Phosphate Materials Research Articles

(Invited) High Rate Cycling in ε-VOPO4 with Niobium Substitution for Lithium-Ion Batteries

In order to push the energy density of current commercialized lithium-ion batteries, a second lithium must be incorporated into the cathode host without causing any structural damage during intercalation. ε-VOPO4 is a promising high energy density cathode material for lithium-ion batteries due to its ability to fully reversibly intercalate two Li+ from the two redox transitions of V3+/V4+ and V4+/V5+. As a result, ε-VOPO4 displays a high discharge capacity of 305 mAh/g at C/50 (C = 2 Li) for over 50 cycles. However, this vanadyl phosphate material experiences poor Li+ kinetics which impedes its high rate capability at the high voltage plateau. In this work, we determine if niobium substitution can improve the electrochemistry of ε-VOPO4. Through X-ray diffraction and scanning electron microscopy, we investigate the incorporation of niobium in the structure and the effect on morphology. The analysis of substitution on the electrochemical performance will also be discussed alongside with X-ray absorption spectroscopy to confirm the oxidation states of the transition metals during cycling. This research is supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012583. CS gratefully acknowledges the financial support from Graduate Assistance in Areas of National Need (GAANN) Fellowship and Binghamton University Provost's Doctoral Summer Fellowship.

Revealing nanoscale mineralization pathways of hydroxyapatite using in situ liquid cell transmission electron microscopy.

To treat impairments in hard tissues or overcome pathological calcification in soft tissues, a detailed understanding of mineralization pathways of calcium phosphate materials is needed. Here, we report a detailed mechanistic study of hydroxyapatite (HA) mineralization pathways in an artificial saliva solution via in situ liquid cell transmission electron microscopy (TEM). It is found that the mineralization of HA starts by forming ion-rich and ion-poor solutions in the saliva solution, followed by coexistence of the classical and nonclassical nucleation processes. For the nonclassical path, amorphous calcium phosphate (ACP) functions as the substrate for HA nucleation on the ACP surface, while the classical path features direct HA nucleation from the solution. The growth of HA crystals on the surface of ACP is accompanied by the ACP dissolution process. The discoveries reported in this work are important to understand the physiological and pathological formation of HA minerals, as well as to engineer the biomineralization process for bone healing and hard tissue repairs.

The Surface Characterisation of Polyetheretherketone (PEEK) Modified via the Direct Sputter Deposition of Calcium Phosphate Thin Films

Polyetheretherketone (PEEK) has emerged as the material of choice for spinal fusion devices, replacing conventional materials such as titanium and its alloys due to its ability to easily overcome a lot of the limitations of traditional metallic biomaterials. However, one of the major drawbacks of this material is that it is not osteoinductive, nor osteoconductive, preventing direct bone apposition. One way to overcome this is through the modification of the PEEK with bioactive calcium phosphate (CaP) materials, such as hydroxyapatite (HA–Ca10(PO4)6(OH)2). RF magnetron sputtering has been shown to be a particularly useful technique for the deposition of CaP coatings due to the ability of the technique to provide greater control of the coating’s properties. The work undertaken here involved the deposition of HA directly onto PEEK via RF magnetron at a range of deposition times between 10–600 min to provide more bioactive surfaces. The surfaces produced have been extensively characterised using X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), stylus profilometry, and Time of Flight Secondary Ion Mass Spectrometry (ToFSIMS). XPS results indicated that both Ca and P had successfully deposited onto the surface, albeit with low Ca/P ratios of around 0.85. ToFSIMS analysis indicated that Ca and P had been homogeneously deposited across all the surfaces. The SEM results showed that the CaP surfaces produced were a porous micro-/nano-structured lattice network and that the deposition rate influenced the pore area, pore diameter and number of pores. Depth profiling, using ToFSIMS, highlighted that Ca and P were embedded into the PEEK matrix up to a depth of around 1.21 µm and that the interface between the CaP surface and PEEK substrate was an intermixed layer. In summary, the results highlighted that RF magnetron sputtering can deliver homogenous CaP lattice-like surfaces onto PEEK in a direct, one-step process, without the need for any interlayers, and provides a basis for enhancing the potential bioactivity of PEEK.

