Fabreication And Electrochemistry Properties Thin Films Based Layered Double Hydroxides

Layered double hydroxides (LDHs), is one kind of environmentally friendly material with potential applications in flame retardant, PVC heat stabilizer, catalysts and biomaterials. Its formula can be generally expressed as [M2+1-x,M3+x(OH)2]x+[An-x/n]x-·mH2O (M2+ and M3+ are divalent and trivalent metal cations, respectively, and A" is an n-valent anion), which represents a large versatility in chemical constitution, aspect ratio, interlayer anions and charge density of host layer. LDHs have been exfoliated into positively charged nanosheets with a theoretical thickness of 0.48 nm which are ideal building blocks for assembly into functional multilayer nanostructures by employing a Langmuir-Blodgett (LB) or layer-by-layer (LBL) technique.In this dissertation, we have successfully fabricated electrochromic films on ITO substrate by LBL assembly of sulfonated poly(styrene sulfonate) (PEDOT:PSS) and LDH nanosheets. The (PEDOT:PSS/LDH)n ultrathin films (UTFs) exhibit a periodic long-range superlattice structure, uniform morphology and controllable thickness on the nanometer scale. The modified electrode exhibits enhanced electrochromic property with rapidly switching, high coloration efficiency and good cycling stability. The contrast of the (PEDOT:PSS/LDH)80 UTFs could reach up to ?T=32%, which is comparable to those of reported PEDOT-CNT/PET, (LPEI/PEDOT:PSS)20 and Au@PEDOT films. Most significantly, the (PEDOT:PSS/LDH)80 UTF displays a fast switching behavior with coloration time and bleaching time of 0.27 s and 0.18 s, respectively, superior to most of the reported electrodes. These excellent electrochromic performances can be attribute to highly distributing PEDOT:PSS within an inorganic layer matrix, which would facilitate Li+ion diffusion channels and improved availability of active sites. Therefore, this work provides an efficient strategy to incorporate electroactive polymer into a 2D inorganic matrix with accelerated ion (or electron) transfer propety, for the construction of high-performance electronic devices and smart windows.We further developed a one-pot method to synthesize sandwich-like nanocomposites with cobalt alumium layered double hydroxide grown on both sides of graphene oxides via a facile ultrasound-assisted method. It is found that the CoAl-LDH nanosheet arrays grow perpendicularly and uniformly on both sides of graphene oxides nanosheets, constructing a hierarchical three-dimensional (3D) nanocomposites with a well-defined sandwich structure. This uniquely structured nanocomposite has a large specific surface area and typical mesoporous distribution, which are favorable for achieving high pseudocapacitance performance. The free standing LDH/GO film exhibits a specific capacitance of 340 F/g with good cycling stability. The one-pot strategy may pave a way to design and fabricate hierarchical LDH/GO composites with interesting structures for potential application in supercapacitors and other fields.