Prussian Blue Analogue‑Templated Nanocomposites for Alkali‑Ion Batteries:Progress and Perspective

Lithium-ion batteries(LIBs)have dominated the portable electronic and electrochemical energy markets since their commercialisation,whose high cost and lithium scarcity have prompted the development of other alkali-ion batteries(AIBs)including sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs).Owing to larger ion sizes of Na^(+)and K^(+)compared with Li^(+),nanocomposites with excellent crystallinity orientation and well-developed porosity show unprecedented potential for advanced lithium/sodium/potassium storage.With enticing open rigid framework structures,Prussian blue analogues(PBAs)remain promising self-sacrificial templates for the preparation of various nanocomposites,whose appeal originates from the well-retained porous structures and exceptional electrochemical activities after thermal decomposition.This review focuses on the recent progress of PBA-derived nanocomposites from their fabrication,lithium/sodium/potassium storage mechanism,and applications in AIBs(LIBs,SIBs,and PIBs).To distinguish various PBA derivatives,the working mechanism and applications of PBA-templated metal oxides,metal chalcogenides,metal phosphides,and other nanocomposites are systematically evaluated,facilitating the establishment of a structure–activity correlation for these materials.Based on the fruitful achievements of PBA-derived nanocomposites,perspectives for their future development are envisioned,aiming to narrow down the gap between laboratory study and industrial reality.

Moderate heat treatment of CoFe Prussian blue analogues for enhanced oxygen evolution reaction performance

Prussian blue analogues(PBAs) with inherent ordered structures and abundant metal ion sites are widely explored as precursors for various electrochemical applications,including oxygen evolution reaction(OER).Using a range of characterization techniques including Fourier-transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD) and energy dispersive spectroscopy(EDS),this work discloses the process of replacement of K^(+)by NH4^(+)in the interstitial spaces of the CoFe PBA by a hot aqueous urea solution,which influences the transformation of PBAs under further heat treatment and the OER performance of the deriva tives.After heat treatment at 400℃ under Ar flow,high-resolution transmission electron microscopy(HRTEM) images reveal that CoFe alloy nanoparticles grew on the crystalline cubes of CoFe PBA with K^(+),while CoFe PBA cubes with NH4^(+)become amorphous.Besides,the derivative of CoFe PBA with NH4^(+)(Ar-U-CoFe PBA) performs better than the derivative of CoFe PBA with K^(+)(Ar-CoFe PBA) in OER,registering a lower overpotential of 305 mV at 10 mA cm^(-2),a smaller Tafel slope of 36.1 mV dec^(-1),and better stability over a testing course of 20 h in 1.0 M KOH.A single-cell alkaline electrolyzer,using Ar-U-CoFe PBA and Pt/C for the anodic and cathodic catalyst,respectively,requires an initial cell voltage of 1.66 V to achieve 100 mA cm^(-2)at 80℃,with negligible degradation after100 h.

Ultralow-Energy-Barrier H_(2)O_(2)Dissociation on Coordinatively Unsaturated Metal Centers in Binary Ce-Fe Prussian Blue Analogue for Efficient and Stable Photo-Fenton Catalysis

The low intrinsic activity of Fenton catalytic site and high demand for light-energy input inhibit the organic-pollution control efficiency of photo-Fenton process.Here,through structural design with density functional theory(DFT)calculations,Ce is predicted to enable the construction of coordinatively unsaturated metal centers(CUCs)in Prussian blue analogue(PBA),which can strongly adsorb H_(2)O_(2)and donate sufficient electrons for directly splitting the O-O bond to produceOH.Using a substitution-co-assembly strategy,binary Ce-Fe PBA is then prepared,which rapidly degrades sulfamethoxazole with the pseudo-first-order kinetic rate constant exceeding reported values by 1-2 orders of magnitude.Meanwhile,the photogenerated electrons reduce Fe(Ⅲ)and Ce(Ⅳ)to promote the metal valence cycle in CUCs and make sulfamethoxazole degradation efficiency only lose 6.04%in 5 runs.Overall,by introducing rare earth metals into transition metal-organic frameworks,this work guides the whole process for highly active CUCs from design and construction to mechanism exploration with DFT calculations,enabling ultrafast and stable photo-Fenton catalysis.