A New Polyanion Na3Fe2(PO4)P2O7 Cathode with High Electrochemical Performance for Sodium-Ion Batteries

Iron-based phosphate materials have been employed as cathodes for sodium-ion batteries (SIBs) because of their low cost and environmental friendliness, but the electrochemical performance of this k...

Iron Oxide/Phosphatic Materials Composites with Potential Applications in Environmental Protection.

Currently, hydroxyapatite is probably the most researched material, due to its multiple applications in medical, environmental, or cultural heritage, when the classical structure is modified and calcium is displaced partially or totally with different metals. By changing the classical structure of the hydroxyapatite, new morphologies can be obtained, thus allowing final applications different from those of the initial hydroxyapatite material. However, their properties should be tuned for the desired application. In this context, the present paper describes the synthesis and characterization (through energy-dispersive X-ray fluorescence, X-ray diffraction, FTIR, thermal analysis, and transmission electron microscopy) of iron oxide/manganese-containing phosphatic phase composite materials, developed in order to obtain the enhancement of final environmental applications (photodegradation of dyes, adsorption of organic compounds). The composite material was tested for photocatalytic properties, after embedding in hydrosoluble film-forming materials. Photocatalytic coatings show different activity during the photodecomposition of Methylene Blue, used as a model of a contaminant. The photocatalytic activities of the materials were discussed in relationship with both the phosphatic materials and the magnetic components. Finally, other environmental applications were studied for the developed materials (adsorption of non-steroidal anti-inflammatory drugs—paracetamol and ibuprofen), revealing an enhancement of the adsorption capacity of the phosphatic material upon addition of the magnetic phase.

Tissue response to biphasic calcium phosphate covalently modified with either heparin or hyaluronic acid in a mouse subcutaneous implantation model.

Biphasic calcium phosphate (BCP) materials are widely employed as bone substitute materials due to their resorption/degradation properties. Inflammation after implantation of such materials represents a prerequisite for bone tissue repair and regeneration but can be also problematic if it is not only transient and if it is followed by fibrosis and scarring. Here, we modified BCP covalently with hyaluronan (HA) and heparin (Hep), glycosaminoglycans that possess anti-inflammatory properties. Beside the characterization of particle surface properties, the focus was on in vivo tissue response after subcutaneous implantation in mice. Histological analysis revealed a decrease in signs of inflammatory response to BCP when modified with either HA or Hep. Reduced vascularization after 30 days was noticed when BCP was modified with either HA or Hep with greater cellularity in all examined time points. Compared to plain BCP, expression of endothelial-related genes Flt1 and Vcam1 was higher in BCP-HA and BCP-Hep group at day 30. Expression of osteogenesis-related genes Sp7 and Bglap after 30 days was the highest in BCP group, followed by BCP-Hep, while the lowest expression was in BCP-HA group which correlates with collagen amount. Hence, coating of BCP particles with HA seems to suppress inflammatory response together with formation of new bone-like tissue, while the presence of Hep delays the onset of inflammatory response but permits osteogenesis in this subcutaneous bone-forming model. Transferring the results of this study to other coated materials intended for biomedical application may also pave the way to reduction of inflammation after their implantation.

Deliquescent behavior of calcium phosphate materials synthesized by sol–gel technique

Water storage and purification, as well as dehydration processes, are a cause of concern for many healthy and industrial issues. In this work, calcium phosphate (CaP) materials with high water capture performance were prepared by sol–gel synthesis. After their structural characterization by several techniques, they were used in water capture tests performed in temperatures ranging from 25 to 45 °C using a climatic chamber kept at a relative humidity of 60%. The CaP samples showed a higher water uptake capacity than a commercial silica sample commonly used as a water adsorbent, despite the low surface area and pore volume displayed by the former. Moreover, different from the silica adsorbent, the studied CaP materials were submerged by the captured water after the first day, which suggests a deliquescent behavior. The CaP mass uptakes reached around 350% when tested at 25 °C and the materials release the adsorbed water quickly when heated at 100 °C. It was also demonstrated that the materials prepared here maintained their structural integrity even after the deliquescence step, which could allow their use for many cycles.

Design Strategies of Transition-Metal Phosphate and Phosphonate Electrocatalysts for Energy-Related Reactions.

