Iron Phosphate Nanoparticles Research Articles

Enhancement of Li intercalation kinetics of LiFePO4 nanoparticles with mesoporous carbon

Carbon-assisted energy storage in Li-ion batteries is a crucial topic in the era of carbon neutrality. This work reports a remarkable synergistic effect between lithium iron phosphate (LiFePO4, LFP) nanoparticles and mesoporous carbon (MC) that greatly improves the rate performance and cycle performance. The rapid capacitive effect of MC helps establish a local Li+-rich environment for LFP, enhancing the Li intercalation kinetics inside LFP nanoparticles during discharge. This synergistic effect is quantificationally evaluated using a single-particle model to compare the Li intercalation extent of LFP particles under the presence and absence of MC, which is further confirmed by high-resolution transmission electron microscopy observation, in-situ X-ray diffraction characterization and electrochemical impedance spectroscopy test. In addition, the LFP/MC composite cathode exhibits a nearly 100% capacity retention after 1,000 cycles under 1C charge and 10C discharge. Overall, the addition of MC proves to be a very simple but robust method to increase the capacity, power density and cycle life of LFP-based devices.

Iron phosphate nanoparticles as oil additives to enhance anti-wear properties

In recent years, nanomaterial lubricant additives have been widely studied in tribology. In this work, a new iron phosphate (FeP) nanoparticle was synthesized to enrich the anti-wear oil-based additives for titanium alloys. A series of tribological experiments were conducted using a reciprocating ball-on-disc tribometer. It has been confirmed that, as additives in polyalphaolefin 8 (PAO8), FeP nanoparticles exhibit excellent friction-reducing and anti-wear properties for TA5 titanium alloys. Compared with the pure PAO8, the friction coefficient (COF) and wear rate (WR) can be significantly reduced by 69.89 % and 99.57 % at a concentration of 30 wt%. The SEM and EDS confirmed that FeP nanoparticles can play a surface repair role and deposit on the titanium alloy surface to form a deposition layer, which was the key to anti-wear property. Besides, XPS characterization demonstrated that the formation of the deposition layer was attributed to the P–O–Ti bond at the interface, through which the phosphate in FeP can bind to and adsorb on the titanium alloy surface. This deposition layer containing FeP can greatly reduce the adhesive wear of the titanium alloy. Meanwhile, the rolling effect of nanoparticles inside the deposition layer promoted the friction-reduction.

Learning heterogeneous reaction kinetics from X-ray videos pixel by pixel

Reaction rates at spatially heterogeneous, unstable interfaces are notoriously difficult to quantify, yet are essential in engineering many chemical systems, such as batteries1 and electrocatalysts2. Experimental characterizations of such materials by operando microscopy produce rich image datasets3–6, but data-driven methods to learn physics from these images are still lacking because of the complex coupling of reaction kinetics, surface chemistry and phase separation7. Here we show that heterogeneous reaction kinetics can be learned from in situ scanning transmission X-ray microscopy (STXM) images of carbon-coated lithium iron phosphate (LFP) nanoparticles. Combining a large dataset of STXM images with a thermodynamically consistent electrochemical phase-field model, partial differential equation (PDE)-constrained optimization and uncertainty quantification, we extract the free-energy landscape and reaction kinetics and verify their consistency with theoretical models. We also simultaneously learn the spatial heterogeneity of the reaction rate, which closely matches the carbon-coating thickness profiles obtained through Auger electron microscopy (AEM). Across 180,000 image pixels, the mean discrepancy with the learned model is remarkably small (<7%) and comparable with experimental noise. Our results open the possibility of learning nonequilibrium material properties beyond the reach of traditional experimental methods and offer a new non-destructive technique for characterizing and optimizing heterogeneous reactive surfaces.

