CoP Particles Research Articles

Co/CoP@NC heterostructures as bifunctional catalysts to enhance the alkaline water splitting

The development of efficient and stable non-precious bifunctional electrocatalysts is of great significance, but it remains a great challenge. Herein, we have constructed Co/CoP@NC heterojunction catalyst loaded with Co and CoP particles on a nitrogen-doped carbon (NC) substrate using the pyrolysis-oxidation-phosphating strategy. The synergistic effect of Co and CoP particles on the NC substrate increases the active specific surface area, accelerates the charge transfer rate, and improves the intrinsic activities of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The Co/CoP@NC catalyst exhibits superior HER and OER performance. Specifically, the overpotentials required for Co/CoP@NC to reach the current density of 10 mA cm−2 are 142 and 186 mV for HER and OER, respectively. This study provides new insights into the design and synthesis of efficient and stable Co-based heterostructure catalysts.

Surface-modified MOFs for synthesizing hollow Fe-CoP polyhedrons encapsulating CoP particles to enhance the performance of OER

Surface-modified MOFs for synthesizing hollow Fe-CoP polyhedrons encapsulating CoP particles to enhance the performance of OER

In-based coordination polymer-derived carbon nanoribbons with abundant CoP nanoparticles in carbon nanotubes for water oxidation.

The sluggish oxygen evolution reaction (OER) in overall electrocatalytic water splitting poses a significant challenge in hydrogen production. A series of transition metal phosphides are emerging as promising electrocatalysts, effectively modulating the charge distribution of surrounding atoms for OER. In this study, a highly efficient OER electrocatalyst (CoP-CNR-CNT) was successfully synthesized through the pyrolysis and phosphatization of a Co-doped In-based coordination polymer, specifically InOF-25. This process resulted in evenly dispersed CoP nanoparticles encapsulated in coordination polymer-derived carbon nanoribbons. The synthesized CoP-CNR-CNT demonstrated a competitive OER activity with a smaller overpotential (η10) of 295.7 mV at 10 mA cm-2 and a satisfactory long-term stability compared to the state-of-the-art RuO2 (η10 = 353.7 mV). The high OER activity and stability can be attributed to the high conductivity of the carbon network, the abundance of CoP particles, and the intricate nanostructure of nanoribbons/nanotubes. This work provides valuable insights into the rational design and facile preparation of efficient non-precious metal-based OER electrocatalysts from inorganic-organic coordination polymers, with potential applications in various energy conversion and storage systems.

Green fabrication of ultrafine N-Mo x C/CoP hybrids for boosting electrocatalytic water reduction

Developing non-noble-metal electrocatalysts for hydrogen evolution reactions with high activity and stability is the key issue in green hydrogen generation based on electrolytic water splitting. It has been recognized that the stacking of large CoP particles limits the intrinsic activity of as-synthesized CoP catalyst for hydrogen evolution reaction. In the present study, N-Mo x C/CoP-0.5 with excellent electrocatalytic activity for hydrogen evolution reaction was prepared using N-Mo x C as decoration. A reasonable overpotential of 106 mV (at 10 mA cm−2) and a Tafel slope of 59 mV dec−1 in 1.0 M KOH solution was achieved with N-Mo x C/CoP-0.5 electrocatalyst, which exhibits superior activity even after working for 37 h. Uniformly distributed ultrafine nanoclusters of the N-Mo x C/CoP-0.5 hybrids could provide sufficient interfaces for enhanced charge transfer. The effective capacity of the hydrogen evolution reaction could be preserved in the complex, and the enlarged electrocatalytic surface area could be expected to offer more active sites for the reaction.

