Electroactive Centers Research Articles

Achieving ultrahigh electrochromic stability of triarylamine-based polymers by the design of five electroactive nitrogen centers

A shortage of long-term stability of electrochromic materials has been hindering their practical application. A series of novel polyamides (PAs) (4) with five electroactive nitrogen atoms within triphenylamine (TPA)-containing structures was synthesized via phosphorylation polyamidation. Polyamide 4b exhibited highly integrated electrochromic performances, including multiple color changes, high contrast of optical transmittance change, and the highest electrochromic stability (only 11.2 and 9.6 % decay of its coloration efficiency (CE) at 450 nm after 50000 and 16000 switching cycles, respectively) compared to all other triarylamine-based polymers to date. This record-high electrochromic cycling is attributed to the enhanced stability of polaron, which was studied through the electron-donating or electron-withdrawing effect of substituents and the resonance effect of electron delocalization over the electroactive nitrogen centers. Importantly, our core design of five electroactive nitrogen centers with electron-donating methoxy groups is the key factor to increase stability of polaron in the resulting polymers 4. More electroactive nitrogen centers are able to create a weaker electronic coupling due to a charge of cation radical dispersed by resonance successfully in-between the different redox states, which is evidenced clearly by the observed longer wavelength absorption in the NIR region. Our research confirms that the key to determining polaron stability is the resonance by the electrons delocalized over all the redox centers, rather than the electronic coupling between the different redox centers. And the resonance leads to increasing electrochromic stability of the polymer.

A new composite electrode based on hemin/copper nanoparticles/oxidized graphitic nitride for sensitive detection of organophosphorus pesticide

A new composite of Hemin, copper oxide nanoparticle, and oxidized g-C3N4 (He/CuO/Oxi-gC3N4) is fabricated and successfully employed for electrocatalysis of the chlorinated Organo-Phosphorous pesticide, Dichlorvos. Hemin (He) is a well-known metalloporphyrin, which has an electroactive center of Fe3+. Pure hemin aggregates easily due to its poor solubility in an aqueous solution and hence is usually composited with other electroactive materials. The composite electrode has been thoroughly characterized including SEM, AFM, FT-IR, Raman spectroscopy, XPS, and Voltammetric techniques for the determination of Dichlorvos in water sample. Herein we have used a composite of Hemin with green synthesized copper oxide nanoparticle, (CuO)-Nps adsorbed on a porous oxidized graphitic carbon nitride surface (Oxi-gC3N4). The obtained linear range for Dichlorvos was found to be 2.5 × 10−10 to 62.5 × 10−10 M with a detection limit of 0.83×10−11 M. The composite electrode performance was further extended for use in real samples like lake water, well water, and tap water containing Dichlorvos. The analysis was carried out based on the standard addition method. Good recovery ranges from 99.0 to 100.0% were observed. Also, the He/CuO/Oxi-gC3N4 showed very good antibacterial activity against gram-positive and gram-negative bacteria.

CuCoP@Cu(OH)2 core-shell nanostructure as a robust electrochemical sensor for glucose detection in biological and beverage samples

The direct growth of transition metal phosphides with a highly accessible surfaces and copper electroactive centers can be considered as an efficient method to modify the electrode surface and use them as an electrochemical sensor. Herein, a direct, efficient, low-cost and rapid method is used for growing core–shell nanostructures of CuCoP nanosheets on Cu(OH)2 nanotubes (pre-deposited on glassy carbon electrode). The Cu(OH)2 nanotubes act as a conductive intermediate and directing agent to obtain CuCoP@Cu(OH)2 core–shell structure. The growth of CuCoP on Cu(OH)2 nanotubes provides structural stability and large surface area as well as increases the availability of the catalytic sites for diffusion of analyte species and electrolyte ions into the electrode surface, leading to excellent electrocatalytic performance towards glucose electro-oxidation. The amperometric studies of glucose for electrode modified with CuCoP@Cu(OH)2 showed two linear ranges of 0.001 mM to 0.105 mM and 0.105 mM to 2.530 mM with very high sensitivities of 8351 and 3932 μA/mM.cm2, respectively. Also, the fabricated sensing platform exhibited excellent selectivity and resistance to chloride ion poisoning, good reproducibility and repeatability, as well as low detection limit of 2.3 μM. In addition, the modified electrode showed a very quick reaction time of 2 s. Finally, to assess the usability of the designed non-enzymatic sensor in practical applications, the as-prepared nanocomposite was examined for measuring the glucose content in biological samples such as human blood serum, saliva, and beverage samples. The outcomes showed that the designed platform can be used as a reliable and efficient sensor for accurate detection and measurement of glucose in real samples.

