Nanocomposite Thin Film Electrodes Research Articles

Ion beam irradiation induced modification of PPy/ZnO nanocomposite thin films for supercapacitor applications

Thin films of Polypyrrole/Zinc Oxide (PPy/ZnO) nanocomposite were fabricated using electrodeposition and subjected to 100 MeV Ag10+ ion beam irradiation at various fluences ranging from 1.0 × 1010 to 1.0 × 1012 ions cm-2. We characterized the well-synthesized PPy/ZnO nanocomposite thin films and examined the modification induced by irradiation using XRD, Raman, FTIR, FESEM-EDS, and AFM techniques. FESEM and AFM images reveal that PPy/ZnO exhibits a cauliflower-like nanosphere structure. An increase in roughness indicates a larger surface area of the electrode, which improves capacitive performance at 1.0 × 1010 ions cm-2, enhancing ion transport from the electrode surface to the bulk. The damage tracks formed by highly energetic ions along their path may contribute to more charge storage by increasing the roughness of the nanocomposite thin film electrodes for energy storage applications. We evaluated the electrochemical performance of thin films using CV, EIS, and GCD measurements. Electrochemical studies reveal enhanced capacitive properties up to 1.0 × 1010 ions cm-2 fluence and decrease at higher fluences. The irradiated nanocomposites achieve a higher specific capacitance of 323.11 F g-1, and the fabricated device shows cyclic stability of 86 %, a remarkable power density (P) of 0.72 kW kg-1, and an energy density (Ep) of 6.32 Wh kg-1.

Effect of precursor solution parameters on the formation of yttria stabilized zirconia coatings on yttria stabilized bismuth oxide substrates

A useful intermediate temperature solid oxide fuel cell design could be the utilization of yttria doped bismuth oxide (YDB) ceramics as electrolyte supports, which would also enable the use of high-performing nanocomposite thin film electrodes. However, to prevent the reduction of YDB down to metal upon contact with hydrogen, a thin, chemically stable ionic conductor ceramic coating must be applied onto the fuel side of the anode. In this work, we aim to determine the optimum parameters to fabricate dense and crack-free yttria-stabilized zirconia (YSZ) doped zirconia coatings onto sintered yttria doped bismuth oxide (YDB) ceramics by a facile, cost effective polymeric precursor method, for the first time in the literature. We have found that the most commonly used Zr source, zirconium oxychloride octahydrate, i) reacts with the YDB substrate to form bismuth yttrium oxychloride and ii) results in crack formation due to reduced extent of polymerization unless the solution is fed with nitric acid. Meanwhile, the use of zirconium oxynitrate hydrate forms dense, crack free thin films. Both thin films had low conductivities, in the range of 10−6 S/cm at 600 °C, likely, due to the lack of crystallization in their as-deposited state.

Au-incorporated NiO nanocomposite thin films as electrochromic electrodes for supercapacitors

Herein, we reported a facile synthesis of nanocomposite thin films containing Au nanoparticles within a NiO matrix using a simple and low-cost deposition apparatus. Au nanoparticle contents were controlled by changing the exposed areas of the nickel foil on the Au foil during sputtering. Surface plasmon resonance peaks were observed in the absorption spectrum, indicating that nano-sized Au particles were formed in the NiO matrix, which was also confirmed by electron microscopy and X-ray photoelectron spectroscopy. Highly conductive Au nanoparticles in NiO improved the electrical conductivity, and the Au-incorporated NiO nanocomposite thin film electrode exhibited greatly enhanced pseudo-capacitive property with a 1.5 times higher specific capacity than that of the pure NiO electrode even if it is not totally capacitive. This study provides a novel and facile method for the direct preparation of metal nanoparticles embedded in oxide nanocomposite films, which will offer exciting opportunities in supercapacitors. In addition, the prepared electrodes showed enhanced electrochromic capabilities and coloration efficiency, suggesting their potential for application in electrochromic smart glass monitoring by color change for energy storage.

Nickel–zinc sulfide nanocomposite thin film as an efficient cathode material for high-performance hybrid supercapacitors

Nickel–Zinc Sulfide nanocomposite (Ni–ZnS) thin film was prepared by RF magnetron co-sputtering method on a stainless steel substrate, which is used as the cathode material for hybrid supercapacitor. The as-prepared Ni–ZnS nanocomposite thin films exhibit a hexagonal structure with uniform morphology. The electrochemical results show that the Ni–ZnS nanocomposite thin film electrode exhibited a higher specific capacity when compared to the ZnS thin film. The Ni–ZnS-3 electrode has the highest specific capacity of 134 C g−1 (67 mC cm−2) at a scan rate of 10 mV s−1 with excellent cycling stability (10% loss of its initial specific capacity) even after 3500 cycles. The obtained results reveal that nickel doping has the significant effect on the electrochemical performance of zinc sulfide material and the as-fabricated material can be used as a potential positive electrode for hybrid supercapacitors.

