Recent advances in transition metal phosphide materials:Synthesis and applications in supercapacitors

Supercapacitors(SCs)are considered promising energy storge systems because of their outstanding power density,fast charge and discharge rate and long-term cycling stability.The exploitation of cheap and efficient electrode materials is the key to improve the performance of supercapacitors.As the battery-type materials,transition metal phosphides(TMPs)possess high theoretical specific capacity,good electrical conductivity and superior structural stability,which have been extensively studied to be electrode materials for supercapacitors.In this review,we summarize the up-to-date progress on TMPs materials from diversified synthetic methods,diverse nanostructures and several prominent TMPs and their composites in application of supercapacitors.In the end,we also propose the remaining challenges toward the rational discovery and synthesis of high-performance TMP electrodes materials for energy storage.

Templated synthesis of transition metal phosphide electrocatalysts for oxygen and hydrogen evolution reactions

Transition metal phosphides(TMPs)have been regarded as alternative hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts owing to their comparable activity to those of noble metal-based catalysts.TMPs have been produced in various morphologies,including hollow and porous nanostructures,which are features deemed desirable for electrocatalytic materials.Templated synthesis routes are often responsible for such morphologies.This paper reviews the latest advances and existing challenges in the synthesis of TMP-based OER and HER catalysts through templated methods.A comprehensive review of the structure-property-performance of TMP-based HER and OER catalysts prepared using different templates is presented.The discussion proceeds according to application,first by HER and further divided among the types of templates used-from hard templates,sacrificial templates,and soft templates to the emerging dynamic hydrogen bubble template.OER catalysts are then reviewed and grouped according to their morphology.Finally,prospective research directions for the synthesis of hollow and porous TMP-based catalysts,such as improvements on both activity and stability of TMPs,design of environmentally benign templates and processes,and analysis of the reaction mechanism through advanced material characterization techniques and theoretical calculations,are suggested.

Integration of morphology and electronic structure modulation on cobalt phosphide nanosheets to boost photocatalytic hydrogen evolution from ammonia borane hydrolysis

The controllable and safe hydrogen storage technologies are widely recognized as the main bottleneck for the accomplishment of sustainable hydrogen energy.Ammonia borane(AB)has regarded as a competitive candidate for chemical hydrogen storage.However,developing efficient yet high-performance catalysts towards hydrogen evolution from AB hydrolysis remains an enormous challenge.Herein,cobalt phosphide nanosheets are synthesized by a facile salt-assisted along with low-temperature phosphidation strategy for simultaneously modulating its morphology and electronic structure,and function as hydrogen evolution photocatalysts.Impressively,the Co_(2)P nanosheets display extraordinary performance with a record high turnover frequency of 44.9 min^(-1),outperforming most of the noble-metal-free catalysts reported to date.This remarkable performance is attributed to its desired nanosheets structure,featuring with high specific surface area,abundant exposed active sites,and short charge diffusion paths.Our findings provide a novel strategy for regulating metal phosphides with desired phase structure and morphology for energy-related applications and beyond.

Stability and melting behavior of boron phosphide under high pressure

Boron phosphide(BP)has gained significant research attention due to its unique photoelectric and mechanical properties.In this work,we investigated the stability of BP under high pressure using x-ray diffraction and scanning electron microscope.The phase diagram of BP was explored in both B-rich and P-rich environments,revealing crucial insight into its behavior at 5.0 GPa.Additionally,we measured the melting curve of BP from 8.0 GPa to 15.0 GPa.Our findings indicate that the stability of BP under high pressure is improved within B-rich and P-rich environments.Furthermore,we report a remarkable observation of melting curve frustration at 10.0 GPa.This study will enhance our understanding of stability of BP under high pressure,shedding light on its potential application in semiconductor,thermal,and light-transmitting devices.

