Progress and perspectives on iron-based electrode materials for alkali metal-ion batteries: a critical review

Iron-based materials with significant physicochemical properties, including high theoretical capacity, low cost and mechanical and thermal stability, have attracted research attention as electrode materials for alkali metal-ion batteries (AMIBs). However, practical implementation of some iron-based materials is impeded by their poor conductivity, large volume change, and irreversible phase transition during electrochemical reactions. In this review we critically assess advances in the chemical synthesis and structural design, together with modification strategies, of iron-based compounds for AMIBs, to obviate these issues. We assess and categorize structural and compositional regulation and its effects on the working mechanisms and electrochemical performances of AMIBs. We establish insight into their applications and determine practical challenges in their development. We provide perspectives on future directions and likely outcomes. We conclude that for boosted electrochemical performance there is a need for better design of structures and compositions to increase ionic/electronic conductivity and the contact area between active materials and electrolytes and to obviate the large volume change and low conductivity. Findings will be of interest and benefit to researchers and manufacturers for sustainable development of advanced rechargeable ion batteries using iron-based electrode materials.

Experimental and theoretical studies of the efficiency of metal-organic frameworks (MOFs) in preventing aluminum corrosion in hydrochloric acid solution

Aluminum corrosion inhibitors "{[CuI (CN)2(phen) CuII (CN)2(phen)]5H2O},(MOF1) and {[CuI(CN)2(phen)CuII(CN)2(phen)]5H2O}@TiO2 (MOF1@TiO2) were studied in one molar HCl solution". The ML results for three different temperatures (25-45 °C) were compared with the results of PDP and EIS analyses. The adsorption of inhibitors on Al surfaces has been calculated and discussed by a Langmuir isotherm. The inhibitors that were created showed great effectiveness, with a noticeable increase in their inhibitory efficiency as the dosage was raised and the temperature was lowered. Inhibition efficiency each amounted to 88.6%, 84.5% at 400 ppm and 25 °C for MOF1@TiO2 and MOF1, respectively. Analyzing the polarization curves of synthesized inhibitors revealed that they were mixed-type inhibitors. Al was found to be surface inhibited when coated with a thin film of inhibitors, and "Al's surface morphology was assessed by different techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and atomic force microscope (AFM)". "Theoretical models like quantum chemical and molecular dynamics simulation authenticated the experimental observation". The MOFs exhibit exceptional corrosion resistance against Al when exposed to acidic environments, according to several tests.

Functionalization strategies of metal-organic frameworks for biomedical applications and treatment of emerging pollutants: A review

One of the representative coordination polymers, metal-organic frameworks (MOFs) material, is of hotspot interest in the multi field thanks to their unique structural characteristics and properties. As a novel hierarchical structural class, MOFs show diverse topologies, intrinsic behaviors, flexibility, etc. However, bare MOFs have less desirable biofunction, high humid sensitivity and instability in water, restraining their efficiencies in biomedical and environmental applications. Thus, a structural modification is required to address such drawbacks. Herein, we pinpoint new strategies in the synthesis and functionalization of MOFs to meet demanding requirements in in vitro tests, i.e., antibacterial face masks against corona virus infection and in wound healing and nanocarriers for drug delivery in anticancer. Regarding the treatment of wastewater containing emerging pollutants such as POPs, PFAS, and PPCPs, functionalized MOFs showed excellent performance with high efficiency and selectivity. Challenges in toxicity, vast database of clinical trials for biomedical tests and production cost can be still presented. MOFs-based composites can be, however, a bright candidate for reasonable replacement of traditional nanomaterials in biomedical and wastewater treatment applications.

Chiral "doped" MOFs: an electrochemical and theoretical integrated study

This work reports on the electrochemical behaviour of Fe and Zn based metal-organic framework (MOF) compounds, which are "doped" with chiral molecules, namely: cysteine and camphor sulfonic acid. Their electrochemical behaviour was thoroughly investigated via "solid-state" electrochemical measurements, exploiting an "ad hoc" tailored experimental set-up: a paste obtained by carefully mixing the MOF with graphite powder is deposited on a glassy carbon (GC) surface. The latter serves as the working electrode (WE) in cyclic voltammetry (CV) measurements. Infrared (IR), X-ray diffraction (XRD) and absorbance (UV-Vis) techniques are exploited for a further characterization of the MOFs' structural and electronic properties. The experimental results are then compared with DFT based quantum mechanical calculations. The electronic and structural properties of the MOFs synthesized in this study depend mainly on the type of metal center, and to a minor extent on the chemical nature of the dopant.

3D nanocrystalline metal-organic framework materials for the improved output performance of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) based on contact electrification and electrostatic induction can effectively convert low-frequency mechanical energy into electrical energy and has attracted considerable attention. However, the low current output performance seriously hinders the wide application of TENGs. Herein, a 3D nanocrystalline metal-organic framework (Cd-MOF) with a specific structure and morphology was reasonably designed as a high-performance triboelectric positive electrode material. The triboelectric test results showed that the maximum instantaneous short-circuit current of Cd-MT was 55.32 μA and the stable output performance maintained a long-term continuous operation for 10 000 s. The peak values of the charge density and electric power density were 102.39 μC m^-2 and 2451.04 mW m^-2, respectively. In addition, the Cd-MT could quickly fully charge commercial capacitors and light a large number of LED lamps. This work provides a new idea for the development and design of functional MOF triboelectric materials.

Deciphering the Thermal and Electrochemical Behaviors of Dual Redox-Active Iron Croconate Violet Coordination Complexes

Interest in coordination compounds based on non-innocent ligands (NILs) for electrochemical energy storage has risen in the last few years. We have focused our attention on an overlooked redox active linker, croconate violet, which has not yet been addressed in this field although closely related to standard NILs such as catecholate and tetracyanoquinodimethane. Two anionic complexes consisting of Fe(II) and croconate violet (-2) with balancing potassium cations were isolated and structurally characterized. By a combination of in situ and ex situ techniques (powder and single-crystal X-ray diffraction, infrared, and ⁵⁷Fe Mössbauer spectroscopies), we have shown that their dehydration occurs through complex patterns, whose reversibility depends on the initial crystal structure but that the structural rearrangements around the iron cations occur without any oxidation. While electrochemical studies performed in solution clearly show that both the organic and inorganic parts can be reversibly addressed, in the solid state, poor charge storage capacities were initially measured, mainly due to the solubilization of the solids in the electrolyte. By optimizing the formulation of the electrode and the composition of the electrolyte, a capacity of >100 mA h g^-1 after 10 cycles could be achieved. This suggests that this family of redox active linkers deserves to be investigated for solid-state electrochemical energy storage, although it requires the solving of the issues related to the solubilization of the derived coordination compounds.

Completely suppressed high-voltage phase transition of P2/O3-Na0.7Li0.1Ni0.1Fe0.2Mn0.6O2via Li/Ni co-doping for sodium storage

A novel P2/O3-Na0.7Li0.1Ni0.1Fe0.2Mn0.6O2 cathode is prepared via Li/Ni co-doping, and delivers attractive cycling and rate performances due to the high Na+ diffusion coefficient and the complete suppression of the high-voltage P2–Z phase transition.

Intercalation pseudocapacitance in 2D N-doped V2O3 nanosheets for stable and ultrafast lithium-ion storage

2D N-doped V2O3 (N-V2O3) is synthesized as an anode material for Li-ion batteries by a facile strategy. Benefiting from the 3D V–V tunnel structure, sufficient active sites and N modifications, N-V2O3 exhibits stable and ultrafast Li-ion storage.