Shell Electrode Research Articles

Needle-like CoO nanowire composites with NiO nanosheets on carbon cloth for hybrid flexible supercapacitors and overall water splitting electrodes.

A nanoscale core–shell NiO@CoO composite is prepared on flexible carbon cloth for electrodes in supercapacitors and overall water splitting. The needle-like CoO nanowires with NiO nanosheets as the active materials improve the elemental constituents as well as surface area. The NiO@CoO electrode boasts a capacity of 2.87 F cm−2 (1024.05 F g−1) at 1 A g−1 current density, and even at a large current density of 20 A g−1 the retention ratio is 80.9% after 5000 cycles. The excellent specific capacity with high rate capability can be ascribed to the unique structure which increases the area of the liquid–solid interface and facilitates electron and ion transport, improving the utilization efficiency of active materials. The asymmetric hybrid supercapacitor prepared with the core–shell electrode shows the energy output of 40.3 W h kg−1 at 750 W kg−1 with a better retention (71.7%) of specific capacitance after 15 000 cycles. In addition, linear sweep voltammetry is performed to assess the performance of the electrode in water splitting and the electrode shows excellent activity in the OER as manifested by a Tafel slope of 88.04 mV dec−1. Our results show that the bifunctional structure and design strategy have large potential in energy applications.

Ge nanocoatings as anode for three dimensional Si based Li ion microbatteries

Three dimensional (3D) hedgehog-like Ge nanoelectrodes coated on patterned Si substrate are successfully fabricated through the facile chemical vapor deposition (CVD) process. The 3D Si substrate with enlarged surface area and the abundant Ge shell electrode configuration are together favorable to enhance the lithiation/delithiation kinetics during cycling. Impressively, the optimized 3D Si@hedgehog-like Ge (Si@H-Ge) NRs composites anodes embrace high reversible areal capacity and superior rate capability when employed as anode material for 3D Si based lithium ion microbatteries (LIMBs).

Diffusion stress analysis of spherical shell electrode

Lithium-ion batteries have a wide range of applications in the field of electronics. It is necessary to conduct in-depth study of the impact of diffusion-induced stress to enhance the performance of lithium-ion batteries. In this study, the diffusion-induced stress of spherical shell electrode is investigated. The effect of initial concentration of lithium ions and the size of electrode on the diffusion stress under constant voltage charge and discharge conditions are analysed by employing single phase diffusion model. In this paper, the evolution of the lithium ion concentration in the spherical shell electrode is calculated by controlling the initial concentration of lithium ions, and then the size of the electrode material is changed to explore the radial and circumferential stress of the spherical shell electrode material. It is found that the lower initial concentration of lithium ions can effectively reduce the diffusion stress. The stress variation of the right peak point of spherical shell electrode with lithium ion concentration is further studied. The results show that the smaller the electrode material size, the smaller the diffusion stress.

Vertically aligned nanostructured FeOOH@MnO2 core shell electrode with better areal capacitance

Present work focuses on hydrothermal preparation of FeOOH@MnO2 core shell as a vertically aligned 1-D nanostructure and improvement in electrochemical charge storage by utilizing MnO2 nanostructure as an active electrode material and vertically aligned FeOOH nanorods for one dimensional electron transfer paths. A FeOOH@MnO2 core shell thin film electrode gives maximum capacitance of 0.252 Fcm−2 for the applied current density of 1 mAcm−2 and maintains 99.5% capacitance retention for 2000 charge discharge cycles at 5 mAcm−2 that attributes to better capacitive charge storage in the material. Assembled solid state symmetric electrochemical capacitor of FeOOH@MnO2 electrode yields maximum of 0.05 mWhcm−2 energy density with power delivery of 1.5 mWcm−2.

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats.