The key challenge to developing renewable energy conversion and storage devices lies in the exploration and rational engineering of cost-effective and highly efficient electrocatalysts for various energy-related electrochemical reactions. Transition-metal phosphates and phosphonates have shown remarkable performances for these reactions based on their unique physicochemical properties. Compared with transition-metal oxides, phosphate groups in transition-metal phosphates and phosphonates show flexible coordination with diverse orientations, making them an ideal platform for designing active electrocatalysts. Although numerous efforts have been spent on the development of transition-metal phosphate and phosphonate electrocatalysts, some urgent issues, such as low intrinsic catalytic efficiency and low electronic conductivity, have to be resolved in accordance with their applications. In this Review, we focus on the design strategies of highly efficient transition-metal phosphate and phosphonate electrocatalysts, with special emphasis on the tuning of transition-metal-center coordination environment, optimization of electronic structures, increase of catalytically active site densities, and construction of heterostructures. Guided by these strategies, recently developed transition-metal phosphate and phosphonate materials have exhibited excellent activity, selectivity, and stability for various energy-related electrocatalytic reactions, showing great potential for replacing noble-metal-based catalysts in next-generation advanced energy techniques. The existing challenges and prospects regarding these materials are also presented.

Unravelling the ultrastructure and mineralogical composition of fireworm stinging bristles

Amphinomid fireworms are notorious for their stinging dorsal bristles (notochaetae), but it is still unclear whether the irritation they cause is merely mechanical or if the notochaetae contain toxins. Furthermore, although fireworm chaetae have always been described as calcareous, their composition has never been investigated to date and strong debates are ongoing on their internal structure. Unravelling the native ultrastructure and composition of fireworm chaetae is the first crucial step to assess whether the hypothesis of toxin vehiculation could be fully considered.We examined for the first time the chemical and mineralogical composition, the ultrastructure and the external structure of the dorsal and ventral chaetae of the large species Hermodice carunculata. All the measurements were carried out on samples prepared without the use of chemical reagents, except for those targeted to investigate if decalcification altered the ultrastructure of the chaetae. A crystal-chemical strategy, combining chemical, diffraction and thermal analyses clearly showed the occurrence of crystalline calcium carbonate and clusters of phosphatic amorphous material. Scanning electron micrographs and energy dispersive X-ray measurements showed that the dorsal chaetae have an extremely shallow insertion point in the body respect to the ventral chaetae, that could facilitate the release of the notochaetae in the environment. Their proximal part is characterized by canals with a hexagonal pattern rich in Ca and P, followed by a large cavity upwards. The harpoon-shaped ends and the central canals of the notochaetae completely disappeared after exposure to EDTA. The notochaetae are hollow and may be able to vehicle toxins. The absence of the honeycomb pattern in the distal part of the notochaetae and their slenderness probably contribute to their brittleness and high sensitivity to breakage on contact. These observations constitute keystone understandings to shed light on fireworm defensive and offensive capacities and their ecological success.

Costimulatory Effect of Rough Calcium Phosphate Coating and Blood Mononuclear Cells on Adipose-Derived Mesenchymal Stem Cells In Vitro as a Model of In Vivo Tissue Repair.

Calcium phosphate (CaP) materials do not always induce ectopic vascularization and bone formation; the reasons remain unclear, and there are active discussions of potential roles for post-implantation hematoma, circulating immune and stem cells, and pericytes, but studies on adipose-derived stem cells (AMSCs) in this context are lacking. The rough (average surface roughness Ra = 2–5 µm) scaffold-like CaP coating deposited on pure titanium plates by the microarc oxidation method was used to investigate its subcutaneous vascularization in CBA/CaLac mice and in vitro effect on cellular and molecular crosstalk between human blood mononuclear cells (hBMNCs) and AMSCs (hAMSCs). Postoperative hematoma development on the CaP surface lasting 1–3 weeks may play a key role in the microvessel elongation and invasion into the CaP relief at the end of the 3rd week of injury and BMNC migration required for enhanced wound healing in mice. Satisfactory osteogenic and chondrogenic differentiation but poor adipogenic differentiation of hAMSCs on the rough CaP surface were detected in vitro by differential cell staining. The fractions of CD73+ (62%), CD90+ (0.24%), and CD105+ (0.41%) BMNCs may be a source of autologous circulating stem/progenitor cells for the subcutis reparation, but allogenic hBMNC participation is mainly related to the effects of CD4+ T cells co-stimulated with CaP coating on the in vitro recruitment of hAMSCs, their secretion of angiogenic and osteomodulatory molecules, and the increase in osteogenic features within the period of in vivo vascularization. Cellular and molecular crosstalk between BMNCs and AMSCs is a model of effective subcutis repair. Rough CaP surface enhanced angio- and osteogenic signaling between cells. We believe that preconditioning and/or co-transplantation of hAMSCs with hBMNCs may broaden their potential in applications related to post-implantation tissue repair and bone bioengineering caused by microarc CaP coating.

