Application Of Transition Metal Phosphides Research Articles

Advanced hollow structure with functional Interface of NiCoP/NC achieved superior hydroxide ion storage for high-rate supercapacitor

Sluggish reaction kinetics and poor structure stability are the main problems that hinder the application of transition metal phosphides. Differing from the traditional single ligand strategy, a hollow spherical NiCoP with large-scale NiCoP//NC interfaces (DL-NiCoP/NC) was synthesized through co-assembling metal-organic framework (MOF) of 2-methylimidazole and 5-aminotetrazole double ligands. The experimental and theoretical calculation results show that the hollow structure with rich NiCoP//NC interfaces adjusts the local electronic environment, increases the adsorption energy of NiCoP for OH− and effectively optimizes the surface/solution pathway for OH− transfer, which contributes to capacitive-controlled and diffusion-controlled reaction. Based on the above research, the electrochemical reaction process and structural evolution of DL-NiCoP/NC electrode were elucidated. Benefits from the synergistic effects of hollow structure and interfacial interaction, DL-NiCoP/NC electrode shows high specific capacitance (1551 F g−1 at 1 A g−1) and high-rate performance (78.1% capacitance retention at 30 A g−1). The assembled hybrid supercapacitor has favorable energy and power output (54.2 Wh kg−1 and 11,948.9 W kg−1), and excellent capacitance retention (83.7% after 8000 cycles). The fabricated pouch-type supercapacitor exhibited good application potential. This work provides a promising method to design structure with interface regulating for fast OH− storage materials.

NiCoP/g-C3N4 Schottky heterojunctions towards efficient photocatalytic NO oxidation

NiCoP/g-C3N4 Schottky heterojunctions were created by a two-step synthesis for enhanced NO oxidation. NiCo-layered double hydroxides (LDH) were grown on superior thin graphic carbon nitride (g-C3N4) nanosheets by a controlling chemical co-precipitation method. A phosphating process at 300 °C resulted in the transformation in situ of NiCo-LDH into NiCoP composite nanoparticles to create Schottky heterojunctions. Using optimized conditions, heterojunction sample 15-NiCoP/CN revealed excellent photocatalytic NO oxidation with a removal rate of 78%. Photogenerated electrons were efficiently separated and transferred because of Schottky barrier, interfacial charge transport channel, and enhanced light absorption efficiency. Photogenerated electrons reacted with adsorbed O2 to generate superoxide radicals (·O2¯) as crucial active species of NO oxidation. The test indicated that the concentration of·O2¯ for sample 15-NiCoP/CN reached 7.1 × 10−5 M which was 6.5 times higher than that of g-C3N4 after light irradiation. In addition, low NO2 generation and mineralization rate (92%) suggested that NO was converted into NO3- or NO2- rather than NO2 to mitigate secondary pollution. This result supplied a novel approach to explore the application of transition metal phosphides and g-C3N4 in photocatalytic NO oxidation.

Yolk-shell nickel–cobalt phosphides as bifunctional catalysts in the solvent-free hydrogenation of Levulinic acid to gamma-Valerolactone

The transformation of Levulinic acid (LA) to gamma-Valerolactone (GVL) is deemed an attractive biomass conversion reaction owing to the attainability of LA as a feedstock and the potential applications of GVL as a versatile building block, green solvent, and fuel additive. In this work, a series of nickel-cobalt phosphides (NixCoyP) was synthesized by a facile fabrication strategy consisting of hydrothermal and phosphating steps and was applied to the solvent-free hydrogenation of LA to GVL. These transition metal phosphides deliver promising catalytic potential due to their cheap cost, wide availability, and superior efficiency. However, their potential catalytic application in biomass-related reactions has not been widely investigated. The effect of the Ni:Co molar ratio, the acidity, and the hydrogen activation capability of these phosphides were studied and correlated with their catalytic performances. Among all the catalysts, Ni2Co1P achieved 100% LA conversion to GVL (100.0% GVL yield). Characterization results revealed that the outstanding catalytic performance of the phosphides could be attributed to their bifunctional substrate- and hydrogen-activating ability and acidic properties, and the synergistic effect manifested by Ni and Co. The catalysts also demonstrated good recyclability after five recycles without significant loss in their activity, which can be credited to the confinement effect provided by their yolk-shell structure. This successful exploitation of nickel-cobalt phosphides in the hydrogenation of LA to GVL opens new opportunities towards the possible catalytic application of transition metal phosphides in biomass transformation reactions.