Three-dimensional hierarchical nanosheets based spherical bismuth metal-organic frameworks: Controllable synthesis and high performance for supercapacitor

Metal-organic frameworks (MOFs) are considered as promising electrode materials in energy storage applications because of tunable chemical composition, large internal pore volume and high specific surface area. In this work, Bi-MOF materials with different molar ratios of Bi3+/benzene-1,3,5-tricarboxylic acid (H3BTC) are successfully prepared by solvothermal method. When the molar ratio of Bi3+/H3BTC is adjusted to 2:1, three-dimensional hierarchical Bi-MOF microspheres composed of many interconnected thin nanosheets are perfectly obtained. As-prepared Bi-MOF displays favorable specific surface area (69.5 m2 g−1) and pore size distribution (mean pore size of 6.43 nm), which provides abundant reactive electroactive centers, thereby exhibiting outstanding electrochemical performance. As-prepared Bi-MOF based electrode demonstrates a specific capacity of up to 896.1 C g−1 at 0.5 A g−1, and still possesses a capacity retention rate of 80.2 % from 0.5 A g−1 to 5.0 A g−1. At the same time, at 2.0 A g−1, it has a retention rate of 71.2 % even after 2000 cycles. The assembled BM-2//activated carbon device exhibits high energy density of 33.7 Wh kg−1 at power density of 1699.2 W kg−1. In addition, the device has capacity retention of 79.5 % after 1000 cycle at 5 A g−1. The results fully prove that as-prepared Bi-MOF based electrode possesses satisfactory electrochemical behavior, which provides a valuable reference for research and application of Bi-based materials in the field of supercapacitors.

Electropolymerized Bipolar Poly(2,3-diaminophenazine) Cathode for High-Performance Aqueous Al-Ion Batteries with An Extended Temperature Range of -20 to 45°C.

Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al3+ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3-diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n-type and p-type active units endow PDAP with an increased number of sites for ions interaction. The long-range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π-π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g-1 with long lifespan and high-rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g-1 at -20 and 45°C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al3+/H3O+ and ClO4 -) storage with 3-electron transfer in dual electroactive centers (C═N and -NH-). This study presents a promising strategy for constructing high-performance organic cathode for AAIBs over a wide temperature range.

Electrodeposition of CoFeS nanoflakes on Cu2O nanospheres as an ultrasensitive sensing platform for measurement of the hydrazine and hydrogen peroxide in seawater sample

