Dendrite growth inhibition in a V6O13 nanorods based non-aqueous Zn-ion battery by a scalable polycarbazole@Carbon nanotubes overlayer

Inhibiting the growth of dendrites, one of the most serious issues faced by zinc-ion batteries (ZIBs) is addressed by coating the Zn anode with a layer of poly(carbazole)-carbon nanotubes (PCz@CNTs) composite. The electrically conducting robust composite overlayer ensures that the Zn-deposition during charging cycles is homogeneous and completely free of any fiber-like growth. This is confirmed from the cross-sectional electron microscopy analysis of post-cycled PCz@CNTs@Zn electrode. A vanadium oxide nanorods-porous graphitic flakes (V6O13 NRs@PGFs) composite is used as a cathode. It has a large specific surface area, affording short ion-diffusion distances and many vacant sites thus permitting facile Zn2+ ion ingress and egress, is used. A remarkable performance results for the non-aqueous ZIB: V6O13 NRs@PGFs//PCz@CNTs@Zn with a capacity of 286 mAh g−1 after 300 cycles at 30 mA g−1 (with 98% capacity retention), energy density of ∼172 Wh kg−1 and a nominal voltage of 1.8 V. It is significantly enhanced compared to its analogous ZIB of V6O13 NRs@PGFs//Zn (193 mAh g−1, and 80% capacity retention). The PCzCNTs overlayer imparts long lifespan with nominal capacity fade, guarantees ultra-safe operation, is cost-effective and also easy to scale-up thus providing a solution that can be adapted to other metal-ion batteries free of dendrites and long term cycling stability

Photo-rechargeable battery with an energetically aligned beetroot Dye/Cl-Graphene quantum dots/MoO3 nanorods composite

A stand-alone, low-cost non-aqueous photo-rechargeable zinc ion battery configuration is presented. The photo-battery integrates the functions of energy conversion and storage in a single device thus minimizing space and material requirements as well as cost. The cell is based on a photocathode with TiO2 and MoO3-nanorods (NRs) as the storage layers, with additional roles of electron transport layer and photosensitizer for TiO2 and MoO3 respectively. Photoactive beetroot (BT) dye and Cl-doped graphene quantum dots (GQDs) were also incorporated therein to yield the TiO2/BT/Cl-GQDs/MoO3-NRs composite photocathode for broad spectral utilization. Under irradiance, the BT dye, Cl-GQDs and MoO3 undergo electron-hole separation, channel the electrons to the external circuit via TiO2 through aligned energy levels and simultaneously charge the battery to ∼1 V, without the application of any external bias or current. The photo-charging and discharge capacities of the photo-battery: TiO2/BT/Cl-GQDs/MoO3-NRs/Zn2+/Zn-AC in the biased mode under an applied current density of 21 mA g−1 and under 1 sun irradiance (100 mW cm−2, AM 1.5 G) are 104 mAh g−1 and 240 mAh g−1 respectively. The photo-charging capacity under 1 sun irradiance in the unbiased mode is ∼75 mAh g−1. A Zn-activated carbon composite (derived from lemon pieces) as the anode electro-catalyzes the reduction of Zn2+ during photo-charging, leading to a power conversion efficiency of 4.03 % under one sun illumination. This has a cycle life of 200 cycles and offers a constant photocurrent of 8.3 mA cm−2 with a hold time of more than 100 s under irradiance which can easily charge any small electronic device. It is an economically viable configuration with huge technological potential for possible commercialization

