Synthesis and Characterization of Silver Nanowires and Mos2/Metal Oxide Hybrids for Electronics and Energy Applications

Abstract

The present study focuses on two important aspects of next-generation electronics and energy storage devices. One is the flexible transparent conductive electrode fabricated using silver nanowires. Another is the ZnO anode used in zinc alkaline batteries. The silver nanowires transparent conductive films are the potential alternative to widely used high-cost, brittle indium tin oxide (ITO). The silver nanowires are synthesised by following the polyol method. Among many synthesis parameters, the oxygen scanger is important for the growth of longer silver nanowires. These oxygen scavengers (ex: Cu or Fe ions) help to prevent the blocking/etching of silver seed particles from atomic oxygen adsorbed on their surface. This work explores the use of manganese ions as the oxygen scavengers during the silver nanowires synthesis due to the multiple oxidative states of manganese. The silver nanowires are synthesised in different chloride conditions: no chloride, NaCl, CuCl2 and MnCl2. The silver nanowires synthesised with the presence of Mn(II) ions and Cl- ions show more uniform, longer nanowires with a smaller diameter than that synthesised with the presence of Cu(II) ions. The transparent conductive films are fabricated by the spray coating method using the silver nanowires synthesised with Mn(II) ions. Three films with optical transparency (at 550 nm) and sheet resistance of 81% & 40 Ω/sq., 79% & 29 Ω/sq. and 80% & 34 Ω/sq. are produced. The silver nanowires film shows excellent mechanical flexibility. The heater test conducted on the silver nanowires film achieved a temperature of 90 °C. Factors like the dissolution of Zn anode, hydrogen gas evolution, shape change make the Zn/ZnO anode in zinc alkaline batteries difficult to recharge. These problems can be mitigated by tailoring the morphology of the anode and incorporating desirable additives with the anode. Tin oxide (SnO2) is an excellent additive to Zn/ZnO. The poor charge transfer within SnO2 due to volume expansion and microcracks are the drawbacks of using SnO2. The liquid phase exfoliated MoS2 nanosheets are used as the support material to facilitate the charge transfer between the SnO2 nanoparticles. The nanocomposite of MoS2 nanosheets and SnO2 nanoparticles (MoS2-SnO2) is prepared by the ligand exchange process. The ratio of MoS2 in SnO2 is optimized by conducting the supercapacitor characterizations such as cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge study. The prepared MoS2-SnO2 nanocomposite is tested as an additive with ZnO. For this purpose, the ZnO with three different morphology is used. First, commercial ZnO nanoparticles with plate-like, spherical-like morphology. Second, ZnO nanorods synthesised by microwave heating method. Third, ZnO microrods synthesised by hydrothermal method. The solubility study conducted by atomic absorption spectroscopy shows that the one-dimensional ZnO microrods and nanorods dissolve slower in KOH electrolyte than the ZnO with plate-like and sphere-like morphology. The three ZnO materials with and without the MoS2-SnO2 additive are subjected to hydrogen gas evolution, corrosion test, electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical performance of ZnO with MoS2-SnO2 additive is better than the bare ZnO. Among all the samples, the performance of MoS2- SnO2/ZnO nanorods is excellent and the most suitable anode material to be used in the alkaline battery.