Nanoarchitectured design of the metal sulfides with highly available surface and abundant electroactive centers and using them as electrocatalyst for fabricate the electrochemical sensors for the detection of hydrazine (N2H4) and hydrogen peroxide (H2O2) is challenging and desirable. Herein, Cu2O nanospheres powder is firstly prepared using chemical reduction of copper chloride and then drop-casted on the glassy carbon electrode (GCE) surface. In the next step, CoFeS nanoflakes are electrodeposited on Cu2O nanospheres by cyclic voltammetry method to form CoFeS/Cu2O nanocomposite as a detection platform for measuring N2H4 and H2O2. Accordingly, Cu2O nanospheres are not only used as substrate, but also guided the CoFeS nanoflakes to adhere to the electrode surface without need to any binder or conductive additive, which enhances the electrical conductivity of the sensing active materials. As the hydrazine sensor, the CoFeS/Cu2O/GCE displayed wide linear ranges (0.0001–0.021 mM and 0.021–1.771 mM), low detection limit (0.12 μM), very high sensitivities (103.33 and 21.23 mA mM−1 cm−2), and excellent selectivity. The as-made nanocomposite also exhibited low detection limit of 1.26 μM for H2O2 sensing with very high sensitivities (12.31 and 3.96 mA mM−1 cm−2) for linear ranges of 0.001–0.03 mM and 0.03–2.03 mM, respectively, and negligible response against interfering substances. The superior analytical performance of the CoFeS/Cu2O for N2H4 electro-oxidation and H2O2 electro-reduction can be attributed to structure stability, high electroactive surface area, and good availability to analyte species and electrolyte diffusion. Moreover, to examine the potency of the prepared nanocomposite in real applications, the seawater sample was analyzed and results display that the CoFeS/Cu2O/GCE can be utilized as a reliable and applicable platform for measuring N2H4 and H2O2.

Superfast hydrous-molten salt erosion to fabricate large-size self-supported electrodes for industrial-level current OER

Durable, active, and cheap oxygen evolution reaction (OER) electrocatalyst to replace the noble metal-based ones is appealing but challenging in energy storage fields. Here, we devise a one-pot low-temperature hydrous molten salt erosion strategy to vertically root the thin and dense bimetal hydroxide (NiFeOxHy) nanosheet on commercial nickel foam in 1 min. The defect-rich nanosheets are interdigitated together to yield a highly porous array, which offers affluent exposed electroactive centers, decreased charge/mass transfer, and augmented mechanical stability, while a strong Ni-Fe synergy elicits the signal redox reactivity of both metal and nonmetal lattice oxygen. Due to such effects, the typical NiFeOxHy electrode accesses a catalytic current of 10 mA cm−2 at a low overpotential 216 mV for freshwater electrolyte and 232 mV for saline one both with a small Tafel slope of 53 mV dec−1, while stably working for 1000 h at 0.1 A cm−2 in freshwater electrolyte and over 550 h at 1 A cm−2 in saline one. This evidences efficient and stable large-current–density OER performance, particularly a strong Cl− anti-erosion. The large-scale NiFeOxHy electrode materials (81 cm2) with a commensurate performance are fabricated on nickel foam, heralding the enormous prospect for practical usage. This exceedingly procedure-, energy- and time-saving erosion tactic can be generalized to common metal foam substrates and hydrous metal molten salts, accenting a momentous stepping stone for integral construction of self-supported and large-size electrodes towards commercially-met OER application and beyond.

Concept of triphenylamine side chains with four electroactive nitrogen centers toward record-high stable electrochromic polyamides

The TPA side chains with four electroactive nitrogen centers in PAs exhibited high EC stability and multiple color changes. The EC stability improved by the electrons delocalized by resonance over all the redox centers is emphasized in this study.

Screening of First-Row Transition Metal Complexes for Aqueous Redox Flow Batteries: Experimental and Density Functional Theory Approaches

