Cobalt Phosphorus Research Articles

Electrochemical deposition of cobalt phosphorus for hard magnetic micro devices and the impact on magnetic anisotropy

When fabricating magnetic components for micro-electro-mechanical systems, the intrinsic material properties as well as the magnetic anisotropy of the deposited material and the fabricated devices must be adjusted to the application. This work focuses on electrochemically deposited cobalt phosphorus layers from a sulfate-based electrolyte to be used as hard magnetic scales in position measurement systems. In preliminary tests round discs (5 mm diameter, 20 or 10 μm height) were fabricated, showing the influence of three process parameters (current density, pH-value and temperature) on the chemical composition and the magnetic behavior of the deposited cobalt phosphorus. Hereby deposition parameters to produce hard magnetic cobalt phosphorus are defined. Deposits with up to 6 wt.-% phosphorus show hard magnetic behavior, whereas deposits with more than 6 wt.-% show soft magnetic behavior. This is correlated with a transition from crystalline to amorphous structures. In further investigations arrays of micro scales (40 μm width, 10 μm height) were fabricated to show the influence of direct current and pulsed current on the properties of the deposits. Pulsed current increases coercive field strength by about 40 %, resulting in maximum values of 23 kA/m (in-plane) and 14 kA/m (out-of-plane). Remanence increases by about 30 %, resulting in maximum values of 0.40 T (in-plane) and 0.2 T (out-of-plane). Pulse plating changes preferred orientation from (110) to (100) and slightly increases grain size by about 20 %, resulting in an average grain size of 25 nm.

Investigation of transverse exchange-springs in electrodeposited nano-heterostructured films through first-order reversal curve analysis

The prerequisite of efficient exchange-spring nano-heterostructures, i.e., tuning both hard and soft phases at a nanometer level, has posed significant preparation challenges to ensure effective exchange-coupling. Here, we present a novel approach to fabricate transverse exchange-spring nano-heterostructures using single starting material through an “in situ” electrodeposition technique at room temperature. Utilizing modified acidic bath chemistry and controlled hydrogen evolution, we successfully prepared stress-free, shiny, fine-grained amorphous, and nanocrystalline Co-rich cobalt phosphorus films. These nano-heterostructured films exhibit a unique non-collinear anisotropy-driven transverse exchange-spring behavior, investigated systematically under ambient conditions. The comprehensive functional analyses reveal that intricate interplay between in-plane (IP) anisotropy of amorphous phase and out-of-plane (OOP) anisotropy generating from a nanocrystalline structure compete with each other, while producing characteristic stripe domain structures to novel corrugated stripe domain shapes. The angle-dependent first-order reversal curve distributions demonstrate new insights into the magnetic reversal mechanisms, further confirming the non-exchange-spring and exchange-spring nature of the films depending on the prevalent interfacial exchange coupling. Formation of anisotropy-driven metastable-state due to competition between IP and OOP anisotropy at a particular OOP orientation has led the normal exchange-spring structures to a transverse exchange-spring structure. Micromagnetic simulations, in excellent agreement with experimental data, further elucidate the formation of characteristic stripe domain patterns and the influence of anisotropy on the magnetic properties. The innovative methodology and detailed functional analysis presented here offer significant understanding to the field of exchange-spring magnetic materials, including anisotropy-driven metastable states, demonstrating the potential for scalable and cost-effective fabrication of advanced nano-heterostructures with tailored magnetic properties.

Synthesis and Characterization of Novel Cobalt Carbonyl Phosphorus and Arsenic Clusters.

Phosphorus- and arsenic-containing cobalt clusters are an interesting class of compounds that continue to provide new structures with captivating bonding patterns. Although the first members of this family were reported 45 years ago, the number of such species is still limited within the broad family of transition metal complexes bearing pnictogen atoms. Herein, we present the reaction of Co2(CO)8 as a cobalt source with a number of phosphorus- and arsenic-containing compounds under variable reaction conditions. These reactions result in various known and novel cobalt phosphorus and cobalt arsenic clusters in which different nuclearity ratios between P/As and Co exist. All those clusters were characterized by X-ray structural analysis and partly by IR, 31P{1H} NMR, EI-MS and elemental analysis. This comprehensive study is the first detailed study in this field that reveals the richness of compounds that could be obtained only by modifying the ratio of used reactants and the involved reaction conditions.

