Cobalt Phosphide Nanowires Research Articles

Optimizing the rate capability of nickel cobalt phosphide nanowires on graphene oxide by the outer/inter-component synergistic effects

Bimetallic phosphides have been identified as promising alternative electrode materials owing to their admirable conductivity and electrochemical activity.

Cobalt Phosphide Anchored on Graphene Naonosheet As High-Capacity Anodes for Li-Ion Battery

Traditional anodes for Li-ion batteries (LIBs) including graphite, TiO2 and Li4Ti5O12, generally have specific capacities less than 200 mAh g-1, which no longer meet rapidly increasing commercial demands. In recent years, various novel anode materials, such as metals, alloys, silicon, transition metal oxides (TMOs) and sulfides, have been widely studied because they can achieve much higher capacity than traditional anodes.[1] Transition metal phosphides (TMPs) have been investigated extensively owing to their high theoretical capacities and relatively low intercalation potentials vs Li/Li+.[2] In particular, cobalt phosphide (CoP), with a theoretical capacity of ∼894 mAh g-1 , has been proven to be one of the most promising candidates for LIB anodes.[3] To date, various CoP materials have been investigated,[4, 5] but their specific capacity and stability are still unsatisfactory due to low electric conductivity and fast structural degradation during high-rate or long-term charge/discharge processes. Herein, we report on a robust high-capacity anode based on CoP/reduced graphene oxide (rGO) nanocomposite.[6] We conduct a facile and versatile strategy involving an oil bath, freeze drying and phosphidation processes, allowing nanostructured CoP particles to be uniformly embedded in rGO nanosheet network. The resulting CoP/rGO nanocomposite can exhibit enough surface area and porosity, which can improve the electrolyte diffusion. Meanwhile, the rGO network can enhance the electrical conductivity and structural stability of active CoP anodes. Electrochemical measurements indicate that the CoP/rGO nanocomposite shows a high specific capacity over 1100 mAh g-1 at a current density of 100 mA g-1. A capacity retention of ~840 mAh g-1 is obtained when the current density increases to 2 A g-1, which reveals an excellent rate capability. The nanocomposite also shows a ultralong cycle life of 2000 stable cycles at a high current density of 2 A g-1. These results indicate that our strategy is very effective and versatile to improve TMP-based anodes for the development of state-of-the-art LIBs. [1] N. Nitta, F. Wu, J.T. Lee, G. Yushin, Li-ion battery materials: present and future, Mater. Today, 18 (2015) 252-264. [2] L. Ji, Z. Lin, M. Alcoutlabi, X. Zhang, Recent developments in nanostructured anode materials for rechargeable lithium-ion batteries, Energy Environ. Sci., 4 (2011) 2682-2699. [3] J. Yang, Y. Zhang, C. Sun, H. Liu, L. Li, W. Si, W. Huang, Q. Yan, X. Dong, Graphene and cobalt phosphide nanowire composite as an anode material for high performance lithium-ion batteries, Nano Res., 9 (2016) 612-621. [4] W. Wang, J. Li, M. Bi, Y. Zhao, M. Chen, Z. Fang, Dual function flower-like CoP/C nanosheets: High stability lithium-ion anode and excellent hydrogen evolution reaction catalyst, Electrochim. Acta, 259 (2018) 822-829. [5] X. Xu, J. Liu, R. Hu, J. Liu, L. Ouyang, M. Zhu, Self-Supported CoP Nanorod Arrays Grafted on Stainless Steel as an Advanced Integrated Anode for Stable and Long-Life Lithium-Ion Batteries, Chem. Eur. J., 23 (2017) 5198-5204. [6] Y. Yang, Y. Jiang, W. Fu, X. Liao, Y. He, W. Tang, F. Alamgir, Z.-F. Ma, Cobalt phosphide embedded in graphene nanosheet network as a high-performance anode for Li-ion batteries, Dalton Trans., (2019) DOI: 10.1039/C1039DT01240K

Cobalt phosphide nanowires for fluorometric detection and in-situ imaging of telomerase activity via hybridization chain reactions.