Calcium Phosphate Coating Prepared by Microarc Oxidation Affects hTERT Expression, Molecular Presentation, and Cytokine Secretion in Tumor-Derived Jurkat T Cells.

Calcium phosphate (CaP) materials are among the best bone graft substitutes, but their use in the repair of damaged bone in tumor patients is still unclear. The human Jurkat T lymphoblast leukemia-derived cell line (Jurkat T cells) was exposed in vitro to a titanium (Ti) substrate (10 × 10 × 1 mm3) with a bilateral rough (average roughness index (Ra) = 2–5 μm) CaP coating applied via the microarc oxidation (MAO) technique, and the morphofunctional response of the cells was studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscope (EDX) analyses showed voltage-dependent (150–300 V) growth of structural (Ra index, mass, and thickness) and morphological surface and volume elements, a low Ca/PaT ratio (0.3–0.6), and the appearance of crystalline phases of CaHPO4 (monetite) and β-Ca2P2O7 (calcium pyrophosphate). Cell and molecular reactions in 2-day and 14-day cultures differed strongly and correlated with the Ra values. There was significant upregulation of hTERT expression (1.7-fold), IL-17 secretion, the presentation of the activation antigens CD25 (by 2.7%) and CD95 (by 5.15%) on CD4+ cells, and 1.5–2-fold increased cell apoptosis and necrosis after two days of culture. Hyperactivation-dependent death of CD4+ cells triggered by the surface roughness of the CaP coating was proposed. Conversely, a 3.2-fold downregulation in hTERT expression increased the percentages of CD4+ cells and their CD95+ subset (by 15.5% and 22.9%, respectively) and inhibited the secretion of 17 of 27 test cytokines/chemokines without a reduction in Jurkat T cell survival after 14 days of coculture. Thereafter, cell hypoergy and the selection of an hTERT-independent viable CD4+ subset of tumor cells were proposed. The possible role of negative zeta potentials and Ca2+ as effectors of CaP roughness was discussed. The continuous (2–14 days) 1.5–6-fold reductions in the secretion of vascular endothelial growth factor (VEGF) by tumor cells correlated with the Ra values of microarc CaP-coated Ti substrates seems to limit surgical stress-induced metastasis of lymphoid malignancies.

Aesthetic Silver-Doped Octacalcium Phosphate Powders Exhibiting Both Contact Antibacterial Ability and Low Cytotoxicity.

Since the introduction of biomaterials, infection has been a serious problem in clinical operations. Although several studies have introduced hybrid materials of calcium phosphate and Ag0 nanoparticles (NPs) that exhibit antibacterial activity, released Ag+ ions and Ag0 NPs are highly cytotoxic and the materials require complex fabrication techniques such as laser irradiation. In this study, we introduce a simple one-pot synthesis method based on crystal-engineering techniques to prepare Ag+-substituted octacalcium phosphate (OCP–Ag) powder that simultaneously exhibits antibacterial activity, little change in color, and low cytotoxicity, thereby overcoming the shortcomings of calcium phosphate as a biomaterial. We used AgNO3-containing (NH4)2HPO4 aqueous solutions as reaction solutions in which Ag+ forms soluble complex [Ag(NH3)2]+ ions that are stable at Ag+ concentrations less than ∼30 mmol/L. Hydrolysis of soluble calcium phosphate in this solution led to pure OCP–Ag when the Ag+ concentration was less than ∼30 mmol/L. Crystallographic analysis showed that Ag+ substituted at the P5 PO4-conjugated sites and was uniformly distributed. When the concentration of Ag+ in the reaction solution was varied, the Ag+ content of the OCP–Ag could be controlled. The obtained OCP–Ag exhibited little color change or Ag+ release when immersed in various media; however, it exhibited contact antibacterial ability toward resident oral bacteria. The prepared OCP–Ag showed no substantial cytotoxicity toward undifferentiated and differentiated MC3T3-E1 cells in assays. Notably, when the Ag+ content in OCP–Ag was optimized (Ag: ∼1 at %), it simultaneously exhibited contact antibacterial ability, little color change, and low cytotoxicity.

