Hierarchical Microflowers Research Articles

Hydrothermal synthesis of self-supported hierarchical microflowers of Co3O4 nanowires for potential supercapacitor application

This study explores the synthesis of ultrathin flower architecture of spinel-structured Co3O4 electrodes, on nickel foam using a double hydrothermal method, followed by annealing at 250 °C for 4 h. We systematically investigate the effects of varying reaction times and additional Co2+ treatment during the second hydrothermal process on the morphology and electrochemical properties of Co3O4. Field emission scanning electron microscopy (FE-SEM) images confirm the formation of self-supported hierarchical flowers, characterized by sharp, spike-like nanowires (16–33 nm in diameter) arranged radially. The self-supported optimized hierarchical Co3O4 thin film, characterized by its unique architecture and substantial mass loading of 4.6 mg cm−2, achieved an impressive specific capacitance of 749.48F g−1 at a scan rate of 10 mV s−1 (specific capacity of 182.16 mAh g−1) in 2 M KOH electrolyte and retained 64 % of its initial capacitance after 5000 cycles. Furthermore, a symmetric device demonstrated the ability to illuminate a red LED for approximately 120 s when two devices were connected in series.

Strong electronic coupling of graphdiyne/CuCo2S4 ohmic junction for boosting photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution is a clean energy technology with sustainable potential. Effective electronic coupling is a crucial approach to enhance hydrogen evolution kinetics. In this work, graphdiyne (GDY) nanosheets were successfully synthesized utilizing a ball-milling-assisted reduction and elimination method, and subsequently coupled with 3D hierarchical CuCo2S4 microflowers forming ohmic junction GDY/CuCo2S4 (GCC) with robust electronic coupling effects. The uniformly distributed pore canal of GDY endow GCC with a substantial specific surface area. The unique porous hierarchical of CuCo2S4 facilitates extensive interaction with solutes, thereby enhancing proton absorption capacity. DFT calculations reveal a robust electronic coupling interface between GDY and CuCo2S4, which increases the local electron density of GDY. In-situ XPS confirms the successful construction of the ohmic junction, which induces electron transfer from GDY to CuCo2S4, thereby suppressing electron-hole recombination in GDY and enhancing photocatalytic hydrogen evolution activity. Consequently, GCC-25 achieved optimal photocatalytic hydrogen evolution activity at 6899.24 μmol h⁻¹ g⁻¹, which is 5.55 and 4.48 times higher than that of pristine GDY and CuCo2S4, respectively. This work provides a novel approach for constructing GDY-based 3D hierarchical ohmic junctions to enhance photocatalytic hydrogen evolution performance.

Superior performance of hierarchical 3D microflower CuS grown on carbon cloth as binder free electrode for supercapacitor applications

Copper sulfide (CuS) was grown on the carbon cloth (CC) utilizing the traditional hydrothermal method. The role of different reaction time of 5 h, 10 h, and 15 h (C15) were investigated with fixed reaction time of 150 °C. XRD confirmed the growth of pure CuS on CC. Macroscopic changes in morphology were observed with increasing the reaction time and C15 showed ∼3.08 μm diameter of CuS microflowers with ∼ 34.68 nm thickness of nanosheets embedded in the microflowers. C15 showed a lowest bandgap of 1.8 eV with high copper content of 34 % and the copper content increases fast electron movement and maintains structural stability. The supercapacitor behavior was investigated in 1 M Mg(NO3)2 aqueous electrolyte and C15 demonstrated the highest specific capacitance of 83.70 F/g at 5 mV/s. An aqueous symmetric electrode made with C15 displays 149 F/g specific capacitance and 87.2 % retention at 1 A/g for 1000 cycles.

