Chemical Blowing Approach for Ultramicroporous Carbon Nitride Frameworks and Their Applications in Gas and Energy Storage

A scalable, template‐free synthetic strategy is presented for the preparation of ultramicroporous carbon nitride frameworks (CNFs) through a chemical blowing approach by using ammonium chloride as blowing agent and hexamethylene tetraamine as the C and N precursor and a subsequent potassium hydroxide chemical activation is employed to obtain CNFs with surface areas up to 1730 m² g^?1 along with a high nitrogen content of 13.3 wt%. CNFs showed CO₂ uptake capacities up to 5.74 mmol g^?1 at 1 bar and 1.67 mmol g^?1 at 0.15 bar, 273 K along with a very high CO₂/N₂ selectivity. In addition, H₂ uptake capacity of 1.9 wt% and the isosteric heats of adsorption (Q _st) value of 9.0 kJ mol^?1 at zero coverage have been also observed. Moreover, the presence of nitrogen‐doped graphene walls in CNFs also facilitated their application as supercapacitors, with capacitance values up to ≈114 F g^?1 at 0.5 A g^?1, along with a good cyclability and capacitance retention. This approach effectively extends unique surface properties of carbon nitrides into the micropore regime for effective capture of small gases and energy storage applications. Importantly, textural properties of CNFs can be simply tuned by judicious choice of organic precursors and the blowing agent.     

Reversibly Compressible,Highly Elastic,and Durable Graphene Aerogels for Energy Storage Devices under Limiting Conditions

High porosity combined with mechanical durability in conductive materials is in high demand for special applications in energy storage under limiting conditions, and it is fundamentally important for establishing a relationship between the structure/chemistry of these materials and their properties. Herein, polymer‐assisted self‐assembly and cross‐linking are combined for reduced graphene oxide (rGO)‐based aerogels with reversible compressibility, high elasticity, and extreme durability. The strong interplay of cross‐linked rGO (x‐rGO) aerogels results in high porosity and low density due to the re‐stacking inhibition and steric hinderance of the polymer chains, yet it makes mechanical durability and structural bicontinuity possible even under compressive strains because of the coupling of directional x‐rGO networks with polymer viscoelasticity. The x‐rGO aerogels retain >140% and >1400% increases in the gravimetric and volumetric capacitances, respectively, at 90% compressive strain, showing reversible change and stability of the volumetric capacitance under both static and dynamic compressions; this makes them applicable to energy storage devices whose volume and mass must be limited.     

Microorganism‐Derived Heteroatom‐Doped Carbon Materials for Oxygen Reduction and Supercapacitors

Heteroatom‐doped carbon (HDC) has attracted tremendous attention due to its promising application in energy conversion and storage. Herein, due to its abundance high rate of reproduction, the microorganism, Bacillus subtilis, is selected as a precursor. An effective ionothermal process is adopted to produce the HDCs. Using acid activation, the obtained sample exhibits excellent electrocatalytic activity, long‐term stability, and excellent resistance to crossover effects in oxygen reduction. Additionally, the base‐treated sample exhibits superior performance in capacitors to most commercially available carbon materials. Even at a high current density, a relatively high capacitance is retained, indicating a great potential for direct application in energy storage.     

Direct Ink Writing of Adjustable Electrochemical Energy Storage Device with High Gravimetric Energy Densities

3D printing graphene aerogel with periodic microlattices has great prospects for various practical applications due to their low density, large surface area, high porosity, excellent electrical conductivity, good elasticity, and designed lattice structures. However, the low specific capacitance limits their development in energy storage fields due to the stacking of graphene. Therefore, constructing a graphene‐based 2D materials hybridization aerogel that consists of the pseduocapacitive substance and graphene material is necessary for enhancing electrochemical performance. Herein, 3D printing periodic graphene‐based composite hybrid aerogel microlattices (HAMs) are reported via 3D printing direct ink writing technology. The rich porous structure, high electrical conductivity, and highly interconnected networks of the HAMs aid electron and ion transport, further enabling excellent capacitive performance for supercapacitors. An asymmetric supercapacitor device is assembled by two different 4‐mm‐thick electrodes, which can yield high gravimetric specific capacitance (C_g) of 149.71 F g^?1 at a current density of 0.5 A g^?1 and gravimetric energy density (E_g) of 52.64 Wh kg^?1, and retains a capacitance retention of 95.5% after 10 000 cycles. This work provides a general strategy for designing the graphene‐based mixed‐dimensional hybrid architectures, which can be utilized in energy storage fields.     