The development of redox flow batteries took new directions in the last decades. From initial metal-based systems, it evolved towards organic and hybrid approaches in aqueous media. Furthermore, redox targeting flow batteries are an emerging alternative to the traditional redox flow battery architecture which offer improved energy density via an added electroactive solid ‘booster’. Whatever the system, there is a need of soluble electroactive species with potentials allowing large cell potentials within the water stability window or imperative redox potentials matching between soluble redox mediator and the solid for redox targeting. Transition metal complexes are a promising class of redox electroactive centers due to the tunability of their solubility and electrochemical potential, and the ability to take into account sustainability1. Recent reports underlined for instance that either the modification of the ligand2 or using heteroleptic complexes3, can lead to iron complexes with solubilities higher than 1 M and potentials higher than 1 V vs SHE. Furthermore, reliable and time-efficient prediction tools for the redox potentials of transition metal complexes are needed to help the search for new potential systems. While density functional theory usually provides a good trade-off between computational cost and accuracy, calculations on transition metal complexes often result in large errors. We thus developed a procedure and compared different solvation methods and levels of theory using an initial experimental data set based on aqueous iron complexes with bidentate ligands (Figure 1).In the present contribution, we will illustrate this coordination approach through a screening of new complexes based on non-toxic and affordable transition metal complexes. In this perspective, electrochemical characterization at different pH, coupled with NMR and UV-Visible studies will be presented, to screen for new candidates as electrolyte in redox flow batteries. Finally, we will show how the calculations corrected using a simple linear regression using training data yields a good prediction of redox potentials (mean average error =0.09 V).

On the Properties of the Si-SiO2 Transition Layer in Multilayer Silicon Structures

Capacitance spectroscopy was used to study the capacitive-voltage characteristics of multilayer structures with a Si-SiO2 transition layer in Al-SiO2-n-Si type samples fabricated by the thermal oxidation of a semiconductor. It is shown that the inhomogeneous distribution of the density of surface states is a localized electroactive center at the very semiconductor-dielectric interface, due to over-barrier charge emission or thermal ionization of impurity centers.

Electrochemical oxidation and superoxide radical scavenging activity of 2-hydroxy/methoxy-phenylbenzothiazole derivatives

Electrochemical characterisation and antioxidant activity against superoxide radical anion of four 2-hydroxy/methoxy-phenylbenzothiazole derivatives (1–4) are reported.The electrochemical oxidation was studied at a glassy carbon electrode using square-wave voltammetry in an aqueous buffer solution (pH = 1–12). In 1 (2-(2-methoxyphenyl)benzothiazole-6-ammonium chloride) and 2 (2-(2-hidroxyphenyl)benzothiazole-6-ammonium chloride), the benzothiazole C6-amino group was the main electroactive centre, undergoing a complex, pH-dependent process, coupled to the follow-up chemical reaction. The initial electrode reaction of 3 (6-(4,5-dihydro-1H-imidazol-3-ium-2-yl)-2-(2,3,4-trihydroxyphenyl)benzothiazole chloride) and 4 (6-amidinium-2-(2,3,4-trihydroxyphenyl)benzothiazole chloride) is a quasireversible, two-electrons, two-protons oxidation of the pyrogallol group.Superoxide radical scavenging activity was evaluated by means of cyclic voltammetry and computational analysis, which was revealed to rely on their ability to undergo the hydrogen atom transfer. In 1 and 2, H• donation from the benzothiazole C6-amino group is favoured, while a considerable improvement in the antioxidant activity was achieved in systems with the pyrogallol moiety 3 and 4, where it is realized from the middle 2-hydroxyl group, which allows for the formation of a stable OH∙∙∙O•∙∙∙HO fragment following the H• liberation.

Tuning electron delocalization of hydrogen-bonded organic framework cathode for high-performance zinc-organic batteries

Stable cathodes with multiple redox-active centres affording a high energy density, fast redox kinetics and a long life are continuous pursuits for aqueous zinc-organic batteries. Here, we achieve a high-performance zinc-organic battery by tuning the electron delocalization within a designed fully conjugated two-dimensional hydrogen-bonded organic framework as a cathode material. Notably, the intermolecular hydrogen bonds endow this framework with a transverse two-dimensional extended stacking network and structural stability, whereas the multiple C = O and C = N electroactive centres cooperatively trigger multielectron redox chemistry with super delocalization, thereby sharply boosting the redox potential, intrinsic electronic conductivity and redox kinetics. Further mechanistic investigations reveal that the fully conjugated molecular configuration enables reversible Zn2+/H+ synergistic storage accompanied by 10-electron transfer. Benefitting from the above synergistic effects, the elaborately tailored organic cathode delivers a reversible capacity of 498.6 mAh g−1 at 0.2 A g−1, good cyclability and a high energy density (355 Wh kg−1).