The authors describe cobalt phosphide (CoP) nanowires for use in sensitive fluorometric determination of the activity of the enzyme telomerase. A hybridization chain reaction (HCR) is applied to amplify the signal and carboxyfluorescein (FAM)-labelled hairpin probes (H1 and H2) are applied to match the telomeric DNA sequence. The CoP nanowires act as both the photoinduced electron transfer (PET) acceptor to induce fluorescence quenching, and also as an efficient probe carrier to facilitate telomerase imaging in living cells. The telomerase-triggered primer extension initiates an alternating hybridization reaction between H1 and H2. These result in the dissociation of FAM-labelled probes from CoP nanowires and thus an enhancement of the green fluorescence. The method is fairly simple and was applied to the detection of three types of cancer cells. The detection limit is as low as 7 cells (in case of HeLa cells). Conceivably, the method has a large potential in terms of inhibitor drug screening. Graphical abstract Schematic presentation of telomerase detection based on cobalt phosphide (CoP) nanowires and hybridization chain reaction (HCR). The telomerase-triggered primer extension can initiate the alternating hybridization reaction between carboxyfluorescein (FAM)-labelled hairpin probes (H1 and H2), and the generated long DNA duplex cannot be adsorbed on theCoP nanowires. This prevents the photoinduced electron transfer (PET) from FAM to CoP nanowires.

Engineering inner-porous cobalt phosphide nanowire based on controllable phosphating for efficient hydrogen evolution in both acidic and alkaline conditions

Cobalt phosphide has been extensively studied as non-precious metal-based robust electrocatalyst for hydrogen evolution reaction. Innovation breakthrough is still highly desired to enhance its catalytic efficiency. In this work, through rational engineering strategy, a controlled inner-porous CoP nanowire array, which is vertical to the carbon fiber (ip-CoP/CF) was in-situ topotactically synthesized. The resulting ip-CoP/CF demonstrates improved hydrogen evolving efficiency in both acidic and alkaline conditions. At a current density of 10 mA∙cm−2, which with small Tafel slopes of 47 mV·dec−1 and 93 mV·dec−1 in acidic and alkaline solution, respectively. Such engineering strategy opens a diverting route to construct controllable inner-porous materials for high efficient electrocatalysts.

Cobalt Phosphide Nanowire Arrays on Conductive Substrate as an Efficient Bifunctional Catalyst for Overall Water Splitting

Hydrogen production via water splitting is a promising pathway to a clean energy resource. Herein we report the direct growth of cobalt phosphide (CoP) nanowires on conductive nickel foam (CoP@NF) ...

Synthesis of ternary nickel cobalt phosphide nanowires through phosphorization for use in platinum-free dye-sensitized solar cells

Nickel cobalt phosphide nanowires are fabricated on titanium foil through phosphating reaction from their nickel and cobalt hydroxide precursors, which are employed as the counter electrode materials for the dye-sensitized solar cell. Electrochemical investigations demonstrate that the ternary nickel cobalt phosphide counter electrode exhibits higher catalytic activity than that of the binary nickel phosphide and cobalt phosphide counter electrodes, which is due to that the introduction of two transition metals can adjust the valence electron and provide two electron donating active sites. The dye-sensitized solar cell with the ternary nickel cobalt phosphide counter electrode achieves a competitive photoelectric conversion efficiency of 8.01%, which is higher than that of the binary nickel phosphide (3.73%) and cobalt phosphide (2.80%) counter electrodes under the same conditions and comparable photovoltaic performance to that using the conventional platinum counter electrode (8.69%) for the dye-sensitized solar cell.

Bifunctional Conducting Polymer Coated CoP Core–Shell Nanowires on Carbon Paper as a Free‐Standing Anode for Sodium Ion Batteries

AbstractThis study proposes a conformal surface coating of conducting polymer for protecting 1D nanostructured electrode material, thereby enabling a free‐standing electrode without binder for sodium ion batteries. Here, polypyrrole (PPy), which is one of the representative conducting polymers, encapsulated cobalt phosphide (CoP) nanowires (NWs) grown on carbon paper (CP), finally realizes 1D core–shell CoP@PPy NWs/CP. The CoP core is connected to the PPy shell via strong chemical bonding, which can maintain a Co–PPy framework during charge/discharge. It also possesses bifunctional features that enhances the charge transfer and buffers the volume expansion. Consequently, 1D core–shell CoP@PPy NWs/CP demonstrates superb electrochemical performance, delivering a high areal capacity of 0.521 mA h cm−2 at 0.15 mA cm−2 after 100 cycles, and 0.443 mA h cm−2 at 1.5 mA cm−2 even after 1000 cycles. Even at a high current density of 3 mA cm−2, a significant areal discharge capacity reaching 0.285 mA h cm−2 is still maintained. The outstanding performance of the CoP@PPy NWs/CP free‐standing anode provides not only a novel insight into the modulated volume expansion of anode materials but also one of the most effective strategies for binder‐free and free‐standing electrodes with decent mechanical endurance for future secondary batteries.