Fabrication of three-dimensional hierarchical NiCo-LDH micro-flowers for enhanced charge storage in battery-type supercapacitors

Layered double hydroxides (LDHs) show great advantage in supercapacitors (SCs) due to their unique layered structure and high theoretical capacity. However, their poor electrical conductivity and structural instability hinder their practical application. Metal-organic framework materials (MOFs) can be utilized to construct transition metal derived materials with adjustable morphology and high electrochemical properties. In this study, we first synthesized flower-like NiCo-based MOFs (NiCo-BTC) using a one-step solvothermal reaction. The formation process followed a sequence of “nucleation-growth-etching” corresponding to Ostwald's maturation theory. Subsequently, novel hierarchical NiCo-LDHs micro-flowers were constructed through treating the NiCo-BTC in an alkaline solution. The morphology of NiCo-LDHs was optimized by adjusting the ratio of Ni to Co, so as to achieve excellent electrochemical properties due to the hierarchical flower-like structure and the bimetallic synergistic effect. As a result, Ni3Co1-LDH exhibited a high specific capacitance of 1978.2 F/g at 1 A/g, excellent rate capability of 82.80 % at 40 A/g and good cycle stability with 70.6 % capacitance retention after 10,000 cycles at a high current density of 10 A/g. Furthermore, the asymmetric SC (ASC) based on Ni3Co1-LDH//AC exhibited high specific capacitance of 162.4 F/g at 1 A/g and excellent energy density of 54.8 Wh/kg at power density of 779.4 W/kg. In addition, the ASC demonstrated remarkable cycle stability with a capacitance retention of 96.5 % after 3500 cycles. The successful synthesis of 3D hierarchical NiCo-LDHs micro-flowers offers an effective approach to developing highly promising electrodes for SCs.

Enhanced pseudocapacitive properties of cobalt-doped manganese oxide electrode utilizing magnesium sulfate electrolyte for supercapacitors

This paper investigates the enhanced pseudocapacitive properties of cobalt-doped manganese oxide (Co-doped MnO2) electrode in magnesium sulfate (MgSO4) electrolyte for supercapacitor applications. Co-doped MnO2 was synthesized on nickel foam through a controlled hydrothermal process and specific heat treatment parameters. This resulted in the transformation into α-MnO2 with a 2 × 2 tunnel structure. Morphological investigation illustrates the presence of a hierarchical micro-flower structure with a substantial surface area and mesoporous distribution. The specific surface area of the Co-doped MnO2 electrode significantly increased to 158 m2 g−1, compared to the pristine (bare MnO2) electrode (80 m2 g−1). Electrochemical analyses revealed a specific capacitance of 527 F g−1 at 1 A g−1 in MgSO4 (1 M), showcasing a 1.6 times improvement over Na2SO4 (1 M). The unique structure of the Co-doped MnO2, combined with magnesium ions as efficient electron donors, contributes to superior charge-storage, making it a promising candidate for high-performance supercapacitors. Comprehensive characterizations, such as XRD, XPS, BET, SEM, GCD, and EIS, confirm the advantageous electrochemical performance and durability of the Co-doped MnO2 electrode in MgSO4 electrolyte.

Deciphering Sodium-Ion Storage: 2D-Sulfide versus Oxide Through Experimental and Computational Analyses.

Transition metal derivatives exhibit high theoretical capacity, making them promising anode materials for sodium-ion batteries. Sulfides, known for their superior electrical conductivity compared to oxides, enhance charge transfer, leading to improved electrochemical performance. Here, a hierarchical WS2 micro-flower is synthesized by thermal sulfurization of WO3. Comprising interconnected thin nanosheets, this structure offers increased surface area, facilitating extensive internal surfaces for electrochemical redox reactions. The WS2 micro-flower demonstrates a specific capacity of ≈334mAhg-1 at 15mAg-1, nearly three times higher than its oxide counterpart. Further, it shows very stable performance as a high-temperature (65°C) anode with ≈180mAhg-1 reversible capacity at 100mAg-1 current rate. Post-cycling analysis confirms unchanged morphology, highlighting the structural stability and robustness of WS2. DFT calculations show that the electronic bandgap in both WS2 and WO3 increases when going from the bulk to monolayers. Na adsorption calculations show that Na atoms bind strongly in WO3 with a higher energy diffusion barrier when compared to WS2, corroborating the experimental findings. This study presents a significant insight into electrode material selection for sodium-ion storage applications.