(Keynote) Learning Electrochemical Models from Images

As illustrated by the work of Ralph White, traditional methods of electrochemical engineering are based on human intelligence: Mathematical models encoding physical hypotheses are proposed, tested against experimental data and refined by fitting adjustable parameters. Artificial intelligence is beginning to challenge this paradigm, since predictions can be made directly from data without the need for models, but such knowledge is often not transferrable to new situations. This talk will present a hybrid approach of solving PDE-constrained inverse problems to derive new multiscale models, in the context of Li-ion batteries. Examples include learning models of reaction kinetics and surface heterogeneities from x-ray adsorption images of phase separation in lithium iron phosphate nanoparticles [1], x-ray diffraction spectra for fictitious phase separation in nickel-rich oxide porous electrodes [2], and optical videos of lithium plating on graphite particles [3].[1] H. Zhao, H. D. Deng, A. E. Cohen, J. Lim, Y. Li, D. Fraggedakis, B. Jiang, B. D. Storey, W. C. Chueh, R. D. Braatz, and M. Z. Bazant, Learning heterogeneous reaction kinetics from X-ray movies pixel-by-pixel, preprint, https://www.researchsquare.com/article/rs-2320040/v1[2] J. Park, H. Zhao, S. D. Kang, K. Lim, C.-C. Chen, Y.-S. Yu, R. D. Braatz, D. A. Shapiro, J. Hong, M. F. Toney, M. Z. Bazant, and W. C. Chueh, Fictitious Phase Separation in Li Layered Oxides Driven by Electro-Autocatalysis, Nature Materials 20, 991-999 (2021).[3] T. Gao, Y. Han, D. Fraggedakis, S. Das, T. Zhou, C.-N. Yeh, S. Xu, W. C. Chueh, J. Li, M. Z. Bazant, Interplay of lithium intercalation and plating on a single graphite particle, Joule 5, 1-22 (2021).

High-throughput synthesis of high-purity and ultra-small iron phosphate nanoparticles by controlled mixing in a chaotic microreactor

High-purity FePO4 with small particle size is pivotal for improving electrochemical performance of LiFePO4-based lithium-ion batteries. Here, an oscillating feedback microreactor (OFM) based on chaotic advection was designed to prepare high-quality FePO4 by coprecipitation. Dye-tracer experiments and CFD simulations were adopted to investigate fluid mixing mechanism and to evaluate mixing efficiency in the reactor. The results indicated that a “flow-focused” OFM (FOFM) performed better than a “Y-junction” OFM in mixing performance, owing to enhanced premixing in focused inlet microchannel of the former. The results of Villermaux-Dushman experiments illustrated that almost complete mixing could be achieved in 0.16 ms in FOFM. Accordingly, FePO4 nanoparticles of good quality was synthesized using FOFM, and the particle size can be easily controlled by adjusting flow rate or reactant concentration. High-purity (P/Fe molar ratio: 0.95–1.04) and ultra-small FePO4 nanoparticles (9 nm) with narrow particle size distribution were generated at a high throughput of 180 mL/min.

Synergy and Symbiosis Analysis of Capacity-Contributing Polypyrrole and Carbon-Coated Lithium Iron Phosphate Nanostructures for High-Performance Cathode Materials

To address the existing problems of commercial inorganic cathodes, including relatively low capacity, poor rate performance, structural instability, and low conductivity, it is critical to introduce a conductive matrix accompanied with electrochemical activity. Conductive polymers have great potential as electrodes with good conductivity, high redox activity, and potential. In this study, carbon-coated lithium iron phosphate (C-LiFePO4) nanoparticles were effectively dispersed in a polypyrrole (PPy) matrix by in situ pulverization. PPy, as an active nanostructure, significantly improves conductivity and accelerates Li+ diffusion. To further explore the synergy and symbiosis mechanism of PPy and C-LiFePO4 (hereinafter called C-LFP in the composite), the nanoparticle dispersion, carburization dependence, and heat treatment preference were investigated. Therefore, a reasonable amount of PPy (25 wt %) hybridization, a moderately wrapped carbon buffer layer (5.3 wt %), and a suitable heat treatment (100 °C) were employed to prepare the (C-LFP)0.75(PPy)0.25 nanocomposite. With a smaller particle size, uniformly dispersed morphology, and good synergy effect between PPy and C-LiFePO4, (C-LFP)0.75(PPy)0.25 delivers a high discharge capacity (209.1 mAh g–1 at 0.1C), a superior rate capability (86.1 mAh g–1 at 10C), and an outstanding capacity retention (83.5% of the initial values after 500 cycles at 0.5C).

