Synthesis of Low-Defect Iron-Based Prussian Blue with Low Water Content for High-Stability Sodium-Ion Batteries

This study proposes an innovative two-step synthesis strategy to significantly enhance the performance of sodium-ion batteries by developing low-defect, low water content iron-based Prussian blue (PB) materials. Addressing the limitations of traditional co-precipitation methods-such as rapid reaction rates leading to excessive crystal defects and interstitial water content-the research team introduced a synergistic approach combining non-aqueous phase precursor synthesis and controlled water-concentration secondary crystallization. The process involves preparing a PB precursor in a glycerol system, followed by secondary crystallization in a water-/ethanol-mixed solvent with a precisely regulated water content, achieving the dual objectives of water content reduction and crystal morphology optimization. Systematic characterization revealed that water concentration during secondary synthesis critically influences the material's crystal structure, morphological features, and water content. The optimized PB50-24 material exhibited a highly regular cubic morphology with a sodium content of 9.2% and a remarkably low interstitial water content of 2.1%. Electrochemical tests demonstrated outstanding performance-an initial charge-discharge capacity of 120 mAh g-1 at a 1C rate, the retention of 105 mAh g-1 after 100 cycles, and a high rate capability of 86 mAh g-1 at 10C, representing significant improvements in cycling stability and rate performance over conventional methods. This work not only establishes a cost-effective, scalable synthesis pathway for Prussian blue materials but also provides theoretical guidance for developing other metal-based Prussian blue analogs, offering substantial value for advancing the industrial application of sodium-ion batteries in next-generation energy storage systems.

Research progress on the synthesis, performance regulation, and applications of Prussian blue nanozymes

Nanocatalytic medicine offers a novel solution to address the issues of low efficacy, potential side effects, and the development of drug resistance associated with traditional therapies. Therefore, developing highly efficient and durable nanozymes is of great significance for treating diseases related to oxidative stress. In recent years, prussian blue nanoparticles (PBNPs) have been demonstrated to possess multiple enzyme-like catalytic activities and are thus referred to as prussian blue nanozymes (PBNZs). Their excellent biocompatibility and biodegradability make PBNZs promising candidates as biomedical materials. Due to their remarkable catalytic activities, PBNZs have shown great potential in various biomedical applications, such as heavy metal detoxification, antioxidative damage, and anticancer therapies. This paper systematically summarizes the Synthetic strategies of PBNZs, analyzes the regulatory factors of their catalytic performance, and highlights the corresponding modulation methods. Furthermore, the biomedical applications of PBNZs are also reviewed. This study aims to provide researchers with insights and inspirations for the design and preparation of high-performance PBNZs.

Sodium-Rich Prussian Blue Analogs Synthesized with Reducing Sodium Salt for Enhanced Rate and Cycling Stability Sodium-Ion Storage

Prussian blue analogs (PBAs) as cathode material for sodium-ion batteries have attracted widespread attention due to their affordability, simple synthesis, and high theoretical capacity. Nevertheless, the oxidation of Fe2+ and sodium loss lead to poor electrochemical properties which restrict the practical use of PBAs. Herein, a simple coprecipitation approach based on sodium salt-reduction-assisted synthesis was proposed to construct high-sodium PBAs. The sodium bisulfite (NaHSO3) not only effectively inhibits the oxidation of Fe2+ but also increases the mole ratio of Na+ in the resulting products. The optimized sample exhibits excellent specific capacity (131.1 mAh g-1 at 0.1C), high rate performance (103.9 mAh g-1 at 10C), and good cyclic performance (94.8% capacity retention after 200 cycles). Experimental results reveal that the sample synthesized with sodium bisulfite possesses improved sodium-ion diffusion kinetics and stable crystal structure. In this study, a scalable method is introduced for the synthesis of PBAs with excellent electrochemical properties and further applications.