Prussian Blue Analogues in Aqueous Batteries and Desalination Batteries

In the applications of large-scale energy storage,aqueous batteries are considered as rivals for organic batteries due to their environmentally friendly and low-cost nature.However,carrier ions always exhibit huge hydrated radius in aqueous electrolyte,which brings difficulty to find suitable host materials that can achieve highly reversible insertion and extraction of cations.Owing to open threedimensional rigid framework and facile synthesis,Prussian blue analogues(PBAs)receive the most extensive attention among various host candidates in aqueous system.Herein,a comprehensive review on recent progresses of PBAs in aqueous batteries is presented.Based on the application in different aqueous systems,the relationship between electrochemical behaviors(redox potential,capacity,cycling stability and rate performance)and structural characteristics(preparation method,structure type,particle size,morphology,crystallinity,defect,metal atom in highspin state and chemical composition)is analyzed and summarized thoroughly.It can be concluded that the required type of PBAs is different for various carrier ions.In particular,the desalination batteries worked with the same mechanism as aqueous batteries are also discussed in detail to introduce the application of PBAs in aqueous systems comprehensively.This report can help the readers to understand the relationship between physical/chemical characteristics and electrochemical properties for PBAs and find a way to fabricate high-performance PBAs in aqueous batteries and desalination batteries.

Ternary Ni-based Prussian blue analogue with superior sodium storage performance induced by synergistic effect of Co and Fe

Prussian blue analogue Na2Ni[Fe(CN)6](Ni-PB)has been widely studied as a cathode material for sodium-ion battery due to its excellent cycling performance.However,Ni-PB has a low theoretical capacity of 85 mAh g^(−1) because of the electrochemical inertness of Ni.Herein,ternary Ni-PB is successfully synthesized by double doping with Co and Fe at Ni-site,and the effect of doping with Co and Fe on the electrochemical performance of Ni-PB is systematically investigated through theoretical calculations and electrochemical tests.The first principles calculations confirm that double doping with Co and Fe can significantly reduce the energy barrier and bandgap of Ni-PB.X-ray diffraction and composition analysis results indicate that ternary NiCoFe-PB composite not only has good crystallinity and high Na content but also has low defects and crystal water.Electrochemical tests reveal that,besides the capacity contribution of high-spin Co/Fe and low-spin Fe,Co-doping enhances the electrochemical activity of low-spin Fe and Fe-doping improves the activity of high-spin Co;moreover,double doping can decrease the diffusion resistance of Na+ions through solid electrolyte interface film,accelerate the kinetics for both ion diffusion process and Faradic reaction,and increase active sites.Under the synergistic effect of Co and Fe,this ternary NiCoFe-PB exhibits outstanding electrochemical performance with a high initial discharge capacity of 120.4 mAh g^(−1) at 20mA g^(−1) and an extremely low capacity fading rate of 0.0044%per cycle at a high current density of 2 A g^(−1) even after 10,000 cycles,showing great application potential of ternary NiCoFe-PB in the field of large-scale energy storage.

Construction of hierarchical photocatalysts by growing ZnIn_(2)S_(4) nanosheets on Prussian blue analogue-derived bimetallic sulfides for solar co-production of H_(2) and organic chemicals

Exploring highly efficient bifunctional photocatalysts for simultaneous H2 evolution and organic chemical production in pure water represents a green route for sustainable solar energy storage and conversion.Herein,a facile strategy was explored for preparing a hierarchical porous heterostructure of Fe_(4)Ni_(5)S_(8)@ZnIn_(2)S_(4)(FNS@ZIS)by the in situ growth of ZIS nanosheets on Prussian blue analogue(PBA)-derived bimetallic FNS sulfides.A series of FNS@ZIS hierarchical structures were facilely prepared by adjusting the loading amount(n%)of FNS(n=19,26,and 32 for FNS@ZIS-1-3).These structures can efficiently drive the solar co-production of H_(2) and organic chemicals.The optimal co-production was achieved with FNS@ZIS-2,affording a H_(2) evolution rate of 10465μmol·g^(-1)·h^(-1),along with high selectivity for the oxidation of benzyl alcohol to benzaldehyde(>99.9%).The performance was 22 and 31 times higher than that of FNS and ZIS,respectively,and even superior to the state-of-the-art results achieved using various sacrificial agents.Further mechanistic study indicated that the unique hierarchical core/shell architecture can facilitate interfacial charge separation,afford bimetallic synergy,abundant active sites and excellent photostability.This work highlights a simple and efficient method for preparing porous multimetallic hierarchical structures for the solar co-production of organic chemicals and H_(2) fuel.