Hydroxyapatite nanoparticles synthesized via reverse microemulsions and their adsorption/desorption properties with enrofloxacin

Calcium phosphates are regularly used in biomedical materials, such as bone cement, bone replacement material and drug carriers, as they are the major inorganic constituents of human hard tissue. Different pH conditions were tested to obtain calcium phosphate materials. In acidic conditions, the brushite or monetite phases with bulk structures were synthesized even while keeping a constant Ca/P ratio of 1.67; by contrast, at alkaline conditions, the hydroxyapatite phase was found to exhibit a needle-like shape. An annealing process on the hydroxyapatite phase generated nanoparticles featuring improved crystallinity and a quasi-spherical shape. The results showed that the pH bears a direct effect on the resulting calcium phosphate phase, and only in alkaline conditions it was possible to reach the hydroxyapatite phase; also, the Ca/P ratio in the starting reagents plays an important role in the morphology of the final product. An analysis of the efficiencies of adsorption and desorption of the antibiotic enrofloxacin was carried out on the quasi-spherical hydroxyapatite nanoparticles. It was demonstrated that these nanoparticles could be loaded with 92% of the enrofloxacin in solution and they can also deliver 74% of the antibiotic during the first 12 h, which could prove useful if these nanoparticles are used as coatings for dental or orthopedic implants.

Alkalinity Effect on Characteristic Properties and Morphology of Magnesium Phosphate Hydrates

Magnesium oxide (MgO) and orthophosphoric acid (H3PO4) have been reacted at different pH values to study the effects of alkalinity on the characteristic features of magnesium phosphate material. The phases of the synthesized samples have been identified as newberyite (with the chemical formula of MgHPO4 ⋅ 3H2O and the pdf no. 01-075-1714) and magnesium phosphate hydrate (with the chemical formula of Mg3(PO4)2 · 22H2O and the pdf no. 00-044-0775), in the X-ray powder diffraction analyses results. The characteristic band values of samples have been characterized by FTIR and Raman spectroscopies. The differences in morphologies have been studied with Scanning Electron Microscope (SEM). The largest particles in the range of 3.16–9.85 µm have been seen in the shape of nested flat sheets at pH 10 while the smallest particles between 1.17–2.04 µm have been obtained in the shape of an ellipse at pH 7. According to the thermogravimetric analyses, the differences in thermal behaviours have been determined. MgHPO4 · 3H2O has lost its crystal water by a two-step reaction while Mg3(PO4)2 · 22H2O has dehydrated by a single-step reaction. Obtained results indicate that the crystal structure and surface morphology of the synthesized compound can be modified by the alkalinity of the reaction medium.

Composites Based on Carbon Tapes with a Copper coating Based on Organic and Inorganic Matrices

The results of experimental investigations into the impregnating kinetics when using the carbon tape with copper coating according to the magnetron sputtering technology are presented. The epoxy and aluminum-boron phosphate materials are used as binders. The composites based on these binders are evaluated by characteristics of porosity, matrix content, and thermal stability. It is established that metallization insignificantly affects the thermal stability but does not make it possible to increase the impregnation rate and leads to lowering the composite porosity.

Boosting Solar Hydrogen Production of Molybdenum Tungsten Sulfide-Modified Si Micropyramids by Introducing Phosphate

Si is regarded as a promising photocathode material for solar hydrogen evolution reaction (HER) because of its small band gap and highly negative conduction band edge. However, bare Si electrodes have high overpotential because of sluggish HER kinetics on the surface. In this study, molybdenum tungsten sulfide (MoS2-WS2) was decorated on Si photocathodes as the co-catalyst to accelerate HER kinetics. The catalytic performance of MoS2-WS2 was further enhanced by introducing phosphate materials. Phosphate-modified molybdenum tungsten sulfide (PO-MoWS) was deposited on Si photoabsorbers to provide an optimal current of -15.0 mA cm-2 at 0 V. Joint characterizations of X-ray photoelectron and X-ray absorption spectroscopies demonstrated that the phosphate material dominantly coordinated with the WS2 component in PO-MoWS. Moreover, this phosphate material induced a large number of sulfur vacancies in the PO-MoWS/Si electrodes that contributed to the ideal catalytic activity. Herein, TiO2 thin films were prepared as the protective layer to improve the stability of photocathodes. The PO-MoWS/2 nm TiO2/Si electrode maintained 83.8% of the initial photocurrent after chronoamperometric measurement was performed for 8000 s.

