Project description:Coevaporation of perovskite films allows for a fine control over the material stoichiometry and thickness but is typically slow, leading to several-hour processes to obtain thick films required for photovoltaic applications. In this work, we demonstrate the coevaporation of perovskite layers using faster deposition rates, obtaining 1 μm thick films in approximately 50 min. We observed distinct structural properties and obtained devices with efficiency exceeding 19%, demonstrating the relevance of this deposition process from a material perspective and also in view of potential industrialization.
Project description:The development of high volumetric or areal capacitance energy storage devices is critical for the future electronic devices. Hence, the hunting for next-generation electrode materials and their design is of current interest. The recent work in the two-dimensional metal hydroxide nanomaterials demonstrates its ability as a promising candidate for supercapacitor due to its unique structure and additional redox sites. This study reports a design of freestanding high-mass-loaded copper-cobalt hydroxide interconnected nanosheets for high-volumetric/areal-performance electrode. The unique combination of hydroxide electrode with high mass loading (26 mg/cm2) exhibits high areal and volumetric capacitance of 20.86 F/cm2 (1032 F/cm3) at a current density of 10 mA/cm2. This attributes to the direct growth of hydroxides on porous foam and conductivity of copper, which benefits the electron transport. The asymmetric supercapacitor device exhibits a high energy density of 21.9 mWh/cm3, with superior capacitance retention of 96.55% over 3500 cycles.
Project description:Self-supporting electrode materials with the advantages of a simple operation process and the avoidance of the use any binders are promising candidates for supercapacitors. In this work, carbon-based self-supporting electrode materials with nanosheets grown on Al foil were prepared by combining hydrothermal reaction and the one-step chemical vapor deposition method. The effect of the concentration of the reaction solution on the structures as well as the electrochemical performance of the prepared samples were studied. With the increase in concentration, the nanosheets of the samples became dense and compact. The CNS-120 obtained from a 120 mmol zinc nitrate aqueous solution exhibited excellent electrochemical performance. The CNS-120 displayed the highest areal capacitance of 6.82 mF cm-2 at the current density of 0.01 mA cm-2. Moreover, the CNS-120 exhibited outstanding rate performance with an areal capacitance of 3.07 mF cm-2 at 2 mA cm-2 and good cyclic stability with a capacitance retention of 96.35% after 5000 cycles. Besides, the CNS-120 possessed an energy density of 5.9 μWh cm-2 at a power density of 25 μW cm-2 and still achieved 0.3 μWh cm-2 at 4204 μW cm-2. This work provides simple methods to prepared carbon-based self-supporting materials with low-cost Al foil and demonstrates their potential for realistic application of supercapacitors.
Project description:Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m(2) g(-1) is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA(+), diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm(-2) and high energy density of 10/39 Wh kg(-1) at power of 52/286 kW kg(-1) in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively.
Project description:Being a low-cost, mass-production-compatible route to attain crystalline silicon, post-deposition crystallization of amorphous silicon has received intensive research interest. Here we report a low-temperature (300 °C), rapid (crystallization rate of ~17 nm/min) means of a-Si:H crystallization based on high-density hydrogen plasma. A model integrating the three processes of hydrogen insertion, etching, and diffusion, which jointly determined the hydrogenation depth of the excess hydrogen into the treated micrometer thick a-Si:H, is proposed to elucidate the hydrogenation depth evolution and the crystallization mechanism. The effective temperature deduced from the hydrogen diffusion coefficient is far beyond the substrate temperature of 300 °C, which implies additional driving forces for crystallization, i.e., the chemical annealing/plasma heating and the high plasma sheath electric field. The features of LFICP (low-frequency inductively coupled plasma) and LFICP-grown a-Si:H are also briefly discussed to reveal the underlying mechanism of rapid crystallization at low temperatures.
Project description:Functional carbonaceous materials for supercapacitors (SCs) without using acid for post-treatment remain a substantial challenge. In this paper, we present a less harmful strategy for preparing three-dimensional (3D) N,O-codoped egg-box-like carbons (EBCs). The as-prepared EBCs with opened pores provide plentiful channels for ion fast transport, ensure the effective contact of EBCs electrodes and electrolytes, and enhance the electron conduction. The nitrogen and oxygen atoms doped in EBCs improve the surface wettability of EBC electrodes and provide the pseudocapacitance. Consequently, the EBCs display a prominent areal capacitance of 39.8 μF cm-2 (340 F g-1) at 0.106 mA cm-2 in 6 M KOH electrolyte. The EBC-based symmetric SC manifests a high areal capacitance to 27.6 μF cm-2 (236 F g-1) at 0.1075 mA cm-2, a good rate capability of 18.8 μF cm-2 (160 F g-1) at 215 mA cm-2 and a long-term cycle stability with only 1.9% decay after 50,000 cycles in aqueous electrolyte. Impressively, even in all-solid-state SC, EBC electrode shows a high areal capacitance of 25.0 μF cm-2 (214 F g-1) and energy density of 0.0233 mWh cm-2. This work provides an acid-free process to prepare electrode materials from industrial by-products for advanced energy storage devices.