Enhanced Capacitive Energy Storage in Polyoxometalate‐Doped Polypyrrole

High‐performance batteries and supercapacitors require the molecular‐level linkage of charge transport components and charge storage components. This study shows how redox‐tunable Lindqvist‐type molecular metal oxide anions [V_nM _6–n O₁₉]^{(2+n )?} (M = W(VI) or Mo(VI); n = 0, 1, 2) can be incorporated in cationic polypyrrole (PPy) conductive polymer films by means of electrochemical polymerization. Electron microscopy and (spectro‐)electrochemistry show that the electroactivity and morphology of the composites can be tuned by Lindqvist anion incorporation. Reductive electrochemical “activation” of the Lindqvist–PPy composites leads to significantly increased electrical capacitance (range: ≈25–38 F g^?1, increase up to ≈25×), highlighting that this general synthetic route gives access to promising capacitive materials with suitable long‐term stability. Electrochemical, electron microscopic, and Raman spectroscopic analyses together with density functional theory (DFT) calculations provide molecular‐level insight into the effects of Lindqvist anion incorporation in PPy films and their role during reductive activation. The study therefore provides fundamental understanding of the principles governing the bottom‐up integration of molecular components into nanostructured composites for electrochemical energy storage.     

Wood‐Derived Lightweight and Elastic Carbon Aerogel for Pressure Sensing and Energy Storage

Lightweight and elastic carbon materials have attracted great interest in pressure sensing and energy storage for wearable devices and electronic skins. Wood is the most abundant renewable resource and offers green and sustainable raw materials for fabricating lightweight carbon materials. Herein, a facile and sustainable strategy is proposed to fabricate a wood‐derived elastic carbon aerogel with tracheid‐like texture from cellulose nanofibers (CNFs) and lignin. The flexible CNFs entangle and assemble into an interconnected framework, while lignin with high thermal stability and favorable stiffness prevents the framework from severe structural shrinkage during annealing. This strategy leads to an ordered tracheid‐like structure and significantly reduces the thermal deformation of the CNFs network, producing a lightweight and elastic carbon aerogel. The wood‐derived carbon aerogel exhibits excellent mechanical performance, including high compressibility (up to 95% strain) and fatigue resistance. It also reveals high sensitivity at a wide working pressure range of 0–16.89 kPa and can detect human biosignals accurately. Moreover, the carbon aerogel can be assembled into a flexible and free‐standing all‐solid‐state symmetric supercapacitor that reveals satisfactory electrochemical performance and mechanical flexibility. These features make the wood‐derived carbon aerogel highly attractive for pressure sensor and flexible electrode applications.     

Breaking the Limits of Ionic Liquid‐Based Supercapacitors: Mesoporous Carbon Electrodes Functionalized with Manganese Oxide Nanosplotches for Dense,Stable, and Wide‐Temperature Energy Storage

Manganese oxide (MnO₂) nanosplotches (NSs) are deposited on N‐ and S‐doped ordered mesoporous carbon (N,S‐CMK‐3) essentially blocking microporosity. The obtained N,S‐CMK‐3/MnO₂ composite materials are assembled into ionic liquid (IL)‐based symmetric supercapacitors, which exhibit a high specific capacitance of 200 F g^?1 (0–3.5 V) at a scan rate of 2 mV s^?1, and good rate stability with 55.5% capacitance retention at a scan rate of 100 mV s^?1. The device can operate in a wide temperature range (?20 to 60 °C), and high cycling stability of N,S‐CMK‐3/MnO₂ composite electrode is demonstrated. Lower energy of ?3.56 eV can be achieved for the adsorption of 1‐ethyl‐3‐methylimidazolium⁺ (EMIM⁺) cation on the edge between MnO₂ NSs and N,S‐CMK‐3 than on the plane of MnO₂ NS (?3.04 eV), both being more preferred than the surface of pristine N,S‐CMK‐3 (?1.52 eV). This strengthening of the ion adsorption at the three‐phase boundary between N,S‐CMK‐3, MnO₂, and IL leads to enhancement of the specific capacity as compared to nondoped or MnO₂‐free reference materials. Supercapacitors based on such composite electrodes show significantly enhanced areal capacity pointing to energy storage in the mesopores rather than in the electrochemical surface layer, demonstrating a new energy storage mechanism in ILs.     