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and human studies to investigate the cortical processing of nociceptive information. These laser-evoked brain potentials (LEPs) consist of several transient responses that are time-locked to the onset of laser stimuli. However, the functional properties of the LEP responses are still largely unknown, due to the lack of a sampling technique that can simultaneously record neural activities at the surface of the cortex (i.e., electrocorticogram [ECoG] and scalp electroencephalogram [scalp EEG]) and inside the brain (i.e., local field potential [LFP]). To address this issue, we present here an animal protocol using freely moving rats. This protocol is composed of three main procedures: (1) animal preparation and surgical procedures, (2) a simultaneous recording of ECoG and LFP in response to nociceptive laser stimuli, and (3) data analysis and feature extraction. Specifically, with the help of a 3D-printed protective shell, both ECoG and LFP electrodes implanted on the rat's skull were securely held together. During data collection, laser pulses were delivered on the rat's forepaws through gaps in the bottom of the chamber when the animal was in spontaneous stillness. Ongoing white noise was played to avoid the activation of the auditory system by the laser-generated ultrasounds. As a consequence, only nociceptive responses were selectively recorded. Using the standard analytical procedures (e.g., band-pass filtering, epoch extraction, and baseline correction) to extract stimulus-related brain responses, we obtained results showing that LEPs with a high signal-to-noise ratio were simultaneously recorded from ECoG and LFP electrodes. This methodology makes the simultaneous recording of ECoG and LFP activities possible, which provides a bridge of electrocortical signals at the mesoscopic and macroscopic levels, thereby facilitating the investigation of nociceptive information processing in the brain.

Electrodeposited nickel aluminum-layered double hydroxide on Co3O4 as binder-free electrode for supercapacitor

Here, we report a heterostructured core–shell electrode consists of cobalt oxide (Co3O4) nanowire core and nickel aluminum (NiAl)-layered double hydroxide (NiAl-LDH; herein Co3O4@LDH) nanosheet shell grown on nickel foam as advanced electrode for supercapacitor. Benefiting from the core–shell configuration and smart hybridization, the optimized Co3O4@LDH core–shell electrode exhibits a high capacitance of 2011 F g−1 at 2 A g−1 and remains 1455 F g−1 at 40 A g−1, which outperforms the electrochemical performance of individual component of Co3O4 (720 F g−1 at 2 A g−1). A hybrid supercapacitor using Co3O4@LDH as positive electrode and carbon nanotube as negative electrode delivers an energy density of 18.1 Wh kg−1 at a power density of 375 kW kg−1 at a current density of 0.5 A g−1. Smart hybridization of core–shell electrode shows great promise as advanced electrode materials for supercapacitor with high electrochemical performance.

Optimization of 3D shell electrode detectors—A type of honeycomb shell electrode detector

In order to reduce dead zone of Closed Shell-Electrode Silicon Detector (CSESD), this paper introduces an optimal scheme of 3D shell electrode type detector– a novel type of Honeycomb Shell Electrode Detector– HSED (Chinese patent #zl 201710 676008.3). In this paper, we first study dead zone of the new structure and find dead zone of non-elongated HSED cell is smaller than that of CSESD. An array arrangement method of CSESD is also proposed, which makes virtually no dead zone in the array comprised by elongated detector cells. Detector electrical simulations with SILVACO TCAD, including I-V and C-V characteristic, will be given. Then, the structure with different nesting depth and dbot is simulated with SILVACO TCAD. It has been found that the closer nesting position is to the surface, the smaller dead zone is, and the deeper the nesting is, the larger the dead zone is. However, through the simulation of the weighting field, it is found that the deeper the nesting depth, the smaller the influence of the weighting field by neighboring cell.

Nickel@Nickel Oxide Core–Shell Electrode with Significantly Boosted Reactivity for Ultrahigh‐Energy and Stable Aqueous Ni–Zn Battery

AbstractThe main bottlenecks of aqueous rechargeable Ni–Zn batteries are their relatively low energy density and poor cycling stability, mainly arising from the low capacity and inferior reversibility of the current Ni‐based cathodes. Additionally, the complicated and difficult‐to‐scale preparation procedures of these cathodes are not promising for large‐scale energy storage. Here, a facile and cost‐effective ultrasonic‐assisted strategy is developed to efficiently activate commercial Ni foam as a robust cathode for a high‐energy and stable aqueous rechargeable Ni–Zn battery. 3D Ni@NiO core–shell electrode with remarkably boosted reactivity and an area of 300 cm2 is readily obtained by this ultrasonic‐assisted activation method (denoted as SANF). Benefiting from the in situ formation of electrochemically active NiO and porous 3D structure with a large surface area, the as‐fabricated SANF//Zn battery presents ultrahigh capacity (0.422 mA h cm−2) and excellent cycling durability (92.5% after 1800 cycles). Moreover, this aqueous rechargeable SANF//Zn battery achieves an impressive energy density of 15.1 mW h cm−3 (0.754 mW h cm−2) and a peak power density of 1392 mW cm−3, outperforming most reported aqueous rechargeable energy‐storage devices. These findings may provide valuable insights into designing large‐scale and high‐performance 3D electrodes for aqueous rechargeable batteries.