Cobalt Hexacyanoferrate Cathode with Stable Structure and Fast Kinetics for Aqueous Zinc-Ion Batteries

Prussian blue analogues (PBAs) show great promise as cathode candidates for aqueous zinc-ion batteries thanks to their high operating voltage, open-framework structure, and low cost. However, suffering from numerous vacancies and crystal water, the electrochemical performance of PBAs remains unsatisfactory, with limited capacity and poor cycle life. Here, a simple coprecipitation method is shown to synthesize well-crystallized cobalt hexacyanoferrate (CoHCF) with a small amount of water and high specific surface area. Benefitting from two redox-active sites, CoHCF could deliver 104.6 mA h g-1 at 0.02 A g-1 and 72 mA h g-1 at 1 A g-1, with good capacity retention of 92.4% after 300 cycles at 0.5 A g-1. Several electrochemical kinetic tests indicate that the reaction is dominated by capacitive behavior and that the diffusion coefficient of Zn2+ ions is approximately 10-9 cm2 s-1. Furthermore, ex-situ XRD indicated a reversible insertion/extraction of Zn2+ ions without any phase transition.

Continuous and Scalable Synthesis of Prussian Blue Analogues with Tunable Structure and Composition in Surfactant-Free Microreactor for Stable Zinc-Ion Storage

We represent a segmented flow surfactant-free microfluidic strategy for continuous synthesis of Prussian blue analogues (PBAs) with high dispersity and high crystallization. Representative zinc hexacyanoferrate (ZnHCF) nanocubes were successfully synthesized in a microfluidic reactor within a few minutes via the cooperation method and possessed lower contents of crystal water and Fe(CN)6 3- vacancies than that of synthesis in bulk solution. The nucleation and particle growth process can be precisely controlled by the exploration of different flow rates and reaction temperatures during the formation of ZnHCF nanocubes in segmented flow microfluidic reactors. High crystallinity, low crystal water and vacancies in the ZnHCF structure were presented at relatively high temperatures for the crystal growth process. High-quality ZnHCF with a low content of crystal water showed excellent electrochemical activity and stability towards zinc-ion storage. The continuous and scalable synthesis approach can be extended to the fabrication of other PBAs such as NiHCF, CoHCF, MnHCF, and CuHCF with high dispersity without using any surfactants. The controllable construction of PBAs with tunable properties in microfluidic reactors provides a promising direction to minimize the gap between commercial reality and laboratory research.

Y-tube assisted coprecipitation synthesis of iron-based Prussian blue analogues cathode materials for sodium-ion batteries

Prussian blue analogues possess numerous advantages as cathode materials for sodium-ion batteries, including high energy density, low cost, sustainability, and straightforward synthesis processes, making them highly promising for practical applications. However, during the synthesis, crystal defects such as vacancies and the incorporation of crystal water can lead to issues such as diminished capacity and suboptimal cycling stability. In the current study, a Y-tube assisted coprecipitation method was used to synthesize iron-based Prussian blue analogues, and the optimized feed flow rate during synthesis contributed to the successful preparation of the material with a formula of Na1.56Fe[Fe(CN)6]0.90□0.10·2.42H2O, representing a low-defect cathode material. This approach cleverly utilizes the Y-tube component to enhance the micro-mixing of materials in the co-precipitation reaction, featuring simplicity, low cost, user-friendly, and the ability to be used in continuous production. Electrochemical performance tests show that the sample retains 69.8% of its capacity after 200 cycles at a current density of 0.5C (1C = 140 mA g-1) and delivers a capacity of 71.9 mA h g-1 at a high rate of 10C. The findings of this research provide important insights for the development of high-performance Prussian blue analogues cathode materials for sodium-ion batteries.

Nanosized Prussian blue and its analogs for bioimaging and cancer theranostics

Prussian blue (PB) nanoparticles (NPs) and Prussian blue analogs (PBAs) can form metal-organic frameworks through the programmable coordination of ferrous ions with cyanide. PB and PBAs represent a burgeoning class of hybrid functional nano-systems with a wide-ranging application spectrum encompassing biomedicine, cancer diagnosis, and therapy. A comprehensive overview of recent advancements is crucial for gaining insights for future research. In this context, we reviewed the synthesis techniques and surface modification strategies employed to tailor the dimensions, morphology, and attributes of PB NPs. Subsequently, we explored advanced biomedical utilities of PB NPs, encompassing photoacoustic imaging, magnetic resonance imaging, ultrasound (US) imaging, and multimodal imaging. In particular, the application of PB NPs-mediated photothermal therapy, photodynamic therapy, and chemodynamic therapy to cancer treatment was reviewed. Based on the literature, we envision an evolving trajectory wherein the future of Prussian blue-driven biological applications converge into an integrated theranostic platform, seamlessly amalgamating bioimaging and cancer therapy. STATEMENT OF SIGNIFICANCE: Prussian blue, an FDA-approved coordinative pigment with a centuries-long legacy, has paved the way for Prussian blue nanoparticles (PB NPs), renowned for their remarkable biocompatibility and biosafety. These PB NPs have found their niche in biomedicine, playing crucial roles in both diagnostics and therapeutic applications. The comprehensive review goes beyond PB NP-based cancer therapy. Alongside in-depth coverage of PB NP synthesis and surface modifications, the review delves into their cutting-edge applications in the realm of biomedical imaging, encompassing techniques such as photoacoustic imaging, magnetic resonance imaging, ultrasound imaging, and multimodal imaging.