Binary Lithium Titanate–Titania Nanocomposite Thin‐Film Electrodes for Electrochemical Energy Storage

AbstractThis work introduces a facile approach for preparation of binary nanocomposite thin film electrodes for lithium‐ion batteries with excellent storage capability, high rate performance, and good electrochemical stability. The Li4Ti5O12‐TiO2 film electrodes are prepared by radio frequency (RF) magnetron sputtering deposition using a Li4Ti5O12 and TiO2 powder mixture target as sputtering source in an argon atmosphere. The Li4Ti5O12–TiO2 electrode yields good electrochemical performance in terms of high capacity (295 mAh g−1) at a current density of 0.1 C, good cycling stability (≈5 % capacity loss after 100 cycles at 0.1 C), and excellent rate capability (158 mAh g−1 at a current density of 5 C). The factors contributing to the excellent electrochemical performance are related to the binary nanocomposite structure. The results suggest that the Li4Ti5O12–TiO2 nanocomposite thin film can be used as an anode material for high‐performance lithium‐ion batteries.

LiF-MO (M=Co, Fe, Ni) Nanocomposite Thin Film as Anode Materials for Lithium-ion Battery

To investigate the electrochemical performance of MO (M=Co, Fe, Ni) nanostructures on lithium insertion and extraction, size-controlled LiF-MO nanocomposite thin-film electrodes, consisting of metallic M and M oxide (MO) nanoparticles in an amorphous, inert LiF matrix, were designed and fabricated using a RF sputtering system with metallic M and LiF mixture targets. The structural and electrochemical properties of nanocomposite thin-film electrodes were characterized using TEM, SAED, XRD, XPS, and electrochemical measurements. The results showed that MO particles with average particle sizes of ca.10nm were well-dispersed in LiF matrix to form a kind of homogeneous LiFMO nanocomposite by the sputtering method. The inert medium of LiF provides an effective matrix to prevent the crystallization and agglomeration of MO during the deposition and electrochemical cycling of the thin film electrode, and then the well-formed nanophase structure in the nanocomposite thin-film electrodes leads to an excellent electrochemical cycling performance with the stable discharge specific capacity above 300mAh/g.

Stabilization of Ni-YSZ Nanocomposite Anodes by Deposition of a Thin YSZ Overlayer

Lowering the operating temperatures of solid oxide fuel cells (SOFCs) to below 600 °C is projected to enhance the long term stability of these devices by slowing down thermally induced microstructural changes in the electrodes. To minimize the electrode resistance caused by the lowered operating temperatures, the fabrication of nanocomposite Ni-YSZ thin film electrodes with high triple phase boundary (tpb) lengths is a possible approach. However, these nanocomposite electrodes will still undergo microstructural changes that could cause performance degradation. Here, it is shown that the long-term stability of nanocomposite Ni-YSZ anodes can be enhanced by the deposition of a thin, poroous, YSZ coating on the outer surface of the Ni-YSZ electrodes, preventing Ni diffusion out of the pores followed by Ni particle formation. A degradation rate of 0.072 Ω·cm2/hour was observed for the standard Ni-YSZ nanocomposite thin film anode, whereas a much lower degradation rate of 0.011 Ω·cm2/hour was achieved after applying the YSZ coating.

High temperature stability of electrically conductive Pt–Rh/ZrO2 and Pt–Rh/HfO2 nanocomposite thin film electrodes

Nanocomposite films made up of either Pt–Rh/ZrO2 or Pt–Rh/HfO2 materials were co-deposited using multiple e-beam evaporation sources onto langasite (La3Ga5SiO14) substrates, both as blanket films and as patterned interdigital transducer electrodes for surface acoustic wave sensor devices. The films and devices were tested after different thermal treatments in a tube furnace up to 1,200 °C. X-ray diffraction and electron microscopy results indicate that Pt–Rh/HfO2 films are stabilized by the formation of monoclinic HfO2 precipitates after high temperature exposure, which act as pinning sites to retard grain growth and prevent agglomeration of the conductive cubic Pt–Rh phase. The Pt–Rh/ZrO2 films were found to be slightly less stable, and contain both tetragonal and monoclinic ZrO2 precipitates that also helps prevent Pt–Rh agglomeration. Film conductivities were measured versus temperature for Pt–Rh/HfO2 films on a variety of substrates, and it was concluded that La and/or Ga diffusion from the langasite substrate into the nanocomposite films is detrimental to film stability. An Al2O3 diffusion barrier grown on langasite using atomic layer deposition was found to be more effective than a SiAlON barrier layer in minimizing interdiffusion between the nanocomposite film and the langasite crystal at temperatures above 1,000 °C.