Facile synthesis of three-dimensional MnOX (MnO2, Mn2O3, Mn3O4) hierarchical microflower for removal of phenol through peroxymonosulfate activation

A novel three-dimensional (3D) manganese oxide (MnOX) hierarchical microflowers materials were prepared and applied to activate peroxymonosulfate (PMS) for the removal of phenol. The 3D α-MnO2 material exhibited higher catalytic activity than 3D Mn2O3 and 3D Mn3O4 materials, with 100% phenol removal within 60 min. The quenching experiment and EPR results indicated that 1O2 played a major role in removing phenol, SO4•–, O2•– and •OH ranked second. The kinetic studies indicated that the removal of phenol followed the pseudo-first-order kinetic model, and the reaction activation energy of 3D α-MnO2 material was 25.67 kJ mol−1. Besides, factors of 3D α-MnO2 catalytic performance such as catalyst dosage, PMS dose and reaction temperature were also investigated. This work provided a new approach for synthesizing 3D MnOX catalysts with high-performance and guidance for analyzing the catalytic activity of multivalent metal oxides.

Construction of Three-Dimensional Hierarchical CoSe2 Microflowers Assembled by Thin Nanosheets for High-Performance Sodium-Ion Batteries

Transition metal selenides are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, they suffer from large volume change, serious polyselenide dissolution and sluggish reaction kinetics during charge/discharge process, resulting in poor cycling stability and low rate performance for SIBs, which further restrict their widespread application. Here, we developed carbon-free three-dimensional (3D) hierarchical microflower-shaped CoSe2 with a diameter size of approximately 2[Formula: see text][Formula: see text]m, composed of nanosheets through a one-step solvothermal method. The thin nanosheets are conducive to shortening the Na[Formula: see text] diffusion channels and relieving the volume expansion, and the 3D hierarchical microflower architecture could effectively prevent the agglomeration of nanosheets; accordingly, the resulting CoSe2 microflowers deliver a high specific capacity of 451.94[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] even at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] after 100 cycles, compared with CoSe2 nanoparticles. This work offers an approach for designing metal selenides with high capacities and rate capability for SIBs.

Hierarchical In2S3 microflowers decorated with WO3 quantum dots: Sculpting S-scheme heterostructure for enhanced photocatalytic H2 evolution and nitrobenzene hydrogenation

Solar energy conversion and high-value chemical production are of utmost importance. However, the development of efficient photocatalysts with strong redox ability remains challenging. Here we report a unique 3D/0D In2S3/WO3 S-scheme heterojunction photocatalyst obtained by depositing WO3 quantum dots (QDs) onto hierarchical In2S3 microflowers. The In2S3/WO3 composite exhibits outstanding visible light absorption, with a maximum optical response of up to 600 nm. The electronic interaction and charge separation at interfaces are explored by in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. The difference in work function causes In2S3 to donate electrons to WO3 upon combination, leading to the formation of an internal electric field (IEF) at the interfaces. Due to the IEF and bent energy bands, the transfer and separation of photogenerated charge carriers follow an S-scheme pathway within In2S3/WO3. Owing to the strong redox ability, spatial charge separation and lower H2-generation barrier of S active sites, the optimized In2S3/WO3 heterojunctions show enhanced photocatalytic hydrogen evolution of 0.39 mmol h–1 g–1, 6.7 times that of pristine In2S3. In addition, the In2S3/WO3 S-scheme heterojunctions afford a remarkable activity for photocatalytic nitrobenzene hydrogenation with nearly 98% conversion and 99% selectivity of aniline within 1 h. Our work might present new insights into developing efficient S-scheme heterojunctions for various photocatalytic applications.

