Novel Iron/Cobalt‐Containing Polypyrrole Hydrogel‐Derived Trifunctional Electrocatalyst for Self‐Powered Overall Water Splitting

Development of efficient, low‐cost, and durable electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is of significant importance for many electrochemical devices, such as rechargeable metal–air batteries, fuel cells, and water electrolyzers. Here, a novel approach for the synthesis of a trifunctional electrocatalyst derived from iron/cobalt‐containing polypyrrole (PPy) hydrogel is reported. This strategy relies on the formation of a supramolecularly cross‐linked PPy hydrogel that allows for efficient and homogeneous incorporation of highly active Fe/Co–N–C species. Meanwhile, Co nanoparticles are also formed and embedded into the carbon scaffold during the pyrolysis process, further promoting electrochemical activities. The resultant electrocatalyst exhibits prominent catalytic activities for ORR, OER, and HER, surpassing previously reported trifunctional electrocatalysts. Finally, it is demonstrated that the as‐obtained trifunctional electrocatalyst can be used for electrocatalytic overall water splitting in a self‐powered manner under ambient conditions. This work offers new prospects in developing highly active, nonprecious‐metal‐based electrocatalysts in electrochemical energy devices.     

影响掺杂聚吡咯(PPy)导电性能的因素

综述了对掺杂聚吡咯的导电能力影响因素的研究成果。主要就溶剂、掺杂离子、合成温度对聚吡咯电导率的影响进行了深入的讨论。通过对各类试验结果和讨论的综合分析 ,以找出其一般性的规律 ,并依据得出的结论提出一些有望改善聚吡咯导电能力的措施     

Electrochemical properties of free‐standing polypyrrole/graphene oxide/zinc oxide flexible supercapacitor

We report the preparation of a polypyrrole/graphene oxide/zinc oxide nanocomposite on a nickel foam using a simple and rapid single‐step electrochemical deposition process under ambient conditions. A free‐standing flexible supercapacitor was fabricated by sandwiching a polyvinyl alcohol hydrogel polymer electrolyte between two layers of the as‐prepared ternary nanocomposite electrodes. The electrochemical properties of the free‐standing supercapacitor were analyzed using a two‐electrode system. The supercapacitor achieved a specific capacitance of 123.8 F/g at 1 A/g, which was greater than its single (39.1 F/g) and binary (81.3 F/g) counterparts. This suggests that ZnO acts as a spacer and support that hinders the ternary structure from collapsing and subsequently enhances the diffusion of ions within the matrix. The flexible supercapacitor exhibited remarkable electrochemical stability when subjected to bending at various angles. The cycling stability of the ternary nanocomposite showed a favorable specific capacitance retention of more than 90% after 1000 cycles for mild alkaline electrolytes compared with strong alkali electrolytes. The presence of glycerin in the polymer electrolyte enabled the supercapacitor to perform better under the vigorous cycling condition. The potential of the as‐fabricated supercapacitor for real applications was manifested by its ability to light up a light‐emitting diode after being charged. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and magnetorheological characteristics of ribbon‐like,polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚吡咯／尼龙6复合导电纤维的研制

采用原位聚合法,在吡咯的水性溶液中可制备具有良好导电性的聚毗咯／尼龙6复合纤维。文章探讨了反应过程中各种因素对所制得的聚吡咯／尼龙6复合导电纤维导电性的影响。结果表明,FeCl3是一种较为有效的氧化剂。采用吡咯单体浓度为0．05 mol/L、氧化剂与吡咯的初始摩尔比为2．3、反应温度为20℃,反应时间为3 h的反应条件,可制得具有较好导电性的复合纤维。电镜照片显示,复合导电纤维呈现皮芯结构,聚吡咯主要集中在皮层,形成导电通道。     

Preparation of a Novel Composite Material Based on a Nafion® Membrane and Polypyrrole for Potential Application in a PEM Fuel Cell

The process of embedding polypyrrole (PPy) on the surface of a Nafion^® membrane was studied. Three methods of PPy synthesis directly on the membrane surface were compared. The diffusion method based on the separation of monomer and oxidant (peroxidisulphate) solutions by the membrane to be modified is proposed as the most promising one. The monomer diffuses through the membrane to the oxidant side, where it is polymerized. In this case sulphate is incorporated into the film as a counter-ion. PPy film prepared in this way adheres well to the Nafion^® surface and shows promising electrochemical activity. The permeability of the composite for monomer in comparison to self-standing Nafion^® film is reduced significantly. This may be important for the potential application of this composite, especially in a direct methanol fuel cell, as an alternative membrane-electrode assembly (MEA), particularly with regard to the currently used MEA’s permeability for fuel.     

