Zeolitic imidazolate framework derived ZnCo2O4 hollow tubular nanofibers for long-life supercapacitors

Facile synthesis of morphology-controlled hybrid structure of ZnCo2O4 nanosheets and nanowires for high-performance asymmetric supercapacitors

Controllable synthesis of electrode materials with desirable morphology and size is of significant importance and challenging for high-performance supercapacitors. Herein, we propose an efficient hydrothermal approach to controllable synthesis of hierarchical porous three-dimensional (3D) ZnCo2O4 composite films directly on Ni foam substrates. The composite films consisted of two-dimensional (2D) nanosheets array anchored with one-dimensional (1D) nanowires. The morphologies of ZnCo2O4 arrays can be easily controlled by adjusting the concentration of NH4F. The effect of NH4F in the formation of these 3D hierarchical porous ZnCo2O4 nanosheets@nanowires films is systematically investigated based on the NH4F-independent experiments. This unique 3D hierarchical structure can help enlarge the electroactive surface area, accelerate the ion and electron transfer, and accommodate structural strain. The as-prepared hierarchical porous ZnCo2O4 nanosheets@nanowires films exhibited inspiring electrochemical performance with high specific capacitance of 1289.6 and 743.2 F g-1 at the current density of 1 and 30 A g-1, respectively, and a remarkable long cycle stability with 86.8% capacity retention after 10 000 cycles at the current density of 1 A g-1. Furthermore, the assembled asymmetric supercapacitor using the as-prepared ZnCo2O4 nanosheets@nanowires films as the positive electrode and active carbon as negative electrode delivered a high energy density of 39.7 W h kg-1 at a power density of 400 W kg-1. Our results show that these unique hierarchical porous 3D ZnCo2O4 nanosheets@nanowires films are promising candidates as high-performance electrodes for energy storage applications.

In situ coordination interactions between metal-organic framework nanoemitters and coreactants for enhanced electrochemiluminescence in biosensing

Coreactant electrochemiluminescence (ECL) is one of the most popular pathways in commercial analysis, which can provide simplicity and convenience for getting intense ECL emission. However, the low efficiency of intermolecular electron transfer could weaken ECL intensity. In this work, we developed an enhanced ECL strategy through in situ coordination interactions between metal-organic framework emitters and coreactants. First, a metal-organic framework (MOF) emitter was synthesized with 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane (TPPE) as aggregation-induced emission linkers and Zn as nodes. Interestingly, compared to TPPE ligand, the resulted MOF nanoemitters demonstrated 49.5 folds enhancement of ECL emission in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as the coreactant. More significantly, different from the constant ECL intensity using TPrA coreactant, DABCO exhibited time-dependent ECL intensity due to the intrareticular electron transfer through coordination interaction between DABCO and Zn²⁺, which was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectral experiments. The enhanced ECL was then applied to construct a sensitive ECL method to detect dopamine in serum samples. The coordination interaction between emitters and coreactants not only provides a universal way to enhance ECL, but also expands the applications of coreactant ECL system in convenience route.

Vertically Aligned ZnCo2O4 Nanoplates on Ti3C2 for High-Efficiency Hybrid Supercapacitors

Electrode materials marking higher structural stability, and electrochemical activity remain the priority in improving the electrochemical performance of supercapacitors (SCs). Herein we report the designed synthesis of novel nanoplate-on-nanosheet architecture...

Energy storage properties of hydrothermally processed ultrathin 2D binder-free ZnCo2O4nanosheets

High energy-density supercapacitors (SCs) with long operating life, cost-effective, and competitive cycling performance is attracted great research attention to competing in the requirements of the modern age. However, despite these benefits, SC hampers inadequate rate-capability and structural deterioration, which primarily affects its commercialization. Herein, ultra-thin two-dimensional (2D) ZnCo₂O₄nanosheets arein situanchored on the conductive surface of nickel foam (denoted as ZCO@NF) by hydrothermal process. The binder-free ZCO@NF is employed as an electrode for SCs and shows impressive charge storage properties. ZCO@NF electrode exhibited a high capacitance of 1250 (750) and 733 F g^-1(440 C g^-1) at 2.5 and 20 A g^-1, respectively, demonstrating the outstanding rate-capability of 58.6% even at 8 times larger current density. Furthermore, the ZCO@NF electrode exhibits admirable capacitance retention of 96.5% after 10 000 cycles. This impressive performance of the ZCO@NF electrode is attributed to the high surface area which gives a short distance for ion/electron transfer, a high conductivity with extensive electroactive cities, and strong structural stability. The binder-free approach provides a strong relationship between the current collector and the active material, which turns into improved electrochemical operation as an electrode material for SCs.

Constructing high-performance electrode materials using core–shell ZnCo2O4@PPy nanowires for hybrid batteries and water splitting

Heterogeneity can be used as a promising method to improve the electrochemical performance of electrode materials; thus, ZnCo₂O₄@PPy samples were prepared using a facile hydrothermal route and an electrochemical deposition process. The as-prepared products possess a specific capacitance of 605 C g⁻¹ at a current density of 1 A g⁻¹. The asymmetric supercapacitor (ASC) possesses an energy density of 141.3 W h kg⁻¹ at a power density of 2700.5 W kg⁻¹ and capacity retention of 88.1% after 10 000 cycles, indicating its promising potential for energy devices. ZnCo₂O₄@PPy-50 exhibited an excellent OER performance and outstanding HER performance in alkaline media. As an advanced bifunctional electrocatalyst for overall water splitting, a voltage of 1.61 V at a current density of 50 mA cm⁻² outperforms the majority of noble-metal-free electrocatalysts.

Heterogeneity can be used as a promising method to improve the electrochemical performance of electrode materials; thus, ZnCo₂O₄@PPy samples were prepared using a facile hydrothermal route and an electrochemical deposition process.