Anisotropic mechanical properties of Si anodes in a lithiation process of lithium-ion batteries

High-capacity active electrodes, such as Si anodes in Li-ion batteries, undergo a significant volume deformation of up to $$\sim $$ 400% during lithiation. Such a huge volume change could cause mechanical fracture and pulverization of electrode materials and result in harmful effects on their electrochemical performance. To have better understanding on this problem, the two-phase lithiation process of hollow core–shell and film structural electrodes is simulated by using a diffusion lithiation model. It is shown that the anisotropic hoop stress is larger than the isotropic one, which may easily induce damage of hollow core–shell negative electrodes. In addition, the anisotropic nature of mechanical properties can also remarkably magnify the edge stress intensity factor of hollow core–shell and film electrodes. These results on the morphological evolution and stress generation shed light on the design of novel and failure-resistant electrodes.

Light‐Driven Water Splitting Mediated by Photogenerated Bromine

AbstractLight‐driven water splitting was achieved using a dye‐sensitized mesoporous oxide film and the oxidation of bromide (Br−) to bromine (Br2) or tribromide (Br3−). The chemical oxidant (Br2 or Br3−) is formed during illumination at the photoanode and used as a sacrificial oxidant to drive a water oxidation catalyst (WOC), here demonstrated using [Ru(bda)(pic)2], (1; pic=picoline, bda=2,2′‐bipyridine‐6,6′‐dicarboxylate). The photochemical oxidation of bromide produces a chemical oxidant with a potential of 1.09 V vs. NHE for the Br2/Br− couple or 1.05 V vs. NHE for the Br3−/Br− couple, which is sufficient to drive water oxidation at 1 (RuV/IV≈1.0 V vs. NHE at pH 5.6). At pH 5.6, using a 0.2 m acetate buffer containing 40 mm LiBr and the [Ru(4,4′‐PO3H2‐bpy)(bpy)2]2+ (RuP2+, bpy=2,2′‐bipyridine) chromophore dye on a SnO2/TiO2 core–shell electrode resulted in a photocurrent density of around 1.2 mA cm−2 under approximately 1 Sun illumination and a Faradaic efficiency upon addition of 1 of 77 % for oxygen evolution.

TiO2–Co3O4 Core–Shell Nanorods: Bifunctional Role in Better Energy Storage and Electrochromism

A suitably designed heterostructured TiO2–Co3O4 core–shell nanorod array has been found to exhibit improved supercapacitive as well as electrochromic properties as compared to the nanowires of either of the oxides when used individually. The core–shell nanostructures have been grown on an FTO coated glass substrate by preparing TiO2 nanorods through hydrothermal reaction followed by growing a Co3O4 shell layer by electrodeposition. The core–shell electrode shows high specific and areal capacitance of ∼342 F/g and ∼140 mF/cm2 (at scan rate of 100 mV/s), respectively. Such an improvement in supercapacitive behavior, as compared to the behavior of the existing ones, is likely due to increased surface area and modified charge dynamics within the core–shell heterojunction. Additionally, these core–shells also exhibit stable and power efficient bias induced color change between transparent (sky blue) and opaque (dark brown) states with coloration efficiency of ∼91 cm2/C. Porous morphology and strong adhesion to...

Ultrafast dye regeneration in a core-shell NiO-dye-TiO2 mesoporous film.

In this study, a core-shell NiO-dye-TiO2 mesoporous film was fabricated for the first time, utilizing atomic layer deposition technique and a newly designed triphenylamine dye. The structure of the film was confirmed by SEM, TEM, and EDX. Excitation of the dye led to efficient and fast charge separation, by hole injection into NiO, followed by an unprecedentedly fast dye regeneration (t1/2 ≤ 500 fs) by electron transfer to TiO2. The resulting charge separated state showed a pronounced transient absorption spectrum caused by the Stark effect, and no significant decay was found within 1.9 ns. This indicates that charge recombination between NiO and TiO2 is much slower than that between the NiO and the reduced dye in the absence of the TiO2 layer (t1/2 ≈ 100 ps).