Nanostructured selenium-doped biphasic calcium phosphate with in situ incorporation of silver for antibacterial applications

Selenium-doped nanostructure has been considered as an attractive approach to enhance the antibacterial activity of calcium phosphate (CaP) materials in diverse medical applications. In this study, the selenium-doped biphasic calcium phosphate nanoparticles (SeB-NPs) were first synthesized. Then, silver was in situ incorporated into SeB-NPs to obtain nanostructured composite nanoparticles (AgSeB-NPs). Both SeB-NPs and AgSeB-NPs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), X-ray photoelectron spectroscopy (XPS), and Raman spectra. The results confirmed that the SeO32− was doped at the PO43− position and silver nanoparticles were deposited on the surface of SeB-NPs. Next, Transmission Electron Microscopy (TEM) analysis displayed that the prepared AgSeB-NPs had a needle-cluster-like morphology. CCK-8 analysis revealed SeB-NPs and AgSeB-NPs had good cytocompatibility with osteoblasts. The antibacterial activity of the prepared AgSeB-NPs was confirmed by using Gram-negative E. coli and Gram-positive S. aureus. The above results manifested the significance of the final AgSeB-NPs for biomedical applications.

Calcium Phosphate Catalysts for Ethanol Coupling to Butanol and Butadiene

The catalytic conversion of ethanol to butanol and butadiene at 633 K and atmospheric pressure (7 vol% ethanol) was studied over calcium phosphate materials pretreated over a wide temperature range. For calcium phosphate pretreated at or below 923 K, the resulting solid had an apatite structure identified by X-ray diffraction and strong acid sites probed by triethylamine (TEA) adsorption microcalorimetry. The low temperature pretreated materials were not effective at ethanol coupling reactions but instead were highly selective to acid-catalyzed products ethene and diethyl ether. Pretreatment of calcium phosphate at 973 K transformed the apatite structure to β-tricalcium phosphate, which exposed both acid and base sites evaluated by TEA and CO2 adsorption microcalorimetry. High temperature pretreated calcium phosphate catalysts formed the coupling products butanol and butadiene during ethanol reaction. The butadiene selectivity was improved by supporting calcium phosphate on zirconia. The influence of catalyst structure on the activity and selectivity of calcium phosphates was elucidated for the conversion of ethanol.

Synthesis and biochemical characteristics of bioactive calcium-phosphate materials obtained from alcohol solutions

Sol-gel method synthesized 2 series of powders with different TiO2 content in the system. The percentage of elements in terms of the oxide system SiO2–P2O5–CaO–TiO2 is: composition 1: 52–14–24–10, composition 2: 52–17–29–2 wt.%, respectively. Solutions of composition 1 are stable up to 11 days Solutions of composition 2 are stable up to 2 days. The physicochemical properties of calcium phosphate materials were studied using the methods of IR spectroscopy, thermal analysis and elemental analysis. The biochemical activity of the tablets according to the Kokubo method showed a significant absorption of Ca2+ and Mg2+ ions within 7 days.

Evidence of CoFeOPO4 activity in Na-ion batteries

Abstract Phosphate materials became attractive electrode materials for sodium ion batteries due to their high capacity and safety properties. Cobalt iron (III) oxyphosphate CoFeOPO4@C was successfully prepared by conventional solid-state reaction at an annealing temperature of 1000 °C in air atmosphere. Our group previously reported the electrochemical properties of this material versus Li+/ Li. In this paper, we study for the first time the electrochemical activity of CoFeOPO4@C in sodium half-cells and evaluate its potential use as an anode material for sodium ion batteries. CoFeOPO4@C shows a high discharge capacity of 479 mAh g−1 at C/2 current rate over 0.01–3.0 V voltage range during the first cycle by accommodating around four sodium ions. Although the first irreversible capacity is relatively high resulting from a conversion mechanism, this phosphate can reversibly exchange about two sodium ions in the subsequent cycles, delivering a capacity of more than 200 mAh g−1 with a coulombic efficiency exceeding 97%.