Isovalent substitution of vanadium in LiFePO4: Evolution of monoclinic α-Li3Fe2(PO4)3 phase

We report the synthesis and characterization of isovalent substitution of vanadium at phosphorus site in orthorhombic lithium iron phosphate (LiFePO4) nanoparticles by non-aqueous sol–gel method. Detailed analysis of X-ray diffraction patterns reveals the evolution of monoclinic α-Li3Fe2(PO4)3 phase and its formation is favored for the vanadium content higher than 20%. A continuous increase in unit cell volume of LiFePO4 is observed with increase in vanadium content from x = 0.05 to 0.20, followed by rapid decrease above x = 0.20, due to the creation of a greater number of Li-ion vacancies. FTIR studies demonstrate that the wavenumbers of various absorption maxima and the covalency strength parameter do not show a variation with x, thus confirm the substitution of vanadium in the form of VO4. Our results through Mössbauer and electron paramagnetic resonance spectroscopy unambiguously demonstrate the enhancement in the formation of α-Li3Fe2(PO4)3 phase for vanadium content higher than 20%.

Self-assembly of novel cobalt iron phosphate nanoparticles for the solid-state supercapattery and high-performance hydrogen evolution reaction

In this article, we report the preparation of novel cobalt iron phosphate nanoparticles which are self-assembled for energy storage, energy conversion, and sustainability. The self-assembled nanoparticles provide an efficient pathway for the transfer of electrons from the bulk of the materials to the interface of the electrode. This hypothesis has been derived from the analysis based on the electrochemical results for the supercapacitor-based energy storage and hydrogen evolution. The electrode consisting of self-assembled nanoparticles exhibits a maximum specific capacity of 280 C g−1 at a specific current of 1 A g−1. The cyclic voltammetric results suggest the prominent charge storage is by the faradaic reaction which has been concluded from Dunn's approach. The supercapattery device utilizing activated carbon (AC) as the negative electrode and cobalt iron phosphate as the positive electrode exhibit a specific capacity of 210 C g−1 at 2 A g−1 while the specific energy of 47.6 Wh kg-1 at 1.6 kW kg−1. Furthermore, the electrode actively catalyzes the electrochemical hydrogen evolution reaction and it can be lowering the overpotential required by the hydrogen generation. It exhibits the overpotential of 197 mV while the electrode represents the long-time (24 h) consistency for hydrogen production. These results indicate that the novel cobalt iron phosphate nanoparticles could be a potential candidate for energy storage and conversion purposes.

Iron phosphate nanoparticles as an effective catalyst for propargylamine synthesis

Iron phosphate nanoparticles as an effective catalyst for propargylamine synthesis

Depletable peroxidase-like activity of Fe3O4 nanozymes accompanied with separate migration of electrons and iron ions

As pioneering Fe3O4 nanozymes, their explicit peroxidase (POD)-like catalytic mechanism remains elusive. Although many studies have proposed surface Fe2+-induced Fenton-like reactions accounting for their POD-like activity, few have focused on the internal atomic changes and their contribution to the catalytic reaction. Here we report that Fe2+ within Fe3O4 can transfer electrons to the surface via the Fe2+-O-Fe3+ chain, regenerating the surface Fe2+ and enabling a sustained POD-like catalytic reaction. This process usually occurs with the outward migration of excess oxidized Fe3+ from the lattice, which is a rate-limiting step. After prolonged catalysis, Fe3O4 nanozymes suffer the phase transformation to γ-Fe2O3 with depletable POD-like activity. This self-depleting characteristic of nanozymes with internal atoms involved in electron transfer and ion migration is well validated on lithium iron phosphate nanoparticles. We reveal a neglected issue concerning the necessity of considering both surface and internal atoms when designing, modulating, and applying nanozymes.