A high-performance electrocatalyst via graphitic carbon nitride nanosheet-decorated bimetallic phosphide for alkaline water electrolysis.

Developing renewable and clean energy systems for overall water electrolysis requires low-cost, highly efficient, and stable catalysts. With this motivation, nickel cobalt phosphorus (NiCoP) was electrodeposited onto nickel foam (NF) and then modified with graphitic carbon nitride (g-C3N4). The designed g-C3N4/NiCoP/NF electrode was used for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline water electrolysis. It exhibited a small overpotential of 80 mV@10 mA cm-2 with a Tafel slope of 89 mV dec-1 for the HER. It also exhibited an overpotential of 370 mV@10 mA cm-2 with a Tafel slope of 64 mV dec-1 for the OER. The g-C3N4/NiCoP catalyst exhibited satisfactory stability in an alkaline electrolyzer system, in which g-C3N4/NiCoP/NF was used as the anode and cathode. Meanwhile, the electrocatalyst requires only a cell voltage of 1.70 V to achieve 10 mA cm-2 current density for overall water electrolysis.

Biocompatible Co-P Metallic Glasses with Superior Degradation Tolerance in Physiological Environments.

Metallic glasses represent a class of metallic alloys with a fully amorphous structure and attractive properties, making them promising in bioimplant applications. Here, the degradation tolerance of biocompatible cobalt-phosphorus (Co-P) metallic glasses was studied in a simulated physiological environment. The metallic glasses were synthesized in the form of coatings through a facile electrodeposition approach. This method utilizes their outstanding surface characteristics and bypasses the size limitations usually associated with their bulk counterparts. The Co-P alloys showed exceptional tribological response with ∼14% lower coefficient of friction and 2 orders of magnitude lesser wear rate compared to SS316 stainless steel. In addition, the Co-P alloys showed a 3 times higher hardness and 4 times higher hardness/modulus ratio compared to SS316, indicating better elastic recovery under dynamic shear stresses that are common in load-bearing bioimplants. The Co-P metallic glasses exhibited excellent hemocompatibility and cytocompatibility in terms of lower platelet adhesion, spreading, and aggregation, a hemolysis ratio lower than 1%, and enhanced surface wettability, suggesting a superlative performance in bioimplant applications.

Fabrication of ultra-stable and high-efficient CoP-based electrode toward seawater splitting at industrial-grade current density

The mild and rapid construction of economical, efficient and ultrastable electrodes for hydrogen production via water splitting at industrial-grade current density remains extremely challenging. Herein, a one-step mild electroless plating method is proposed to deposit cobalt phosphorus (CoP)-based species on robust nickel net (NN, denoted as Co–P@NN). The tight interfacial contact, corrosion-proof self-supporting substrate and synergistic effect of Co–P@Co-O contribute greatly to the rapid electron transport, high intrinsic activity and long-term durability in the alkaline simulated seawater (1.0 M KOH + 0.5 M NaCl). Attractively, Co–P@Co-O also achieves ultrastable catalysis for over 2880 h with negligible activity attenuation under various alkaline extreme conditions (simulated seawater, high-salt environment, domestic sewage and so on). Furthermore, this work successfully constructs a series of ternary elemental doped (Ni, S, B, Fe and so on) CoP-based catalytic electrodes for highly efficient overall seawater splitting (OSWS). This work demonstrates not only an ideal platform for the versatile strategy of mildly obtaining CoP-based electrocatalysts but also the pioneering philosophy of large-scale hydrogen production.

Enrichment of hydrogen-oxidizing bacteria using a hybrid biological-inorganic system.