Cobalt phosphide nanowires as efficient co-catalyst for photocatalytic hydrogen evolution over Zn0.5Cd0.5S

Previous studies have shown that co-catalysts play a pivotal role for improving both the activity and reliability of semiconductors in photocatalytic hydrogen production, however, designing highly efficient and cost-effective co-catalysts to replace expensive and rare metals is still a big challenge. In this work, DFT (density functional theory) is utilized to guide the application of CoP NWs (nanowires) as an earth-abundant co-catalyst for photocatalytic hydrogen production. Metallic 1D CoP NWs is rationally integrated with Zn0.5Cd0.5S solid solution semiconductor for the first time, to induce a remarkably improved photocatalytic hydrogen production activity of 12,175.8 μmol h−1 g−1, which is 22 times higher than that of the pristine Zn0.5Cd0.5S. This outstanding activity benefits from the collaborative advantages of excellent metallic conductivity and the rigid 1D nanostructure of CoP NWs. Moreover, the mechanism investigations demonstrate that this excellent activity arises from the strong electronic coupling, favourable band structure, highly efficient charge separation and migration based on the powerful characterizations, such as time-resolved PL decay spectra and photoelectrochemical methodology. This work brings new opportunities to employ 1D co-catalysts on photocatalysts for improving the catalytic activities in hydrogen production from water.

Carbon cloth-supported cobalt phosphide as an active matrix for constructing enzyme-based biosensor

A self-supported nanoporous cobalt phosphide (CoP) nanowire arrays on the carbon cloth (CC) as an active matrix was fabricated and utilized as an interface for the construction of hemoglobin (Hb)-based biosensors. This matrix was wrapped in a thin aluminum sheet by handmade. Moreover, the electrochemistry and electrocatalytic properties of Hb were investigated on such a matrix. The results revealed that the self-supported nanoporous CoP nanowire arrays on CC significantly enhanced the electrochemical responses of Hb. In the meantime, the immobilized Hb remained its good bioactivity and high catalytic activity to hydrogen peroxide (H2O2). This matrix is thus a suitable platform to develop highly sensitive enzyme-based biosensor, which has the linear range of H2O2 concentration from 2 to 2670 μM with a detection limit of 0.7 μM (S/N = 3). Consequently, it is desirable to explore the possibility of developing a kind of simpler and cheaper matrix electrode.

Hierarchical three-dimensional manganese doped cobalt phosphide nanowire decorated nanosheet cluster arrays for high-performance electrochemical pseudocapacitor electrodes.

Ternary metal phosphides with a self-assembled hierarchical nanostructure are promising electrode materials for energy storage and conversion, due to the unique architecture and synergistic effects in bimetallic nanostructures. In this communication, we demonstrate hierarchical Mn-doped cobalt phosphide nanowire decorated nanosheet cluster arrays with robust adhesion on Ni foam (Mn-CoP/NF) as a binder-free electrode for supercapacitors. Such a 3D electrode exhibits boosted areal specific capacitance over that for a single metal counterpart, with the accomplishment of 8.66 F cm-2 capacitance at 1 mA cm-2. Utilizing the Mn-CoP/NF electrode as an anode and an activated carbon (AC) electrode as a cathode, an asymmetric supercapacitor (ASC) of Mn-CoP//AC attains a high area capacitance of 2.05 F cm-2 at 5 mA cm-2 and a high capacitance retention of 88.9% after 4000 cycles. In addition, the assembled ASC shows superior electrochemical performances with a high energy density of 35.21 W h kg-1 at a power density of 193 W kg-1 and of 30.87 W h kg-1 even at 1939 W kg-1.

Three-Dimensional Cobalt Phosphide Nanowire Arrays as Negative Electrode Material for Flexible Solid-State Asymmetric Supercapacitors.