A general synthetic strategy for N, P co-doped graphene supported metal-rich noble metal phosphides for hydrogen generation

The exploitation of electrocatalysts with high activity and durability for HER is desirable for future energy systems,but it is still a challenge.NMPs have attracted increasing attentions,but the preparation process often needs toxic regents or dangerous reaction conditions.Herein,we develop a general green method to fabricate metal-rich NMPs anchored on NPG through pyrolyzing DNA cross-linked complexes.The obtained Ru_(2) P-NPG exhibits an ultrasmall overpotential of 7 mV at 10 mA cm^(2) and ultralow Tafel slope of 33 mV dec^(-1) in 1.0 mol L?1 KOH,even better than that of commercial Pt/C.In addition,Ru 2 P-NPG also shows low overpotentials of 29 and 78 mV in 0.5 mol L^(-1) H_(2)SO_(4) and 1.0 mol L^(-1) PBS,respectively.The superior activity can be attributed to the ultrafine dispersion of Ru 2 P nanoparticles for more accessible sites,more defects formed for abundant active sites,the two-dimensional plane structure for accelerated electron transfer and mass transport,as well as the regulation of electron distribution of the catalyst.Moreover,the synthetic method can also be applied to prepare other metal-rich noble metal phosphides(Pd_(3)P-NPG and Rh_(2)P-NPG),which also exhibits high activity for HER.This work provides an effective strategy for designing NMP-based electrocatalysts.

Enhancing water-dissociation kinetics and optimizing intermediates adsorption free energy of cobalt phosphide via high-valence Zr incorporating for alkaline water electrolysis

Developing high-efficiency electrocatalysts for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) is required to enhance the sluggish kinetics of water dissociation and optimize the adsorption free energy of reaction intermediates.Herein,we tackle this challenge by incorporating high-valence Zr into CoP(ZrxCo_(1-x)P),which significantly accelerates the elementary steps of water electrolysis.Theoretical calculations indicate that the appropriate Zr incorporation effectively expedites the sluggish H2O dissociation kinetics and optimizes the adsorption energy of reaction intermediates for boosting the alkaline water electrolysis.These are confirmed by the experimental results of Zr_(0.06)Co_(0.94)P catalyst that delivers exceptional electrochemical activity.The overpotentials at the current density of 10 mA cm^(-2)(j10) are only 62(HER) and 240 mV(OER) in alkaline media.Furthermore,the Zr_(0.06)Co_(0.94)P/CC‖Zr_(0.06)Co_(0.94)P/CC system exhibits superior overall water splitting activity(1.53 V/j10),surpassing most of the reported bifunctional catalysts.This high-valence Zr incorporation and material design methods explore new avenues for realizing high-performance non-noble metal electrocatalysts.

Unveiling the Optimal Interfacial Synergy of Plasma-Modulated Trimetallic Mn-Ni-Co Phosphides:Tailoring Deposition Ratio for Complementary Water Splitting

Designing highly active,durable,and nonprecious metal-based bifunctional electrocatalysts for overall water electrolysis is of urgent scientific importance to realize the sustainable hydrogen production,which remains a grand challenge.Herein,an innovative approach is demonstrated to synthesize flower-like 3D homogenous trimetallic Mn,Ni,Co phosphide catalysts directly on nickel foam via electrodeposition followed by plasma phosphidation.The electrochemical activity of the catalysts with varying Mn:Ni:Co ratios is assessed to identify the optimal composition,demonstrating that the equimolar trimetallic phosphide yields an outstanding HER catalytic performance with a current density of 10 mA cm^(-2) at an ultra-low overpotential of~14 mV,outperforming the best reported electrocatalysts.This is asserted by the DFT calculations,revealing strong interaction of the metals and the P atom,resulting in enhanced water activation and optimized G_(H)^(*)values for the HER process.Moreover,this optimal composition appreciably catalyzes the OER by exposing more intrinsic active species in-situ formed on the catalyst surface during the OER.Therefore,the Mn_(1)-Ni_(1)-Co_(1)-P-(O)/NF catalyst exhibits a decreased overpotential of~289 mV at 10 mA cm^(-2).More importantly,the electrocatalyst sustains perfect durability up to 48 h at a current density of 10 mA cm^(-2) and continued 5000 cycling stability for both HER and OER.Meanwhile,the assembled MNC-P/NF||MNC-P/NF full water electrolyzer system attains an extremely low cell voltage of 1.48 V at 10 mA cm^(-2).Significantly,the robust stability of the overall system results in a remarkable current retention of~96%after a continuous 50-h run.Therefore,this study provides a facile design and a scalable construction of superb bifunctional ternary MNC-phosphide electrocatalysts for efficient electrochemical energy production systems.