Electrochemical decomposition of Li2CO3 in NiO–Li2CO3 nanocomposite thin film and powder electrodes

Two types of NiO–Li2CO3 nanocomposite electrodes have been prepared for the electrochemical decomposition studies. The thin film electrode with a thickness of 225 nm and grain size around 5–8 nm is prepared by a pulsed laser deposition method. The powder sample is prepared by a solution evaporation and calcination method with primary particle size in the range of 20–50 nm. Using ex situ TEM, Raman and FTIR spectroscopy and synchrotron based in situ XRD, the electrochemical decomposition of Li2CO3 phase in both types of the NiO–Li2CO3 nanocomposite electrodes after charging up to about 4.1 V vs Li+/Li at room temperature is clearly confirmed, but not in the electrode containing only Li2CO3. The NiO phase does not change significantly after charging process and may act as catalyst for the Li2CO3 decomposition. The potential of using NiO–Li2CO3 nanocomposite material as additional lithium source in cathode additive in lithium ion batteries has been demonstrated, which could compensate the initial irreversible capacity loss at the anode side.

Pt/AlPO4 nanocomposite thin-film electrodes for ethanol electrooxidation

The enhanced catalytic properties toward ethanol electrooxidation on Pt/AlPO4 nanocomposite thin-film electrodes were investigated. The Pt/AlPO4 nanocomposites with various Al/Pt ratios (0.27, 0.57, and 0.96) were fabricated by a co-sputtering method. All of the Pt/AlPO4 nanocomposites showed a negative shift in the onset potential and a higher current density than those of pure Pt electrode for the electrooxidation of ethanol. Among the various Pt/AlPO4 nanocomposite thin-film electrodes, the electrode with an atomic ratio of Al to Pt of 0.57 showed the highest electrocatalytic activity for ethanol electrooxidation. The activation enthalpy for the optimum Pt/AlPO4 nanocomposite was approximately 0.05 eV lower than that of pure Pt. It is believed that the enhancement in catalytic activity is due to the electron-rich Pt resulting from the Fermi-energy difference between Pt and AlPO4.

Manganese oxide embedded polypyrrole nanocomposites for electrochemical supercapacitor

Abstract MnO2 embedded PPy nanocomposite (MnO2/PPy) thin film electrodes were electrochemically synthesized over polished graphite susbtrates. Growing PPy polymer chains provides large surface area template that enables MnO2 to form as nanoparticles embeded within polymer matrix. Co-deposition of MnO2 and PPy has a complimentary action in which porous PPy matrix provides high active surface area for the MnO2 nanoparticles and, on the other hand, MnO2 nanoparticles nucleated over polymer chains contribute to enhanced conductivity and stability of the nanocomposite material by interlinking the PPy polymer chains. The MnO2/PPy nanocomposite thin film electrodes show significant improvement in the redox performance as cyclic voltammetric studies have shown. Specific capacitance of the nanocomposite is remarkably high (∼620 F g−1) in comparision to its constituents MnO2 (∼225 F g−1) and PPy (∼250 F g−1). Photoelectron spectroscopy studies show that hydrated manganese oxide in the nanocomposite exists in the mixed Mn(II) to Mn(IV) oxidation states. Accordingly, chemical structures of MnO2 and PPy constituents in the nanocomposite are not influenced by the co-deposition process. The MnO2/PPy nanocomposite electrode material however shows significantly improved high specific capacitity, charge–discharge stability and the redox performance properties suitable for application in the high energy density supercapcitors.

Net-like SnS/carbon nanocomposite film anode material for lithium ion batteries

SnS particles with sizes of 5.0–6.5 nm were prepared by a facile method. Resorcinol–formaldehyde sol with addition of the as-prepared SnS nanoparticles was spin-coated on a copper foil to prepare net-like SnS/C composite thin-film electrode for lithium ion batteries after carbonization at 650 °C. The SnS/C nanocomposite thin-film electrode showed preferable first coulombic efficiency and excellent cycling stability. The discharge and charge capacities were respectively 542.3 and 531.3 mAh/g after 40 cycles. The attractive electrochemical performances were mainly ascribed to the ultra fine particle, which showed no evident aggregation in high-resolution TEM image, and the effects of 3-dimensional net-like carbon structure, which uniformly surrounded the SnS nanoparticles to guarantee the contact, acted as a buffer matrix to alleviate the volume expansion of Li–Sn alloy and provided enough paths for electrolyte to reach SnS active material during discharge–charge process.