Freestanding hierarchically 3D porous Co2P-Co@C films with superior electrochemical kinetics for enhanced lithium-ion batteries anode performance

Rapid electrochemical dynamics and stable structures are critical for the practical application of transition metal phosphides (TMPs)-based lithium-ion batteries anode materials. Herein, a facile strategy is developed to construct a self-supporting 3D porous dual-phase Co2P-Co film covered by a carbon layer (Co2P-Co@C) based on the bubble template method electrodeposition of CoP film, glucose adsorption, and annealing treatment. The electron/ion transport is improved due to a large number of active sites and increased conductivity of Co2P by Co and carbon coating. Meanwhile, the volume expansion is alleviated, benefiting from the sufficient space provided by porous structure and the protection of carbon layer. Consequently, the Co2P-Co@C film exhibits high reversible capacity (823 mAh g−1 at 0.2 A g−1 after 100 cycles), excellent rate capability (506 mA h g−1 at 4 A g−1) and outstanding long-term cycling stability (567.9 mAh g−1 at 2 A g−1 after 400 cycles).

General Method for Synthesis Transition‐Metal Phosphide/Nitrogen and Phosphide Doped Carbon Materials with Yolk‐Shell Structure for Oxygen Reduction Reaction

AbstractThe transition metal phosphides have gradually emerged as promising electrocatalysts candidate for oxygen reduction reaction in recent years. As a research hotspot of transition metal phosphides, exploring their mechanism of catalytic activity and the influence of unique morphology is of great significance. In this study, a series of yolk‐shell structure catalysts are fabricated only by pyrolyzing cyclophosphazene microspheres and metal salt without using any other templates, which M2P (M=Fe, Co, Ni) act as the core and N, P co‐doped carbon as the shell. The yolk‐shell structures aim to overcome the inferior conductivity and aggregation problems traditionally existed in application of transition metal phosphides through combination of transition metal phosphides and doped carbon materials. The prepared Fe2P/NPC, Co2P/NPC and Ni2P/NPC catalysts exhibit excellent ORR catalytic activity through the four‐electron pathway, together with large electrochemically active surface area, superior stability and admiring methanol tolerance.

Phytic Acid-Assisted Formation of Hierarchical Porous CoP/C Nanoboxes for Enhanced Lithium Storage and Hydrogen Generation.

Application of transition metal phosphides (TMPs) for electrochemical energy conversion and storage has great potential to alleviate the energy crisis. Although there are many methods to get TMPs, it is still immensely challenging to fabricate hierarchical porous TMPs with superior electrochemical performances by a simple, green, and secure approach. Herein, we report a facile method to synthesize the CoP/C nanoboxes by pyrolysis of phytic acid (PA) cross-linked Co complexes that are acquired from reaction of PA and ZIF-67. The PA can not only slowly etch ZIF-67 and gain a hollow structure but also act as a source of phosphorus to prepare CoP/C nanoboxes. The CoP/C nanoboxes deliver an ultrahigh specific capacity (868 mA h g-1 at 100 mA g-1) and excellent cycle stability (523 mA h g-1 after 1000 cycles at 500 mA h g-1) when used as anode materials for lithium-ion batteries. Moreover, when used as an electrocatalyst for hydrogen evolution reaction, the CoP/C nanoboxes exhibit ultralow overpotential, small Tafel slope, and excellent durability in acidic media. The method to produce CoP/C nanoboxes is easy and environmentally friendly and can be readily extended to design other TMPs/C nanocomposites.