Redox Poly-Counterion Doped Conducting Polymers for Pseudocapacitive Energy Storage

Conducting polymers (CPs) have been widely studied for electrochemical energy storage. However, the dopants in CPs are often electrochemically inactive, introducing “dead-weight” to the materials. Moreover, commercial-level electrode materials with high mass loadings (e.g., >10 mg cm⁻²) often encounter the problems of inferior electrical and ionic conductivity. Here, a redox-active poly-counterion doping concept is proposed to improve the electrochemical performance of CPs with ultra-high mass loadings. As a study prototype, heptamolybdate anion (Mo₇O₂₄⁶⁻) doped polypyrrole (PPy) is synthesized by electro-polymerization. A 2 mm thick PPy electrode with mass loading of ≈192 mg cm⁻² reaches a record-high areal capacitance of ≈47 F cm⁻², competitive gravimetric capacitance of 235 F g⁻¹, and volumetric capacitance of 235 F cm⁻³. With poly-counterion doping, the dopants also undergo redox reactions during charge/discharge processes, providing additional capacitance to the electrode. The interaction between polymer chains and the poly-counterions enhances the electrical conductivity of CPs. Besides, the poly-counterions with large steric hindrance could act as structural pillars and endow CPs with open structures for facile ion transport. The concept proposed in this work enriches the electrochemistry of CPs and promotes their practical applications.     

Nitrogen‐Doped Carbon Networks for High Energy Density Supercapacitors Derived from Polyaniline Coated Bacterial Cellulose

Bacterial cellulose (BC) is used as both template and precursor for the synthesis of nitrogen‐doped carbon networks through the carbonization of polyaniline (PANI) coated BC. The as‐obtained carbon networks can act not only as support for obtaining high capacitance electrode materials such as activated carbon (AC) and carbon/MnO₂ hybrid material, but also as conductive networks to integrate active electrode materials. As a result, the as‐assembled AC//carbon‐MnO₂ asymmetric supercapacitor exhibits a considerably high energy density of 63 Wh kg^?1 in 1.0 m Na₂SO₄ aqueous solution, higher than most reported AC//MnO₂ asymmetric supercapacitors. More importantly, this asymmetric supercapacitor also exhibits an excellent cycling performance with 92% specific capacitance retention after 5000 cycles. Those results offer a low‐cost, eco‐friendly design of electrode materials for high‐performance supercapacitors.     

Mesoporous NiCo2O4 Nanowire Arrays Grown on Carbon Textiles as Binder‐Free Flexible Electrodes for Energy Storage

Binary metal oxides has been regarded as a promising class of electrode materials for high‐performance energy storage devices since it offers higher electrochemical activity and higher capacity than mono‐metal oxide. Besides, rational design of electrode architectures is an effective solution to further enhance electrochemical performance of energy storage devices. Here, the advanced electrode architectures consisting of carbon textiles uniformally covered by mesoporous NiCo₂O₄ nanowire arrays (NWAs) are successfully fabricated by a simple surfactant‐assisted hydrothermal method combined with a short post annealing treatment, which can be directly applied as self‐supported electrodes for energy storage devices, such as Li‐ion batteries, supercapacitors. The as‐prepared mesoporous NiCo₂O₄ nanowires consist of numerous highly crystalline nanoparticles, leaving a large number of mesopores to alleviate the volume change during the charge/discharge process. Electrode architectures presented here promise fast electron transport by direct connection to the growth substrate and facile ion diffusion path provided by both the abundant mesoporous structure in nanowires and large open spaces between neighboring nanowires, which ensures every nanowire participates in the ultrafast electrochemical reaction. Benefiting from the intrinsic materials and architectures features, the unique binder‐free NiCo₂O₄/carbon textiles exhibit high specific capacity/capacitance, excellent rate capability, and cycling stability.     