One-Step Chemiluminescent Assay for Hydrogen Peroxide Analysis in Water

The detection of hydrogen peroxide is of great importance in the environmental field. For this, a homogeneous technique has been developed here for sensitive and rapid quantification of hydrogen peroxide. In this technique, hemoglobin was used as a bioreceptor, where heme groups acted as electroactive centers to catalyze hydrogen peroxide reduction. The chemiluminescence reagent luminol is also a peroxidase substrate and can be oxidized by hemoglobin—thus generating a CL signal. The principle of the designed biosensor was based on the competition between hydrogen peroxide and luminol towards hemoglobin. Under optimized conditions, the chemiluminescent signal decreased with increasing hemoglobin concentrations within the linear range of 0.5 to 12 mM, with a correlation coefficient R2 of 0.99762. The limit of detection was calculated to be as low as 0.308 mM. The selectivity of the biosensor was successfully demonstrated against different interferents. The developed strategy provides a one step, simple, and low-cost bioanalytical method which can be applied for the monitoring of other peroxidase substrates.

One-pot synthesis of 3D surface-wrinkled PdAu nanospheres for robust alcohols electrocatalysis

Three dimensional (3D) noble-metal nanomaterials with special surface structures have been regarded as high-performance catalysts for alcohol oxidation on account of their superior thermal stability, electrical conductivity and large specific surface area. Although extensive efforts have been devoted to the preparation of 3D Pd-based catalysts with superior activity and stability, designing a simple, effective and eco-friendly method remains a challenge. Herein, we developed a facile one-step coreduction strategy to synthesize a series of 3D surface-wrinkled PdAu nanospheres (NSs) with tunable Pd/Au atomic ratios and found a universal method to prepare surface-wrinkled PdM (M = Au, Pt, Cu and Pb) NSs. Benefiting from the function of the surfactant cetyltrimethylammonium chloride (CTAC), the synthesized PdAu NSs with different composition possess abundant surface wrinkles, which is beneficial for exposing more electroactive centers. Attributed to the unique geometric morphology and optimized atomic ratio, the PdAu-2 NSs exhibited an optimal mass activity (MA) of 8103 mA mg−1 and 5113 mA mg−1 for the ethylene glycol oxidation reaction (EGOR) and ethanol oxidation reaction (EOR), which was 6.1 and 4.1 times that of commercial Pd/C, respectively. Moreover, the PdAu-2 NSs exhibited superb stability after long-term current–time (i-t) and cyclic voltammetry (CV) tests of the EGOR and EOR. This work not only provides new avenues to engineer PdAu NSs with enhanced electrocatalytic performance but also offers guidance for extending to more 3D PdM (M = other metals) NSs with novel morphology applied to fuel cell fields.

Constructing nickel sulfide @ nickel boride hybrid nanosheet arrays with crystalline/amorphous interfaces for supercapacitors

Designing a heterostructure with unique morphology and nanoarchitecture is regarded as an efficient strategy to achieve high-energy-density supercapacitors (SCs). Herein, a rational nickel sulfide @ nickel boride (Ni9S8@Ni2B) heterostructure is in situ synthesized on carbon cloth (CC) substrate via a simple electrodepositon strategy followed by a chemical reduction method. The three-dimensional hierarchically porous Ni9S8@Ni2B nanosheet arrays, consisting of crystalline Ni9S8 nanosheets and amorphous Ni2B nanosheets, can expose ample electroactive centers, shorten ion diffusion distance, and buffer volume changes during charging/discharging process. More importantly, the generation of crystalline/amorphous interfaces in the Ni9S8@Ni2B composite modulates its electrical structure and improves electrical conductivity. Owing to the synergy of Ni9S8 and Ni2B, the as-synthesized Ni9S8@Ni2B electrode acquires a specific capacity of 901.2C g−1 at 1 A g−1, a sound rate capability (68.3% at 20 A g−1), along with good cycling performance (79.7% capacity retention over 5000 cycles). Additionally, the assembled Ni9S8@Ni2B//porous carbon asymmetric supercapacitor (ASC) exhibits a cell voltage of 1.6 V and a maximum energy density of 59.7 Wh kg−1 at 805.2 W kg−1. These findings might offer a simple and innovative approach to fabricate advanced electrode materials for high-performance energy storage systems.