One dimensional nickel phosphide polymorphic heterostructure as carbon-free functional support loading single-atom iridium for promoted electrocatalytic water oxidation

Although conducting materials such as carbon nanotube and carbon fiber paper(CFP)have been extensively employed as support of electrocatalytic active sites,most of them are of poor catalytic functionality by themselves and undesirable stability during strong acid/alkaline environments or oxidation process.Here we report a novel one-dimensional(1D)nickel phosphide polymorphic heterostructure(denoted as NPPH)to work as one effective carbon-free functional support for loading of single-atom Ir water oxidation electrocatalyst.Specifically,the NPPH composed of both Ni12P5and Ni2P phases is not only active for robust alkaline water oxidation but also is of good stability and hydrophilicity for favorable loading of single-atom dispersed iridium.The NPPH supported single-atom Ir electrocatalyst(Ir/NPPH)is found to exhibit remarkably superior water oxidation activity with respect to the NPPH itself or CFP supported single-atom Ir catalyst(Ir/CFP),demonstrating the synergetic promotion effect between NPPH and single-atom Ir catalyst.Furthermore,the NPPH supported single-atom Ir catalyst can bear alkaline water oxidation for over 120 h at current density of 50 mA cm^(-2).The NPPH developed here is expected as functional support to composite with other water oxidation catalysts,as may be an alternative strategy of developing highly efficient carbon-free electrocatalysts.

Heterostructured bimetallic phosphide nanowire arrays with latticetorsion interfaces for efficient overall water splitting

Designing cost-effective and high-efficiency electrocatalysts is critical to the water splitting performance during hydrogen generation.Herein,we have developed Fe_(2)P-Co_(2)P heterostructure nanowire arrays with excellent lattice torsions and grain boundaries for highly efficient water splitting.According to the microstructural investigations and theoretical calculations,the lattice torsion interface not only contributes to the exposure of more active sites but also effectively tunes the adsorption energy of hydrogen/oxygen intermediates via the accumulation of charge redistribution.As a result,the Fe_(2)P-Co_(2)P heterostructure nanowire array exhibits exceptional bifunctional catalytic activity with overpotentials of 65 and 198 mV at 10 mA cm^(-2) for hydrogen and oxygen evolution reactions,respectively.Moreover,the Fe_(2)P-Co_(2)P/NF-assembled electrolyzer can deliver 10 mA cm^(-2) at an ultralow voltage of1.51 V while resulting in a high solar-to-hydrogen conversion efficiency of 19.8%in the solar-driven water electrolysis cell.

Recent advances of metal phosphides for Li-S chemistry

Li-S batteries have been considered as one of advanced next-generation energy storage systems owing to their remarkable theoretical capacity(1672 m Ah g^(-1))and high energy density(2600 Wh kg^(-1)).However,critical issues,mainly pertaining to lithium polysulfide shuttle and slow sulfur reaction kinetics,have posed a fatal threat to the electrochemical performances of Li-S batteries.The situation is even worse for high sulfur-loaded and flexible cathodes,which are the essential components for practical Li-S batteries.In response,the use of metal compounds as electrocatalysts in Li-S systems have been confirmed as an effective strategy to date.Particularly,recent years have witnessed many progresses in phosphidesoptimized Li-S chemistry.This has been motivated by the superior electron conductivity and high electrocatalytic activity of phosphides.In this tutorial review,we offer a systematic summary of active metal phosphides as promoters for Li-S chemistry,aiming at helping to understanding the working mechanism of phosphide electrocatalysts and guiding the construction of advanced Li-S batteries.