Monometallic and bimetallic metal–organic frameworks derived CoP embedded in porous carbon: Monodisperse CoP nanoparticles for highly reversible potassium ion storage

Metal phosphides show promise as anode materials for high-energy potassium-ion batteries due to their high capacity. However, their cycling performance is hampered by volume changes. Although nanoparticle/carbon composites are commonly employed to tackle this issue, achieving uniform embedding within confined carbon structures still presents a challenge. In this study, we investigate the synthesis strategies of CoP/porous carbon composites using isostructural bimetallic and monometallic-zeolitic imidazolate framework (ZIF), and achieve uniform embedding of ∼4 nm CoP nanoparticles in porous carbon by utilizing a bimetallic Co/Zn ZIF. Conversely, monometallic ZIF-67 leads to substantial coarsening and non-uniform distribution of ∼25 nm CoP particles. The resulting bimetallic-ZIF-derived CoP/porous carbon composite exhibits a specific capacity of 490.5 mAh/g at 0.05 A/g for potassium-ion storage and remarkable cycling stability, retaining 100 % capacity over 500 cycles at 0.1 A/g. Differential capacity plots confirm improved reversibility of the CoP conversion reaction. Notably, the evaporation of Zn generates a pore structure that effectively confines CoP, preventing further aggregation during electrochemical cycling. This work showcases a unique synthesis strategy using a bimetallic ZIF for high-performance potassium-ion battery materials.

Facile and Cost-effective Synthesis of CoP@N-doped Carbon with High Catalytic Performance for Electrochemical Hydrogen Evolution Reaction.

The manufacture of efficient and low-cost hydrogen evolution reaction (HER) catalysts is regarded as a critical solution to achieve carbon neutrality. Herein, we developed an economical method to synthesize a CoP-anchored N-doped carbon catalyst via one-step pyrolysis using inexpensive starting materials (cobalt ion salt, phytic acid, and glycine). The size of the CoP nanoparticles was controlled by adjusting the Co/P ratio of the catalysts. Nanoscale CoP particles with adequate exposure to active sites were uniformly anchored on the surface of the conductive nitrogen-doped carbon substrate, ensuring the rapid transfer of electrons and species. When Co/P=0.89, the as-made catalyst exhibited outstanding HER activity, with an extraordinarily low overpotential of 202 mV at 10 mA cm-2 and long-term stability.

Chemical-etching strategy tailoring hollow carbon confined highly dispersed CoP nanoparticles for durable potassium storage

Implanting nano-scaled CoP particles into hollow carbon is usually regarded as an effective strategy to improve structural stability for potassium ion batteries (PIBs). Hence, we employ tannic acid (TA) as the chemical-etching agent to elaborately synthesize a novel hollow hybrid composite composed of highly dispersed CoP nanoparticles (10-20 nm) embedded in well-developed carbon shell (CoP/C-2). The nano-sized CoP significantly shortens the diffusion distance of K-ions within electrode, while the highly dispersed features can expose more active surface to electrolyte by avoiding self-agglomeration, endowing improved reaction kinetics. Besides, the presence of carbon shell provides sufficient buffer space for volume variation, all of which are conducive to maintaining structural integrity against pulverization upon repeated cycling. When used as an anode for PIBs, the optimized CoP/C-2 exhibits an extraordinary cycling stability by keeping a high reversible capacity of 103.4 mAh g−1 after 1000 cycles at 2 A g−1, outperforming most previously reported literatures. The strategy presented in this work may provide a reference for constructing other advanced CoP-based abodes for PIBs.

Vacuum brazed Ni-based coating reinforced with core-shell WC@Cu/Co-P

Improving the wettability and bond strength of WC with Ni-based matrix and preventing the growth of WC in the melt of Ni-based alloy are always the challenges that should be considered in the fabrication of Ni/WC infiltration brazed coatings. In this research, to improve interface in Ni/WC infiltration brazed coatings, a thin shell of Cu/Co-P was employed. The shell had a thickness of about 80 nm and it was deposited on WC powders by electroless plating. The morphology of WC@Cu/Co-P powders and its microstructure as the reinforcement phase in Ni-based matrix were characterized by field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that this proposed coating had very low porosity, resulting a dense free porosity coating with homogenous distribution of WC. Also, the average growth rate of WC@Cu/Co-P particles was approximately 75 % lower than the same figure for the bare WC particles during liquid phase sintering. These results led to a desirable wear property; the pin on disk test was carried out to investigate the wear behavior of coatings. The wear rate reduction was reduced by 52 % compared to the coatings processed without the shell layer. The average hardness of WC@Cu/Co-P/NiCrBSi coatings was reported about 1590 Vickers, which is 30 % higher than the average hardness of conventional WC/NiCrBSi coatings.