Unveiling anomalous lattice shrinkage induced by Pi-backbonding in Prussian blue analogues

Transition-metal(TM)-based Prussian blue and its analogues(TM-PBAs) have attracted considerable attention as cathode materials owing to their versatile ion storage capability with tunable working voltages. TM-PBAs with different crystal structures, morphologies, and TM combinations can exhibit excellent electrochemical properties because of their unique and robust host frameworks with well-defined<100> ionic diffusion channels. Nonetheless, there is still a lack of understanding regarding the performance dependence of TM-PBAs on structural changes during charging/discharging processes. In this study, in situ X-ray diffraction and X-ray absorption fine structure analyses elucidate the TMdependent structural changes in a series of TM-PBAs during the charging and discharging processes.During the discharging process, the lattice volume of Fe-PBA increased while those of Ni-and Cu-PBAs decreased. This discrepancy is attributed to the extent of size reduction of the cyanometallate complex([Fe(CN)_(6)]) via pi-backbonding from Fe to C due to redox flips of the low-spin Fe^(3+/2+) ion. This study presents a comprehensive understanding of how TM selection affects capacity acquisition and phase transition in TM-PBAs, a promising class of cathode materials.

Toward the Design of High-performance Supercapacitors by Prussian Blue, its Analogues and their Derivatives

Supercapacitors(SCs)with high power output have attracted increasing attention as efficient and environmentally friendly energy storage devices.Prussian blue and its analogues(PB/PBAs)are simple coordination polymers with tunable chemical compositions and open framework.Prussian blue can act as electrode materials in its pristine form and has also been utilized to derive various metallic nanostructures for electrochemical applications due to their simple fabrication process,non-toxic characteristics,and low price.Here,we firstly describe the charge storage mechanisms of SCs briefly followed by an introduction of the fabrication methods of PB/PBAs and their derivatives.Then,a comprehensive review on recent studies of the use of PB/PBAs and their derivatives as the electrode materials for SCs are given with a focus on strategies to improve their electrochemical performances.Finally,we discuss critical challenges in this research area and propose some general ideas for future research.

Abnormal magnetic behavior of prussian blue analogs modified with multi-walled carbon nanotubes

This work examines the origin of the abnormal magnetism exhibited by Cu Mn Fe-PBAs modified with multi-walled carbon nanotubes(MWCNTs).The system of Cu Mn Fe-PBAs@MWCNTs coexists with both large and small clusters.Cu Mn Fe-PBAs clusters have an average particle size of 28 nm,and some of the smaller particles are adsorbed on the surface of MWCNTs.Surprisingly,the magnitude of magnetization increases linearly with decreasing temperature.When above the Curie temperature,the magnitude of magnetization is significantly greater than that of PBAs without being modified.This phenomenon can be attributed to magnetostatic interactions between ultra-fine magnetic nanoparticles adsorbed on the surface of MWCNTs.Using the Monte Carlo method,we simulated the magnetostatic interaction of cylindrical adsorbed particles,and the simulation results are almost identical to those observed experimentally.The results indicate that 0.089Cu Mn Fe-PBAs clusters per 1 nm^(2)can be adsorbed onto the surface area of MWCNTs.We demonstrate that MWCNTs adsorbing magnetic particles exhibit magnetic behavior,and suggest a method for producing ultrafine materials.It also introduces a new method of calculating the adsorption efficiency of carbon nanotubes,offering theoretical guidance for future research on nanomaterials with enhanced adsorption efficiency.