The preparation of ionic liquid based iron phosphate/CNTs composite via microwave radiation for hydrogen evolution reaction and oxygen evolution reaction

Water electrolysis is a promising method for hydrogen production, so the preparation of low-cost and efficient electrocatalysts with a quick and simple procedure is crucial. Herein, iron phosphate (Fe 7 (PO 4 ) 6 ) was prepared via microwave radiation using ionic liquid (IL) as iron and phosphorus dual-source. This method is simple and rapid, and the product can be directly used as electrocatalysts without further treatment. The experimental results show that the IL can influence the morphology and electrocatalytic performance. Moreover, the addition of carbon nanotubes (CNTs) is favorable for formation of iron phosphate nanoparticles to improve the catalytic activities. As hydrogen evolution reaction (HER) catalyst, this iron phosphate/CNTs exhibits an onset overpotential of 120 mV, Tafel slope of 32.9 mV dec -1 , and current densities of 10 mA cm −2 at overpotential of 185 mV. Then, it obtains a good activity for oxygen evolution reaction (OER) with a low onset potential of 1.48 V, Tafel slope of 73.3 mV dec -1 , and it only needs an overpotential of 300 mV to drive the 10 mA cm −2 . This bifunctional catalyst also shows good durability for HER and OER. This microwave-assisted method provides an outstanding strategy to prepare iron phosphate in a simple and fast process with good catalytic performance for water splitting.

Synthesis and antimicrobial activity assessment of calcium and iron phosphate nanoparticles prepared by a facile and cost-effective method

This article focuses on the influence of monetite calcium phosphate nanowhiskers (CaP) and iron phosphate produced by the chemical hydrothermal reflux method on the antibacterial and microbial properties. The two types of produced iron phosphate by reflux method are amorphous iron phosphate (A-FeP) and crystalline iron phosphate (C-FeP). The introduced materials are characterized using several techniques including field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The antimicrobial activities for different phosphates are evaluated against different types of bacteria involving gram-negative, gram-positive, and C. Albicans fungal pathogen. The inhibition zone of the growth of the selected pathogens for different concentrations for metal phosphates indicates the high efficiency of these phosphates against all used bacteria. However, their effectiveness against G-negative was more superior to that of G-positive, indicating good selectivity against Gram-negative bacteria. Moreover, C-FeP NPs showed a higher antimicrobial impact than that of A-FeP.

Pulse‐assisted fluidization of nanoparticles: Case of lithium iron phosphate material

AbstractPulse‐assisted fluidization was developed for the fluidization of nanoparticles at high‐temperature processes (eg, above 600°C, depending on the material of interest). The technique was employed for carbon coating of lithium iron phosphate (LFP) nanoparticles with a gas‐phase carbon precursor (ie, propylene) through chemical vapour deposition (PAFB‐CVD). LFP has been extensively investigated as an environmentally friendly and cost‐effective cathode material of rechargeable lithium‐ion batteries. LFP nanoparticles of this research were, in fact, cohesive secondary particles of Geldart's group C. The CVD tests were carried out at temperatures between 600°C‐750°C. Uniform layers of carbon were deposited on the surface of LFP nanoparticles with a thickness less than 10 nm while particles were not sintered under high temperature operations. Also, the generated C‐LFP material held a superior electrical conductivity of 1010 times more than the conductivity of uncoated raw LFP; it also featured a significant enhancement of discharge capacity despite the considerable delay between the production of raw LFP nanoparticles and the CVD process.