Hierarchically Structured Porous Materials for Energy Conversion and Storage

Materials with hierarchical porosity and structures have been heavily involved in newly developed energy storage and conversion systems. Because of meticulous design and ingenious hierarchical structuration of porosities through the mimicking of natural systems, hierarchically structured porous materials can provide large surface areas for reaction, interfacial transport, or dispersion of active sites at different length scales of pores and shorten diffusion paths or reduce diffusion effect. By the incorporation of macroporosity in materials, light harvesting can be enhanced, showing the importance of macrochannels in light related systems such as photocatalysis and photovoltaics. A state‐of‐the‐art review of the applications of hierarchically structured porous materials in energy conversion and storage is presented. Their involvement in energy conversion such as in photosynthesis, photocatalytic H₂ production, photocatalysis, or in dye sensitized solar cells (DSSCs) and fuel cells (FCs) is discussed. Energy storage technologies such as Li‐ions batteries, supercapacitors, hydrogen storage, and solar thermal storage developed based on hierarchically porous materials are then discussed. The links between the hierarchically porous structures and their performances in energy conversion and storage presented can promote the design of the novel structures with advanced properties.     

Substantial Recoverable Energy Storage in Percolative Metallic Aluminum‐Polypropylene Nanocomposites

Chemisorption of the activated metallocene polymerization catalyst derived from [rac‐ethylenebisindenyl]zirconium dichlororide (EBIZrCl₂) on the native Al₂O₃ surfaces of metallic aluminum nanoparticles, followed by exposure to propylene, affords 0–3 metal‐isotactic polypropylene nanocomposites. The microstructures of these nanocomposites are characterized by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Electrical measurements show that increasing the concentration of the filler nanoparticles increases the effective permittivity of the nanocomposites to ?_r values as high as 15.4. Because of the high contrast in the complex permittivities and conductivities between the metallic aluminum nanoparticles and the polymeric polypropylene matrix, these composites obey the percolation law for two‐phase composites, reaching maximum permittivities just before the percolation threshold volume fraction, v_f ≈ 0.16. This unique method of in situ polymerization from the surface of metallic Al particles produces a new class of materials that perform as superior pulse‐power capacitors, with low leakage current densities of ≈10^?7–10^?9 A/cm² at an applied field of 10⁵ V/cm, low dielectric loss in the 100 Hz–1 MHz frequency range, and recoverable energy storage as high as 14.4 J/cm³.     

Prolifera‐Green‐Tide as Sustainable Source for Carbonaceous Aerogels with Hierarchical Pore to Achieve Multiple Energy Storage

The increasing demand for efficient energy storage and conversion devices has aroused great interest in designing advanced materials with high specific surface areas, multiple holes, and good conductivity. Here, we report a new method for fabricating a hierarchical porous carbonaceous aerogel (HPCA) from renewable seaweed aerogel. The HPCA possesses high specific surface area of 2200 m² g^?1 and multilevel micro/meso/macropore structures. These important features make HPCA exhibit a reversible lithium storage capacity of 827.1 mAh g^?1 at the current density of 0.1 A g^?1, which is the highest capacity for all the previously reported nonheteroatom‐doped carbon nanomaterials. It also shows high specific capacitance and excellent rate performance for electric double layer capacitors (260.6 F g^?1 at 1 A g^?1 and 190.0 F g^?1 at 50 A g^?1), and long cycle life with 91.7% capacitance retention after 10 000 cycles at 10 A g^?1. The HPCA also can be used as support to assemble Co₃O₄ nanowires (Co₃O₄@HPCA) for constructing a high performance pseudocapacitor with the maximum specific capacitance of 1167.6 F g^?1 at the current density of 1 A g^?1. The present work highlights the first example in using prolifera‐green‐tide as a sustainable source for developing advanced carbon porous aerogels to achieve multiple energy storage.     

Understanding the Charge Storage Mechanism to Achieve High Capacity and Fast Ion Storage in Sodium‐Ion Capacitor Anodes by Using Electrospun Nitrogen‐Doped Carbon Fibers