The Electrochemical Properties of LiF-Ni Nanocomposite Thin Film

Nanocomposite of LiF-Ni with a highly heterogeneous mixture was fabricated using pulsed laser deposition (PLD) method, and it exhibited remarkable electrochemical activity. The electrochemical reaction of LiF-Ni nanocomposite thin-film electrode with Li was first investigated by the discharge/charge and cyclic voltammetry. The initial charge capacity of the LiF-Ni/Li cell was found to be 107 mAh·g −1. The process of releasing Li from the as-deposited LiF-Ni nanocomposite thin films was confirmed by the ex-situ high-resolution transmission electron microscopy and the selected area electron diffraction measurements. These results provided a direct experimental evidence to support the electrochemical decomposition of LiF driven by the transition metal Ni in the potential range from 1.0 V to 4.0 V. LiF-Ni nanocomposite electrodes could be a novel and appropriate candidate for Li-storage materials.

Electrochemical and structural properties of MoO 3–V 2O 5 nanocomposite thin film electrodes for lithium rechargeable batteries

We have investigated the electrochemical properties of V 2O 5-based thin film electrodes as a function of the amount of MoO 3 by means of X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). XRD results show that the V 2O 5-based thin film electrodes give an amorphous characteristic. XPS results reveal the formation of V 2O 5 and MoO 3 phases. TEM results show that MoO 3 dots (5–30 nm in size) are embedded in the amorphous V 2O 5 matrix. It is further shown that cells fabricated with the MoO 3–V 2O 5 nanocomposite thin film electrodes give better cycling performance than those made with the single V 2O 5 thin film electrodes. A possible explanation for the MoO 3 nano-dot dependence on the cycling performance of the V 2O 5-based thin film electrodes is described.

Electrochromic properties of Au–WO 3 nanocomposite thin-film electrode

We observed proton transfer phenomenon of WO 3 in Au–WO 3 nanocomposite thin-film electrode prepared by sputtering deposition method. The Au–WO 3 nanocomposite electrode formed using both the Au and WO 3 targets consisted of a nano-sized Au crystalline phases and a tungsten oxidative phase, indicating the formation of crystalline Au nanophases, as confirmed by X-ray diffraction analysis and X-ray photoelectron spectroscopy. In particular, due to Au metallic nanophases, the modified electrochromic and electrochemical properties of WO 3 were observed. The Au–WO 3 electrode showed a reverse optical modulation with respect to applied potential compared to that of WO 3 electrode.

PtRu Alloy and PtRu−WO3 Nanocomposite Electrodes for Methanol Electrooxidation Fabricated by a Sputtering Deposition Method

PtRu alloy and PtRu−WO3 nanocomposite thin-film electrodes for methanol electrooxidation were fabricated by means of a sputtering method. The structural and electrochemical properties of well-defined PtRu alloy thin-film electrodes were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and electrochemical measurements. The alloy thin-film electrodes were classified as follows: Pt-based (10−40 atom % of Ru) and Ru-based (60 atom % of Ru) alloy structure. Among the electrodes formed by the sputtering method, PtRu-80, with 62 atom % Pt confirmed by XRD, showed the best catalytic activity for methanol electrooxidation. In particular, surface enrichment of Pt in the PtRu alloy thin-film electrodes, e.g. 65 atom % Pt for PtRu-80, was observed by XPS. Then, based on structural and electrochemical understanding of the PtRu alloy electrodes, PtRu−WO3 nanocomposite thin-film electrodes were formed. Th...

Modulation of electrode performance and in situ observation of proton transport in Pt–RuO2 nanocomposite thin-film electrodes

The relationship between the properties of ruthenium oxide and its electrode performance with respect to methanol electro-oxidation was investigated using a Pt–RuO2 nanocomposite thin-film electrode fabricated by a cosputtering system. The performance of the nanocomposite electrode, consisting of a Pt nanophase and a RuO2, was modified by heat treatment at different temperatures (100, 250, and 400 °C) which altered the proton and electron contributions in the electrodes. The transport of protons produced during methanol electro-oxidation in the Pt–RuO2 nanocomposite electrode was directly observed during electrochemical reaction by means of the ectrochromism of RuO2. It is concluded that improved electrical conduction that maintains the transport of protons is responsible for the enhanced electro-oxidation of methanol for 250 °C Pt–RuO2.