FeNi Prussian blue analogues on highly graphitized carbon nanosheets as efficient glucose sensors

Meeting the continuous glucose monitoring requirements of individuals necessitates the research and development of sensors with high sensitivity and stability.In this study,a straightforward strategy was proposed for synthesizing ultra-thin oxygen-rich graphitized carbon nanosheets(denoted as GCS-O).These nanosheets are obtained by calcining a topologically two-dimensional indium-based coordination polymer.Subsequently,the growth of FeNi Prussian blue analogue(PBA)on GCS-O effectively introduces active sites and increases the nitrogen content within the carbonaceous matrix.The resulting FeNi-PBA/GCS-O composite exhibits excellent glucose sensing performance with a broad linear range of 1 to 1300μmol·L^(-1).Meanwhile,it also achieves a high sensitivity of 2496μA·mmol^(-1)·L·cm^(-2),a limit of detection of 100nmol·L^(-1)(S/N=3),and commendable long-term durability.The relatively simple synthesis process,exceptional sensitivity,and satisfactory electrochemical sensing performance of FeNi-PBA/GCS-O open up new directions for biosensor applications.

In Situ Electron Paramagnetic Resonance Reveals Fading Mechanism of Mn-Based Prussian Blue Analogue:Accelerated Mn Dissolution Due to Charge Delocalization

Contrasting with Fe-based Prussian blue analogues(PBAs),Mn-based PBAs with higher energy density are more promising cathode materials for Na-ion batteries.However,fast capacity fading has severely impeded its practical use,which is still not well understood.To elucidate the fading mechanism,in situ and ex situ electron paramagnetic resonance are employed here.The results first demonstrate the charge delocalization of Mn2+and Mn dissolution during cycles,which are further proved to be highly related.Our work reveals the inherent shortcoming of Mn-based PBA cathodes in liquid electrolyte.

Prussian blue analogues-derived nitrogen-doped carboncoated FeO/CoO hollow nanocages as a high-performance anode material for Li storage

The design of electrode materials with specific structures is considered a promising approach for improving the performance of lithium-ion batteries(LIBs).In this paper,FeO/CoO hollow nanocages coated with a N-doped carbon layer(FCO@NC)was prepared using Fe-Co-based Prussian blue analogs(PBA)as a precursor.During the synthesis,dopamine was the carbon and nitrogen source.The reducing atmosphere was assured via NH_3/Ar,which regulated the vacancies in the structure of FCO@NC as well as increased its conductivity.When used as anode materials for LIBs,the FCO@NC nanocages deliver a high reversible capacity of 774.89 mAh·g^(-1)at 0.3 A·g^(-1)after200 cycles with a capacity retention rate of 80.4%and426.76 mAh·g^(-1)after 500 cycles at a high current density of 1 A·g^(-1).It is demonstrated that the hollow nanocage structure can effectively enhance the cycle stability,and the heat treatment in NH_(3)/Ar atmosphere contributes to the oxygen vacancy content of the electrode materials,further facilitating its conductivity and electrochemical performance.

Active cation-integration high-entropy Prussian blue analogues cathodes for efficient Zn storage

Mn-based Prussian blue analogues(Mn-PBAs),featuring a three-dimensional(3D)metal-organic framework and multiple redox couples,have gained wide interests in Zn-ion batteries(ZIBs).However,owing to the Jahn-Teller distortion and disproportionation reaction of Mn^(3+),these materials suffer from poor electrochemical performances and inferior structural stability.Herein,we prepare a typical high-entropy Prussian blue analogue(HE-PBA)with increased configuration entropy through integrating five transition metal elements of Mn,Co,Ni,Fe and Cu into the nitrogen-coordinated-M-lattice sites.Consequently,the HE-PBA presents enhanced uptake of Zn^(2+)with 80 mAh·g^(−1)compared to those medium-entropy PBAs,low-entropy PBAs and conventional PBAs,which can be assigned to“cocktail”effect of multiple transition metal active redox couples.Furthermore,a phase transition process from monoclinic phase to rhombohedral phase occurs in HE-PBA cathode,resulting in a stable structure of MN6(M=Mn,Co,Fe,Ni,Cu)and ZnN4 co-linked to FeC6 through the cyanide ligands.Additionally,the advantages of entropy-driven stability are also confirmed by the calculated reduction energy and the density of states between HE-PBA and KMn[Fe(CN)6](KMnHCF).This work not only presents a high-performance HE-PBA cathode in ZIBs,but also introduces a novel concept of high entropy benefiting for designing advanced materials.