V6O13 Micro-Flower Arrays Grown In Situ on Ni Foam as Efficient Electrocatalysts for Hydrogen Evolution at Large Current Densities

Developing a high-activity, robust and economic electrocatalyst for large-scale green hydrogen production is still of great significance. Herein, a novel V6O13 nanosheets self-assembled micro-flower array self-supporting electrode is synthesized using a facile one-pot hydrothermal route. Owing to the large electrochemically active surface area of a unique hierarchical micro-flower and the stable all-in-one structure, the as-prepared V6O13/NF electrode delivers impressive HER activity with extremely low overpotentials of 125 and 298 mV at large current densities of 100 and 1000 mA cm−2, respectively, and a long-term durability for at least 90 h in an alkaline condition. This work extends the application of vanadium oxides to the realm of electrocatalytic hydrogen fuel production.

Ultrafine Co-Mo oxide nanocrystals embedded in hierarchical N-doped carbon microflowers for high-performance lithium-ion batteries

Constructing hierarchical architecture consisting of low-dimensional building blocks is attracting attention as an efficient strategy for achieving high electrochemical performance for lithium-ion batteries (LIBs). Herein, convenient synthesis of Co-Mo oxide composites embedded in a hierarchical N-doped carbon microflower (Co-Mo oxide/NC) is demonstrated. The Co-Mo/polydopamine (PDA) precursor prepared by the spontaneous coordination between the metal ion and dopamine can be easily transformed into Co-Mo oxide/NC by a two-step thermal annealing process. The as-obtained hierarchical microflowers have the advantages of hierarchical structured electrode materials, such as increased contact area with the electrolyte, abundant ion storage sites, and high electrical conductivity. Concurrently, the synergistic effect between molybdenum and cobalt ions can improve the electrochemical performance. Consequently, the hierarchical microflowers as LIB anode materials exhibit a high reversible specific capacity of 1115 mA h g−1 at 1.0 A g−1 after 200 cycles and superior rate performance with a capacity of 577 mA h g−1 at 30.0 A g−1. Moreover, in the long-term cycling stability at a high current density (10.0 A g−1), the electrode shows excellent cycling stability with a capacity of 508 mA h g−1 for 500 cycles. The present study reveals the importance of designing hierarchical structured materials to enhance electrochemical energy storage applications.

Hierarchical CoNiO2 Microflowers Assembled by Mesoporous Nanosheets as Efficient Electrocatalysts for Hydrogen Evolution Reaction

In order to alleviate the energy crisis and propel a low-carbon economy, hydrogen (H2) plays an important role as a renewable cleaning resource. To break the hydrogen evolution reaction (HER) bottleneck, we need high-efficiency electrocatalysts. Based on the synergistic effect between bimetallic oxides, hierarchical mesoporous CoNiO2 nanosheets can be fabricated. Combining physical representations with electrochemical measurements, the resultant CoNiO2 catalysts present the hierarchical microflowers morphology assembled by mesoporous nanosheets. The ultrathin two-dimensional nanosheets and porous surface characteristics provide the vast channels for electrolyte injection, thus endowing CoNiO2 the outstanding HER performance. The excellent performance with a fewer onset potential of 94 mV, a smaller overpotential at 10 mA cm-2, a lower Tafel slope of 109 mV dec-1 and better stability after 1000 cycles makes CoNiO2 better than that of metallic Co and metallic Ni.

