Mantry, Swarna P.Mohapatra, Biswaranjan D.Behera, Rajesh K.Varadwaj, Kumar S. K....
9页
查看更多>>摘要：We report the electrochemical activity of transition metal ion (Fe, Co and Ni) doped MnOx@N-graphene (MnOx@NG) hybrid catalysts towards oxygen reduction reaction (ORR). The doped catalysts displayed significantly enhanced electrochemical performance than the undoped one. The Fe doped MnOx@NG exhibited highest positive shift in onset potential (0.93 V vs. RHE), highest electron transfer number (n) (3.87) and lowest peroxide yield (6.35 %) in 0.1 M KOH solution. The Co doped catalyst showed highest current density, which is comparable to that of benchmark 20 wt% Pt/C. The XRD analysis showed that the catalyst samples are poorly crystalline and the doping of either Fe or Co or Ni cation induces formation of Mn2O3, whereas the undoped catalyst consists of both Mn2O3 and MnOOH. The STEM (scanning transmission electron microscope) micrographs revealed that in all the samples the MnOx nanostructures are well dispersed on NG and the elemental mapping of the doped catalysts showed uniform distribution of dopants. The X-ray photoelectron spectroscopy (XPS) studies revealed that doping of either cation results an increase in the average Mn valency of the host MnOx. The change in crystal structure and corresponding ORR activity has also been investigated with increase in dopant amount for Fe doped samples.
查看更多>>摘要：The composite comprised of graphene and carbon nanotubes (CNTs) exhibited significantly enhanced electro-chemical performance due both to the improved dispersion and inhibition of restacking of graphene and CNTs. In this work, graphene nanoribbons (GNRs)/CNTs composite (GNRs/CNTs) was synthesized on gram-scale by chemical vapor deposition. Under optimal growth conditions, the yield of GNRs/CNTs as high as 26 g per gram catalyst could be achieved in 30 min growth time. The morphology and quality of the as-synthesized composite was verified by using SEM, TEM and Raman spectroscopy. The electrochemical properties of GNRs/CNTs was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge techniques. GNRs/CNTs exhibited specific capacitance of 242.3 F/g at 0.5 A g(-1), which was over 4 times of that of CNTs. The GNRs/ CNTs based electrodes exhibited excellent cycling stability at 1 A g(-1) for over 4000 cycles, which can be attributed to the excellent electrical conductivity and the unique structure. When employed as electrode for membrane capacitive desalination, the desalination capacity of 16.46 mg g(-1) has been achieved under 1.2 V with 500 mg L-1 NaCl solution as feeding water.
查看更多>>摘要：The conductive metal organic framework (MOF) discloses efficient electron transfer ability and its specific framework structure could realize ion recognition. The state-of-the-art solid-contact ion-selective electrodes (SC-ISEs) rely on both solid contact (SC) and ion-selective membrane (ISM) for respective functions of ion-to-electron transduction and ion recognition. Herein, we report an ISM-free SC-ISE by using the conductive MOF of Cu-3(HHTP)(2) (Cu as metallic nodes and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as triph-enylene-based organic linkers) as a bifunctional role of SC and ISM for Cu2+ sensing. The experimental results demonstrated a Nernstian and selective response to Cu2+ with a slope of 29.5 +/- 0.3 mV dec(-1). Compared with traditional Cu2+-ISM-based SC-ISEs, the potentiometric response time has been greatly reduced from similar to 50 s to 10 s. Moreover, the ISM-free conductive MOF could offer normal potentiometric responses even under a short conditioning time in solution (minutes). In addition, organic solvent tolerance has also been proved for the ISM-free conductive MOF-based SC-ISE. This work demonstrates that the MOF could be feasible for constructing a type of ISM-free solid potentiometric ion sensors.
Haider, Syed ShabhiZakar, SanaIqbal, Muhammad ZahirDad, Sania...
