Controlled growth of hollow polyaniline structures: From nanotubes to microspheres

Carbon-Induced Generation of Hierarchical Structured Ni0.75Co0.25(CO3)0.125(OH)2 for Enhanced Supercapacitor Performance

Hierarchical nanostructures with heteroatom doping have been considered as an important component in electrode materials for advanced supercapacitors. Herein, with the aid of C, N, and S codoped Ni_0.75Co_0.25(CO₃)_0.125(OH)₂/C (NSH) with a hierarchical structure was synthesized through a facile one-step hydrothermal method. Notably, it is the first report on a carbon precursor as a structure inducer for designing a three-dimensional (3D) carnation-like hierarchical structure. Thanks to the carbon induction effect and the introduction of N/S dopants, the obtained NSH with a 3D architecture exhibits superior performances as electrode materials for supercapacitors. For example, NSH offers a high specific capacity of 277.3 mAh/g at 0.5 A/g. Moreover, the assembled NSH//reduced graphene oxide hydrogel-based hybrid supercapacitor exhibits high energy densities of 44.4 and 11.7 Wh/kg at power densities of 460 W/kg and 9.8 kW/kg, respectively. This result opens up opportunities for carbon-induced methods to control the morphology and structure of other similar materials.

Facile Synthesis of Polyaniline Nanotubes Using Self-Assembly Method Based on the Hydrogen Bonding: Mechanism and Application in Gas Sensing

Based on hydrogen bonding, the highly uniform polyaniline (PANI) nanotubes were synthesized by self-assembly method using citric acid (CA) as the dopant and the structure-directing agent by optimizing the molar ratio of CA to aniline monomer (Ani). Synthesis conditions like reaction temperature and mechanical stirring were considered to explore the effects of hydrogen bonding on the morphologies. The effects of CA on the final morphology of the products were also investigated. The as-synthesized CA doped polyaniline (PANI) nanomaterials were further deposited on the plate electrodes for the test of gas sensing performance to ammonia (NH₃). The sensitivity to various concentrations of NH₃, the repeatability, and the stability of the sensors were also tested and analyzed. As a result, it was found that the PANI nanomaterial synthesized at the CA/Ani molar ratio of 0.5 has highly uniform tubular morphology and shows the best sensing performance to NH₃. It makes the PANI nanotubes a promising material for high performance gas sensing to NH₃.

Pure Nanoscale Morphology Effect Enhancing the Energy Storage Characteristics of Processable Hierarchical Polypyrrole

We report a new synthesis approach for the precise control of wall morphologies of colloidal polypyrrole microparticles (PPyMPs) based on a time-dependent template-assisted polymerization technique. The resulting PPyMPs are water processable, allowing the simple and direct fabrication of multilevel hierarchical PPyMPs films for energy storage via a self-assembly process, whereas convention methods creating hierarchical conducting films based on electrochemical polymerization are complicated and tedious. This approach allows the rational design and fabrication of PPyMPs with well-defined size and tunable wall morphology, while the chemical composition, zeta potential, and microdiameter of the PPyMPs are well characterized. By precisely controlling the wall morphology of the PPyMPs, we observed a pure nanoscale morphological effect of the materials on the energy storage performance. We demonstrated by controlling purely the wall morphology of PPyMPs to around 100 nm (i.e., thin-walled PPyMPs) that the thin-walled PPyMPs exhibit typical supercapacitor characteristics with a significant enhancement of charge storage performance of up to 290% compared to that of thick-walled PPyMPs confirmed by cyclic voltametry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. We envision that the present design concept could be extended to different conducting polymers as well as other functional organic and inorganic dopants, which provides an innovative model for future study and understanding of the complex physicochemical phenomena of energy-related materials.

Facile route to synthesis and morphology control of anionic waterborne polyurethane hollow microspheres via self-crosslinking reaction

Porous waterborne polyurethane (WPU) hollow microspheres were synthesized via a self-crosslinking reaction of WPU prepolymer terminated by 3-aminopropyltriethoxysilane (APTES).