N, P, S triple-doped honeycomb porous carbon multi-dimensionally enhanced CoP for pseudocapacitance-driven high-power lithium storage

Enhancing the electrical conductivity and relieving the volume expansion is essential to boost the lithium storage performance of CoP. Herein, carbon-coated CoP particles are uniformly embedded into N, P, and S triple-doped honeycomb porous carbon (CoP@NPSC) synthesized via a one-step foaming method. In this structure, N, P, and S doping improved the charge transfer kinetics, ion transport capacity, and pseudocapacitance contribution of the CoP@NPSC electrode, respectively. The synergistic effect of the three elements further endows CoP@NPSC with abundant electrochemical reaction sites, optimized pore structure and high electrical conductivity. In addition, the CoP nanoparticles are stably embedded in the pore channels by forming surface chemical bonds with the honeycomb porous carbon, and the carbon sheets are connected by triangular branched chains, which enhances the structural stability and effectively mitigates the volume expansion of CoP. Based on the excellent structure with triple-doping synergistic effect, the CoP@NPSC anode applied to lithium-ion batteries delivers ultra-high reversible capacity (1237.7 mAh g−1 at 0.5 A g−1) and ultra-long cycle stability at high rates (280.3 and 241.8 mAh g−1 at 5.0 and 10.0 A g−1 after 5000 cycles with no significant capacity decay). This study provides an effective strategy for designing high-performance doped electrode materials.

Engineering structure constructed CoP anode with enhanced bulk phase diffusion ability for superior potassium-ion storage

Due to its considerable theoretical capacity and high availability through conversion reaction, CoP is regarded as a promising candidate for potassium-ion batteries (PIBs). However, huge volume change and low intrinsic conductivity seriously impede the further development of CoP anode in PIBs. Generally, structural design and composition regulation can well improve potassium storage performance of CoP via increasing capacitive contribution rate, but are unfavorable for realizing a high energy density in a K-full cell. Therefore, how to optimize the bulk phase diffusion ability of CoP to enhance the diffusion-dominated potassium storage is of great importance. Herein, CoP nanoparticles (about 20–40 nm) with enormous voids embedded in carbon-cage structure encapsulated in N-doped amorphous carbon are reported (CoP/C@NC-PDA), in which CoP particles with appropriate nano-size benefit the bulk phase diffusion process. Besides, the existence of amorphous carbon coating layer and voids can provide sufficient space to buffer volume expansion, while carbon-cage architecture and its high graphitization degree accelerate fast ions/electrons transfer, respectively. As a result, CoP/C@NC-PDA achieves an excellent diffusion-controlled capacity ratio (77.5% at 0.05 A g−1, 75.0% at 1.0 A g−1), and a good cycle lifespan over 1000 cycles with nearly 100% Coulombic efficiency.

Fabrication of Cubic and Porous Carbon Cages with In-Situ-Grown Carbon Nanotube Networks and Cobalt Phosphide for High-Capacity and Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have attracted considerable attention due to their high specific capacity, low cost, and eco-friendly raw material. However, the insulating property of sulfur and dissolution of lithium polysulfides (LiPSs) lead to rapid capacity decay and low Coulombic efficiency. In this work, we smartly synthesized a composite material as the host material of active S by a facile one-step pyrolysis method. It was composed of in-situ-grown carbon nanotubes (CNTs) and CoP particles inside the porous carbon cages (denoted as CoP-CNT@C). The CNT networks in porous carbon cages can improve the conductivity of the cathode, while the CoP particles are capable of enhancing the adsorption of LiPSs, thereby effectively mitigating the “shuttle effect”. Moreover, the porous structure of the carbon cages could effectively store the elemental sulfur. As a matter of fact, the Li–S battery based on the CoP-CNT@C/S cathode exhibited an ultrahigh initial specific capacity of 1456.8 mAh g–1 at 0.1C and superior performance (663.3 mAh g–1) at a high current rate of 3C. It is worth mentioning that a capacity of 473.9 mAh g–1 has been retained after 750 cycles tested at 0.5C, indicating the outstanding stability of the Li–S battery based on the CoP-CNT@C/S cathode. Overall, the CoP-CNT@C composite prepared is promising for the application of Li–S batteries as the host material.