Hybrid biological-inorganic (HBI) systems comprising inorganic water-splitting catalysts and aerobic hydrogen-oxidizing bacteria (HOB) have previously been used for CO2 conversion. In order to identify new biocatalysts for CO2 conversion, the present study used an HBI system to enrich HOB directly from environmental samples. Three sediment samples (from a brackish water pond, a beach, and a tide pool) and two activated sludge samples (from two separate sewage plants) were inoculated into HBI systems using a cobalt phosphorus (Co-P) alloy and cobalt phosphate (CoPi) as inorganic catalysts with a fixed voltage of 2.0V. The gas composition of the reactor headspaces and electric current were monitored. An aliquot of the reactor medium was transferred to a new reactor when significant consumption of H2 and CO2 was detected. This process was repeated twice (with three reactors in operation for each sample) to enrich HOB. Increased biomass concomitant with increased H2 and CO2 consumption was observed in the third reactor, indicating enrichment of HOB. 16S rRNA gene amplicon sequencing demonstrated enrichment of sequences related to HOB (including bacteria from Mycobacterium, Hydrogenophaga, and Xanthobacter genera) over successive sub-cultures. Finally, four different HOB belonging to the Mycobacterium, Hydrogenophaga, Xanthobacter, and Acidovorax genera were isolated from reactor media, representing potential candidates as HBI system biocatalysts.

One-Step Electrochemical Synthesis and Surface Reconstruction of NiCoP as an Electrocatalyst for Bifunctional Water Splitting.

We adopted a simple one-step electrochemical deposition to acquire an efficient nickel cobalt phosphorus (NiCoP) catalyst, which avoided the high temperature phosphatization engineering involved in the traditional synthesis method. The effects of electrolyte composition and deposition time on electrocatalytic performance were studied systematically. The as-prepared NiCoP achieved the lowest overpotential (η10 = 111 mV in the acidic condition and η10 = 120 mV in the alkaline condition) for the hydrogen evolution reaction (HER). Under 1 M KOH conditions, optimal oxygen evolution reaction (OER) activity (η10 = 276 mV) was also observed. Furthermore, the bifunctional NiCoP catalyst enabled a high-efficiency overall water-splitting by applying an external potential of 1.69 V. The surface valence and structural evolution of NiCoP samples with slowly decaying stability under alkaline conditions are revealed by XPS. The NiCoP is reconstructed into the Ni(Co)(OH)2 (for HER) and Ni(Co)OOH (for OER) on the surface with P element loss, acting as real "active sites".

Electrodeposited cobalt phosphide film with regulated interfacial structure and wetting for enhanced hydrogen evolution performance: Effect of saccharin

The exploration of earth-abundant and highly efficient catalysts for water electrolysis is vital for the sustainable development of future hydrogen economies but remains challenging. The rational construction of the special-interfacial structure is identified as one of the most efficient strategies to enhance the performance of water-electrolysis catalysts. Herein, cobalt phosphorus nanosheet arrays mediated by saccharin grown on copper foam (Co-P(SA)/CF) are rationally prepared via a facile one-step electrodeposition approach from a deep eutectic solvent (DES) consisting of choline chloride and ethylene glycol, known as Ethaline. Introducing SA increases the P content in the deposited Co-P composites with an optimized electronic structure and creates a superaerophobic surface to accelerate the hydrogen evolution reaction (HER). Such results significantly enhance the HER activity of Co-P(SA)/CF, requiring a small overpotential of 148.18 mV to drive 100 mA cm−2 in 1.0 M KOH. Impressively, Co-P(SA)/CF provides remarkable HER stability and can maintain 100 mA cm−2 over 165 h for continuous electrolysis operation in 6 M KOH at 80°C. Our work provides a promising avenue to regulate the interface super-wetting property of Co-P electrodes and offers a facile and efficient strategy for designing high-efficiency catalysts with superaerophobic surfaces for practical water electrolysis.