Construction of visible light-driven Eu-doped BiOBr hierarchical microflowers for ameliorated photocatalytic 2,4-dichlorophenol and pathogens decomposition with synchronized hexavalent chromium reduction

The presence of diverse environmental contaminants has posed unprecedented challenges to wastewater treatment. Herein, Eu-doped BiOBr hierarchical microflowers (Eu-BiOBr) were fabricated via a surfactant-free hydrothermal route as highly efficient photocatalysts for multipurpose wastewater remediation applications. Under visible light irradiation, the Eu-BiOBr products demonstrated meritorious photoactivity when exposed to the mixture solution of 2,4-dichlorophenol (2,4-DCP) and Cr(VI). Noticeably, 97.6% of 2,4-DCP was degraded after 80 min, and a complete Cr(VI) reduction was obtained within 60 min over the optimized 2 at% Eu-BiOBr. This was ascribed to Eu-doping efficiently accelerated charge separation and migration, thus proliferating more reactive species and enhancing photocatalytic performance. Moreover, the 2 at% Eu-BiOBr possessed good photoactivity after four successive runs, which confirmed its recyclability. Further, as an evaluation of electrical energy consumption, the 2 at% Eu-BiOBr was found to be more economical in decomposing both 2,4-DCP and Cr(VI). The reactive species scavenging tests validated that the hydroxyl radical played a major role for the photodegradation of 2,4-DCP whereas photogenerated electron served as predominant reactive species for Cr(VI) to be reduced to Cr(III). Additionally, the 2 at% Eu-BiOBr demonstrated much enhanced bactericidal activities against Escherichia coli and Bacillus cereus compared to pristine BiOBr. These results revealed that the Eu-BiOBr can be employed as visible light-driven photocatalytic and antibacterial candidates for practical applications in environmental cleanup.

Synergistic Coupling of Hierarchical Heterostructured Ni3P/Ni/VN Microflower Electrocatalyst for Enhanced Hydrogen Evolution Reaction

AbstractThe exploration of economical and highly efficient electrocatalysts for hydrogen evolution reaction (HER) is paramount for the development of sustainable hydrogen economy. Herein, a novel three‐dimensional (3D) hierarchical microflower electrocatalyst comprised of N‐doped carbon‐armored Ni3P/Ni/VN heterogeneous nanoparticles (Ni3P/Ni/VN@NC) is developed by combining a hydrothermal method with in‐situ carbonization‐phosphating strategy. The unique robust hierarchical structure derived from 3D NiV layered double hydroxide (NiV‐LDH) skeleton as precursor provides multidimensional mass and charge transport channels as well as numerous active sites for HER, leading to the improved HER activity. More importantly, the possible electron transfer route of Ni3P→Ni→VN is demonstrated due to the charge pumping capability of VN during interfacial electron intercoupling among the tri‐component, which endows Ni3P/Ni/VN with the favorable absorption of hydrogen‐intermediates and thus upgraded HER kinetics over such heterostructure. The resulting Ni3P/Ni/VN@NC catalyst exhibits extremely low overpotentials of 81 mV and 134 mV to deliver a current density of 10 mA cm−2 without iR‐compensation in alkaline and acidic media, respectively, and maintains continuous operation for over 90 h. This work enlightens the rational design of hierarchical multi‐component heterostructured catalysts for efficient hydrogen production.

Enhanced corrosion resistance and self-cleaning properties of superhydrophobic nickel coating fabricated by one-step electrodeposition

In order to fabricate the stable superhydrophobic coatings with antifouling and anticorrosion functions. In this study, a series of nickel-coated superhydrophobic surfaces were designed on carbon steel (CS) using a one-step electrodeposition route. The structures of the prepared superhydrophobic Ni (SN) coatings were identified by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), and the wettability was also tested by contact angle goniometer. The findings displayed that the hierarchical micro-flower structures of the optimal SN coating (0.64 A of circuit density and 9.5 min of deposition time) imparted it excellent superhydrophobic property; the water contact angle (CA) and sliding angle (SA) were 168 ± 1.1° and 4.7 ± 0.6°, respectively. The optimal SN coating was found to have superior mechanical and chemical stabilities, as tested by knife scratching, adhesive tape peeling, sandpaper abrasion, and chemical corrosion resistance. Additionally, the optimal SN coating exhibited outstanding self-cleaning property, anti-corrosion, and superhydrophobic stability. Based on these results, it appears that SN coating prepared by one-step electrodeposition can solve the defect of insufficient long-term durability of electrodepositied superhydrophobic coatings, and has potential industrial application prospects.