Variable HOF-derived carbon-coated cobalt phosphide for electrocatalytic oxygen evolution

A structural and morphological transformation of a hydrogen-bonded organic framework (HOF) based on 1,3,5-benzentricarboxylic acid (H3BTC) is observed. With the introduction of metal cations, especially Co(II) ion, these weaker hydrogen bonds linked in this bulk HOF of BTC can be easily broken to obtain the ultrathin wire-shaped product, denoted as Co-Fiber. That is mainly for the reason that the divalent cobalt ions with modest polarity exhibit moderate disturbance and destruction to H-bonding networks. Following calcination and phosphatization, abundant HOF-derived porous carbon-coated CoP particles in CoP/NCNT/PC inherit the morphology of Co-Fiber and endow with in-situ formed N-doped multi-walled carbon nanotubes. Initial electrochemical activation of the CoP/NCNT/PC catalyst promotes the formation of the electrocatalytically active species of cobalt oxyhydroxide for efficient oxygen evolution reaction (OER) in 1.0 M KOH aqueous solution. The obtained CoP/NCNT/PC composite exhibits an outstanding OER performance with the low overpotential of 282 mV at 10 mA cm−2, the relatively small Tafel value (103.7 mV dec−1), and the long-term durability remaining 90.5% over 10 h. The reasonable and facile method to synthesize low-cost, efficient and robust CoP/NCNT/PC shows great potential to substitute noble-metal based electrocatalysts for OER. Meanwhile, it will provide a new way for the application of HOF-derived carbon nanomaterials in the new energy field.

Synthesis of Spherical Carbon‐Coated CoP Nanoparticles for High‐Performance Lithium‐Ion Batteries

Transition metal phosphides are emerging as potential anode materials for lithium‐ion batteries (LIBs) due to their high theoretical capacity and good thermal stability, but the severe volume changes during the charge/discharge process and low electrical conductivity have hampered their practical application. Herein, the facile synthesis of carbon‐coated CoP nanoparticles (CoP@C) with uniform spherical morphology is demonstrated through the solvothermal method followed by annealing and phosphating treatments, in which an interesting precursor, the Co–gluconate complex, is prepared as the Co/C sources. When used as the LIB anode, the CoP@C electrode displays excellent cycling stability with a reversible capacity of 483.4 mA h g−1 upon 1000 cycles at 0.5 A g−1. The superior lithium storage performance is attributed to the unique composite structure of CoP@C with the nanosized CoP particles wrapped into the carbon matrices, which can enhance the electrical conductivity, provide sufficient reaction sites, shorten the Li+ transport path, and buffer the volume changes of the electrode upon lithiation/delithiation. More importantly, the strategy of generating gluconate–metal complex as the metal‐ and carbon‐containing precursor can be widely applied in the synthesis of various functional materials for energy‐related applications.

Killing two birds with one stone: Constructing tri-elements doped and hollow-structured carbon sphere by a single template for advanced potassium-ion hybrid capacitors

Integrating the merits of long lifespan and excellent energy as well as power densities, potassium-ion hybrid capacitors (PIHCs) exhibit great prospects for future energy storage devices. To boost comprehensive performance of PIHCs, heteroatom-doping and morphology-tuning as two comprehensive strategies have been devoted to designing uniquely structural carbon-based materials with favorable advantages. An ideal strategy for simultaneous atomic doping and structural regulation is expected to be developed. Herein, we propose a novel “Killing Two Birds with One Stone” strategy to prepare a tri-elements doped hollow carbon sphere (TED-HCS) as PIHCs anodes, that is, a single template of spherical CoP particles is rationally adopted, which not only provides both a P source for heteroatom-doping but also acts as a self-sacrificial template for hollow-structure engineering. The multifunctional TED-HCS presents a high capacity of 473.0 mAh g−1 and excellent rate performance of 212.5 mAh g−1 at 5.0 A g−1. Remarkably, the as-assembled PIHCs show outstanding energy/power density (40.4 Wh kg−1/10500 W kg−1) and remain high-capacity retention of 89.15% even cycling 12,000 times. The “Killing Two Birds with One Stone” strategy offers new insight into the search for the preparation of carbon-based materials with multi-elements doping and specific morphology structure.

