar electric field along the P → Co → N axis, leaded to electron withdrawal near the Co-P bond, improving Co electron delocalization weakened by dispersed phosphorus distribution. Such enhanced delocalization increased the likelihood of Co(IV)=O formation through the loss of double electrons by Co, consistent with the coupled electron–proton transfer (CEPT) mechanism. This research introduced an innovative approach to the targeted development of potent catalysts for the production of HVMOs.

Pomegranate-like cobalt Phosphides@P-Doped carbon Nanostructures with controlled phase as anode materials for Lithium-Ion batteries

Transition metal phosphides (TMPs) have recently emerged as prominent energy conversion and storage materials owing to their unique physicochemical property. Nevertheless, it’s still a difficult task to obtain phase-control of TMPs owing to multiple energetically favorable stoichiometries. Herein, a phase-controllable cobalt phosphide@C with the pomegranate core–shell structure are successfully realized by employing Co-glycerate as precursors and phytic acid (PA) as P sources, etching and coordination agents. With the presence of six phosphoryl groups and the strong coordination ability, PA allows the self-phosphating of Co atoms and the P-doped carbon shell, as well as the confinement of the obtained nanoparticles Additionally, as an organic acid, PA can etch the Co-glycerate precursors with the formation of hollow structures. With different etching time, metal-rich phosphides Co2P@C and monophosphides CoP@C are successfully achieved. When applied as anode materials, CoP@C demonstrates superior lithium storage performance by delivering a prominent reversible capacity up to 1187 mAh/g at 0.1 A/g and shows no capacity loss at 1 A/g after 500 cycles. This work presents a simple protocol to obtain TMPs with tunable metal/phosphorus ratios, phase selectivity and interface engineering, which could be applied in the field of energy storage and electrocatalysis.

Heterointerfacial engineering of N,P-doped carbon nanosheets supported Co/Co2P nanoparticles for boosting oxygen reduction and oxygen evolution reactions towards rechargeable Zn-air battery

Transition metal phosphides (TMPs) with high electrocatalytic activity for the oxygen evolution reaction (OER) are reckoned as a substitution of precious group metals catalysts in rechargeable Zn-air battery. In this work, Co/Co2P heterojunction nanoparticles supported N,P-doped carbon nanosheets (Co/Co2P@NPCNS) were designed and prepared via a facile one-step molten salt-assisted pyrolysis process. Density function theory calculations reveal that the heterogeneous interactions of Co/Co2P effectively enhance the bifunctional electrocatalytic activity for oxygen reduction reaction (ORR) and OER. The synergistic interaction between the Co/Co2P heterojunction nanoparticles with highly exposed active sites and excellent catalytic activity and the two-dimensional doped carbon nanosheets with high conductivity contributes to Co/Co2P@NPCNS exhibiting preeminent bifunctional ORR/OER activity and stability with a high half-wave potential for ORR (0.87 V), a low overpotential for OER (302 mV at 10 mA cm−2) and a low potential gap (0.66 V). The homemade rechargeable Zn-air battery performs high peak power density (187 mW cm−2) and exceptional endurance. This heterogeneous interface tactic of integrating TMPs with heteroatom-doped carbon materials may shed light on the research and development of non-precious metal electrocatalysts.

Oxygen-doped FeP on Ti Foil with Ti3O Interlayer for Efficient and Durable Electrolysis.

The development of electrocatalysts with low cost, high efficiency, and long-term durability is crucial for advancing green hydrogen production. Transition metal phosphides (TMPs) have been proved to be efficient electrocatalyst, while the improvement in the performance and durability of the TMPs remains a big challenge. Employing atmospheric pressure chemical vapor deposition (APCVD) and phosphorization, FeP/Ti electrodes are fabricated featuring controllable oxygen ingredients (O-FeP/Ti). This manipulation of oxygen content fine-tunes the electronic structure of the catalyst, resulting in improved surface reaction kinetics and catalytic activity. The optimized O-FeP-400/Ti exhibits outstanding HER activity with overpotentials of 142 and 159 mV at -10 mA cm-2 in 0.5 M H2SO4 and 1 M KOH, respectively. Notably, the obtained O-FeP/Ti cathode also displays remarkable durability of up to 200 h in acidic electrolyte with surface topography remaining intact. For the first time, the low-valence titanium oxide (Ti3O) interlayer is identified in the composite electrode and ascribed for the superior connection between Ti substrate and the surface O-FeP catalyst, as supported by experimental results and density functional theory (DFT) analysis. This work has expanded the potential applications of transition metal phosphides (TMPs) as a cost-effective, highly efficient and durable catalyst for water splitting.

Direct Conversion of Metal Organic Frameworks into Porous Rugby Phosphides by Plasma for Oxygen Evolution.

Electrolytic seawater is a green, sustainable, and promising approach for hydrogen production. Benefiting from the cost-effectiveness, crystal structures, and tailorable modification, transition metal phosphides become a highly attractive catalyst for the electrolysis of water. Considering the sufficient exposure and intrinsic catalytic activity of metal sites, here, carbon layer-coated NiFeP nanocrystals with a porous rugby structure are synthesized by Ar-H2 plasma. Activated PH radical in plasma is the key point to achieve phosphatization at a low temperature. The obtained porous rugby NiFeP catalyst exhibits excellent catalytic activity under alkaline conditions (300 mV in freshwater and 370 mV in seawater, 1000 mA cm-2), good corrosion resistance, and superior operational stability (>100 h). Theoretical calculations prove that Fe introduction and subsequent phosphorization weaken the adsorption of *O and *OH, thus improving the oxygen evolution reaction performance. Plasma phosphorization offers exciting opportunities for the in situ modification of other types of framework materials.

Free-standing medium-entropy porous needle-like FeCoCuNi phosphide nanowires-formed flower clusters/carbon fiber anode with high capacity and long durability for sodium-ion batteries

The drastic volume expansion and slow sodium-ion kinetics hinder the practical application of phosphides with high specific capacity and low discharge voltage in sodium-ion batteries (SIBs). Herein, we introduced entropy configuration into nanostructures and prepared a novel free-standing, three-dimensional, porous needle-like medium-entropy Fe, Co, Cu, Ni phosphide (ME-FCCNP) nanowires-formed flower clusters/carbon fiber cloth (CFC) anode (ME-FCCNP@CFC) for SIBs. The distorted lattices caused by medium-entropy configuration provide abundant sites for sodium-ion reactions and improve the electron transfer rate. The medium-entropy effects improve the mechanical stability, while the three-dimensional networks and porous needle-like nanowires provide sufficient space for the volume expansion. These combined properties enable the ME-FCCNP@CFC electrode to exhibit a high-rate capability of 170.8 mAh g−1 at 5.0 A g−1 and deliver a specific capacity of 325.8 mAh g−1 after 2000 cycles at 2.0 A g−1, far surpassing most of reported transition-metal phosphides. Moreover, the Na3V2(PO4)3 || ME-FCCNP@CFC full cell showcases a high-energy density of 256.8 Wh kg−1 and a long cycling life (267.8 mAh g−1 at 2.0 A g−1 with a capacity retention of 83.2 % after 1000 cycles). These results provide significantly promising implications for the anode design of SIBs by employing self-supporting and medium-entropy structures.