Microporous nitrogen‐rich carbon fibers (HAT‐CNFs) are produced by electrospinning a mixture of hexaazatriphenylene‐hexacarbonitrile (HAT‐CN) and polyvinylpyrrolidone and subsequent thermal condensation. Bonding motives, electronic structure, content of nitrogen heteroatoms, porosity, and degree of carbon stacking can be controlled by the condensation temperature due to the use of the HAT‐CN with predefined nitrogen binding motives. The HAT‐CNFs show remarkable reversible capacities (395 mAh g^?1 at 0.1 A g^?1) and rate capabilities (106 mAh g^?1 at 10 A g^?1) as an anode material for sodium storage, resulting from the abundant heteroatoms, enhanced electrical conductivity, and rapid charge carrier transport in the nanoporous structure of the 1D fibers. HAT‐CNFs also serve as a series of model compounds for the investigation of the contribution of sodium storage by intercalation and reversible binding on nitrogen sites at different rates. There is an increasing contribution of intercalation to the charge storage with increasing condensation temperature which becomes less active at high rates. A hybrid sodium‐ion capacitor full cell combining HAT‐CNF as the anode and salt‐templated porous carbon as the cathode provides remarkable performance in the voltage range of 0.5–4.0 V (95 Wh kg^?1 at 0.19 kW kg^?1 and 18 Wh kg^?1 at 13 kW kg^?1).     

Hierarchically Divacancy Defect Building Dual‐Activated Porous Carbon Fibers for High‐Performance Energy‐Storage Devices

Renewable and environmentally friendly biomass‐based carbon electrode materials naturally possess fast ion transport, high adsorption, and excellent chemical stability for high‐performance energy‐storage devices. However, intelligently building the effectively biomass‐transferred carbon materials for the requirement of high energy density is still a big challenge to date. Here, a hierarchically divacancy defect building platform is reported for effectively biomass‐transferred and highly interconnected 3D dual‐activated porous carbon fibers (DACFs) based on the internal?external dual‐activation function of the pre‐embedded KOH and CO₂ molecular. This uniquely interconnected frameworks not only fully provide the abundant active sites for ion interaction, but also efficiently guarantee the substantial accommodation for ion storage. Based on this, the as‐prepared DACFs‐based supercapacitors deliver a high energy density of 61.3 Wh kg^?1 at a power density of 875 W kg^?1 in the EMIMBF₄ ionic liquid. This work not only provides a simple and efficient technique to enhance the energy density of carbon materials, but also probably promotes its additional application in environmental remediation.     

Optical Power Limiters Based on Colorless Di‐, Oligo‐, and Polymetallaynes: Highly Transparent Materials for Eye Protection Devices

The synthesis, characterization, and photophysics of a series of solution‐processable and tractable di‐, oligo‐, and polymetallaynes of some group 10–12 transition metals are presented. Most of these materials are colorless with very good optical transparencies in the visible spectral region and exhibit excellent optical power limiting (OPL) for nanosecond laser pulse. Their OPL responses outweigh those of the state‐of‐the‐art reverse saturable absorption dyes such as C₆₀, metalloporphyrins, and metallophthalocyanines that are all associated with very poor optical transparencies. On the basis of the results from photophysical studies and theoretical calculations, both the absorption of triplet and intramolecular charge‐transfer states can contribute to the enhancement of the OPL properties for these materials. Electronic influence of the type, spatial arrangement, and geometry of metal groups on the optical transparency/nonlinearity optimization is evaluated and discussed in detail. The positive contribution of transition metal ions to the OPL of these compounds generally follows the order: Pt > Au > Hg > Pd. The optical‐limiting thresholds for these polymetallaynes can be as low as 0.07 J cm^–2 at 92 % linear transmittance and these highly transparent materials manifest very impressive figure of merit σ_ex/σ_o values (up to 22.48), which are remarkably higher than those of the benchmark C₆₀ and metal phthalocyanine complexes. The present work demonstrates an attractive approach to developing materials offering superior OPL/optical transparency trade‐offs and these metallopolyynes are thus very promising candidates for use in practical OPL devices for the protection of human eyes and other delicate optical sensors.     

Nitridation and Layered Assembly of Hollow TiO2 Shells for Electrochemical Energy Storage