10页
查看更多>>摘要：The versatile importance of hybrid supercapacitors in energy storage applications craves the outstanding electrochemical behavior of electrode material. In this study, we have grown several electrodes of cobalt-coppermanganese sulfide (CCMS) with different concentration of cobalt and copper on a current collector (Ni foam) by espousing one-step co-electrodeposition approach. The morphological aspects of contrived electrodes have been characterized by FESEM.. Electrochemical characterization reveals the substantial performance of S2 electrode (Co25Cu75MnS) as compared to other compositions. After the experimental investigation, the dependence of inherent charge storage mechanism of CCMS on the concentration of Co and Cu have been scrutinized thru stimulating theoretical approaches. Different mathematical models employed to ascertain the dominant charge storage mechanism involved during electrochemical charge storage and scrutinizing their redox reaction stability. The finding illumines the enhanced electrochemical performances of electrodes with prevalent battery-type charge storing phenomenon which support for the construction of advance hybrid energy storage devices.
查看更多>>摘要：Lithium-ion batteries with the merits of no memory effect, cycle stability, and proven technology have attracted greatly attention as an energy storage system in daily life. However, the anode of commercial lithium-ion batteries is layered graphite, delivering an unsatisfied capacity of 372 mAh g-1. In this work, Si nanoparticles were in-situ coated with Nb2O5 with core-shell structure via a simple hydrothermal method. The effect of the content of Nb2O5 shell on the Si core was investigated. As a result, Si@Nb2O5 composite (SN-1) exhibits high capacity (2383 mAh g-1) and stable cycle life as anode materials for lithium-ion batteries. Even rate current improves to 5C, the SN-1 composite anode still delivers a high capacity (1221 mAh g-1). Such a superior electrochemical performance are attributed to the fact that Nb2O5 is evenly coated on the surface of the Si nanoparticles, acting as a stress buffer layer and surface stabilization layer, ensuring rapid ion diffusion. Meanwhile, Pseudocapacitance contribution is vital for enhanced lithium storage. Therefore, the cycling stability of the electrodes is further improved. These superior electrochemical properties make the method of in-situ coating Si particles hold promising potential for energy storage systems.
查看更多>>摘要：This work reports the synthesis and application of nitrogen and sulfur co-doped Nb2C MXene (NS-Nb2C) for the sensing of dopamine (DA) in gastric juice. NS-Nb2C MXene was successfully synthesized in a one-step treatment of Nb2C using thiourea as N,S resource. The heteroatom doping strategy enables introduction of N,S into MXene nanosheets and simultaneously induces the increased interlayer spacing, high surface area, and enhanced electrical conductivity. It was found that NS-Nb2C is more electrochemically active than multilayered Nb2C nanosheets (ML-Nb2C) and delaminated Nb2C nanosheets (DL-Nb2C). Based on this, the as-prepared NSNb2C/Nafion/GCE was used to study the electrochemical behavior of dopamine in pH = 3.0. The sensing interface not only utilizes the unique two-dimensional (2D) nanosheet morphology of Nb2C that has a larger surface area and conducive network, but also takes advantage of the more active sites provided by doping. This enables the sensor to achieve ultra-sensitive detection of dopamine (S/N = 3) with a low limit of detection (LOD) of 0.12 mu M. In addition, the prepared sensor has good stability and selectivity, and the results of detecting DA in simulated gastric juice is satisfactory. The results indicated that the Nb-based MXenes provided a promising tool for acidic electrochemical sensing applications.