Controlled 3D Carbon Nanotube Architecture Coated with MoOx Material by ALD Technique: A High Energy Density Lithium‐Ion Battery Electrode

Due to its high theoretical capacity, energy density, and excellent reversibility with Li/Li+, molybdenum oxide is one of the vastly studied electrode material in lithium‐ion batteries. However, like most of the oxides, it also suffers from poor cyclic stability because of its low electrical conductivity. In 3D core–shell structure prepared by atomic layer deposition coating, it can provide superiority in nanoscale decoration than other deposition methods because of its extreme conformality and precise thickness control on high aspect ratio surfaces. This report illustrates the electrochemical activity of 3D core–shell type amorphous MoOx material coated by atomic layer deposition technique on conducting carbon nanotubes (CNT) scaffold which exhibits excellent overall cell capacity. The obtained capacity is manifold higher than its planar 2D counterpart and that can become an advanced nanoscale fabrication methodology of such 3D nanostructures for electrode preparation. Such binder free MoOx/CNT core–shell electrode structure shows very high and stable electrochemical activity toward Li/Li+ system. An optimal thickness of MoOx on CNT is also found out in order to attain the most stable cyclic performance of this nanostructure. A stable reversible areal capacity of 645 µAh cm−2 with specific capacity of 915 mAh g−1 is achieved from optimized MoOx/CNT assembly.

A Shell‐Shaped Carbon Architecture with High‐Loading Capability for Lithium Sulfide Cathodes

Lithium sulfide (Li2S) is considered a highly attractive cathode for establishing high‐energy‐density rechargeable batteries, especially due to its high charge‐storage capacity and compatibility with lithium‐metal‐free anodes. Although various approaches have recently been pursued with Li2S to obtain high performance, formidable challenges still remain with cell design (e.g., low Li2S loading, insufficient Li2S content, and an excess electrolyte) to realize high areal, gravimetric, and volumetric capacities. This study demonstrates a shell‐shaped carbon architecture for holding pure Li2S, offering innovation in cell‐design parameters and gains in electrochemical characteristics. The Li2S core–carbon shell electrode encapsulates the redox products within the conductive shell so as to facilitate facile accessibility to electrons and ions. The fast redox‐reaction kinetics enables the cells to attain the highest Li2S loading of 8 mg cm−2 and the lowest electrolyte/Li2S ratio of 9/1, which is the best cell‐design specifications ever reported with Li2S cathodes so far. Benefiting from the excellent cell‐design criterion, the core–shell cathodes exhibit stable cyclability from slow to fast cycle rates and, for the first time, simultaneously achieve superior performance metrics with areal, gravimetric, and volumetric capacities.

ZnO/TiO2 core–shell photoelectrodes for dye-sensitized solar cells by screen printing and room temperature ALD

Mesoporous photoelectrodes for dye-sensitized solar cells (DSSCs) in a ZnO/TiO2 core–shell structure have been fabricated at low temperature by combination of screen printing of ZnO nanoparticles and room temperature atomic layer deposition (ALD) of TiO2. ALD nicely achieved a uniform coating of the individual ZnO particles with a thin skin of TiO2 of uniform thickness. The overall mesoporous structure was unchanged, so that a high surface area for dye adsorption and pores for penetration of the electrolyte solution were preserved. DSSCs employing the core–shell electrode sensitized with D149 indoline dye achieved a higher open circuit voltage (V OC) than that with ZnO, but accompanied with a decrease of short circuit photocurrent density (J SC) due to decreased efficiency of electron injection. Increase of the recombination resistance to extend the electron lifetime by the TiO2 shell has been confirmed by electrochemical impedance spectroscopy (EIS). X-ray diffraction analysis has revealed that the ALD TiO2 is amorphous and can only be converted to crystalline anatase TiO2 by annealing at 450 °C. The crystallization recovered current but lost the advantage of the voltage increase. EIS has indicated a high trap density introduced by the amorphous ALD TiO2, which could be reduced by crystallization, but accompanied with an increased rate of recombination.