Project description:Over the past few years, the flexible quasi-solid-state zinc-ion hybrid supercapacitors (FQSS ZHSCs) have been found to be ideal for wearable electronics applications due to their high areal capacitance and energy density. The assembly of desirable ZHSCs devices that have promising practical applications is of high importance, whereas it is still challenging to assemble ZHSCs devices. In this study, a ZHSC that exhibited ultrahigh areal capacitance and high stability was developed by using an active carbon cloth (ACC) cathode, which could improve ionic adsorption. The as-obtained ACC cathode had an energy storage mechanism due to the electrical double-layer capacitive behavior of Zn2+, which was accompanied by the dissolution/deposition of Zn4SO4(OH)6·5H2O. The ACC//Zn@ACC ZHSC device exhibited an areal capacitance of 2437 mF cm-2 (81 F cm-3, 203 F g-1 under the mass of ACC with ∼12 mg cm-2) at 1 mA cm-2, an areal energy density of 1.354 mWh cm-2 at 1 mW cm-2, as well as high stability (with an insignificant capacitance decline after 20000 cycles), which was demonstrated to outperform the existing ZHSCs. Furthermore, the assembled flexible device still had competitive capacitance, energy density and service life when integrated into a FQSS ZHSC. When applied in practice, the device could achieve high mechanical flexibility, wearable stability and output. This study can inspire the development of the FQSS ZHSC device to satisfy the demands for wearable energy storage devices with high performance.
Project description:Layered hierarchical CoMoO4 nano-structured arrays grown on nickel foam were designed and synthesized by a two-step hydrothermal method following by annealing. With the increase in the nearly three times loading mass of active materials, the specific capacitance of the layered hierarchical CoMoO4 nano-structured arrays only shows a slight loss compared with the single-layer CoMoO4 nano-structured arrays, which dramatically improved the areal capacitance from 2.47 to 6.79 F cm-2. Also, the layered hierarchical CoMoO4 nano-structured arrays showed 94.8% capacitance retention after 2500 cycles, which is mainly due to the well-designed layered hierarchical structure and good conductivity.
Project description:The recent high-resolution structure of the thick filament from Lethocerus asynchronous flight muscle shows aspects of thick filament structure never before revealed that may shed some light on how striated muscles function. The phenomenon of stretch activation underlies the function of asynchronous flight muscle. It is most highly developed in flight muscle, but is also observed in other striated muscles such as cardiac muscle. Although stretch activation is likely to be complex, involving more than a single structural aspect of striated muscle, the thick filament itself, would be a prime site for regulatory function because it must bear all of the tension produced by both its associated myosin motors and any externally applied force. Here we show the first structural evidence that the arrangement of myosin heads within the interacting heads motif is coupled to the structure of the thick filament backbone. We find that a change in helical angle of 0.16° disorders the blocked head preferentially within the Lethocerus interacting heads motif. This observation suggests a mechanism for how tension affects the dynamics of the myosin heads leading to a detailed hypothesis for stretch activation and shortening deactivation, in which the blocked head preferentially binds the thin filament followed by the free head when force production occurs.
Project description:Metal-organic frameworks (MOFs) with hierarchical porous structures have been attracting intense interest currently due to their promising applications in catalysis, energy storage, drug delivery, and photocatalysis. Current fabrication methods usually employ template-assisted synthesis or thermal annealing at high temperatures. However, large-scale production of hierarchical porous metal-organic framework (MOF) particles with a simple procedure and mild condition is still a challenge, which hampers their application. To address this issue, we proposed a gelation-based production method and achieved hierarchical porous zeolitic imidazolate framework-67 (called HP-ZIF67-G thereafter) particles conveniently. This method is based on a metal-organic gelation process through a mechanically stimulated wet chemical reaction of metal ions and ligands. The interior of the gel system is composed of small nano and submicron ZIF-67 particles as well as the employed solvent. The relatively large pore size of the graded pore channels spontaneously formed during the growth process is conducive to the increased transfer rate of substances within the particles. It is proposed that the Brownian motion amplitude of the solute is greatly reduced in the gel state, which leads to porous defects inside the nanoparticles. Furthermore, HP-ZIF67-G nanoparticles interwoven with polyaniline (PANI) exhibited an exceptional electrochemical charge storage performance with an areal capacitance of 2500 mF cm-2, surpassing those of many MOF materials. This stimulates new studies on MOF-based gel systems to obtain hierarchical porous metal-organic frameworks which should benefit further applications in a wide spectrum of fields ranging from fundamental research to industrial applications.