Porous palladium phosphide nanotubes for formic acid electrooxidation

The development of an efficient catalyst for formic acid electrocatalytic oxidation reaction(FAEOR)is of great significance to accelerate the commercial application of direct formic acid fuel cells(DFAFC).Herein,palladium phosphide(PdxPy)porous nanotubes(PNTs)with different phosphide content(i.e.,Pd3P and Pd5P2)are prepared by combining the self-template reduction method of dimethylglyoxime-Pd(II)complex nanorods and succedent phosphating treatment.During the reduction process,the self-removal of the template and the continual inside-outside Ostwald ripening phenomenon are responsible for the generation of the one-dimensional hollow and porous architecture.On the basis of the unique synthetic procedure and structural advantages,Pd3P PNTs with optimized phos phide content show outstanding electroactivity and stability for FAEOR.Im portantly,the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction,which effectively enhances the FAEOR electroactivity of Pd3P PNTs.In view of the facial synthesis,excellent electroactivity,high stability,and unordinary selectivity,Pd3P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC.

Metal-organic framework-derived phosphide nanomaterials for electrochemical applications

Because of features,such as adjustable structures,high porosity,and high crystallinity,metal-organic frameworks(MOFs)deservedly have received considerable attention.Nevertheless,there is still room for improvements in the electrical conductivity and chemical stability of some MOFs,because of which they cannot be utilized as electrode materials.Fortunately,MOF derivatives have received widespread attention in recent years,especially phosphide materials,which are widely used in practical applications because of their outstanding conductivity,excellent specific surface area,and standout charge mobility.In this review,the latest developments of MOF-derived phosphides in electrocatalysis related to energy,including the excellent performance in terms of electrochemical energy storage and ingenious strategies,and diversified synthetic approaches are emphasized and summarized.Additionally,the arduous task and feasible proposals of MOF-derived phosphides are also discussed.

Toward Flexible and Wearable Embroidered Supercapacitors from Cobalt Phosphides-Decorated Conductive Fibers

Wearable supercapacitors(SCs)are gaining prominence as portable energy storage devices.To develop high-performance wearable SCs,the significant relationship among material,structure,and performance inspired us with a delicate design of the highly wearable embroidered supercapacitors made from the conductive fibers composited.By rendering the conductive interdigitally patterned embroidery as both the current collector and skeleton for the SCs,the novel pseudocapacitive material cobalt phosphides were then successfully electrodeposited,forming the first flexible and wearable in-plane embroidery SCs.The electrochemical measurements manifested that the highest specific capacitance was nearly 156.6 mF cm?2(65.72 F g?1)at the current density of 0.6 mA cm?2(0.25 A g?1),with a high energy density of 0.013 mWh cm?2(5.55 Wh kg?1)at a power density of 0.24 mW cm?2(100 W kg?1).As a demonstration,a monogrammed pattern was ingeniously designed and embroidered on the laboratory gown as the wearable in-plane SCs,which showed both decent electrochemical performance and excellent flexibility.

Deoxygenation of methyl laurate to hydrocarbons on silica-supported Ni-Mo phosphides: Effect of calcination temperatures of precursor

SiO2-supported Ni-Mo bimetallic phosphides were prepared by temperature-programmed reduction （TPR） method from the phosphate precur- sors calcined at different temperatures. Their properties were characterized by means of ultraviolet-visible diffuse reflectance spectroscopy （UV-Vis DRS）, H2 temperature-programmed reduction （H2-TPR）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, CO chemisorption, H2 and NH3 temperature-programmed desorptions （H2-TPD and NH3-TPD）. Their catalytic performances for the deoxygena- tion of methyl laurate were tested in a fixed-bed reactor. When the precursors were calcined at 400 and 500 ℃, respectively, NiMoP2 phase could be formed apart from Ni2P and MoP phases in the prepared C400 and C500 catalysts. However, when the precursors were calcined at 600, 700 and 800 ℃, respectively, only Ni2P and MoP phases could be detected in the prepared C600, C700 and C800 catalysts. Also, in C400, C500 and C600 catalysts, Mo atoms were found to be entered in the lattice of Ni2P phase, but the entering extent became less with the increase of calcination temperature. As the calcination temperature of the precursor increased, the interaction between Ni and Mo in the prepared catalysts decreased, and the phosphide crystallite size tended to increase, subsequently leading to the decrease in the surface metal site density and the acid amount. C600 catalyst showed the highest activity among the tested ones for the deoxygenation of methyl laurate. As the calcination temperature of the precursor increased, the selectivity to C12 hydrocarbons decreased while the selectivity to C11 hydrocarbons tended to increase. This can be mainly attributed to the decreased Ni-Mo interaction and the increased phosphide particle size. In sum, the structure and performance of Ni-Mo bimetallic phosphide catalyst can be tuned by the calcination temperature of precursor.