Reduced graphene oxide supported ZIF-67 derived CoP enables high-performance potassium ion storage

Potassium-ion batteries (PIBs) are currently recognized as an emerging battery technology because of the rich resources and low cost of potassium. Nevertheless, investigations on exploiting suitable anode materials to meet stable potassium-ions storage remain to be a problem owing to the big radius size of potassium-ions. Herein, we designed N-doped carbon restricted CoP polyhedra embedded into reduced graphene oxide (rGO) sheet (CoP/NC@rGO) through coupling the function of ZIF-67 and rGO. For this composite, nano-scale CoP particles can be encapsulated by ZIF-67 derived carbon matrix, which significantly alleviates the volume change and promotes K+/e− transfer. Additionally, the combination of CoP/NC polyhedra and rGO nanosheets can build a fascinating 3D architecture to further improve the electronic conductivity of materials, as well as effectively preventing the aggregation of CoP/NC polyhedra. As a result, such composites can exhibit remarkable long-cycle performance, maintaining remarkable capacities of 177 mAh g−1 after 2800 cycles at 1 A g−1. This work provides a hopeful strategy that the combination of MOF-derived porous structures with rGO can effectively promote K+/e− transfer and improve the stability of electrode materials.

MOF‐derived Core‐Shell CoP@NC@TiO2 Composite as a High‐Performance Anode Material for Li‐ion Batteries

AbstractTransition‐metal phosphides have been regarded as promising anode materials for high‐energy lithium‐ion batteries (LIBs) due to their high capacity and low cost. However, the mechanical pulverization and resultant capacity fade critically limit their further development. Here, we have designed an innovative core‐shell CoP@NC@TiO2 composite with an exotic rhombic dodecahedral morphology derived from ZIF‐67 precursor, which combines both advantages from TiO2 with excellent cycling stability and CoP with high capacity. The additional MOF‐derived N‐doped carbon framework is considered to improve the electrical conductivity and accommodate the volume expansion of CoP particles. Moreover, the outer TiO2 shell can also buffer the mechanical stress and maintain the integrity of composite. With the unique structure, the core‐shell CoP@NC@TiO2 composite material exhibits excellent electrochemical performance with a considerable discharge specific capacity of 706.3 mAh g−1 at a current density of 100 mA g−1 after 200 cycles and outstanding rate capacity. Hence, our work demonstrates that this core‐shell structure strategy combined with MOF‐derived carbon framework could provide a practical pathway towards enhanced electrode materials for energy storage and conversion.

Construction of CoP@C embedded into N/S-co-doped porous carbon sheets for superior lithium and sodium storage

To improve the electrical conductivity and relief the large volume variation, carbon coated CoP particles were designed to homogeneously embed into porous carbon sheets, which were synthesized though a simultaneous carbonization and phosphorization method. Notably, the uniform carbon shells and porous carbon sheets constructed a tough conductive matrix to enhance the electron transfer and structural stability during charging/discharging processes. Moreover, the heteroatom doping of nitrogen and sulfur could not only introduce more active sites and defects on the carbon sheets, but also increased electrical conductivity. Owing to the unique structure, the obtained material displayed good electrochemical performance for lithium storage (638.8 mA h g−1 at 0.2 A g−1 after 500 cycles and 334.9 mA h g−1 at 10 A g−1) and sodium storage (329.4 mA h g−1 at 0.2 A g−1 after 150 cycles and 162.4 mA h g−1 at 5 A g−1). More importantly, the reaction mechanism and the ion diffusion coefficient were explored by ex-situ XRD and EIS for both LIBs and SIBs. This versatile approach may avail to predigest the tedious phosphating process to obtain high-performance TMPs-based hybrids (such as Ni2P/C) by employing other metal salts.