Strategies for solder joints with high shear strength, slow interfacial consumption, ductile intermetallic compounds using hybrid crystalline-amorphous Co-P coatings

Crystalline and amorphous cobalt-phosphorus (Co-P) coatings have their own advantages in interfacial diffusion resistance and mechanical ductility of solder joints, respectively, but it cannot be better at both. In this work, the hybrid crystalline-amorphous Co-P coating (Co-9.1 at.% P) was fabricated and applied on the Cu/Sn interface by controlling the crystallinity through compositional design. Combining the advantages of crystalline and amorphous Co-P, strategies for solder joints with high shear strength, ductile intermetallic compounds (IMCs) and slow interface consumption was proposed. The evolution, microstructure, phase, and mechanical properties of the Co-Sn, Co-Sn-P and P-rich layers in solid-state diffusion were systematically characterized and tested by means of SEM, EPMA, EBSD, TEM, nanoindentation, and shear test. It was found that the hybrid Co-P coating achieved a low consumption rate, 14.2 nm/h, attributing to the partially crystalline structure and the Co-Sn-P exfoliation behavior. In addition, solder joints containing large-thickness ductile Co-Sn IMCs, 3.2–3.6 GPa of hardness, was established. The shear strength after aging reached 75.4 MPa relying on the large thickness of Co-Sn IMCs. Severe mechanical loads would be able to be withstand by virtue of the plastic deformation of ductile IMCs. Hybrid crystalline-amorphous Co-P would be a promising interface material in microelectronic packaging.

Crystallinity of Co-P coating on microstructure and mechanical properties of Co-Sn intermetallic compounds at Sn-Ag/Co-P/Cu Interface

In advanced microelectronic packaging technology, the interfacial brittleness of Cu/Sn solder joints puts forward higher requirements for high-performance diffusion barriers. Cobalt–Phosphorus (Co-P) alloy coating becomes ideal candidates for its good wettability and diffusion resistance. In this work, for Co-P with different crystallinity, the barrier properties of electrodeposited Co-P coatings as well as the mechanical properties of Co-Sn intermetallic compounds (IMCs) at the Co-P/Sn-Ag interface were investigated. According to the XRD results, the crystallinity of the Co-P coating was directly related to the phosphorus (P) content, and Co-P were classified into three types: crystalline state, mixed state and amorphous state. The morphology, composition, phase characterization, and mechanical properties of the Co-Sn IMCs at the interface were investigated by SEM, EPMA, TEM, and nanoindentation methods, respectively. After 180 °C aging test for 120 h, the thickness of CoSn3 generated at the interface of crystalline Co-4.2 at.% P/Sn-Ag was the smallest among a total of 18 Co-P coatings, where P content ranged from 0.9 at.% to 20.8 at.%, showing the best barrier properties. The hardness of (Co,Cu)Sn3 at the amorphous Co-P/Sn-Ag interface was the lowest (3.2 GPa), which was only 47% of that of Ni3Sn4, exhibiting the lowest brittleness tendency. The mixed crystalline-amorphous Co-P could greatly improve the diffusion barrier properties while sacrificing a small degree of brittleness comparing to the amorphous coatings, and had the potential to become a general-purpose alloy coating. This work could provide a scientific basis for the selection of Co-P barrier layers with excellent barrier properties and mechanical properties leading to different application scenario in electronic packaging.

Uniform Formation of Amorphous Cobalt Phosphate on Carbon Nanotubes for Hydrogen Evolution Reaction†

Main observation and conclusionTremendous efforts have been made to the development of highly active, stable hydrogen evolution reaction (HER) electrocatalysts based on earth‐abundant metal compounds. Recently, cobalt phosphorus (Co‐P) catalysts have received particular attention owing to their good performances for the HER. However, the reported Co‐P catalysts were not uniformly anchored on the substrates. Hence, developing Co‐P catalysts with a uniform surface structure for HER remains a major challenge. Herein, we utilized small molecule tris(4‐fluorophenyl)phosphane (PF) for preliminarily functionalizing carbon nanotubes (PF‐CNTs) via π–π stacking interactions. Using these as the substrate, amorphous cobalt phosphate (CoPi) catalysts could then be uniformly anchored on PF‐CNTs by electrodeposition method. These obtained CoPi/PF‐CNTs catalysts show an onset potential low to 29 mV, a low overpotential (105 mV in 0.5 mol/L H2SO4 at a current density of 10 mA·cm–2 with a Tafel plot of 32 mV·dec–1) and an excellent stability for HER in acidic electrolyte, which is a promising noble‐metal‐free HER catalyst.