Potential modulation of Nickel-Cobalt hydroxide nanosheets with conductive Poly(3,4-Ethylenedioxythiophene) skin for aqueous hybrid supercapacitors

Transition metal hydroxides with tuned structure and superior electrochemical activities are of potential as positive electrodes for aqueous hybrid supercapacitors (AHSs), yet their conductivities and stacking behaviors need to be optimized to further improve the electrical potential distribution from the electronic multi-contact border to the electroactive center. Herein, we report a new approach to coat poly(3,4-ethylenedioxythiophene) (PEDOT) skin with a controlled thickness on nickel–cobalt layered double hydroxide (NiCo-LDH) nanosheets via a simple yet efficient oxidative chemical vapor deposition (oCVD). The conductive PEDOT skin is ionically permeable, resulting in uniform distribution of the electrical potential and fast transport of ions to active sites. The density functional theory (DFT) calculations reveal that the PEDOT layer can build an embedded electric field at the interface and enable a low desorption energy of hydrogen for electrochemical redox reactions. The as-obtained NiCo-LDH nanosheets with the PEDOT skin of 10 nm thick (LDH/PEDOT-10) as the battery-type electrode deliver a high specific capacity of 167 mAh g−1 (1250F g−1) with a greatly improved rate capability of 79 % at 50 A g−1 and cycling stability of 92 % for 6000 cycles, which endows AHS devices with superior charge-storage performance. This study has demonstrated for the first time that the modulation of electrical potential for redox electrodes via an interface engineering strategy can achieve simultaneously fast reaction kinetics and excellent structure stability for aqueous energy-storage devices.

Heterointerface of vanadium telluride and zinc iron telluride nanosheets for highly efficient hydrogen production via water and urea electrolysis

Interface design is a promising strategy for electrocatalysis to optimize charge transfer ability and active sites of a catalyst. Herein, interfacially coupled vanadium telluride and zinc iron telluride nanosheets are synthesized on nickel foam (VTe2@ZnFeTe/NF) by a facile hydrothermal method, which furnishes low overpotentials of 119/217 mV for the hydrogen evolution reaction (HER) and 240/300 mV for the oxygen evolution reaction (OER) at 20/50 mA cm−2 in potassium hydroxide. The alkaline and urea electrolyzer formed by VTe2@ZnFeTe/NF requires an operating voltage of 1.58 V and 1.46 V to yield a current density of 10 mA cm−2 respectively. Density functional theory analysis reveals that the superb activity of VTe2@ZnFeTe/NF is related to its optimal adsorption free energy, extended electroactive centers, excellent charge transfer ability, and reasonable density of states near the Fermi level. These findings provide new insights for the design of transition metal telluride heterointerfaces as catalysts for water and urea electrolyzers.