Performance evaluation of HCOOH micro-fluidic fuel cell using Ni wire electrode

A membrane-free low cost microfluidic fuel cell (μFFC) consisting a trident shaped channel is molded into a poly(dimethyl siloxane) block and Ni wires affixed therein that doubled up as the catalyst and electrical connectors. Streams of aqueous acidic solutions of formic acid as the anolyte (fuel), KMnO4 as the catholyte (oxidant) and an acid electrolyte, flown through the respective channels at a constant rate ensured laminar flow across the length of the channels, while being in contact with the Ni wires, thereby tapping its’ catalytic activity for good electrochemical performance. The effect of varying fuel or oxidant concentration on the μFFC performance is studied. In the chronopotentiometric mode, the high catalytic activity of Ni allows high currents of the order of 1.25 mA to be sustained by the cell, particularly when the surface is fresh, and this current drops when the deposition of Mn, K, and S occurs. A flow rate of 150 μL/min. is found to be optimal, as the highest open-circuit voltage (OCV) of 1.33 V is attained at this flow rate. While the cell performance is largely unaffected by formic acid concentration, but it is controlled by KMnO4 concentration. Higher oxidant concentrations yielded higher OCVs, due to more amount of the five-electron reaction, occurring at the cathode enhancing the charge separation and hence the OCV. DRT studies of the EIS data resolved two different time constants for the anodic and cathodic processes. The μFFC delivers a maximum power density of 2.1 mW/cm2 and a stable current of 3.5 mA/cm2 for more than 10 min. at 0.6 V, thus validating its deployment in a variety of applications like diagnostic devices and as an independent power supply for MEMS devices

Revelation of graphene-Au for direct write deposition and characterization

Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties

Solar Cell with PbS Quantum Dots Sensitized TiO 2 -Multiwalled Carbon Nanotubes Composite, Sulfide-titania gel and Tin Sulfide Coated C-fabric

Novel approaches to boost quantum dot solar cell (QDSC) efficiencies are in demand. Herein, three strategies are used: (i) a hydrothermally synthesized TiO2–multiwalled carbon nanotube (MWCNT) composite instead of conventional TiO2, (ii) a counter electrode (CE) that has not been applied to QDSCs until now, namely, tin sulfide (SnS) nanoparticles (NPs) coated over a conductive carbon (C)-fabric, and (iii) a quasi-solid-state gel electrolyte composed of S2−, an inert polymer and TiO2 nanoparticles as opposed to a polysulfide solution based hole transport layer. MWCNTs by virtue of their high electrical conductivity and suitably positioned Fermi level (below the conduction bands of TiO2 and PbS) allow fast photogenerated electron injection into the external circuit, and this is confirmed by a higher efficiency of 6.3% achieved for a TiO2–MWCNT/PbS/ZnS based (champion) cell, compared to the corresponding TiO2/PbS/ZnS based cell (4.45%). Nanoscale current map analysis of TiO2 and TiO2–MWCNTs reveals the presence of narrowly spaced highly conducting domains in the latter, which equips it with an average current carrying capability greater by a few orders of magnitude. Electron transport and recombination resistances are lower and higher respectively for the TiO2–MWCNT/PbS/ZnS cell relative to the TiO2/PbS/ZnS cell, thus leading to a high performance cell. The efficacy of SnS/C-fabric as a CE is confirmed from the higher efficiency achieved in cells with this CE compared to the C-fabric based cells. Lower charge transfer and diffusional resistances, slower photovoltage decay, high electrical conductance and lower redox potential impart high catalytic activity to the SnS/C-fabric assembly for sulfide reduction and thus endow the TiO2–MWCNT/PbS/ZnS cell with a high open circuit voltage (0.9 V) and a large short circuit current density (∼20 mA cm−2). This study attempts to unravel how simple strategies can amplify QDSC performances

Electrochemistry of poly(3,4-ethylenedioxythiophene)-polyaniline/Prussian blue electrochromic devices containing an ionic liquid based gel electrolyte film