Impact of In2S3 shells thickness on the electrochemical and optical properties of oriented ZnO/In2S3 core/shell nanowires

In this paper, we address the effect of shell thickness and core/shell structure on the electrochemical and photoelectrochemical cell (PEC) measurements properties of ZnO/In2S3 core/shell nanowires (NWs). The objective is to elucidate the mechanisms responsible for the extended photoresponse of ZnO/In2S3 core/shell NWs to solar radiation. Well aligned ZnO/In2S3 core/shell NWs were fabricated on indium tin oxide substrates using electrochemically grown ZnO NWs as the cores and electrodeposited In2S3 as the shells. The samples structure was characterized by X-ray diffraction, revealing the mixed wurtzite and tetragonal structures of both ZnO cores and In2S3 shells, and the improvement in the structure with the increases of In2S3 shell thickness. The optical properties were studied through optical absorbance and photoluminescence measurements, showing the optical properties featured with type-II heterogeneous nanostructures constructed from ZnO and In2S3. Electrochemical impedance spectroscopy (EIS) is employed and an equivalent circuit model is designed suggesting that the cell performances were affected by increasing In2S3 shell deposition times. From Mott–Schottky plots, several parameters such as flat-band potential and free carrier concentration were determined. Next, from (PEC) measurements, the highest photocurrent density produced by the In2S3 shell electrode prepared at deposition time of 5 min reached 9.30 mA cm2 at an applied potential of 0.8 V vs. Ag/AgCl. This value was about 6.8 times as much as more than that measured on ZnO NWs one and provided the highest value of solar-to-hydrogen energy efficiency η (%). These results are very encouraging and suggest that In2S3 covered ZnO NWs nanostructures are valuable photo-anodes in order to build cheap devices for solar energy-to-hydrogen generation devices.

Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode

Ultra-fast (∼1 s) and highly sensitive (1889.8 μA mM−1 cm−2) enzyme-free glucose biosensing on a unique NiNiO core–shell electrode.

Correction: Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode

Correction for ‘Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode’ by Halima Begum et al., RSC Adv., 2017, 7, 3554–3562.

A single wire as all-inclusive fully functional supercapacitor

A key challenge in wire-shaped energy storage devices is their complete encapsulation for practical applications. Hence it is of great importance to design and fabricate an all-inclusive structure in which inner and outer current collectors, active materials, electrolyte and separator are all enclosed in a single wire structure. However, due to the surface area differences between the shell and core electrodes, the matching of the capacitance on both electrodes become a challenging task. We solved this problem by using multiple thin Ni wires with three-dimensional MnO2-carbon nanotubes (CNTs)-graphene hybrids as the core electrode and a Ni tube as the shell electrode in a coaxial-cable supercapacitors structure. Within the seamless tubular electrode, all the necessary components are included and protected by the metal tube shell. The fully encapsulated single wire devices show a high area-normalized capacitance of 31mFcm−2 at a current density of 0.29mAcm−2, comparable to the best cable devices with more exposed structures. Such devices are more suitable for applications by providing more mechanical stability and avoiding exposure and loss of electrolytes during operation.

Light-Driven Water Splitting by a Covalently Linked Ruthenium-Based Chromophore–Catalyst Assembly

The preparation and characterization of new Ru(II) polypyridyl-based chromophore–catalyst assemblies, [(4,4′-PO3H2-bpy)2Ru(4-Mebpy-4′-epic)Ru(bda)(pic)]2+ (1, bpy = 2,2′-bipyridine; 4-Mebpy-4′-epic = 4-(4-methylbipyridin-4′-yl-ethyl)-pyridine; bda = 2,2′-bipyridine-6,6′-dicarboxylate; pic = 4-picoline), and [(bpy)2Ru(4-Mebpy-4′-epic)Ru(bda)(pic)]2+ (1′) are described, as is the application of 1 in a dye-sensitized photoelectrosynthesis cell (DSPEC) for solar water splitting. On SnO2/TiO2 core–shell electrodes in a DSPEC configuration with a Pt cathode, the chromophore–catalyst assembly undergoes light-driven water oxidation at pH 5.7 in a 0.1 M acetate buffer, 0.5 M in NaClO4. With illumination by a 100 mW cm–2 white light source, photocurrents of ∼0.85 mA cm–2 were observed after 30 s under a 0.1 V vs Ag/AgCl applied bias with a faradaic efficiency for O2 production of 74% measured over a 5 min illumination period.