Organic phase PPO biosensor based on hydrophilic films of electropolymerized polypyrrole

We described herein, the construction of an organic phase enzyme electrode (OPEE) via polyphenol oxidase (PPO) entrapment within a hydrophilic polypyrrole film electrogenerated from on a new bispyrrolic derivative (1) containing a long hydrophilic spacer. The so-called “adsorption step procedure” was adopted for the preparation of the organic phase PPO biosensor. The amperometric detection of catechol was carried out in anhydrous chloroform at −0.2 V versus Ag/AgCl. The electroanalytical parameters of the biosensor strongly depend on its configuration and on the hydration state of the enzyme matrix. The best sensitivity obtained for catechol in chloroform was 15.6 mA M⁻¹ cm⁻².     

Shrinking rate of conducting grains in HCl–protonated polyaniline,polypyrrole, and polypyrrole/polyaniline blends with their thermal aging

The dc electrical conductivity (σ) of HCl‐protonated polyaniline, polypyrrole, and their blends was measured from 80 to 300 K for thermal aging times between approximately 0 and 600 h. The thermal aging took place at 70°C under room atmosphere. The change of σ with the temperature (T) and the decrease of σ with the thermal aging time (t) are consistent with a granular metal type structure, in which conductive grains are randomly distributed into an insulating matrix. Aging makes the grains shrink in a corrosion‐like process. From σ = σ(T) measurements the ratio s/d, where s is the average separation between the grains and d their diameter, as well as the rate d(s/d)/dt of their decrease with t were calculated. These revealed that the conductive grains consist of a shell, in which aging proceeds at a decreasing rate, and a central core, which is consumed at a much slower rate. Our measurements not only permitted the estimation of the shell thickness, which lies between 0 and 5 Å, but also gave quantitative information about the quality of the shells and the cores from their aging rates. The shells are consumed with an average rate of d(s/d)/dt = 6.6 × 10^?4 (h^?1), which is about 5 times greater than the more durable cores. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 117–122, 2005     

Polydopamine‐Assisted Electrochemical Fabrication of Polypyrrole Nanofibers on Bone Implants to Improve Bioactivity

Dopamine is a molecule that facilitates biomineralization, and it is used to prepare electropolymerization‐induced polydopamine (PDA). For the first time, dopamine is used for template‐free electrochemical polymerization to form biocompatible polypyrrole (PPy) nanofiber coatings on bone implants. Dopamine monomers are electropolymerized to PDA chains affixed to biomedical titanium after the nanomicelles are tuned to self‐assemble by triggering the potential, resulting in nanofiber formation. Dopamine serves as a dopant to induce the formation of conductive PPy nanofibers and as a promoter to accelerate biomineralization, cell proliferation, and adhesion.

     

Electrochemically stimulated 2‐ethylhexyl phosphate (EHP) release through redox switching of conducting polypyrrole film and polypyrrole/poly (N‐methylpyrrole) or self‐doped polyaniline bilayers

2‐Ethylhexyl phosphate (EHP) released from poly(pyrrole 2‐ethylhexyl phosphate) (PP‐EHP) was investigated at open circuit and compared with electrochemically stimulated release during potential cycling. It was found that the fast EHP release from the PP‐EHP single layer is substantially retarded and that amounts of spontaneously and electrochemically released EHP can be reduced by constructing bilayers, consisting of a PP‐EHP inner layer and a poly(N‐methylpyrrole)‐poly(styrene sulfonate) (PNMP‐PSS) or self‐doped poly(aniline) sulfonate (SPANI) as the outer films. The presence of outer film over the PP‐EHP allowed surface‐property modification, as well as the control of the rate of EHP release, while electrochemically stimulated EHP release from inner films was not substantially hampered by the outer layer. The quantity of the EHP released was investigated using UV‐vis spectrophotometery and an electrochemical quartz‐crystal microbalance (EQCM) during reduction of PP‐EHP from single layer and bilayers through electrochemical stimulation. EHP was reincorporated to the inner film by applying an anodic potential and then the release of EHP was performed again. The results showed that the outer film could act as a barrier to ion‐and solvent‐transport between the inner film and electrolyte, yielding a more balanced counter‐directional movement of anions. © 2002 Society of Chemical Industry