Electrochromic devices based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the cathodic coloring electrode and polyaniline (PANI) or Prussian blue (PB) as the counter electrode containing a highly conductive, self-supporting, distensible and transparent polymer–gel electrolyte film encapsulating an ionic liquid, 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide, have been fabricated. Polarization, charge transfer and diffusion processes control the electrochemistry of the functional electrodes during coloration and bleaching and these phenomena differ when PEDOT and PANI/PB were employed alternately as working electrodes. While the electrochemical impedance response shows good similitude for PEDOT and PANI electrodes, the responses of PEDOT and PB were significantly different in the PEDOT–PB device, especially during reduction of PB, wherein the overall amplitude of the impedance response is enormous. Large values of the coloration efficiency maxima of 281 cm2 C−1 (λ = 583 nm) and 274 cm2 C−1 (λ = 602 nm), achieved at −1.0 and −1.5 V for the PEDOT–PANI and PEDOT–PB devices have been correlated to the particularly low magnitude of charge transfer resistance and high polarization capacitance operative at the PEDOT–ionic liquid based electrolyte interface at these dc potentials, thus allowing facile ion-transport and consequently resulting in enhanced absorption modulation. Moderately fast switching kinetics and the ability of these devices to sustain about 2500 cycles of clear-to-dark and dark-to-clear without incurring major losses in the optical contrast, along with the ease of construction of these cells in terms of high scalability and reproducibility of the synthetic procedure for fabrication of the electrochromic films and the ionic liquid based gel electrolyte film, are indicators of the promise these devices hold for practical applications like electrochromic windows and displays

Highly conductive poly(3,4-ethylenedioxypyrrole) and poly(3,4-ethylenedioxythiophene) enwrapped Sb2S3 nanorods for flexible supercapacitors

Composites of poly(3,4-ethylenedioxypyrrole) or PEDOP and poly(3,4-ethylenedioxythiophene) or PEDOT enwrapped Sb2S3 nanorods have been synthesized for the first time for use as supercapacitor electrodes. Hydrothermally synthesized Sb2S3 nanorods, several microns in length and 50-150 nm wide, offer high surface area and serve as a scaffold for coating conducting polymers, and are a viable alternative to carbon nanostructures. Fibrillar morphologies are achieved for the PEDOP-Sb2S3 and PEDOT-Sb2S3 films in contrast to the regular granular topologies attained for the neat polymers. The remarkably high nanoscale (similar to 5 S cm(-1)) conductivity of the Sb2S3 nanorods enables facile electron transport in the composites. We constructed asymmetric supercapacitors using the neat polymer or composite and graphite as electrodes. High specific capacitances of 1008 F g(-1) and 830 F g(-1) (at 1 A g(-1)), enhanced power densities (504 and 415 W kg(-1)) and excellent cycling stability (88 and 85% capacitance retention at the end of 1000 cycles) are delivered by the PEDOP-Sb2S3 and PEDOT-Sb2S3 cells relative to the neat polymer cells. A demonstration of a light emitting diode illumination using a light-weight, flexible, supercapacitor fabricated with PEDOP-Sb2S3 and carbon-fiber cloth shows the applicability of Sb2S3 enwrapped conducting polymers as sustainable electrodes for ultra-thin supercapacitors

A Dual Electrochrome of Poly-(3,4-Ethylenedioxythiophene) Doped by N,N’-Bis(3-sulfonatopropyl)-4-4’-bipyridinium—Redox Chemistry and Electrochromism in Flexible Devices

An electrochromic zwitterionic viologen, N,N’-bis(3-sulfonatopropyl)- 4-4’-bipyridinium, has been used for the first time for doping poly (3,4-ethylenedioxythiopene) (PEDOT) films during electropolymerization. Slow and fast diffusional rates for the monomer at deposition potentials of +1.2 and +1.8 V, respectively yielded the viologen-doped PEDOT films with granular morphology and with dendrite-like shapes. The dual electrochrome formed at +1.8 V, showed enhanced coloration efficiency,larger electrochemical charge storage capacity, and superior redox activity in comparison to its analogue grown at +1.2 V, thus demonstrating the role of dendritic shapes in amplifying electrochromism. Flexible electrochromic devices fabricated with the viologen-doped PEDOT film grown at +1.8 V and Prussian blue with an ionic liquid-based gel electrolyte film showed reversible coloration between pale and dark purple with maximum coloration efficiency of 187 cm2C1 at l=693 nm. The diffusional impedance parameters and switching kinetics of the device showed the suitability of this dual electrochrome formed as a single layer for practical electrochromic cells