Preparation Of Layered Double Hydroxide Films By Secondary (Seed) Growth Method And Their Electrochemical Properties

The nucleation and growth processes involved in forming an inorganic film have a significant effect on the microstructure of the resulting films, Which with controlled surface area, porosity, crystalline orientation, and crystal morphologies are desirable for many applications, including microelectronic devices, chemical and biological sensing, energy conversion and storage. Layered double hydroxides (LDHs, a family of anionic clays) have recently attracted increasing attention in view of their potential applications in the fields of catalysis, adsorption, additives in polymers, drug delivery, environmental remediation and energy storage, when LDH crystallites were organized into aligned two-dimensional arrays or films on various substrates, we would broaden new applications in practical devices, including superhydrophobic films, anti-corrosion coatings for metals and alloys, heterogeneous catalysts, functional films for use in optical, electrical and magnetic devices. Up to now, there are mainly three different ways to prepare LDH films:physical deposition, electrochemistry deposition and in situ growth method, in which the in situ growth film and the substrate has a relatively stronger binding force.Based on our previous experimental results of the evolution of formation process, a rough two-stage formation process was commonly proposed for the synthesis of LDH by coprecipitation:colloidal amorphous aluminum hydroxide (AAH) is formed from the aluminum precursor salt solution at the early stage of the synthesis; subsequently, the amorphous hydroxides are transformed into the crystallites of oxide-hydroxide aluminum, accompanying the continuous incorporation of surrounding Mg2+ into the sheet for the forming LDH crystallites. From the above studies we can reasonably infer that LDH film upon in situ growth under the hydrothermal crystallization condition may suffer from problems including the localized segregation of components and possible loss of stoichiometry, which could result in a significant decrease in application properties. Thus, fabrication of LDH film with improved performance for specific applications by developing novel strategy is essential.In this study, we report the synthesis of NiAl-LDH films on nickel foil and nickel foam substrates by secondary (seeded) growth method. Firstly prepare a stable and homogeneous LDH suspensions with uniform particle sizes, then dip-coat seed colloidal solution on the substrate, finally under secondary growth hydrothermal conditions to yield continuous films. For comparison, NiAl-LDH films were prepared by in situ growth technique on substrate.The formation process of both kinds of LDH films upon secondary growth and in situ growth, such as the evolution of phase composition, structure, and particle morphology during the whole process was verified and the formation mechanism was postulated based on the characterization results, pointing out that the second layer has accelerated crystallization rate.we further evaluated the electrochemical performance of the secondary-grown NiAl-LDH film as positive electrode material by means of particular microstructure and high crystallinity of secondary growth film. Finally, we also adopt secondary growth method to prepare MgAl-LDH film by a similar NiAl-LDH film growth process approach, which obtain surface microstructure morphology and crystallinity different from in situ method film, confirming the seed layer in thin film growth during hydrothermal process accelerate crystal rate...