High-efficiency nitrate electroreduction to ammonia on electrodeposited cobalt-phosphorus alloy film.

Electrocatalytic eight-electron nitrate (NO3-) reduction is a sustainable strategy to degrade NO3- and convert it into high value-added ammonia (NH3) but needs efficient catalysts with high activity and selectivity. Our study shows the use of Ti plate supported cobalt-phosphorus alloy film (Co-P/TP) as a highly active and selective electrocatalyst for ambient NO3--to-NH3 conversion. In 0.2 M Na2SO4 with 200 ppm NO3-, Co-P/TP offers an NH3 yield rate of 416.0 ± 7.2 μg h-1 cm-2 and a high faradaic efficiency of 93.6 ± 3.3% at -0.6 V and -0.3 V vs. reversible hydrogen electrode, respectively, with good durability. Noticeably, a conversion rate of 86.9% is achieved after 10 h bulk electrolysis.

Electroless nickel–phosphorus and cobalt–phosphorus coatings on multi-walled carbon nanotubes

The multi-walled carbon nanotubes (MWCNTs) have drawn great attention due to their exceptional mechanical, physical, thermal and electrical properties. The MWCNTs as the reinforcements significantly improved the properties of materials. However, the major challenges in composites containing CNTs are the poor wettability and poor interfacial bonding between matrix and CNTs. In this study, the used MWCNTs have a diameter of 8–10 nm and 1.5 μm in length. MWCNTs are purified in HNO3: H2SO4, sensitized in Sn solution and activated in Pd solution at 90 °C, and coated with the Nickel and Cobalt elements using an electroless coating method. The holding time in the bath is 15, 30 and 60 min, and the bath concentration is also changed. The coatings are characterized by Scanning Electron Microscopy (SEM) equipped with electron dispersive spectrum (EDS), elemental mapping, x-ray diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM) and Fourier Transform Infrared (FTIR) spectrometer. The results showed that the Ni and Co coating layers are successfully formed on the surface of MWCNTs. The deposition rate is affected by the holding time and the bath concentration. The optimal results are obtained at the holding time of 60 min in the C concentration sample.

Kinetics of the Diffusion Chromium Plating of Steels with Nickel-Cobalt-Phosphorus Coating

We study the kinetics of formation of a diffusion layer after chromium plating with a nickel–cobalt–phosphorus coating. It is shown that the presence of phosphorus in the chemical coating affects the formation of an outer composite zone formed by columnar chromium carbides and the matrix of solid solution of chromium in α-iron. At the same time, in the early stages, atomic chromium displaces nickel and cobalt into the bulk of the material but does not affect the distribution of phosphorus. We also explain the appearance of directed zones with higher degrees of damage in the process of diffusion. Atomic chromium is intensely transported through these zones, which leads to the formation of a regular structure of the outer composite zone.

A cobalt–phosphorus nanoparticle decorated N-doped carbon nanosheet array for efficient and durable hydrogen evolution at alkaline pH

In 1.0 M KOH, Co–P@NC/CC, prepared by electrodeposition of cobalt–phosphorus nanoparticles on a polyimide derived N-doped carbon nanosheet array supported on carbon cloth, shows outstanding catalytic activity with the demand of an overpotential of 75 mV to drive 10 mA cm−2.

Cobalt–phosphorus–titanium oxide nanocomposite coatings: structures, properties, and corrosions studies

Chromium coatings are largely restricted in electrical and electronic industries due to the environmental concerns. To address these concerns, a cobalt–phosphorus–titanium oxide (Co–P–TiO2) nanocomposite coating is developed in this study using a nanoparticle-reinforced electrodeposition process. The effects of TiO2 nanoparticles on the properties of co-deposited Co–P–TiO2 nanocomposite coatings are investigated. The surface characterisation is carried out by scanning electron microscopy and atomic force microscopy, while the crystal structure is studied using X-ray diffraction. The mechanical properties of nanocomposite coatings including microhardness and wear resistance are also determined. To study the electrochemical behaviour of the coatings, the potentiodynamic polarisation analysis combined with electrochemical impedance spectroscopy is performed. The Co–P–TiO2 coating at 1 g/L TiO2 addition displays the best physicochemical performance. Compared to Co–P coating, the mechanical properties of the nanocomposite coating are significantly improved by the strengthening effects of the well-dispersed TiO2 particles. Excellent corrosion resistance is also achieved for the Co–P–TiO2 at proper TiO2 addition due to its smooth and defect-free microstructure. However, it is found that the excessive addition of TiO2 decreases the coating quality, resulting in an unfavourable microstructure and properties.