Despite the great progress that has been accomplished in supercapacitors, the imbalance of the development of positive and negative electrode materials still remains a critical issue to achieve high energy density; therefore, exploring high-performance negative electrode materials is highly desirable. In this article, three-dimensional cobalt phosphide (CoP) nanowire arrays were synthesized on a carbon cloth and were utilized as a binder-free supercapacitor negative electrode. The as-synthesized CoP nanowire arrays presented a high capacitance of 571.3 mF/cm2 at a current density of 1 mA/cm2. By using CoP nanowire arrays as the negative electrode and MnO2 nanowire arrays as the positive electrode, a flexible solid-state asymmetric supercapacitor has been fabricated and has exhibited excellent electrochemical performance, such as a high energy density of 0.69 mWh/cm3 and a high power density of 114.2 mW/cm3. In addition, the solid-state asymmetric supercapacitor shows high cycle stability with 82% capacitance retention after 5000 charge/discharge cycles. This work demonstrates that CoP is a promising negative electrode material for high-performance supercapacitor applications.

Nickel–Cobalt phosphide nanowires supported on Ni foam as a highly efficient catalyst for electrochemical hydrogen evolution reaction

The design and synthesis of highly active hydrogen evolution reaction (HER) catalyst with strong stability is highly desirable and challenging. In this work, we followed simple two-step strategy to grow Nickel–Cobalt phosphide nanowires (NiCoP NWs) directly on the Ni foam (NF) by hydrothermal method. Catalytic current density of 10 mA cm−2 at an overpotential of 118 mV has been obtained. Prepared material exhibited long-term stability and nearly 100% Faradaic efficiency in 0.5 M H2SO4 for HER. Ni and Co composite materials with amorphous structure are considered as better catalysts by exhibiting the higher activity. The results in this paper might promote further development of the advanced catalysts for special electrochemical properties and other devices.

Cobalt phosphide nanowire arrays grown on carbon cloth as novel electrode material for supercapacitors

It is very important to exploit new electrode materials to enhance supercapacitor performances. In this study, the mesoporous cobalt phosphide (CoP) nanowire arrays on carbon cloth have been fabricated by low-temperature phosphidation of hydrothermally obtained Co precursor. The CoP electrode shows a remarkable areal capacitance of 1.89F/cm2 at current densities of 3mA/cm2. Furthermore, the electrode exhibits excellent cycling stability (~3% loss after the repetitive 4000 cycles at 18mA/cm2) and Coulombic efficiency (~97.6% after 4000 cycles).

Vapor-solid synthesis of monolithic single-crystalline CoP nanowire electrodes for efficient and robust water electrolysis.

Electrochemical water splitting into hydrogen and oxygen is a promising technology for sustainable energy storage. The development of earth-abundant transition metal phosphides (TMPs) to catalyze the hydrogen evolution reaction (HER) and TMP-derived oxy-hydroxides to catalyze the oxygen evolution reaction (OER) has recently drawn considerable attention. However, most monolithically integrated metal phosphide electrodes are prepared by laborious multi-step methods and their operational stability at high current densities has been rarely studied. Herein, we report a novel vapor-solid synthesis of single-crystalline cobalt phosphide nanowires (CoP NWs) on a porous Co foam and demonstrate their use in overall water splitting. The CoP NWs grown on the entire surface of the porous Co foam ligaments have a large aspect ratio, and hence are able to provide a large catalytically accessible surface over a given geometrical area. Comprehensive investigation shows that under the OER conditions CoP NWs are progressively and conformally converted to CoOOH through electrochemical in situ oxidation/dephosphorization; the latter serving as an active species to catalyze the OER. The in situ oxidized electrode shows exceptional electrocatalytic performance for the OER in 1.0 M KOH, delivering 100 mA cm-2 at an overpotential (η) of merely 300 mV and a small Tafel slope of 78 mV dec-1 as well as excellent stability at various current densities. Meanwhile, the CoP NW electrode exhibits superior catalytic activity for the HER in the same electrolyte, affording -100 mA cm-2 at η = 244 mV and showing outstanding stability. An alkaline electrolyzer composed of two symmetrical CoP NW electrodes can deliver 10 and 100 mA cm-2 at low cell voltages of 1.56 and 1.78 V, respectively. The CoP NW electrolyzer demonstrates exceptional long-term stability for overall water splitting, capable of working at 20 and 100 mA cm-2 for 1000 h without obvious degradation.