Core-shell Prussian blue analogues derived from metal-organic frameworks as efficient electrocatalysts for oxygen evolution reaction

Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction(OER)is still a great challenge for water-splitting technologies.Herein,an innovative metal-organic frameworks(MOFs)hybrid-assisted strategy is reported to synthesize core-shell Co/Mn-ZIF@Fe-Co-Mn Prussian blue analogues(PBAs)toward highly efficient OER electrocatalysts in alkaline electrolyte.Physical characterization indicates that the amorphous hydroxide transformed from Co/Mn-ZIF@Fe-Co-Mn PBA(ZIF:zeolitic imidazolate frameworks)during the electrochemical process acted as the electroactive species.Benefiting from these structural and compositional features,the developed composite delivers a remarkably low overpotential of 270 mV with a current density of 10 mA·cm^(−2)in 1.0 M KOH solution.Moreover,water splitting is catalyzed to reach a current density of 10 mA·cm^(−2)at 1.62 V.

Rational design of Prussian blue analogue-derived manganese-iron oxides-based hybrids as high-performance Li-ion-battery anodes

The unique components and architecture of Prussian blue analogous(PBAs) offer great potential for the construction of various functional nanostructures. Herein, we reported the preparation of a series of Mn–Fe oxides-based hybrids using Mn–Fe PBA as a template and an organic carbon source by calcination.The study focuses on revealing the interaction between the microstructure and electrochemical performance of the products obtained at different calcination temperatures. Notably, the as-derived porous Fe–Fe0.33Mn0.67O/C nanocubes(i.e., M600) exhibited the best rate capability and cycle life compared with other samples(~890 m Ah/g at 0.1 A/g, 626.8 m Ah/g after 1000 cycles at 1.0 A/g with a 99% capacity retention). These can be attributed to the fact that the porous structure provides shorter Li+diffusion path and promotes the penetration of electrolyte. Besides, the N-doped C formed by the carbonization of organic ligands can buffer the volume change and prevent the aggregation of Fe_(0.33)Mn_(0.67)O nanoparticles during the discharge/charge cycles. Moreover, the presence of metallic Fe enhances the conductivity and the electrochemical activity, which accelerates the electrochemical reactions. Therefore, reasonable design of microstructure and compositions of functional nanocomposites is the key to obtain ideal electrochemical properties.

Hollow and substrate-supported Prussian blue,its analogs,and their derivatives for green water splitting

To meet the current energy needs of society,the highly efficient and continuous production of clean energy is required.One of the key issues facing the green hydrogen evolution is the construction of efficient,low-cost electrocatalysts.Prussian blue(PB),Prussian blue analogs(PBAs),and their derivatives have tunable metal centers and have attracted significant interest as novel photo-and electrochemical catalysts.In this review,recent research progress into PB/PBA-based hollow structures,substrate-supported nanostructures,and their derivatives for green water splitting is discussed and summarized.First,several remarkable examples of nanostructured PB/PBAs supported on substrates(copper foil,carbon cloth,and nickel foam)and hollow structures(such as single-shelled hollow boxes,open hollow cages,and intricate hollow structures(multi-shell and yolk-shell))are discussed in detail,including their synthesis and formation mechanisms.Subsequently,the applications of PB/PBA derivatives((hydr)oxides,phosphides,chalcogenides,and carbides)for water splitting are discussed.Finally,the limitations in this research area and the most urgent challenges are summarized.We hope that this review will stimulate more researchers to develop technologies based on these intricate PB/PBA structures and their derivatives for highly efficient,green water splitting.

Boosting the sodium storage performance of Prussian blue analogues via effective etching

Prussian blue analogues(PBAs)have gained significant popularity as cathode materials for sodium-ion batteries(SIBs)due to their remarkable features such as high capacity and convenient synthesis.However,PBAs usually suffer from kinetic problems during the electrochemical reactions due to sluggish Na~+diffusion in the large crystals,resulting in low-capacity utilization and inferior rate capability.In this study,we present a facile etching method aiming at activating the sodium storage sites and accelerating the Na~+transport of Na_2NiFe(CN)_6(denoted as NaNiHCF)by precisely controlling its morphologies.A progressive corner passivation phenomenon occurred in NaNiHCF during the etching process,which led to a substantial augmentation of the specific surface area as the morphology transitioned from a standard cube to a dice shape.Notably,by controlling the etching time,the obtained NaNiHCF-3 electrode exhibited boosted electrochemical performance with high reversible capacity of 83.5mAh g~(-1)(98.2%of its theoretical capacity),superior rate capability(71.2 mAh g~(-1)at 10 C),and stable cycling life-span at different temperatures.Both experimental and computational methods reveal the remarkably reversible structural evolution process and improved Na~+diffusion coefficient.We believe that this work can serve as an indispensable reference to tailor the structure of PBAs to obtain improved electrochemical performance.