In situ Electrochemical Evaluation of the Interaction of dsDNA with the Proteasome Inhibitor Anticancer Drug Bortezomib

Bortezomib is an inhibitor of proteasomes and an anti-cancer drug. Although bortezomib is considered a safe drug, as confirmed by cytotoxicity assays, recent reports highlighted the possibility of interaction between bortezomib and cellular components, with detrimental long-term effects. The evaluation of the interaction between bortezomib and dsDNA was investigated in bulk solution and using a dsDNA electrochemical biosensor. The binding of bortezomib to dsDNA involved its electroactive centers and led to small morphological modifications in the dsDNA double helix, which were electrochemically identified through changes in the guanine and adenine residue oxidation peaks and confirmed by electrophoretic and spectrophotometric measurements. The redox product of bortezomib amino group oxidation was electrochemically generated in situ on the surface of the dsDNA electrochemical biosensor. The redox product of bortezomib was shown to interact primarily with guanine residues, preventing their oxidation and leading to the formation of bortezomib-guanine adducts, which was confirmed by control experiments with polyhomonucleotides electrochemical biosensors and mass spectrometry. An interaction mechanism between dsDNA and bortezomib is proposed, and the formation of the bortezomib redox product-guanine adduct explained.

Spinel-structured CuCo2O4 with a mixed 1D/2D morphology for asymmetric supercapacitor and oxygen evolution electrocatalyst applications

Transition metal oxides with multifunctional properties have attracted attention for use in various electro-catalytic applications, but their weak electroactive centers have severely limited their commercialization. In the present study, we describe an efficient bifunctional material whose structural morphology makes it both an effective oxygen evolution reaction (OER) electrocatalyst and a reliable power source for supercapacitor (SC) electrodes. We successfully fabricated spinel-structured CuCo2O4 consisting of a mix of one-dimensional (1D) nanorods and two-dimensional (2D) nanoplates using precipitation followed by hydrothermal treatment and calcination. For comparison purposes, CuO nanoplates and Co3O4 nanorods were synthesized individually, and their multifunctional features were examined. The synthesized mixed-morphology CuCo2O4 delivered an excellent electrochemical performance for SC and OER electrocatalyst applications. The mixed-morphology CuCo2O4 produced a specific capacity of 561 C g−1 (1122 F g−1) at 1 A g−1 and exhibited a superior rate capability and excellent stability, with 92% retention of capacity after 5000 cycles at 30 A g−1 in a three-electrode cell. In addition, a fabricated asymmetric supercapacitor device (CuCo2O4//activated carbon) delivered an energy density of 47.6 W h kg−1 and a power density of 1280 W kg−1, with outstanding long-term cyclic stability. Furthermore, the prepared CuCo2O4 had a low Tafel slope, a high electrochemical surface area, and excellent long-term durability. Therefore, mixed-morphology CuCo2O4 holds significant promise for use in SC and OER catalyst applications. Moreover, this study offers a useful method for preparing multifunctional materials.

A novel high entropy perovskite fluoride anode with 3D cubic framework for advanced lithium-ion battery

High-entropy materials are recently attracted significant attention due to their variability of composition and entropy stabilizing phase structure. However, the current mainstream synthesis methods of high-entropy materials require high-energy ball milling and calcination, which limits their further generalization. In this work, a new class of high-entropy perovskite fluorides (HEPFs) as an anode material using for LIBs is reported. In particular, a high-entropy fluoride of KMgMnFeCoNiF3 (TM5) and a series of medium-entropy fluorides (TM4) including KMnFeCoNiF3 (TM4-Mg), KMgFeCoNiF3 (TM4-Mn), KMgMnCoNiF3 (TM4-Fe), KMgMnFeNiF3 (TM4-Co), and KMgMnFeCoF3 (TM4-Ni) are prepared by a facile ball milling with hydrothermal method. Interestingly, the TM5 electrode shows better cycling performance (120 mAh g−1 at 2 A g−1 over 1000 cycles with ∼99% coulombic efficiency) and rate performance (472–57 mAh g−1 at 0.1–3.2 A g−1 current densities) than TM4. The key to such improvement depends on the high-entropy effect together with the synergistic effects of multiple electroactive redox centers. It is believed that this work can provide a new idea for the design and synthesis of high-entropy perovskite materials in the future.