Cobalt phosphide nanowires: an efficient electrocatalyst for enzymeless hydrogen peroxide detection

In this letter, we demonstrate for the first time that cobalt phosphide nanowires (CoP NWs) exhibit remarkable catalytic activity toward electrochemical detection of hydrogen peroxide (H2O2). As an enzymeless H2O2 sensor, such CoP NWs show a fast amperometric response within 5 s and a low detection limit of 0.48 μM. In addition, this nonenzymatic sensor displays good selectivity, long-term stability and excellent reproducibility.

Graphene and cobalt phosphide nanowire composite as an anode material for high performance lithium-ion batteries

The synthesis of a composite of cobalt phosphide nanowires and reduced graphene oxide (denoted CoP/RGO) via a facile hydrothermal method combined with a subsequent annealing step is reported. The resulting composite presents large specific surface area and enhanced conductivity, which can effectively facilitate charge transport and accommodates variations in volume during the lithiation/de-lithiation processes. As a result, the CoP/RGO nanocomposite manifests a high reversible specific capacity of 960 mA·h·g–1 over 200 cycles at a current density of 0.2 A·g–1 (297 mA·h·g–1 over 10,000 cycles at a current density of 20 A·g–1) and excellent rate capability (424 mA·h·g–1 at a current density of 10 A·g–1).

Cobalt Phosphide Nanowires: Efficient Nanostructures for Fluorescence Sensing of Biomolecules and Photocatalytic Evolution of Dihydrogen from Water under Visible Light

AbstractThe detection of specific DNA sequences plays an important role in the identification of disease‐causing pathogens and genetic diseases, and photochemical water splitting offers a promising avenue to sustainable, environmentally friendly hydrogen production. Cobalt–phosphorus nanowires (CoP NWs) show a high fluorescence quenching ability and different affinity toward single‐ versus double‐stranded DNA. Based on this result, the utilization of CoP NWs as fluorescent DNA nanosensors with a detection limit of 100 pM and a selectivity down to single‐base mismatch was demonstrated. The use of a thrombin‐specific DNA aptamer also enabled the selective detection of thrombin. The photoinduced electron transfer from the excited dye that labels the oligonucleotide probe to the CoP semiconductor led to efficient fluorescence quenching, and largely enhanced the photocatalytic evolution of hydrogen from water under visible light.

Cobalt phosphide nanowires: efficient nanostructures for fluorescence sensing of biomolecules and photocatalytic evolution of dihydrogen from water under visible light.

The detection of specific DNA sequences plays an important role in the identification of disease-causing pathogens and genetic diseases, and photochemical water splitting offers a promising avenue to sustainable, environmentally friendly hydrogen production. Cobalt-phosphorus nanowires (CoP NWs) show a high fluorescence quenching ability and different affinity toward single- versus double-stranded DNA. Based on this result, the utilization of CoP NWs as fluorescent DNA nanosensors with a detection limit of 100 pM and a selectivity down to single-base mismatch was demonstrated. The use of a thrombin-specific DNA aptamer also enabled the selective detection of thrombin. The photoinduced electron transfer from the excited dye that labels the oligonucleotide probe to the CoP semiconductor led to efficient fluorescence quenching, and largely enhanced the photocatalytic evolution of hydrogen from water under visible light.

Self-supported nanoporous cobalt phosphide nanowire arrays: an efficient 3D hydrogen-evolving cathode over the wide range of pH 0-14.

In this Communication, we report the topotactic fabrication of self-supported nanoporous cobalt phosphide nanowire arrays on carbon cloth (CoP/CC) via low-temperature phosphidation of the corresponding Co(OH)F/CC precursor. The CoP/CC, as a robust integrated 3D hydrogen-evolving cathode, shows a low onset overpotential of 38 mV and a small Tafel slope of 51 mV dec(-1), and it maintains its catalytic activity for at least 80,00 s in acidic media. It needs overpotentials (η) of 67, 100, and 204 mV to attain current densities of 10, 20, and 100 mA cm(-2), respectively. Additionally, this electrode offers excellent catalytic performance and durability under neutral and basic conditions.

Temperature and Chemical Bonding‐Directed Self‐Assembly of Cobalt Phosphide Nanowires in Reaction Solutions into Vertical and Horizontal Alignments

The preparation of vertically or horizontally aligned self-assemblies of CoP nanowires is demonstrated for the first time by aging them in the reaction solution for a sufficient time at 20 or 0 °C. This strategy opens up a way for exploring the controlled self-assembly of various highly anisotropic nanostructures into long-range ordered structures with collective properties.