Metal-organic frameworks derived transition metal phosphides for electrocatalytic water splitting

It is critical to synthesize high-efficiency electrocatalysts to boost the performance of water splitting to meet the requirements of industrial applications. Metal-organic frameworks(MOFs) can function as ideal molecular platforms for the design of highly reactive transition metal phosphides(TMPs), a kind of candidates for high-efficiently electrocatalytic water splitting. The intrinsic activity of the electrocatalysts can be greatly improved via modulating the electronic structure of the catalytic center through the MOF precursors/templates. Moreover, the carbon layer converted in-situ by the organic ligands can not only protect the TMPs from being degraded in the harsh electrochemical environments, but also avoid agglomeration of the catalysts, thereby promoting their activities and stabilities. Furthermore,heteroatom-containing ligands can incorporate N, S or P, etc. atoms into the carbon matrixes after conversion, regulating the coordination microenvironments of the active centers as well as their electronic structures. In this review, we first summarized the latest developments in MOF-derived TMPs by the unique advantages in metal, organic ligand, and morphology regulations for electrocatalytic water splitting. Secondly, we concluded the critical scientific issues currently facing for designing state-of-the-art TMP-based electrocatalysts. Finally, we presented an outlook on this research area, encompassing electrocatalyst construction, catalytic mechanism research, etc.

Tin phosphide-carbon composite as a high-performance anode active material for sodium-ion batteries with high energy density

Tin phosphide(Sn_(4)P_(3))is a promising anode material for sodium-ion batteries because of its relatively large theoretical capacity,appropriate Na^(+) alloying potential,and good cyclic stability.Herein,the Sn_(4)P_(3) embedded into a carbon matrix with good rate performance and long cycle life is reported.The Sn_(4)P_(3)-C composite exhibits excellent rate performance(540 mAh g^(-1) at 5 A g^(-1))and the highest reversible capacity(844 mAh g^(-1) at 0.5 A ^(g-1))among Sn4P3-based anodes reported so far.Its reversible capacity is as high as 705 mAh g^(-1) even after 100 cycles at 0.5 A g^(-1).Besides,its initial Coulomb efficiency can reach 85.6%,with the average Coulomb efficiency exceeding 99.75%from the 3rd to 100th cycles.Na_(2)C_(6)O_(6) is firstly used as a cathode when Sn_(4)P_(3) acts as anode,and the Na-Sn_(4)P_(3)-C//Na_(2)C_(6)O_(6) full cell shows excellent electrochemical performance.These results demonstrate that the Sn_(4)P_(3)-C composite prepared in this work displays high-rate capability and superior cyclic performance,and thus is a potential anode for sodium ion batteries.

Cobalt phosphide nanoparticles supported within network of N-doped carbon nanotubes as a multifunctional and scalable electrocatalyst for water splitting

In order to realize industrial production of hydrogen through water splitting,it is essential to develop a cost-efficient and scalable approach to synthesize nonprecious electrocatalysts with sufficiently high activity and stability to replace commercial noble-metal-based electrocatalysts.Herein we synthesize cobalt phosphide nanoparticles dispersed within nitrogen-doped carbon nanotube network(CP@NCNT) via scalable spray drying and thermal treatments.As a multifunctional electrocatalyst,the CP@NCNT hybrid delivers outstanding activity for HER(in both acidic and alkaline electrolytes),OER and overall water splitting.Remarkably,it shows an ultra-low overpotental of 94 mV to obtain 10 mA cm-2 in HER.It also demonstrates outstanding activity in overall water splitting,requiring only 1.619 V to deliver 10 mA cm-2with more than 72 h’ long-term stability.The combination of notable performance,multi-functionality and highly scalable spray-drying synthesis method enables this material as a novel and cost-efficient transition metal-based electrocatalysts for overall water splitting.