Hierarchical Ti-MOF Microflowers for Synchronous Removal and Fluorescent Detection of Aluminum Ions.

Bifunctional luminescence metal-organic frameworks with unique nanostructures have drawn ongoing attention for simultaneous determination and elimination of metal ions in the aqueous environment, but still remain a great challenge. In this work, three-dimensional hierarchical titanium metal-organic framework (Ti-MOF) microflowers were developed by a secondary hydrothermal method for not only highly sensitive and selective detection of Al(III), but also simultaneously efficient decontamination. The resulting Ti-MOF microflowers with a diameter of 5-6 μm consisted of nanorods with a diameter of ∼200 nm and a length of 1-2 μm, which provide abundant, surface active sites for determination and elimination of Al(III) ions. Because of their substantial specific surface area and superior fluorescence characteristics, Ti-MOF microflowers are used as fluorescence probes for quantitative determination of Al(III) in the aqueous environment. Importantly, the specific FL enhancement by Al(III) via a chelation-enhanced fluorescence mechanism can be utilized for selective and quantitative determination of Al(III). The Al(III) detection has a linear range of 0.4-15 µM and a detection limit as low as 75 nM. By introducing ascorbic acid, interference of Fe(III) can be avoided to achieve selective detection of Al(III) under various co-existing cations. It is noteworthy that the Ti-MOF microflowers exhibit excellent adsorption capacity for Al(III) with a high adsorption capacity of 25.85 mg g-1. The rapid adsorption rate is consistent with a pseudo-second order kinetic model. Ti-MOF is a promising contender as an adsorbent and a fluorescent chemical sensor for simultaneous determination and elimination of Al(III) due to its exceptional water stability, high porosity, and intense luminescence.

Long-lifespan benzoquinone-intercalated vanadium oxide with vacancies and disorders on the (00l) facets for efficient sodium-ion battery: A facile approach to Na+ capture and pre-sodiation

Via a facile one-step hydrothermal method, it was synthesized (m-BQ)0.15V2O5·0.5H2O (m-BQ = m-benzoquinone) (denoted as (m-BQ)-VO) three-dimensional (3D) porous hierarchical microflowers, which possesses a large (001) lattice spacing of 13.7 Å with crystalline vacancies and disorders on the (00l) facets. Rietveld refinement and high-angle annular dark field-scanning transmission election microscopy (HAADF-STEM) of (m-BQ)-VO unveil that the successful intercalation of m-BQ into layered V2O5 leads to the elongation of V-O bonds. As a result, the V centers of the sample are unsaturated with structural oxygen vacancies, and the V-O-V bilayer is split into two V-O-V monolayers with the (001) facet as the division plane. Consequently, upon lower-temperature annealing, the dehydrated sample can deliver a high initial capacity of 252 mAh/g at 0.05 A/g with excellent capacity retentions of 90 % over 210 cycles at 0.1 A/g, and 87 % over 2100 cycles at 2 A/g, respectively, in which no apparent phase change is observed. It is associated with the large interlayer channel with a lower Na+ migration barrier of 0.48 eV. And the anchoring effect of layered V-O-V framework can prevent the leaching of m-BQ into electrolyte. Furthermore, the redox-active m-BQ can provide extra capacity, whose affinity towards Na+ can induce the partial inclusion of Na+ ions in the sample even only immersion in Na+ solution undisturbed under room temperature, giving rise to improved electron conductivity and a facile approach to pre-sodiation, as evidenced by density functional theory (DFT) calculations.