学科前沿案例融合下的物理化学实验教学设计——以“高熵普鲁士蓝的合成及应用”为例

培养更多拔尖创新人才是现阶段大学教育的重要任务。化学专业学生的培养不仅需要重视扎实的专业知识学习,还要重视科研创新思维的培养。系统熵变是热力学部分的重要教学内容,在课程原来包含的实验中,有的实验开了十几年甚至几十年,更新速度缓慢,跟不上科研发展的步伐,缺乏新颖性、趣味性及时代性。因此,设计开展高熵材料的合成及应用的创新型实验,不仅可以让学生掌握合成高熵材料的方法,了解高熵材料的研究进展,而且能够让学生探究熵值对材料性质的影响,为后续科学研究打下良好的基础。

强钴—氧键合作用提升缺陷型Co_(2)MnO_(4)酸性析氧反应稳定性

通过实验和理论已经验证钴基氧化物是一种很有前景的析氧反应(OER)催化剂。然而,普通的钴基催化剂在酸性环境中非常不稳定,在酸性电解质中容易被腐蚀。因此,在目前的研究中,设计出能在强酸性条件下同时保持活性和稳定性的析氧催化剂是实现大规模工业制氢应用的一项重要挑战。因此,我们报道了通过在四氧化三钴的尖晶石晶格中引入锰(Mn)从而产生富含缺陷的催化剂(CoMn_(1)O),它在酸性电解质中具有较长的使用寿命。我们利用X射线衍射(XRD)、X射线光电子能谱(XPS)、高分辨率透射电子显微镜(HRTEM)和能量色散光谱(EDS)元素图研究了晶相结构和化学价态。在引入锰后,由于局部晶体结构的改变,产生了大量的缺陷。此外,随着锰含量的增加,可以观察到Co 2p光谱的红移,这表明Co的总价逐渐增加,形成了更稳定的Co-O键。此外,当Mn与Co的比例达到1(CoMn_(1)O)时,目标催化剂表现出良好的OER活性,在10和50mA·cm^(-2)时,过电位分别为415和552 mV。详细的物理表征和电化学测试表明,CoMn_(1)O比不含锰的Co_(3)O_(4)(CoMn_(0)O)能稳定4倍以上的时间。这可以归因于锰的引入调节了Co的电子密度偏向O,从而形成更稳定的Co-O键。Mn可以通过延缓Co活性位点的氧化速率来促进酸性氧的进化,并进一步提升稳定性。密度泛函理论(DFT)计算进一步分析了CoMn_(1)O和CoMn_(0)O的电子结构。与CoMn_(0)O相比,CoMn_(1)O中Co 3d的d带中心(εd)向费米能级(EF)移动。这表明CoMn_(1)O通过加强与OER中间物的键合作用从而降低了反应能垒。本研究为设计非贵金属电催化剂实现高效稳定的酸性析氧提供有前景的策略。

阶梯形貌铁基普鲁士蓝制备及性能

采用柠檬酸辅助单一源法水热制备了具有表面从边缘向中心依次凹陷降低形貌的铁基普鲁士蓝(SFePBA)。与典型立方形貌FePBA(C-FePBA)相比,BET测试证明阶梯型特殊形貌使其具有增大一倍的比表面积,EIS测试证明其具有更低的阻抗。不同扫描速率下的循环伏安分析证明其具有赝电容效应,从而具有优异的倍率性能。电流密度由0.1 A/g增大到5 A/g,容量几乎不变,保持率为94%。此外不同电压下的非原位XRD测试证明其具有良好的结构可逆性,循环稳定性优良,在0.6 A/g电流密度下循环1500次后容量保持率为89%。