Electrodeposited cobalt phosphides with hierarchical nanostructure on biomass carbon for bifunctional water splitting in alkaline solution

Low cost and high-performance bifunctional catalysts for water splitting under alkaline conditions still face many challenges. CoP/C were synthesized by electrodeposition in the presence of different sodium hypophosphite concentrations with porous carbon membranes as working electrodes. The morphology of CoP/C is strongly dependent on the concentration of sodium hypophosphite. We prepared the CoP/C with varying contents of phosphorus to investigate influence of phosphorus content on the morphology of CoP/C and the corresponding catalytic capability of water splitting in alkaline conditions. When the sodium hypophosphite in the electrodeposition electrolyte reaches to 0.6 M, the malformed octahedral CoP particles appear on nanofibers of carbon membrane coated with CoP films. The CoP/C with such hierarchical structure exhibits superior electrocatalytic activities for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with the overpotential of 140 mV and 250 mV at a current density of 10 mA cm−2, respectively in the alkaline solution. Furthermore, the CoP/C with hierarchical structure as both anode and cathode for water splitting achieves 10 mA cm−2 only need 1.56 V. The CoP/C with hierarchical structure keeps stable catalytic performance even after 24 h. This work provides a facile strategy for designing high-efficient phosphides based catalyst for overall water splitting.

Zeolitic imidazolate framework-67 derived ultra-small CoP particles incorporated into N-doped carbon nanofiber as efficient bifunctional catalysts for oxygen reaction

Herein ultra-small CoP nanoparticles incorporated into nitrogen-doped carbon nanofibers derived from zeolitic imidazolate framework-67 (ZIF-67) are found active as a bifunctional catalyst for oxygen electrocatalysis. The composite nanofibers of polyacrylonitrile-cobalt acetate are firstly prepared by the electrostatic spinning and then immersed into 2-methylimidazole ethanol solution for the growth of restricted ZIF-67. The hybrid is further annealed and phosphided to obtain the ultra-small CoP nanoparticles incorporated into nitrogen-doped carbon nanofibers (CoP/NC). The degree of carbonization and retention of the nanofiber topology structure are determined by the annealing temperature. Excellent bifunctional oxygen electrocatalysis performance is observed on CoP/NC and the performance improvement can be attributed to the more active site exposure, good conductivity and co-action of CoP and N-doped carbon nanofiber. An overpotential of 290 mV is required to drive 10 mA cm−2 for oxygen evolution reaction, and an onset potential of 0.90 V and half-wave potential of 0.78 V are obtained for the oxygen reduction reaction in the alkaline electrolyte. A strong application in Zn-air battery is also demonstrated compared with the device configured by Pt/C catalyst. The current work demonstrates a significant technique to boost the catalytic performance of MOF derived catalysts for energy-relevant catalytic reactions.

One-Step Synthesis of N, P-Codoped Carbon Nanosheets Encapsulated CoP Particles for Highly Efficient Oxygen Evolution Reaction.

Oxygen electrocatalysis, especially oxygen evolution reaction (OER), is a central process during the actual application of rechargeable metal-air battery. It is still challenging to develop ideal electrocatalysts to substitute the commercial noble metal-based materials. In this work, we have constructed a new material, CoP nanoparticles, which are encapsulated by a biomolecule-derived N, P-codoped carbon nanosheets via a simple and facile one-step strategy. The as-prepared material releases a high electrocatalytic activity and stability for OER, with an overpotential of 310 mV to achieve 10 mA/cm2 in 1 M KOH. Importantly, we found that the phosphoric acid can not only introduce phosphorus dopant into 2D N-doped carbon nanosheets and play a role of pore-forming agent, but also participate in the formation of active center (cobalt phosphide). Moreover, the coverage of N, P-doped carbon can prevent the CoP nanoparticles from corrosion under the harsh reaction medium to achieve high and stable activity. We believe that our strategy can offer a novel pathway to synthesize new transition metal-based catalysts for electrocatalysis or other heterogeneous catalysis.