A metal organic framework-derived octahedral Cu1.95S@CoS2 for secondary batteries displaying long cycle life and stable temperature tolerance

Low-cost and safe batteries are considered to be promising energy-storage systems. Here, a metal organic framework (MOF)-derived octahedral Cu1.95S@CoS2 composite is developed as a high-performance cathode of aluminium-ion (Al-ion) batteries. CoS2 nanoparticles on Cu1.95S provide active sites, making AlCl4- intercalation/deintercalation highly reversible, and reducing polarization. Cycling at 0.5 A g-1, Cu1.95S@CoS2 maintains stable capacities of 136.6 and 122.4 mA h g-1 after 200 cycles at room temperature and -10 °C, respectively. Stable rate-performance is also achieved. These findings will accelerate the application of Al-ion batteries and MOF-derived energy-storage composites.

Promising Cathode Materials for Sodium-Ion Batteries from Lab to Application

Sodium-ion batteries (SIBs) are seen as an emerging force for future large-scale energy storage due to their cost-effective nature and high safety. Compared with lithium-ion batteries (LIBs), the energy density of SIBs is insufficient at present. Thus, the development of high-energy SIBs for realizing large-scale energy storage is extremely vital. The key factor determining the energy density in SIBs is the selection of cathodic materials, and the mainstream cathodic materials nowadays include transition metal oxides, polyanionic compounds, and Prussian blue analogs (PBAs). The cathodic materials would greatly improve after targeted modulations that eliminate their shortcomings and step from the laboratory to practical applications. Before that, some remaining challenges in the application of cathode materials for large-scale energy storage SIBs need to be addressed, which are summarized at the end of this Outlook.

Progress in the preparation of Prussian blue-based nanomaterials for biomedical applications

Prussian blue (PB) is composed of the coordination network of Fe²⁺-CN-Fe³⁺ mixed valence state as a classic metal complex, which includes a C atom and Fe²⁺ (low spin), N atom and Fe³⁺ (high spin). PB and its analogues (PBA) have excellent biosafety, good magnetic properties, outstanding photothermal properties and the ability to mimic enzymatic behaviors due to their stable structure, tunable size, controllable morphology, abundant modification methods and excellent physicochemical properties. They have received increasing research interest and have shown promising applications in the biomedical field. Here, progress in the preparation of PB-based nanomaterials for biomedical applications is summarized and discussed. The preparation strategies, traditional synthesis and emerging preparation methods of PB are summarized systematically in this review. The design and preparation of PBA, PB(PBA)-based hollow structures and PB(PBA)-based composites are also included. While introducing the preparation status, some PB-based nanomaterials that have performed well in specific biomedical fields are emphasized. More importantly, the key factors and future development of PB for the clinical translation as multifunctional nanomaterials are also discussed. This review provides a reference for the design and biomedical application of PB-based nanomaterials.

A high areal capacity sodium-ion battery anode enabled by a free-standing red phosphorus@N-doped graphene/CNTs aerogel

A novel and facile strategy for fabricating red phosphorus@nitrogen doped graphene/carbon nanotube aerogel (P@NGCA) is proposed as a free-standing anode for high energy sodium-ion batteries. Owing to an optimized structure of red P uniformly confined in porous NGCA with high conductivity and mechanical stability, the free-standing P@NGCA anode exhibits outstanding sodium storage performance with a high areal capacity of 3.3 mA h cm^-2 and superior initial Coulombic efficiency of 80%.