Enhanced electrochemiluminescence at single lithium iron phosphate nanoparticles for the local sensing of hydrogen peroxide efflux from single living cell under a low voltage

The pursuit of strong electrochemiluminescence (ECL) at a low voltage is crucial, but challenging, for further development of ECL based bioanalysis, especially at single cells. In this work, single lithium iron phosphate (LiFePO4, LFP) nanoparticles at the surface of indium tin oxide (ITO) is firstly applied to produce enhanced ECL from luminol and hydrogen peroxide under a low voltage of 0.5 V. Lithium ions from single LFP particles are proposed to be de-intercalated during the charging process and then inserted into ITO to form LiSnO2, in which the oxidation of a luminol derivative (L012) is promoted resulting in an ECL emission at a low voltage. Meanwhile, the transformation of LiFePO4 into FePO4 under this voltage accelerates the generation of oxygen intermediates from hydrogen peroxide, and thus, leads to an elevated ECL intensity. Eventually, the efflux of hydrogen peroxide from single living cells is directly visualized under a voltage of 0.5 V using the ECL imaging approach, which is significantly lower than the previous voltage of 1.0 V. The first coupling of lithium migration in ECL reaction will pave a new direction to improve the ECL emission efficiency, and ultimately, push the development of ECL technology in highly spatial sensing of single cells.

Customized Kirigami Electrodes for Flexible and Deformable Lithium-Ion Batteries.

Customized deformable lithium-ion batteries (LIBs) have attracted interest in the emerging power systems for flexible and wearable electronics. However, a key challenge for developing these batteries is the fabrication of customized deformable electrodes that exhibit strong mechanical tolerance and robust electrochemical performance during deformation. Here, free-standing customized kirigami electrodes for deformable LIBs are fabricated by an evolutionary printing method with universal viscous electrode inks and a customizable polydimethylsiloxane template. The electrodes comprise lithium iron phosphate or lithium titanium oxide nanoparticles with a conductive carbon nanotubes/poly(vinylidene fluoride) scaffold, which is ideal for electron transfer. The compact microstructure and kirigami pattern endow the electrodes with superior mechanical robustness (over 500 stretch-release cycles) and resistance stability both in unstretched and stretched states. Finite element analysis and corresponding experiment tests reveal ultralow strain inside the materials, showing less than 3% strain even under 100% stretch ratio. With 500-times stretched electrodes, the full-cell LIBs can still deliver a considerable discharge capacity of average 94.5 mA h g-1 at 0.3 C after 100 discharge/charge cycles. The integration of such outstanding mechanical stability, excellent electrochemical performance, and simple printing method with accessible starting materials presents promising opportunities for customizing deformable components for flexible energy storage devices.

Iron Doping Effect for Oxygen Evolution Hybrid Catalysts based on Nickel Phosphate/Nitrogen‐Doped Carbon Nanoflakes

AbstractDeveloping highly efficient and earth‐abundant oxygen evolution reaction (OER) electrocatalysts is of great significance for sustainable energy conversion technologies. Herein, a facile thermal transformation strategy was developed to synthesize nickel iron phosphate nanoparticles incorporated in N‐doped carbon (NiFeP/N−C) nanoflakes as highly efficient OER electrocatalysts based on a metal organophosphonate precursor. The amino trismethylene phosphonic acid ligand used here has excellent affinity toward various metals and thus can act as a P, C, and N source on a molecular scale, which simplifies the synthesis of conductive material‐supported multi‐metal phosphates. Benefiting from the derived N‐doped carbon and the synergistic effect of bimetal ions, the sample denoted NiFeP/N−C‐700 exhibits outstanding electrocatalytic activity. It exhibits a lower overpotential of 280 mV, a small Tafel slope of 48 mV dec−1 at a current density of 10 mA/cm2, and superior stability in 1 M KOH solution.