查看更多>>摘要：Soft materials, such as hydrogels, polymers or biomaterials associated with electrodes provide interfaces revealing electrocatalytic, photoelectrocatalytic and controlled release of loads functions. These will be addressed by three examples demonstrated by our laboratory, including: (i) The assembly of a stimuli-responsive nucleic acid-based hydrogel on an electrode support, consisting of a hydrogel matrix crosslinked by duplex nucleic acid bridges and K+-ion-stabilized G-quadruplex bridges. By cyclic and reversible formation and dissociation of the G-quadruplexes by K+-ions and crown ether (CE), the switchable stiffness properties of the hydrogel are demonstrated. The integration of hemin into the G-quadruplex bridging units on electrocatalytic interface for the electrocatalyzed reduction of H2O2 is introduced. In the presence of K+-ions/crown ether the switchable electrocatalytic functions of the electrode are demonstrated. (ii) A pH-responsive nucleic acid-based hydrogel matrix is immobilized on an electrode surface. The hydrogel interface is crosslinked by permanent nucleic acid bridges and pH-responsive crosslinking units. At acidic pH values, the pH responsive bridges are unlocked via generating i-motif structures, leading to an hydrogel interface of lower stiffness. Immobilization of ferrocene-modified glucose oxidase (GOx) in the hydrogel yields an electrically contacted enzyme electrode that stimulates the bioelectrocatalyzed oxidation of glucose and the acidification of the hydrogel. By incorporating a load into the hydrogel, the electrocatalyzed oxidation of glucose and the accompanying acidification of the hydrogel lead to a hydrogel of lower stiffness, allowing the controlled release of the load. (iii) A supramolecular, electrochemically contacted, photoresponsive matrix consisting of native photosystem I (PS I) interlinked to glucose oxidase (GOx) by an electrically contacting redox polymer consisting of polyvinyl imidazole Os2+/3+(bipyridine)2Cl complex is introduced. The organized assembly acts as a photobioelectrochemical fuel cell where photoinduced electron transfer from PS I to the electrode stimulates the bioelectrocatalyzed oxidation of glucose. The system demonstrates the light-induced oxidation of the glucosefuel and the concomitant generation of electrical power.
查看更多>>摘要：Using scanning electrochemical microscopy (SECM), we have clarified the enhancement effect of silica nanochannel membrane (SNM) on electrochemiluminescence (ECL) generation by tris(2,20-bipyridyl) ruthenium(II) (Ru(bpy)32+) and coreactant tri-n-propylamine (TPrA) in this work. Compared with the bare electrode, the electrochemical oxidation of both Ru(bpy)32+ and TPrA was significantly enhanced, especially for the former, which can be attributed to the enrichment and electrostatic attraction effects provided by the negatively charged and ultrasmall nanochannels of SNM. We further measured quantitatively the mass transfer rate of Ru (bpy)32+ within the channels of SNM by SECM approach curve measurements in conjunction with using finite element simulations, that is ca. 0.3 mm/s, a much faster rate than that in bulk solution. Benefiting from the mass transfer enhancement effect of SNM towards positively charged species in ECL, the ECL signal can be significantly enhanced.
查看更多>>摘要：Simultaneous highly sensitive and accurate detection of dopamine (DA) and uric acid (UA) is of great importance since they are important biomolecules that are commonly coexisted in the human body and play a crucial role in numerous physiological and pathological features. In this work, Fe-N5 single atom catalyst (SAC) supported on graphene was firstly employed for simultaneous electrochemical detection DA and UA. Owing to its unique electronic structure and abundant active sites, under optimal conditions, the enzyme-like Fe-N5 SAC constructed electrochemical (bio)sensor exhibits excellent linear characteristic responses in the range of 0.005-500 and 0.01-480 mu M, as well as the low limit of detection of 0.007 and 0.027 nM for DA and UA, respectively. More critically, the developed electrochemical system shows promising merits of exceptional stability, good repeatability, and, consequently, it was successfully applied for simultaneous sensitive detection of DA and UA in human serum samples.
查看更多>>摘要：Given the growing need for renewable energy and related technologies, researches have shifted to develop lowcost, stable, high-efficiency electrocatalysts in clean energy generation reactions such as water electrolysis. In the present paper, a three-dimensional Fe2TiO5/nitrogen-doped graphene (3D FTO/NG) nanocomposite is prepared using a simple, cheap and fast method, called chemical bath deposition (CBD). Structural and physical characterizations of the prepared electrocatalysts are performed by different methods such as Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), Fourier Transform InfraRed spectra (FT-IR), Dynamic Light Scattering (DLS), X-ray Diffraction (XRD), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The fabricated binder-free 3D FTO/NG, 3D NG and 3D G on nickel foam (NF) electrodes, were applied to study oxygen evolution reaction (OER) in alkaline medium. Among these electrodes, the 3D FTO/NG electrocatalyst, has an overpotential of 264.15 mV at 10 mA cm-2 and its Tafel slope was 35 (mV/dec). Its long-term stability and excellent performance are due to the simultaneous effect of nitrogen doping and presence of metal oxide nanoparticles, which helped to increase the number of active sites for reaction, adsorption of hydroxide ions and electrode conductivity.
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Elsevier