The nitridation of hollow TiO₂ nanoshells and their layered assembly into electrodes for electrochemical energy storage are reported. The nitridated hollow shells are prepared by annealing TiO₂ shells, produced initially using a sol–gel process, under an NH₃ environment at different temperatures ranging from 700 to 900 °C, then assembled to form a robust monolayer film on a water surface through a quick and simple assembly process without any surface modification to the samples. This approach facilitates supercapacitor cell design by simplifying the electrochemical electrode structure by removing the need to use any organic binder or carbon‐based conducting materials. The areal capacitance of the as‐prepared electrode is observed to be ≈180 times greater than that of a bare TiO₂ electrode, mainly due to the enhanced electrical conductivity of the TiN phase produced through the nitridation process. Furthermore, the electrochemical capacitance can be enhanced linearly by constructing an electrode with multilayered shell films through a repeated transfer process (0.8 to 7.1 mF cm^–2, from one monolayer to 9 layers). Additionally, the high electrical conductivity of the shell film makes it an excellent scaffold for supporting other psuedocapacitive materials (e.g., MnO₂), producing composite electrodes with a specific capacitance of 743.9 F g^–1 at a scan rate of 10 mV s^–1 (based on the mass of MnO₂) and a good cyclic stability up to 1000 cycles.     

Hybrid Graphene Titanium Nanocomposites and Their Applications in Energy Storage Devices: a Review

Emissions of natural gas and carbon dioxide due to fossil fuels have become a global issue which influences the development of various technologies. Demand for clean renewable power sources is ever increasing. However, renewable sources are intermittent in nature, which poses a challenge in electricity generation and power load stability. Lately, supercapacitors have attracted remarkable interest in the field of electricity storage due to their ability to store large amounts of electric charge, enabling high power output. Reduced graphene oxide incorporated with titanium dioxide (rGO/TiO₂) nanocomposites are well considered as potential supercapattery materials due to their superior mechanical properties, notable strength, and abundance in Nature. rGO carbon material acts as the ion reservoir, facilitating faster electron transfer mobility, whereas mesoporous TiO₂ provides a larger surface area and more active sites, which improve the cycling stability and specific capacitance. Literature reports that supercapacitor performance mainly depends on the choice of the electroactive material, electrolyte, and current collector. This review focuses on recent developments in supercapacitor technology, storage mechanisms of different electrodes, a comprehensive discussion of different challenges related to energy storage devices, as well as the formation mechanism of rGO/TiO₂ hybrid electrodes.

     

Exploring the Energy Storage Mechanism of High Performance MnO2 Electrochemical Capacitor Electrodes: An In Situ Atomic Force Microscopy Study in Aqueous Electrolyte

The basic microstructure‐dependent charge storage mechanisms of nanostructured MnO₂ are investigated via dynamic observation of the growth and in situ probing the mechanical properties by using in situ AFM in conjunction with in situ nanoindentation. The progressive nucleation followed by three‐dimensional growth yields pulsed current deposited porous nanostructured γ‐MnO₂, which exhibits a high specific capacitance of 437 F/g and a remarkable cycling performance with >96% capacitance retention after 10 000 cycles. The proton intercalation induced expansion of MnO₂ can be self‐accommodated by the localized compression and reduction of the porosity. More coincidentally, the proton intercalation induced softening is favorable for the elastic deformation of MnO₂. This self‐adaptive capability of nanostructured MnO₂ could generate high structural reliability during cycling. These discoveries offer important mechanistic insights for the design of advanced electrochemical capacitors.     

All-Climate Iron-Based Sodium-Ion Full Cell for Energy Storage

The anode materials for sodium-ion batteries (SIBs) such as soft carbon, hard carbon, or alloys suffer from low specific capacity, poor rate capability, and high cost. Various transition metal oxides materials possess high specific capacity and suitable working potential, however, huge volume change and unstable electrode/electrolyte interfaces limit their practical applications. Herein, an ultrathin carbon-coated iron-based borate, (Fe₃BO₅), as an anode material for SIBs is reported. The carbon coated Fe₃BO₅ composite as an anode material possesses a reversible specific capacity of 548 mAh g⁻¹ with a high initial coulombic efficiency of 72.6% at a current density of 50 mA g⁻¹, and maintains a capacity retention ratio of 99% after 1000 cycles at 2000 mA g⁻¹. Moreover, this anode can work well over a wide temperature range (-40–60 °C). Furthermore, a sodium-ion full cell using this anode coupling with iron-based cathode (Na₃Fe₂(PO₄)₂(P₂O₇)@rGO) cathode is fabricated, which exhibits a wide operating temperature range from −40 to 60 °C with a maximum energy density of 175 Wh Kg⁻¹ and a maximum power density of 1680 W Kg⁻¹. Most importantly, this full-cell configuration is low-cost due to its inexpensive iron based raw material for both anode and cathode.