Metal phosphides and borides as the catalytic host of sulfur cathode for lithium–sulfur batteries

Lithium−sulfur batteries are one of the most competitive high-energy batteries due to their high theoretical energy density of _(2)600 W·h·kg^(−1).However,their commercialization is limited by poor cycle stability mainly due to the low intrinsic electrical conductivity of sulfur and its discharged products(Li_(2)S_(2)/Li_(2)S),the sluggish reaction kinetics of sulfur cathode,and the“shuttle effect”of soluble intermediate lithi-um polysulfides in ether-based electrolyte.To address these challenges,catalytic hosts have recently been introduced in sulfur cathodes to en-hance the conversion of soluble polysulfides to the final solid products and thus prevent the dissolution and loss of active-sulfur material.In this review,we summarize the recent progress on the use of metal phosphides and borides of different dimensions as the catalytic host of sulfur cathodes and demonstrate the catalytic conversion mechanism of sulfur cathodes with the help of metal phosphides and borides for high-en-ergy and long-life lithium-sulfur batteries.Finally,future outlooks are proposed on developing advanced catalytic host materials to improve battery performance.

Amorphous iron-nickel phosphide nanocone arrays as efficient bifunctional electrodes for overall water splitting

The synthesis of low-cost and highly active electrodes for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is very important for water splitting.In this work,the novel amorphous iron-nickel phosphide(FeP-Ni)nanocone arrays as efficient bifunctional electrodes for overall water splitting have been in-situ assembled on conductive three-dimensional(3D)Ni foam via a facile and mild liquid deposition process.It is found that the FeP-Ni electrode demonstrates highly efficient electrocatalytic performance toward overall water splitting.In 1 M KOH electrolyte,the optimal FeP-Ni electrode drives a current density of 10 mA cm^(-2) at overpotential of 218 mV for the OER and120 mV for the HER,and can attain such current density for 25 h without performance regression.Moreover,a two-electrode electrolyzer comprising the FeP-Ni electrodes can afford 10 mA cm^(-2) electrolysis current at a low cell voltage of 1.62 V and maintain long-term stability,as well as superior to that of the coupled RuO_(2)/NFk Pt/C/NF cell.Detailed characterizations confirm that the excellent electrocatalytic performances for water splitting are attributed to the unique 3D morphology of nanocone arrays,which could expose more surface active sites,facilitate electrolyte diffusion,and benefit charge transfer and also favorable bubble detachment behavior.Our work presents a facile and cost-effective pathway to design and develop active self-supported electrodes with novel 3D morphology for water electrolysis.

Size-dependent catalytic activity of cobalt phosphides for hydrogen evolution reaction

Transition metal phosphides are a class of promising electrocatalysts for hydrogen evolution reaction(HER) to replace noble metals.In this work,we for the first time synthesize carbon supported CoP nanoparticles with the average particle sizes from 3.3 to 9.2 nm,via a solvothermal process followed by low-temperature topological phosphorization,and the size-dependent HER activity of the CoP is investigated by virtue of TEM,XRD,XPS and the electrochemical techniques.It is discovered that the 9.2nm-CoP particles possess high intrinsic HER catalytic activity as compared to the 3.3nm-CoP,although the smaller one displays a high mass activity due to the large surface area.Detailed studies manifest that the small CoP particles suffer from serious oxidation once exposing to air.In contrast,most cobalt remains in the quasi-metallic state in the relatively large CoP particles,which is beneficial for the desorption of Hads,the rate determining step of the HER process over CoP surface.In addition,the low charge transfer resistance across the liquid/solid interfaces also contributes to the excellent HER activity of the relatively large CoP particles.