Enhanced adsorption and removal of urea from aqueous solutions using eco-friendly iron phosphate nanoparticles

This work reports of using iron phosphate nanoparticles (nano-FePh) as adsorbent for removing urea. Hence, the adsorption of urea on nano-FePh was investigated as a function of reaction time, temperature, catalyst weight, shaking speed and solution pH. Amorphous iron phosphate is synthesized by a cost-effective method reflux. The nano-FePh is characterized by different techniques including; X-ray diffraction (XRD), transmission electron micrograph (TEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray Spectroscopy (EDX), FT-IR and BET surface area determination. Highest adsorption extent obtained at pH range of 7–9 with uptake of urea equals to 1.2 × 102 mg/g (gram of nano-FePh). The reaction kinetics of the adsorption of urea follows a pseudo-first-order model. Application of homogenous film diffusion model and matrix diffusion model is carried out and analyzed. The model of the diffusion liquid film controls the process at the first adsorption step and then at the final stage is under control by matrix diffusion model. Frumkin adsorption isotherm is found to fit with the experimental data. The kinetics and thermodynamic parameters have been determined and analyzed. The nano-FePh adsorbent was stable and the adsorption capacity was remaining excellent after 10 cycles.

Synthesis of crystalline and amorphous iron phosphate nanoparticles by simple low-temperature method

A simple and well-designed route for controlled synthesis of crystalline iron phosphate (FePhcry) and amorphous iron phosphate (FePhamph) with simple reflux-based method at 90 °C is introduced. The method allows for mass production at low cost. The crystalline is formed at initial pH of 0.38 to final pH = 1.0 and the amorphous form is obtained at initial pH of 1.3 to final pH (after completed reflux) of 8.0. Characterization techniques such as FT-IR spectroscopy, energy dispersive x-ray analysis (EDS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and BET surface area determination are used for the investigation of the phase structure and morphological properties of the FePhcry and FePhamph nanomaterials. The average values of particle size are ∼50–100 nm and ∼5–15 nm with surface area of 16.013 m2 g−1 and 154 m2 g−1 for FePhcry and FePhamph, respectively. Based on the XRD pattern, the obtained phase structure of the FePhcry is FePO4.2H2O (80%) and Fe12 (OH)7.3 (PO4)8.4.7H2O (20%) with a monoclinic and orthorhombic crystallographic form, respectively. For the FePhamph sample the phase structure is completely amorphous with chemical structure of FePO4.

Remediation of cadmium in soil by biochar-supported iron phosphate nanoparticles

A type of biochar-supported iron phosphate nanoparticle stabilised by a sodium carboxymethyl cellulose (CMC@BC@ Fe3(PO4)2) composite was synthesised to remediate cadmium (Cd)-polluted soil. The surface morphology and functional groups of the composite were characterised by scanning electron microscopy and Fourier transform infrared spectrometry, respectively. Batch experiments showed that the composite (soil-to-solution ratio 1g:10mL) could effectively immobilise Cd in soil. The immobilisation efficiency of Cd was 81.3% after 28days of remediation, and physiological-based extraction test bioaccessibility was reduced by 80.0%. The results of sequential extraction procedures indicated that the transformation from more easily extractable Cd to the least available form was responsible for the decrease in Cd bioavailability in soils. Plant growth experiments proved that the composite could inhibit Cd uptake to the belowground and aboveground parts of cabbage mustard by 44.8% and 70.2%, respectively, thus promoting cabbage mustard growth and development after remediation.

Iron phosphate nanoparticles for food fortification: Biological effects in rats and human cell lines

Nanotechnology offers new opportunities for providing health benefits in foods. Food fortification with iron phosphate nanoparticles (FePO4 NPs) is a promising new approach to reducing iron deficiency because FePO4 NPs combine high bioavailability with superior sensory performance in difficult to fortify foods. However, their safety remains largely untested. We fed rats for 90 days diets containing FePO4 NPs at doses at which iron sulfate (FeSO4), a commonly used food fortificant, has been shown to induce adverse effects. Feeding did not result in signs of toxicity, including oxidative stress, organ damage, excess iron accumulation in organs or histological changes. These safety data were corroborated by evidence that NPs were taken up by human gastrointestinal cell lines without reducing cell viability or inducing oxidative stress. Our findings suggest FePO4 NPs appear to be as safe for ingestion as FeSO4.