Morphology-dependent photocatalytic and photoelectrochemical performance of bismuth oxybromide crystals applied to malachite green dye degradation

Bismuth oxybromide (BiOBr) has received notable attention as a possible active solar photocatalyst with rationally high catalytic yield, although it still requires further alteration to enhance the photocatalytic activity. In this work, the BiOBr microstructures are synthesized in a controlled manner using two bromide sources, i.e., ammonium bromide (NH4Br) and cetyltrimethylammonium bromide (CTAB), which has been found to have a significant effect on the architecture of the BiOBr photocatalyst. CTAB induces the formation of 3D spherical hierarchical microflowers with curved nanoflakes, while NH4Br results in the formation of 3D flower-like open petal structures. The nature of final BiOBr products which were synthesized with different bromide sources is studied by their photo-electrocatalytic performances with a series of analytical techniques. The CTAB-assisted synthetic BiOBr sample (BiOBr-CT) showed the best photocatalytic and photoelectrochemical activities compared to NH4Br-assisted BiOBr (BiOBr-NH). BiOBr-CT shows a rate constant of 0.057 min−1 for the degradation of malachite green dye which is mostly used in the textile industry.

Lamellar flower inspired hierarchical alpha manganese vanadate microflowers for high-performance flexible hybrid supercapacitors

Hybrid flexible supercapacitors (HFS) offer high power density and stability making them an ideal choice for the energy storage system in wearable devices. In this work, the synthesis of lamellar flower-like alpha manganese vanadate (α-Mn 2 V 2 O 7 ) on nickel foam was proposed for efficient and highly stable HFS applications for the first time. The voltammetric characterization indicated that the capacitance contribution of α-Mn 2 V 2 O 7 is derived from the diffusion-controlled (battery-type, 89.93%) and capacitive controlled (10.07%) mechanisms in aqueous electrolyte (0.5 M KOH). The optimized α-Mn 2 V 2 O 7 electrode exhibited an impressive specific capacity of 125.6 mAhg −1 (760.3 Fg -1 ). In the HFS device configuration, the utilization of α-Mn 2 V 2 O 7 resulted in a remarkable specific capacitance of 35.7 F g −1 with energy, and a power density of 28.4 Whkg −1 and 8.5 kWkg −1 , respectively. Furthermore, the α-Mn 2 V 2 O 7 fabricated device is found to operate in a wide potential window exhibiting remarkable and stable electrochemical performance in the gel electrolyte even under mechanical stress conditions. Importantly, the α-Mn 2 V 2 O 7 HFS showed an impressive and stable performance over 5000 cycles. The superior specific capacitance performances obtained in the present study are noted to be the best results reported for vanadium-based ternary oxides so far.

High-performanced flexible solid supercapacitor based on the hierarchical MnCo2O4 micro-flower

Transition metal oxides have attracted much attention in supercapacitors(SCs) research field due to their eco-friendly characteristics and high theoretical specific capacity. However, the slow reaction kinetics process and poor long-cycle performance hinder its potential application. To overcome these shortcomings, MnCo2O4 micro-flowers (MnCo2O4-MF) with hierarchical structure were prepared. The spinel MnCo2O4 has a variety of metal valence states, which can provide more electrochemical active sites compared to mono-metal oxides. Moreover, the unique hierarchical structure of MnCo2O4-MF shortens the transmission distance of ions and electrons, and reduce the volume expansion and structural collapse during the cycles. Benefiting from the crystal phase and structure advantages of MnCo2O4-MF, the reaction kinetics process was accelerated and it showed excellent long-cycle stability. In aqueous alkaline electrolyte, MnCo2O4-MF exhibits an ultra-high specific capacity of 1230 F g−1 at a current density of 1 A g−1. Even after 10,000 cycles at 10 A g−1, the capacity of 102.67% is still maintained. In addition, we constructed the sandwich structured flexible flexible hybrid solid supercapacitor (FHSC) based on MnCo2O4-MF // carbon nanoboxes. The FHSC devices not only expand the working voltage window of SCs, but also show flexibility and excellent electrochemical performance.