Room-Temperature Preparation of Cobalt-Based Electrocatalysts through Simple Solution Treatment for Selectively High-Efficiency Hydrogen Evolution Reaction in Alkaline or Acidic Medium

The versatile cobalt-phosphorus (Co-P) precursor was synthesized on Ni foam (NF) with an electrodeposition method. Simple room-temperature treatment of the precursor with 1 M NaOH and 0.5 M H2SO4 allows for the production of cobalt oxide nanorods (CoxOy/NF) and cobalt phosphate/phosphide (Co-Pi/CoP/NF), respectively. The resulting CoxOy/NF shows a low overpotential (η10) of 80 mV at −10 mA/cm2 in an alkaline electrolyte (pH = 14) for a hydrogen evolution reaction (HER) toward electrocatalytic water splitting. The Co-Pi/CoP/NF exhibits a low η10 of 112 mV in an acidic electrolyte (pH = 0), in which the synergy between Co (+2) and Co (+3) may play an important role in the reaction.

Addition of H2 Across a Cobalt–Phosphorus Bond

AbstractAddition of H2 across the cobalt–phosphorus bond of (PPP)CoPMe3 (3) is demonstrated, where PPP is a monoanionic diphosphine pincer ligand with a central N‐heterocyclic phosphido (NHP−) donor. The chlorophosphine CoII complex (PPClP)CoCl2 (2) can be generated through coordination of the chlorophosphine ligand (PPClP, 1) to CoCl2. Subsequent reduction of 2 with KC8 in the presence of PMe3 generates (PPP)CoPMe3 (3), in which both the phosphorus and cobalt centers have been reduced. The addition of 1 atm of H2 to complex 3 cleanly affords (PPHP)Co(H)PMe3 (4), in which H2 has ultimately been added across the metal–phosphorus bond. Complex 4 was characterized spectroscopically and using computational methods to predict its geometry.

Effect of Waveform and Heat Treatment Processes on the Performance of Electrodeposited Co-P Coating

Cobalt-phosphorus (Co-P) alloy is a promising material for the replacement of traditional hard chromium alloy of high hardness. In this paper, the cobalt-phosphorus alloy layer with high phosphorus content was formed by electrodeposition in a cobalt sulfate solution system under direct current (DC), single pulse (SP) current and double pulse (DP) current, separately. Surface morphology, structure and properties of the deposited layer were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Vickers microhardness and a neutral salt spray test, respectively. The results showed that the dense Co-P coatings could be obtained by DC, SP and DP with P content of 9.6, 8.9 and 9.1 wt %, respectively. After 30 min heat treatment at 400 °C, coatings deposited under DC, SP and DP currents transformed from an amorphous to a nanocrystalline state, while the grain size was 12–13 nm, 10–12 nm and 8–10 nm, respectively. Among all these conditions, the microhardness of coatings deposited under DP current was the highest, which was 1211 HV, while the microhardness of coatings deposited under DC current was the lowest but higher than that of hard chromium. The wear rate of Co-P coatings was 4 × 10−6–5 × 10−6 mm3/N m with Si3N4 ball as bearing material, which was lower than that of hard chromium. In coatings deposited under different currents with a thickness of ca. 40 μm, no visible corrosion area appeared after 1000 h of a neutral salt spray test. Coatings heated at 300 and 400 °C reached the corrosion grade 7 and grade 4–5, respectively after 1000 h of a neutral salt spray test, so the wear resistance of Co-P coatings was better than that of hard chromium.